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(BQ) Part 2 book “Dynamic reconstruction of the spine” has contents: Minimally invasive posterior dynamic stabilization system, anterior exposure to the lumbar spine, the mobidisc prosthesis, complications of lumbar disc arthroplasty, annulus repair, assessment of lumbar motion kinematics in vivo,… and other contents.
| 20.02.15 - 13:27 Dynamic Stabilization for Revision of Lumbar Spinal Pseudarthrosis 29 Dynamic Stabilization for Revision of Lumbar Spinal Pseudarthrosis with Transition Paul C McAfee, Liana Chotikul, Erin M Shucosky, and Jordan McAfee 29.1 Introduction With the Agile and N-Hance spinal devices being withdrawn from the market and not being available for sale in the United States, the practical application of dynamic stabilization is limited Furthermore, the prospective randomized Food and Drug Administration (FDA) study of the Dynesys Dynamic Stabilization System (Zimmer Spine, Minneapolis, MN) was not approved This leaves the Transition Stabilization System (Globus Medical, Inc., Audubon, PA) as the main remaining instrumentation system available for clinical use in the treatment of spinal pseudarthrosis It was felt in the original design that the use of a bumper of polycarbonate urethane (PCU) would be effective in damping the force of correction transitioning from the rigid titanium rod portion of an instrumentation system to the uninstrumented mobile portion of the spine outside the vertebral levels of surgery.1 There were three indications for using the Transition: (1) topping off, (2) hybrid cases with one or two levels of solid rod combined with one or more levels of PCU, and (3) load sharing between the posterior dynamic rod and an anterior poly ether ketone (PEEK) spacer at the same vertebral level We reviewed a series of 85 consecutive cases treated as one of these three indications in the setting of revision surgery.2 Spinal fusion revision should be more reliably achieved with the use of a dynamic instrumentation system that allows more of the load to be sequentially borne by the spinal fusion If 100% of the load is absorbed by the spinal instrumentation the pedicle screws bear higher cantilever bending stresses, there are higher strains on the solid metal rods, and a higher incidence of pedicle screw breakage can be expected The focus of this study of 85 consecutive patients was to take a discrete unarguable definition of failure—reoperation—and apply dynamic, shock-absorbing instrumentation in the setting of prior failure of lumbar fusion, thereby to determine whether the reoperation rate is more favorable than with conventional instrumentation All of the 85 cases were treated on label in strict accordance with the FDA-approved indicated labeling of the Transition instrumentation system 29.2 Definitions of Successful Clinical Fusion All cases in this series were Lenke grade D in appearance on radiographs All patients had mechanical back pain, fulfilled the criterion of disability for a minimum of months preoperatively, and had over mm of angular motion of preoperative flexionextension radiographs In a review of 56 cases of isthmic spondylolisthesis, treated with uninstrumented posterolateral fusion using autogenous iliac crest bone graft, Lenke et al classified the different grades of fusion from radiographs as follows: (a) Definitely solid (50%)—large, solid, trabeculated bilateral fusion masses (b) Possibly solid (18%)—unilateral large fusion mass with contralateral small fusion mass (c) Probably not solid (11%)—small, thin fusion masses bilaterally (d) Definitely not solid (21%)—graft resorption bilaterally or fusion mass with obvious bilateral pseudarthrosis 29.2.1 Clinical Experience Eighty-five patients were treated with Transition segmental spinal pedicle screw instrumentation for pseudarthrosis Thirtythree of the prior surgical procedures had used spinal instrumentation, which had to be removed at the start of the revision procedure The indications for the secondary procedure were pseudarthrosis (85 cases), recurrent herniated disc (14 cases), recurrent lumbar spinal stenosis (22 cases), adjacent segment disease (2 cases), and progression of the patient’s deformity— scoliosis, spondylolisthesis, or retrolisthesis (19 cases)3 (▶ Table 29.1) 29.2.2 Transition Surgical Technique and Design Features Transition is a pedicle screw–based system consisting of a PCU bumper and spacer to provide a soft stop at the limits of spinal flexion and extension The amount of flexibility is determined by the total amount of PCU in the bumper and the spacers, which can be of various lengths, from 20 to 42 mm The Transition system uses a semirigid rod that provides translational stability to horizontal shear forces because the spools overlap and encompass the sleeves The unique feature of the system is that it provides for angulation of the adjacent pedicle screws and variation of the interpedicular distance throughout flexion and extension The spools can be selected in a straight configuration, lordotic, or extralordotic so that the overall construct lordosis can be varied from straight to 40 degrees of global lumbar lordosis from L1 to S1 The polyethylene terephthalate (PET) cord has greater than 3,100 tensile strength and pullout strength of over 1,000 N where it attaches to the end of the titanium rod In fatigue testing to million cycles the Transition rods did not fail with shear stresses, whereas two other competitive FDA-approved dynamic systems failed at a mean of Table 29.1 Predominant indications (much overlap) Indication Number of patients Pseudarthrosis 85 Recurrent herniated nucleus pulposus 14 Recurrent lumbar spinal stenosis 22 Adjacent segment disease Deformity progression (scoliosis, spondylolisthesis, retro) 19 207 | 20.02.15 - 13:27 Restoration of the Lumbar Motion Segment Fig 29.1 (a) Bench-top laboratory testing reproduced the mechanism of failure for the AGILE system (Medtronic) using polycarbonate urethane (PCU) and a cable to provide dynamic posterior stabilization The laboratory failure is shown on the left, demonstrating cable breakage with mm of anterior-posterior shear during fatigue loading This was predictive of clinical failure shown on the right, with cable breakage and dry frictional wear particulate around the pseudarthrosis mass (b) This is a fractured Agile rod–cable bilaterally in a 32-year-old man 12 months after the original surgery elsewhere demonstrating pseudarthrosis The mechanism of failure is identical to that predicted in (a) Notice that on the lateral radiograph the L4 vertebra is retrodisplaced mm posterior relative to the L5 vertebra, indicating that the Agile device was not able to withstand posterior shear (c) This was successfully revised with repair of the pseudarthrosis with autologous bone graft and replacement with the Transition system (Globus Medical) from L4 to S1 Notice that the posterior shear forces are stabilized by the instrumentation by means of titanium spools, which overlap and encompass the polycarbonate urethane (PCU) spacers (d) At 3-years post–revision surgery the flexion-extension radiographs document stability The is degrees of angular motion and mm of compression-elongation of the PCU spacers There is no longer any posterior translation on the extension radiograph 12,685 cycles (Agile) (▶ Fig 29.1) and 13,465 cycles (N-Hance) (▶ Fig 29.2) The goals of a compressible semirigid fusion system are threefold4–7: (1) to optimize load sharing between the anterior and posterior spinal columns to re-create the natural 80:20 balance or load distribution Static titanium and stainless steel pedicle screw systems increase the load on the posterior column well beyond 80%; (2) to promote more uniform loading of an interbody spacer (as does the Transition) by allowing the pedicle-to-pedicle or interpedicular distance to compress as the spine is loaded in an axial direction PEEK rods and static rods that not vary the interpedicular distance keep the middle column at a fixed length and cannot provide for compression loading of an interbody spacer Only the anterior column can compress an interbody spacer with a static rod Transition is designed to allow telescoping of the middle column to the same extent as the anterior column; therefore the interbody spacer is 208 loaded uniformly across the vertebral end plates; (3) to minimize stress at the bone–screw interface Because the PCU rods absorb some of the loads, there is less stress at the bone–screw interface The incidence of screw loosening and breakage should be reduced, particularly in challenging revision procedures with documented pseudarthrosis and windshield-wiper-type failure with less compliant static instrumentation systems8,9 (▶ Fig 29.3) 29.2.3 Patient Demographics The mean age of the 85 patients was 54.5 years (range, 31–81 years) The mean estimated blood loss of the surgery was 806 mL (range, 200–2,900 mL), including the revision decompression, fusion, and Transition segmental instrumentation system The mean length of surgery was 147 minutes (range, 85–297 min) The mean length of hospital stay was 3.54 days (range, 2–5 d) | 20.02.15 - 13:27 Dynamic Stabilization for Revision of Lumbar Spinal Pseudarthrosis Fig 29.2 (a) On the left is the failure of the N-Spine (N-Hance, Synthes, Inc.) instrumentation system in the laboratory, and on the right is shown a clinical failure Notice that cyclical bench-top testing with mm of shear was predictive of instrumentation failure at the welds between the largerdiameter 5.5 mm rods and the step-down in diameter at the location of a welded collar The polycarbonate urethane (PCU) failure is secondary in both the in vivo and the in vitro situations (b) A 66-year-old woman presented from elsewhere general with failure of both N-Spine rods at the weld marks 13 months postoperatively following an attempted L4 to S1 fusion (c) Two years following revision to the Transition system (Globus Medical) from L4 to S1 with repair of pseudarthrosis she demonstrates a radiographic Lenke A fusion, and she is asymptomatic Fig 29.3 (a) A 55-year-old woman presented with severe mechanical back pain months following facet screw placement from L4 to S1 The anteroposterior and lateral radiographs demonstrate windshield-wiper toggling of the facet screws at all levels, indicative of screw loosening (b) Two years postoperatively she had relief of mechanical pain with repair of pseudarthrosis and insertion of the Transition system (Globus Medical) improving from a visual analog scale score of down to (c) Lateral radiograph after revising the multilevel pseudarthrosis with Transition segmental instrumentation from L3 to S1 The patient’s clinical symptoms of instability resolved 209 | 20.02.15 - 13:27 Restoration of the Lumbar Motion Segment All 85 patients presented to our institution with a symptomatic pseudarthrosis and/or instrumentation failure The mean visual analog scale (VAS) score for self-assessment of pain disability was 6.59 (range, 10–1) Thirty-three of the patients had prior surgical instrumentation with a wide variety of methods and biomaterials —Agile, N-Hance, Dynesys, Expedium Spine System (DePuy Spine, Inc., Raynham, MA), CD Horizon, Harrington rods, Quantum rods, Revere 4.5 Stabilization System (Globus Medical, Inc., Audubon, PA), Silhouette Spinal Fixation System (Zimmer Spine, Minneapolis, MN), ISOLA/VSP Spine System (DePuy Spine, Inc., Raynham, MA), VersiLok, Moss-Miami Spinal System (DePuy Spine, Inc., Raynham, MA), and TSRH Spinal System Pedicle Screw (Medtronic, Minneapolis, MN) instrumentation systems The Transition segmental instrumentation required 15 single-level fusion procedures, 44 two-level repairs of pseudarthroses, 20 three-level repairs, and procedures that were four or more levels The autograft was always placed bilaterally in the intertransverse or posterolateral location, and it was placed the entire length of the instrumentation, including across the PCU spacer portion of the Transition rods This is the on-label approved use consistent with the FDA clearance for the Transition product ▶ Table 29.2 lists the risk factors10–17 for pseudarthrosis in the 85 patients—all 85 by definition presented with failure of a prior fusion procedure 85/85 (100%); multilevel spinal fusions, 68/85 (80%); cigarette smoking, 18/85 (21.2%); body mass index over 30 (41.2%); and adult-onset (type 2) diabetes mellitus (11.8%) 29.2.4 Clinical Results Reoperation Rate Four of the 85 patients (4.7%) experienced device-related adverse events Three had broken porous ingrowth hydroxyapatite (HA) coated pedicle screws within the 2-year minimum follow-up time period There was one patient who had a broken spool pedicle screw connector and a broken screw noted months postoperatively One patient each had reoperations for an epidural hematoma, a misplaced pedicle screw, and a total lumbar interbody fusion (TLIF) spacer that migrated into the spinal canal Therefore, in this revision series of 85 patients there were a total of 7/85 (8.24%) reoperations within years of the index procedure There were no permanent iatrogenic neurological adverse events for any of the 85 patients One patient (case 36) developed a postoperative epidural hematoma, which was successfully decompressed with a reoperation 10 days after the index Transition procedure The Transition rod on the symptomatic side was removed during the exploration to improve visualization of the symptomatic nerve roots A Transition rod was reinserted following the decompression, and there was no long-term effect on the Table 29.2 Risk factors for pseudarthrosis Risk factor Incidence Multilevel spinal fusion 68/85 = 80% Cigarette smoking Body mass index > 40 Fusion performed as a revision procedure 210 85/85 = 100% patient’s clinical outcome 24 months following the hematoma decompression The VAS self-assessment of back pain improved from a mean of 6.59 (range 10 to 1) down to a mean of 3.61 (range 10 to 1) There was a mean of 25.2% improvement for the 85 patients Kelly reported a minimum clinically significant difference (MCSD) in VAS pain score of 12 mm (95%: confidence interval [CI] 9–15 mm) Therefore we used 15 mm as the MCSD to be conservative and capture all the patients within the 95% CI For the total cohort of 85 patients there were 53 patients who experienced 15 points or more improvement in VAS at 24 months or more follow-up There were 23 patients whose VAS was unchanged (0 to 14 mm) There were nine patients who judged their pain as being worse, including the seven patients who required repeat surgery at some point within the 24-month follow-up interval In summary, in this challenging group of salvage procedures there were 53 of 85 consecutive patients (62.4%) with pseudarthrosis and/or instrumentation failure who met or exceeded the MCSD for chronic lumbar pain at 24 months or more follow-up after the Transition reconstructive procedures.18 Fusion Assessment The follow-up anteroposterior and lateral radiographs were assessed according to the Lenke classification.19 To aid as a historical control reference point the percentage Lenke obtained in his original series is shown in parenthesis: (a) Definitely solid, 25/85 patients = 29.4% (Lenke, 50%)—solid big trabeculated bilateral fusion masses (b) Possibly solid, 17/85 patients = 20% (Lenke, 18%)—unilateral large fusion mass with contralateral small fusion mass (c) Probably not solid, 14/85 patients = 16.5% (Lenke, 11%)— small, thin fusion masses bilaterally (d) Definitely not solid, 29/85 patients = 34.1% (Lenke, 21%)— graft resorption bilaterally or fusion mass with obvious bilateral pseudarthrosis It is important to remember that the Lenke series consisted of single-level fusions and instrumentation, whereas the Transition revision series largely consisted of multilevel procedures Optimum Rigidity for Lumbar Instrumentation and Fusion Mass It is beyond the scope of this chapter to define optimum rigidity The optimum rigidity of spinal instrumentation for achieving a successful lumbar fusion has been the subject of decades of spinal research.20–23 A published symposium attempted to resolve a critical discrepancy on the “criteria of successful arthrodesis following interbody spinal fusions”—eight spinal experts presented their views, particularly in terms of motion in flexion-extension lateral radiographs and computed tomographic (CT) imaging.4 The authors concluded that a large difference of opinion exists regarding the definition of successful spinal fusion Most experts believed that, even in the presence of solid fusion, some degree of motion may be perceived in flexion-extension lateral radiographs, which may vary from to degrees It was also generally believed that the absence of motion does not | 20.02.15 - 13:27 Dynamic Stabilization for Revision of Lumbar Spinal Pseudarthrosis guarantee solid fusion, most possibly because rigid instrumentation may still hold the segment rigid, masking an underlying pseudarthrosis Furthermore, there are differences in patient cooperation and effort with regard to the amount of flexion and extension due to pain The only convincing evidence of fusion that was unequivocally agreed on was finding a bony continuity on reexploration and no perceived motion against applied force after removal of implants Most authors agreed that clinical success may be different from technical success Although bony arthrodesis is the objective of surgery, it is probably unnecessary to prove bony arthrodesis in patients who have had a successful clinical result Therefore it may be possible that a stable pseudarthrosis may achieve clinical success, despite the failure of solid fusion Based on the difference of opinion as to what constitutes successful spinal fusion in the published reports, it appears that there may be gradations of successful spinal fusion, with varying degrees of rigidity (▶ Fig 29.4) McAfee made an interesting observation,12 that even in the presence of a well-consolidated posterolateral fusion, intervertebral motion may still be demonstrated following anterior disc space clearance This phenomenon is due to springing through the pedicles, which may also permit a small amount of movement through the posterior complex in the presence of a well-consolidated interbody fusion Weatherley et al presented five cases with definitive posterolateral fusion with persistent motion between the vertebral bodies.4 These clinical observations are not surprising from a study of the mechanical properties of bone.12 Bone is not a stiff structure like steel; it has a degree of elasticity that increases its toughness, which has been reported in some detail With the background of the prior discussion the authors concede the limitations of any investigation of the success of spinal fusion We have used the Lenke classification due to its widespread application and accept its limitations as being somewhat subjective and somewhat arbitrary, and it requires compartmentalization of bone healing, which is a continuous process, into a discrete classification of four categories Reoperation Rates of Historical Studies Unlike the definition of successful lumbar fusion, there is universal agreement that a reoperation or a return to the operating theater is a failure of the index procedure So how does the reoperation rate of 7/85 (8.24%) within years of the index procedure in a revision pseudarthrosis series match up in the literature? In all large series the outcomes following the multioperated spine are less favorable than primary procedures Ten of the patients in this series had undergone three or more spinal procedures prior to the index Transition procedure.24,25 Bago et al21 reported a fairly representative series of 133 patients with Cotrel Dubousset instrumentation, 22% of whom needed a total of 28 additional operations and 21% required implant removal Pihlajämaki et al22 reported the complication rates and pseudarthrosis incidence in a consecutive series of 102 patients treated with pedicle screw and rod fixation for nontraumatic disorders There were 75 multilevel and 27 single-level fusions Forty-six patients had at least one further operation for one or several complications (38.3%), including 20 fusion procedures for nonunions (19.6%) Brook et al23 Fig 29.4 (a) Topping off A 68-year-old man sustained an acute lumbar vertebral body fracture simply by bending forward due to the stress concentration of the pedicle screws at the upper instrumented vertebra (b) This is the typical appearance at the upper level of long Transition system (Globus Medical) constructs with a supplemental total lumbar interbody fusion There were no cases of failure at the upper instrumented vertebrae in any of the 85 cases in this series, including 20 three-level cases and cases requiring four or more instrumented levels (c,d) This is a more recently treated case indicating our currently preferred instrumentation method, which uses a cobalt-chromium (CoCr) 5.5 mm rod for adults that is connected to the Transition system at the upper vertebral levels This technique provides the increased rigidity of the cobalt chrome instrumentation such that there are actually two transitions in rod stiffness provided along the construct—from CoCr to titanium (Ti) and from Ti to polycarbonate urethane (PCU) The goal is to provide a less abrupt change in modulus between long instrumented constructs and the normally mobile spinal segments above performed an analysis of a database of 24,882 cases performed in Washington State hospitals Their follow-up was longer than that for the Transition series, up to 11 years with most of the reoperations occurring in the first years The cumulative incidence of reoperations was 19% with a higher reoperation rate of 21.5% following fusion procedures and 18.8% following decompression alone After fusion surgery 62.5% of reoperations were associated with a diagnosis suggesting device complication or pseudarthrosis Javalkar et al24 studied 335 patients who underwent surgical treatment of lumbar spinal stenosis with 63 undergoing spinal instrumentation and fusion, and 21 were reoperations The overall reoperation rate was 44/335 (13%), with 50 reoperations performed in 44 patients The risk of reoperation hazard ratio (HR) was highest in patients with prior instrumentation (HR 1.7, 95% CI 0.684–4.640) There are no reports in the literature that study identical patient 211 | 20.02.15 - 13:27 Restoration of the Lumbar Motion Segment indications, have identical numbers of vertebral levels, and have the same patient demographics as the Transition cohort of 85 patients described earlier However, the studies show a consistent pattern of more reoperations than conventional primary fusion studies With a reoperation range of between 13 and 38.3%, the Transition incidence of reoperations at 8.24% seems encouraging enough to recommend more rigorous, carefully controlled studies 29.3 Summary Two prospective randomized trials are under way as a result of the findings of this study (1) A prospective randomized controlled trial to compare Transition with titanium segmental pedicle screw instrumentation one- and two-level fusions with and without interbody spacers This is part of an FDA postmarket surveillance study required of all products in the posterior dynamic instrumentation field.25 (2) Headed by Berven et al,26 a prospective randomized controlled trial is currently enrolling for treating and preventing the progression of proximal junctional kyphosis at the cephalad end of long scoliosis constructs (four levels or more) It is hoped that the use of a compressible rod will help to reduce the stress concentration that occurs at the cephalad end of rigid static instrumentation constructs (▶ Fig 29.4) 29.4 References [1] Durrani A, Jain V, Desai R et al Could junctional problems at the end of a long construct be addressed by providing a graduated reduction in stiffness? A biomechanical investigation Spine 2012; 37: E16–E22 [2] Kelly AM The minimum clinically significant difference in visual analogue scale pain score does not differ with severity of pain Emerg Med J 2001; 18: 205–207 [3] McAfee PC, Boden SD, Brantigan JW et al Symposium: a critical discrepancya criteria of successful arthrodesis following interbody spinal fusions Spine 2001; 26: 320–334 [4] Weatherley CR, Prickett CF, O’Brien JP Discogenic pain persisting despite solid posterior fusion J Bone Joint Surg Br 1986; 68: 142–143 [5] Currey JD The many adaptations of bone J Biomech 2003; 36: 1487–1495 [6] Deckey JE, Court C, Bradford DS Loss of sagittal plane correction after removal of spinal implants Spine 2000; 25: 2453–2460 [7] Johnston CE II Welch RD, Baker KJ, Ashman RB Effect of spinal construct stiffness on short segment fusion mass incorporation Spine 1995; 20: 2400–2407 [8] Asher MA, Carson WL, Hardacker JW, Lark RG, Lai SM The effect of arthrodesis, implant stiffness, and time on the canine lumbar spine J Spinal Disord Tech 2007; 20: 549–559 212 [9] Kotani Y, Cunningham BW, Cappuccino A, Kaneda K, McAfee PC The role of spinal instrumentation in augmenting lumbar posterolateral fusion Spine 1996; 21: 278–287 [10] Craven TG, Carson WL, Asher MA, Robinson RG The effects of implant stiffness on the bypassed bone mineral density and facet fusion stiffness of the canine spine Spine 1994; 19: 1664–1673 [11] Shirado O, Zdeblick TA, McAfee PC, Cunningham BW, DeGroot H, Warden KE Quantitative histologic study of the influence of anterior spinal instrumentation and biodegradable polymer on lumbar interbody fusion after corpectomy A canine model Spine 1992; 17: 795–803 [12] McAfee PC, Farey ID, Sutterlin CE, Gurr KR, Warden KE, Cunningham BW The effect of spinal implant rigidity on vertebral bone density A canine model Spine 1991; 16 Suppl: S190–S197 [13] McAfee PC, Farey ID, Sutterlin CE, Gurr KR, Warden KE, Cunningham BW 1989 Volvo Award in basic science: device-related osteoporosis with spinal instrumentation Spine 1989; 14: 919–926 [14] Saphier PS, Arginteanu MS, Moore FM, Steinberger AA, Camins MB Stressshielding compared with load-sharing anterior cervical plate fixation: a clinical and radiographic prospective analysis of 50 patients J Neurosurg Spine 2007; 6: 391–397 [15] Heggeness MH, Esses SI Classification of pseudarthroses of the lumbar spine Spine 1991; 16 Suppl: S449–S454 [16] Kleiner JB, Odom JA Jr Moore MR, Wilson NA, Huffer WE The effect of instrumentation on human spinal fusion mass Spine 1995; 20: 90–97 [17] McAfee PC, Regan JJ, Farey ID, Gurr KR, Warden KE The biomechanical and histomorphometric properties of anterior lumbar fusions: a canine model J Spinal Disord 1988; 1: 101–110 [18] Hilibrand AS, Robbins M Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion? Spine J 2004; Suppl: 190S–194S [19] Lenke LG, Bridwell KH, Bullis D, Betz RR, Baldus C, Schoenecker PL Results of in situ fusion for isthmic spondylolisthesis J Spinal Disord 1992; 5: 433–442 [20] Sengupta DK Dynamic stabilization system In: Yue JJ, Bertagnoli R, McAfee PC, An HS, eds Motion Preservation Surgery of the Spine—Advanced Techniques and Controversies Philadelphia, PA: Saunders Elsevier: 2008:472–475 [21] Bago J, Ramirez M, Pellise F, Villanueva C Survivorship analysis of CotrelDubousset instrumentation in idiopathic scoliosis Eur Spine J 2003; 12: 435– 439 [22] Pihlajämaki H, Myllynen P, Böstman O Complications of transpedicular lumbosacral fixation for non-traumatic disorders J Bone Joint Surg Br 1997; 79: 183–189 [23] Martin BI, Mirza SK, Comstock BA, Gray DT, Kreuter W, Deyo RA Reoperation rates following lumbar spine surgery and the influence of spinal fusion procedures Spine 2007; 32: 382–387 [24] Javalkar V, Cardenas R, Tawfik TA et al Reoperations after surgery for lumbar spinal stenosis World Neurosurg 2011; 75: 737–742 [25] TRANSITION Stabilization System 510K PreMarket notification FDA K073439.US Food and Drug administration posting of Post-market Surveillance Studies http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPMN/pmn.cfm?ID=26567 [26] Berven, Sig Proximal junctional kyphosis (PJK) following long instrumented spinal fusion: the effect of implant selection Clinical Trials.gov identifier: NCT01441999 http://clinicaltrials.gov/ct2/show/NCT01441999 | 20.02.15 - 13:27 Nonfusion Stabilization of the Degenerated Lumbar Spine with Cosmic 30 Nonfusion Stabilization of the Degenerated Lumbar Spine with Cosmic Archibald von Strempel The degeneration of the lumbar motion segment starts with a height loss of the disc caused by water loss of the nucleus pulposus The facet joints lose their congruence, which may cause a consecutive spondylarthritis.1 The fibers of the annulus fibrosus and the vertebral column ligaments lose tension so that a structural loosening occurs, complete with increased rotation instability.2,3,4 To compensate for the instability, hypertrophy of the ligamentum flavum as well as the facet joints occurs very frequently, which may lead to a reduction of the cross-sectional surface of the central as well as the lateral spinal canal At the same time, the motion segment may lose its original position, and scoliosis, flat back, rotation, and rotation sliding may develop Further along the course of degeneration, lateral and frontal spondylophytes up to and including syndesmophytes may form, which in turn may lead to spontaneous stiffening of the segment The complaints depend on the stage of the vertebral column degeneration In the first phase, with a reduction of the height of the vertebral disc and loss of the congruence of the facet joints, chronically recurrent low back pain may occur that increases under load stress When the stenosis of the spinal canal increases, additional symptoms may occur in one or both legs, with the indications of a claudicatio spinalis If spontaneous ankylosis of the segment occurs before a symptomatic spinal channel stenosis occurs, the frequency and intensity of low back pain decreases Leg symptoms can be caused by the compression of the neural structures, which results from a narrow spinal canal or recessus or neural foramen As a rule, adequate decompression of the neural structures leads to good clinical success The etiology of low back pain is less clear; also, clinical success does not occur in the same measure as the fusion rate of a spondylodesis What is certain is that the instability in the motion segment caused by the vertebral disc shrinkage is a trigger for the frequency of low back pain Nonphysiologic movements that have become possible due to the vertebral disc shrinkage lead to shifting of the nucleus pulposus or nucleus pulposus fragments within the vertebral disc, with the vertebral disc itself experiencing increased ingrowth of pain-conducting nerve ends as a result of the degeneration.5 This increased innervation of the degenerative vertebral disc is also responsible for the “memory pain” in the discography.6 The term instability used in this context has been better defined by Panjabi as a “clinical instability” that leads to a pathological movement capability and to pain, deformities, and neurologic failures.7 Operative treatment of the symptomatic lumbar vertebral column degeneration has thus far consisted of stabilizing, correcting, and adequately decompressing the diseased segments, always in connection with a spondylodesis In recent years, the various forms of the spondylodesis (anterior and posterior lumbar interbody fusion [ALIF and PLIF], total lumbar interbody fusion [TLIF], and posterior lumbar fusion [PLF]) were discussed intensively because 360-degree fusions were believed to provide the greatest clinical success rate This theory was disproved in a prospective, randomized, double-blind study The clinical results were independent of the selected fusion form Complications naturally increased with increased surgical effort (360-degree fusion) In this study, pseudarthroses did not have any influence on the clinical result.8 A possible disadvantage of spondylodesis in the treatment of degenerative lumbar vertebral column diseases is the increased risk of accelerating degenerative processes in the neighboring segment Following a spondylodesis, 16.5% symptomatic vertebral disc degenerations after years were expected in the neighboring segment, and 36.1% after 10 years.9 Obviously there is a lower risk for spondylodeses without the use of pedicle screw systems.10 It must be questioned whether the risk for the adjacent segment increases with the rigidity of the spondylodesis, which would above all concern the currently favored 360-degree fusions that use a cage in combination with a pedicle screw system.11,12,13 This does not appear to apply to spondylodeses that were performed for the correction of extended deformities Thus, even after more than 20 years following a Harrington spondylodesis, low back pain was found in only 13% of cases.14 30.1 Indications for Fusion 30.1.1 Why Are Spondylodeses Performed in the Treatment of Degenerative Lumbar Vertebral Column Diseases? Until recently, there were few alternatives to a standard spondylodesis One important reason is that the surgery of the degenerative lumbar vertebral column is a relatively young chapter in spine surgery The techniques of correction and fusion, so successful in scoliosis surgery, were transferred to this new area of spine surgery, increasing in usage since the early 1980s An essential task of the spondylodesis consists of protecting the implants used against failure (dislocation, breakage) 30.1.2 When Is a Correction Necessary? In contrast to the treatment of adolescent scoliosis, where the correction of the deformity is also the objective of the treatment, there are not very many indications for correction of the degenerative lumbar vertebral column that actually serve the direct objective of the operation with pain release and restoration of neurological functions Positional deformities in the sagittal and frontal planes that in total not lead to a loss of the body vertical plumb line need not be corrected This concerns most lateral deviations 213 | 20.02.15 - 13:27 Restoration of the Lumbar Motion Segment Therefore, the correction of a degenerative lumbar scoliosis is necessary only in exceptional cases The reduction of the vertebral disc always leads to flattening of the lumbar vertebral column, which also does not need to be corrected as long as the patient assumes an upright, wellbalanced posture True and degenerative olisthies at an adult age are not usually progressive Stabilization and decompression without correction lead to the objective of the treatment Therefore, it is not meaningful to transfer the principles of scoliosis surgery noncritically to the surgery of the degenerative lumbar vertebral column 30.1.3 When Is a Fusion Necessary? A fusion is required when corrections (mostly in the sagittal plane) are necessary to treat pain 30.1.4 When Will It Be Possible to Do Without a Fusion? The precondition is a dynamic implant that does not require the protection of a spondylodesis It must be possible to achieve the treatment objective (pain release, restoration of the neurologic function) without correction The stabilization does not need to include more than three segments 30.2 The Cosmic Implant System A posterior nonfusion implant system, which can without protection by a spondylodesis, should not have any rigid characteristics However, to be able to control instabilities effectively, the system must also feature stable characteristics The Cosmic Posterior Dynamic System (Ulrich Medical, Ulm, Germany) is a stable, nonrigid implant Stability is ensured by the 6.25 mm rod, and nonrigidity is assured by the hinged screw head The screw features a hinged joint between the head and threaded part, which causes the load to be shared between the implant system and the anterior vertebral column (▶ Fig 30.1) Laboratory tests show that Cosmic allows the same Fig 30.1 Cosmic Posterior Dynamic System screw (Ulrich Medical) 214 rotation stability as a healthy motion segment.15 In a cyclic loading test with 0.3 to 3.0 kN/1 Hz, we did not find an implant breakage or any debris after 10 million cycles.16 Because Cosmic is used like a stability endoprosthesis, the bone healing of the pedicle screws is of major importance For this reason, the threaded part of the screw is coated with Bonit Bonit (Dot GmbH, Rostock, Germany) is the second generation of bioactive calcium phosphate coatings on implants In 1995, it was originally used for the first time in oral surgery for dental implants.17 In the area of vertebral column surgery, a study on the use of a first-generation bioactive calcium phosphate coating on Schanz screws found significantly improved fixation of the coated screws in comparison with uncoated screws.18 Thus the screw is introduced transpedicularly into the vertebral body, in a manner similar to that for an orthopedic endoprosthesis To achieve a sufficient press-fit, the pedicle is widened by drilling to 3.2 mm maximum, but only along ~50% of the screw The screw has a self-tapping thread so that the tapping instrument is needed only in cases of extremely hard spongiosa To prevent early loosening of the screw, the screw must not be manipulated in any major way Before being implanted, the rods must be prebent such that they can be connected without any problems to the screw heads After the screw heads have been connected to the longitudinal rods, there remains only a micromobility in the hinges, which, without rod connections, are caudally and cranially mobile by ~20 degrees (▶ Fig 30.2) Due to its good rotation stability, Cosmic is used for purely discogenic pain conditions and is also combined with conventional laminectomy or even facetectomy A transverse stabilizer is used for a monosegmental application in combination with a laminectomy For two- or three-segmental applications, no transverse stabilizer is used The screws are implanted either by means of a conventional midline approach (point of entry lateral to the facet joint, angle ~15 degrees horizontal to the sagittal plane) or by means of the more laterally situated Wiltse access (a somewhat ventrally located point of entry close to the base of the transverse continuations, angle 20–25 degrees horizontal to the sagittal plane) (▶ Fig 30.3) A purely sagittal implantation direction is not recommended because this will lead to parallel positioning of the hinges and thus to increased mobility in the sagittal plane Fig 30.2 (a) Flexion-extension view, (b) 1-year postoperatively | 20.02.15 - 13:27 Nonfusion Stabilization of the Degenerated Lumbar Spine with Cosmic facet joints is not taken into consideration In addition, low back pain and deformities may increase as an expression of the increased clinical instability For this reason, we always carry out an additional stabilization with Cosmic (▶ Fig 30.4a-c) 30.3.2 Chronically Recurring Low Back Pain in the Case of Discogenic Pain and Facet Syndrome Fig 30.3 Angle of screw direction in the horizontal plan 15 to 25 degrees Before the rod is implanted, the correct positioning of the patient will be rechecked by means of lordosis that is as physiologic as possible To avoid any early loosening, correction forces must not be applied to the screw 30.3 Indications for Dynamic Stabilization with Cosmic 30.3.1 Symptomatic Lumbar Stenosis (Claudicatio Spinalis) Stand-alone decompression of the spinal channel carries the risk of a recurrence of spinal narrowed because the instability that led to the hypertrophy of the ligamentum flavum and the Degenerated disc disease is present if, in the magnetic resonance imaging (MRI) scan, vertebral disc dehydration with height loss and positive Modic signs is detected If there are further changed vertebral discs (black discs), we carry out an additional discography A positive memory pain confirms the suspicion of symptomatic vertebral disc degeneration.19 In the case of a facet syndrome, we carry out a diagnostic local anesthesia under X-ray control, using mL local anesthetic, respectively If the pain subsides for some hours, the suspected diagnosis is confirmed In such cases we carry out the Cosmic stabilization using a paraspinous transmuscular approach according to Wiltse20 (▶ Fig 30.5a-c) 30.3.3 Recurrent Disc Herniation In the case of a second recurrence of a disc herniation we carry out a stabilization with Cosmic in addition to the nerve root decompression 30.3.4 In Combination with a Spondylodesis Cosmic can also be used if, in addition to the nonfusion stabilization, there is an indication of a spondylodesis in one or two segments; for example, if there is a spondylolisthesis with a clear shift in the functional X-rays and, in a further segment, a symptomatic vertebral disc degeneration In addition to the Fig 30.4 (a) Spinal stenosis, (b) pseudospondylolisthesis, (c) decompression and stabilization with the Cosmic Posterior Dynamic System (Ulrich Medical) 215 | 20.02.15 - 13:27 Restoration of the Lumbar Motion Segment Fig 30.5 (a) Degenerated disc disease (the “flat tire” disc), (b) positive Modic sign, (c) contrast computed tomographic scan Cosmic stabilization in situ, a posterolateral fusion is set up within the area of the spondylolisthesis A laminectomy or facetectomy is performed if there is an indication for this purpose (▶ Fig 30.6) 30.3.5 Extension of an Existing Spondylodesis in the Case of Painful Adjacent Level Degeneration Typically, in the case of a rigid 360-degree spondylodesis with cage and pedicle screw rod or pedicle screw plate fixation, there is a risk for development of a painful connection instability In these cases, we remove the pedicle screw rod or plate system and stabilize the adjacent segment with Cosmic Fig 30.6 Unstable spondylolisthesis vera, stenosis L5–S1, degenerative disc disease L4–L5 Cosmic Posterior Dynamic System screws (Ulrich Medical) L4–S1, laminectomy L5, posterior fusion L5–S1 216 together with a decompression, if indicated We fill up the existing pedicle drilling holes with bone chips and use a mm revision screw for this purpose (▶ Fig 30.7) 30.4 Contraindications Cosmic should be used for a maximum of only three segments If corrections are necessary, to influence the complaints of the patient (as already stated, in almost all cases of a degenerative deformity this is not indicated), a spondylodesis must be provided in addition to the Cosmic instrumentation Such a case exists, for example, for a postfusion kyphosis where a correction such as a closing wedge-osteotomy is necessary to treat the pain In adulthood, in the case of a spondylolisthesis vera, there is as a rule no significant shift in the lateral functional X-rays If this is the case, Cosmic is used in combination with a posterolateral fusion in situ In cases of greater instability, as typically found in younger adults or youths, we carry out a posterior partial repositioning with Cosmic in combination with a posterolateral and interbody spondylodesis Fig 30.7 Cosmic Posterior Dynamic System screws (Ulrich Medical) L3–L5, (a) laminectomy L3, (b) preexisting fusion L4–L5 | 20.02.15 - 13:31 Advancements in Lumbar Motion Preservation Effectiveness Effectiveness The clinical applicability of adenoviruses has been well documented, with both in vitro and in vivo testing In vitro studies tracked luciferase production in adenovirus-infected cells, finding adequate luciferase production in both healthy and degenerative human nucleus pulposus cells.55,56 Further in vitro studies monitoring adenovirus transgene expression of growth factors including TGF-β1, insulin-like growth factor-1 (IGF-1), and BMP-2 showed increased levels of proteoglycan synthesis when compared with normal controls, indicating biological plausibility for an anabolic effect.22 In the in vivo studies, adenovirus-transferred lacZ expression was found in NZW rabbits 12 weeks after intradiscal injection.56 Also, single injections of adenovirus-containing growth factors, including BMP-7, IGF-1, and GDF-5 have shown gene production and maintenance of ECM production within the nucleus in rabbit models at 1- to 16-week follow-up.49,57,58 AAV function as a delivery vector has been demonstrated in both in vitro and in vivo environments by observing luciferase production in an NZW rabbit model In vitro data showed AAVs to have an acceptable transduction efficiency yet a lower overall transgene expression profile when compared with other viral vectors such as adenovirus.65 Similarly, in vivo data also showed transgene expression to be approximately 50% that of adenoviral vectors in certain tissues.65 Despite this disparity between the viral vectors, overall luciferase activity was significantly elevated in the AAV-treated animals when compared with untreated control groups Moreover, luciferase activity was highly specific for the intervertebral disc A study by Afione et al showed the intracellular conversion of the singlestranded AAV viral genome to a replicative double-stranded genetic sequence capable of integration into host DNA to be a rate-limiting step in the action of AAV vectors.66 Recent modifications to AAV vectors have made this expression lag time less pronounced and may promote quicker transgene expression.67 Regardless, because IDD is a chronic condition, viral vectors capable of sustained transgene expression will likely provide more effective therapy than viral vectors with a quick onset of effect, such as adenoviral vector following a severe immune reaction Leckie et al also recently published an in vivo study analyzing the clinical effects of AAV-carried BMP-2 or TIMP-1 genes on IDD.68 Rabbits treated with AAV-delivered transgenes showed evidence of improved MRI scores (T2 and T2-map sequences), improved preservation of disc histologic structure on histologic sectioning, and restored biomechanical function with regard to axial loading when compared with unrelated rabbits These effects persisted throughout the 12-week course of the study Safety Although promising, concerns exist regarding the safety of using adenoviral vectors Specifically, with regard to the intervertebral disc’s proximity to neural structures, two studies have shown severe inflammatory reactions after administration of adenoviral vectors Although the efficiency of gene transduction is not always disrupted, the local inflammatory response has the potential of causing demyelinating conditions.59,60 Other studies have shown the presence of systemic inflammatory states following adenoviral vector administration, as well as activation of peripheral CD4 + cells involved in immunity.61,62 Also, two studies observing clinical, biochemical, and histological outcomes following errant injection placement or dosing of TGF-β or BMP-2 into the epidural space of NZW rabbits showed significant morbidity in 80% of animals.63,64 Another important note is that virtually every person has been exposed to adenoviral pathogens and upward of 55% of individuals may have humoral immunity capable of neutralizing adenoviral vectors, a potential drawback of clinical utility.61 Adenoassociated Viruses Derived from the parvovirus family, wild-type adeno-associated viruses consist of either single- or double-stranded DNA viral genome (~5 kb), which allows these viral vectors to carry a maximal 4.7 kb in a single-strand adenoassociated viral (AAV) vector and 2.5 kb in a double-strand AAV vector for packaging gene expression cassette, respectively Like the adenoviral vector, AAV vectors are capable of infecting many different cells, including both dividing and nondividing cells Many serotypes of AAVs have been developed for gene therapy application, in which AAV2 and AAV2.5 have proven the predominantly used strains for clinical trials Although having relatively small capacities for foreign genes as compared with adenoviral vectors, AAVs have been created that are capable of transferring genes important to the intervertebral degeneration pathway, including BMP-2, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), and TGF-β Addition of larger genetic sequences may prove difficult due to size limitation of the AAV vector 444 Safety AAVs distinguish themselves from both retroviruses and adenoviruses with regard to their safety profile such as low toxicity, high persistence of gene transferred, and lack of pathogenicity rAAV vectors lacking the Rep 78 sequence, which primarily persist in an extrachromosomal form known as episomal chromatin, carry a significantly lower risk of potential mutagenesis Also, although AAVs have a very low possibility to insert into the host genome, when integration does occur, it reliably occurs at a specific site on chromosome 19 with no known pathogenic consequences.54 The immunogenic profile for AAVs is also more benign than that of adenoviruses, primarily because AAVs contain only two viral genes that are not expressed in the host cell in the absence of a helper virus.61 This will theoretically lead to diminished host cell–mediated immune reactions against the virus and permit a longer duration of gene expression AAVs have been shown to have a better safety profile than adenoviruses when errantly injected into tissues other than the intervertebral disc, but more confirmatory studies are needed.63 For the safety issue, two recent studies also introduced control systems for AAV-mediated gene expression in which separate reagents were required to initiate gene expression.69 The first study introduced tetracycline (Tet-on system) as a means to appropriately modulate transgene expression in human nucleus pulposus cells in vitro.70 Also, in a second study, | 20.02.15 - 13:31 Molecular and Genetic Therapy in Repair of the Degenerative Disc Fig 62.4 (a) In vivo gene therapy involves the direct injection of vector-gene constructs into target tissues within the host (b) In the ex vivo method target cells are harvested from the host and are then transduced, expanded, and propagated in culture before reimplantation (Reprinted with permission from Woods BI, Vo N, Sowa GA, et al Gene Therapy for Intervertebral Disc Degeneration Ortho Clin Am 2011;42 (4):563–574.) AAVs were tagged with a RheoSwitch green fluorescence protein (GFP) (Intrexon Corp., Blacksburg, VA) and introduced to NZW rabbit nucleus pulposus cells both in vitro and in vivo In vivo data showed transgene expression in animals treated with both the AAV and the activator Controls with treatment with either the AAV or the activator alone led to no gene expression The advantages of the RheoSwitch GFP system are improved gene expression regulation and diminished toxicity of the activator compound compared to the tetracycline regulation system These regulatory mechanisms serve to further increase the safety of AAV therapies by providing tighter control over transgene expression Such transgene expression regulation can potentially diminish transgene product toxicity in the event of errant injections or leakage of transgene products into surrounding tissues, as well as can be sued for transient gene expression, such as anti-inflammation Lastly, to date there are no documented diseases caused by the AAV in humans Asymptomatic viral exposure can occur, which is notable because preimmunized hosts can mount humoral-mediated immune responses to AAV vectors Although this has no known clinical pathogenicity, it can serve to decrease transgene expression by up to 90%, which may be a potential drawback for AAV treatment of human disease.65 Newer strains, including AAV2.5, are genetically modified to avoid immune responses in patients, decreasing risk and also potentially improving transgene expression.71 Due to their documented effectiveness and improved safety profiles compared with other viral vectors, they are currently the most frequently used mediators of gene therapy.65,66,72,73 Future Directions Gene therapy for the intervertebral disc has made significant progress over the past decade as the understanding of disc physiology and degeneration has improved As gene therapy continues to evolve, new techniques will be introduced and examined Currently, ex vivo means of gene transfer are being investigated (▶ Fig 62.4) In vitro, bovine chondrocytes prior transduced with various genes, including BMP-2, -4, -7, and -10, showed significantly improved production of matrix proteoglycans and collagen when cocultured with nucleus pulposus cells.74 Further studies also showed that in vitro transduction of various adenovirus and AAV vectors into annulus fibrosus and nucleus pulposus cells was successful and that the transduced cells maintained their phenotype.75,76 These results imply that ex vivo gene therapy may hold promise in the treat- ment of disc degeneration Future studies will move toward in vivo animal model testing of the ex vivo gene therapy technique 62.2 Conclusion The understanding of the pathological cascade involved in disc degeneration has significantly advanced the field of molecular and gene therapy Animal-based studies involving growth factors and gene therapy have shown promise in addressing the underlying processes of disc degeneration 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indicate headings or figures, respectively A AAVs, see See Adenoassociated viruses (AAVs) Abnormal load theory 186, 186 – See also See Loads Abnormal motion, see See Motion – quality 187 – quantity 185 Absolute motion 46 ACADIA Facet Replacement System 263 – clinical applications for 263 – clinical outcomes for 264 – design of 263, 264 – preclinical studies of 263 Accelerated adjacent segment degeneration 408 Acceleration 32 Access complications 403 – See also See Complications ACCF, see See Anterior cervical corpectomy and fusion (ACCF) ACDF, see See Anterior cervical discectomy and fusion (ACDF) Activ-L disc 308, 308 Activities of daily living (ADLs) 54–55 Acute neurological complications 157 – See also See Complications Adenoassociated viruses (AAVs) 444 Adenoviruses 443 Adjacent level degeneration 376, 376 Adjacent level effect (ALE) 172 Adjacent segment degeneration 98, 408 Adjacent segment disease (ASD) 98, 98 ADLs, see See Activities of daily living (ADLs) ADR (artificial disc replacement), see See Total disc replacement (TDR) Adverse reactions, see See Complications – inflammatory 110 – local tissue 383 Aggrecan 441 Albee, Fred ALE, see See Adjacent level effect (ALE) ALL, see See Anterior longitudinal ligament (PLL) Anabolic mediators 441 Anatomical planes 32 Angle 32 Animal experiments 22 Anionic glycosaminoglycan side chains 441 Annulus repairs 432 – alternative approaches to 435 – anatomy of 432 – BioDisc for 433 – black discs 433, 433 – fibrosis 432, 441 – functions of 432 – future directions for 435 – interventional strategies for 434, 434 – intervertebral prostheses for 435 – intradiscal electrothermal therapy (IDET) 434, 434 – motion-preservation devices 435 448 – NuCore Injectable Nucleus for 432 – overviews of 435 – pathology treatments for 433, 433, 434 – post-microdiscectomy treatments for 432 – references for 435 – regenerative methods for 435 – reherniation prevention 432 – strategies for 432 – symptomatic tears 433 – treatment indications for 432 – Ultrazonix Spine Minimal-Invasive Disc System 435 – Xclose tissue repair system for 433 Anterior cervical corpectomy and fusion (ACCF) 98 Anterior cervical discectomy and fusion (ACDF) 90 – goals of 90 – historical perspectives of 90 – indications for 98 – rationales for 98 Anterior column support 199 – See also See Graf ligamentoplasty Anterior exposures 298 Anterior longitudinal ligament (ALL) 178, 432, 435 Anticatabolic factors 443 Aperius Percutaneous Lumbar Interspinous Decompression Spacer 240–241, 244 Apparatus testing 54 – See also See Biomechanical testing Area 32 Arthroplasty, disc 2, – cervical 110 –– biomechanical aspects of 90 –– Bryan Cervical Disc 118 –– ceramic 135 –– disadvantages of 100 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials of 152 –– indications for 98 –– M6-C 125 –– metal-on-metal 104 –– metal-on-poly 112 –– overviews of 98, 101 –– polyether-ether-ketone (PEEK) 135 –– rationales for 98 –– references for 102 –– retrieval analyses for 162 – lumbar 292, 415 –– advancements in 408 –– anatomy of 304 –– biomechanics of 287, 304 –– case studies of 293 –– Charité 334 –– classification of 304 –– clinical results for 364, 367 –– clinical success related classification (CSRC) 292 –– complications of 380, 386, 390 –– contraindications for 293 –– definition of 305 –– design of 305, 408 –– –– –– –– –– elastomeric 408 first-generation 307, 307, 308–309 FlexiCore 350 Flexuspine 415 Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 386 –– indications for 292 –– long-term outcomes of 371 –– M6-L 343 –– Maverick TDR 350 –– metal-on-metal 350, 359 –– minimally-invasive spine surgery (MISS) 437 ––– See also See Minimally-invasive spine surgery (MISS) –– Mobidisc 350 –– multilevel 399 –– overviews of 305, 311, 367, 368 –– Physio-L 408 –– polymer-on-metal 339 –– posterior approach 415 –– references for 311, 371 –– salvage procedures 390 –– second-generation 309, 310 –– status quo of 306 –– Theken disc 408 –– third-generation 311 – vs dynamic stabilization –– See also See Dynamic stabilization Arthrosis, facet 383 – See also See Facet joints Artificial disc replacement (ADR), see See Total disc replacement (TDR) ASD, see See Adjacent segment disease (ASD) Atraumatic loosening 167 Axial compression 79 Axis 32 Axis of rotation 47 B Backside wear 166 Balance, optimal 290 Band placement 197, 198 Biocompatibility 85 BioDisc 433 Bioflex 193 Biomaterials 85 – future directions for 85 – overviews of 95 – properties of 85, 85, 86 – references for 96 – selection criteria for 85 –– biocompatibility 85 –– ductility 85, 85 –– durability 85 –– load-deformation curves 86 –– load/applied load demands 85 –– premarket approval processes 87 –– preparation processes 85 –– regulatory controls 87 –– standardization 87 –– stress-strain curves 85, 85–86 –– structural aspects 85 –– toughness 85, 85 Biomechanical testing 54 – See also See Biomechanics – activities of daily living (ADLs) and 54–55 – apparatus for 54 – for cervical disc evaluations 70 – functional spinal units (FSUs) 54 – goals of 54 – limitations of 59 – multisegment spines 54 – overviews of 54, 59 – protocols for 54, 55 –– continuous vs stepwise loads 59 –– cyclic loads 59 –– displacement-control protocols 54 –– flexibility 55 –– hybrid protocols 54 –– kinematic response measurements 59 –– load types 55 –– load-control 54, 55 –– magnitudes 55 –– preloads 56 ––– See also See Preloads –– range of motion (ROM) and 54, 55 –– static loads 59 – references for 59 Biomechanics 32, 90 – coordinate systems 32, 33 – definition of 38 – equilibrium 35, 36 – force 34 –– See also See Force –– definition of 34 –– force couple 34, 35 –– moment of force about a point 34, 35 – free-body analyses 35, 36 – fundamentals of 32 – kinematics 38 –– See also See Kinematics – Newton‘s laws of motion 35 – of facet joints 253 –– See also See Facet joints – of total disc replacement (TDR) 90, 287 –– See also See Total disc replacement (TDR) –– analyses, degenerative lumbar disc 288 –– analyses, normal lumbar spine 287, 288 –– designs 90, 90, 91, 91, 92, 92–93 –– disc height restorations 289 –– finite element modeling 93, 94–96 –– goals of 90 –– optimal balance 290 –– overviews of 90, 95, 287, 290 –– peer-reviewed literature for 91 –– references for 96, 290 –– segmental mobility restorations 289 –– vs fusion 287 – overviews of 32, 36 – references for 36 – scalars 32 – testing 54 –– See also See Biomechanical testing – units of measure 32, 32 | 20.02.15 - 13:31 Index – vectors 32 –– analyses of 34, 34 –– definitions of 32, 33 –– loads 34 –– unit 33 Black discs 433 BMPs, see See Bone morphogenetic proteins (BMPs) Bone graft donor site morbidity 99 Bone morphogenetic proteins (BMPs) 442 Bristol Artificial Cervical Joint 104 Bryan Cervical Disc 118 – clinical results for 121, 153 – detailed wear analyses for 118 – features of 118, 118 – heterotopic ossification (HO) and 122, 123 – implant failure of 122, 123–124 – overviews of 122 – references for 124 – surgical techniques for 119, 119, 120–122 –– device placement 120 –– neutral element decompression 120 –– operative set-ups 119 –– preoperative planning 119 Burnishing, metallic 166 C CA-6000 Spine Motion Analyzer 62, 62–63 Cadisc-L disc 310, 310 Cartesian coordinate systems 32, 33, 38 – three-dimensional 33 – two-dimensional 32 Cartilaginous end plates 441 Catabolic mediators 441 CD Horizon Agile Dynamic Stabilization Device 4, 194 Center of mass (CM) 41 Center of rotation (COR) 46 – definition of 46, 61 – determinations of 66 – functional spinal units (FSUs) and 47 – kinematics and 46 –– See also See Kinematics – overviews of 46, 53 – parameters of 46 –– axis of rotation 46, 47 –– centroid of rotation 48 –– coordinate systems and 46 –– coupled motion and 48 –– degrees of freedom (DOFs) 46, 48 –– flexion-extension (FE) motion 46– 48 –– instantaneous axis of rotation (IAR) 46, 48 –– instantaneous core of rotation (ICR) 46 –– mean center of motion 48 –– pure rotation motion 46, 47 –– pure translation motion 46, 46 –– spinal motion segment and 47, 47 –– uniform rotation motion 46, 47 – post-disc replacement and 67 – quality of motion parameters 46, 46 –– global vs relative motion 46 –– plane motion 46, 46 –– vs quantity of motion 46 –– vs range of motion (ROM) 46, 48 ––– See also See Range of motion (ROM) – rotation, definition of 46 – three-dimensional (3-D) motion 49 –– helical axis of motion (HAM) 48, 48 ––– See also See Helical axis of motion (HAM) –– instantaneous axis of rotation (IAR) and 48, 49–51 Ceramic and polyether-ether-ketone (PEEK) discs 135 – clinical results for 139 – development of 135 – Discocerv disc 135, 135, 136 –– biomechanical testing for 136, 137, 137 –– clinical results for 139, 140–141 –– design of 135, 135 –– sizes of 136 –– surgical techniques for 138 – NuNec disc 135 –– biomechanical testing for 136, 138 –– clinical results for 141, 142, 143, 143 –– design of 135, 135 –– sizes of 136 –– surgical techniques for 139, 139 – overviews of 135, 141 – PEEK-on-PEEK discs 141, 142, 143, 143 – preclinical biomechanical testing of 136 – references for 144 – spacers – surgical techniques for 138 –– ceramic-on-ceramic discs 138, 140 –– PEEK-on-PEEK discs 139, 139 Ceramic-on-ceramic discs 138, 140 Cerebrospinal fluid (CSF) leakage 382 Cervical total disc replacement (CTDR) 110, 162 – See also See Total disc replacement (TDR) – complications of 157, 160 –– See also See Complications –– acute neurological 157 –– adjacent segment degeneration 160 –– approach-related 157 –– device-related 159 –– intraoperative 157 –– migration 159, 159 –– overviews of 157, 160 –– patient positioning-related 157 –– postoperative 158 –– references for 160 –– risk factors for 160 –– risk reduction strategies 160 –– subsidence 159, 159 –– technical 159 –– vertebral body fractures 159 – Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials of 152 – indications for 98 –– adjacent segment disease (ASD) prevention 98 –– advantages 100, 101 –– iliac crest bone donor site morbidity avoidance 99 –– overviews of 98, 101 –– postoperative dysphagia avoidance 99, 100 –– potential disadvantages 100, 101 –– pseudoarthrosis avoidance 99 –– quality-adjusted life years (QALYs) and 98 –– references for 102 – prostheses 104, 112, 135 –– Bryan Cervical Disc 118 –– ceramic 135 –– M6-C Artificial Cervical Disc 125 –– metal-on-metal 104 –– metal-on-poly 112 –– polyether-ether-ketone (PEEK) 135 – rationales for 98 – retrieval analyses of 162 CerviCore disc 106 – clinical results for 109 – design of 106, 108–109 – Food and Drug Administration (FDA) status of 109 Charité disc 304, 308, 308, 325, 408 – Charité III trials 386 – complications of 386 –– See also See Complications Chondroitin 441 Claudicatio spinalis 215, 215 Clinical instability vs instability 189 Clinical success related classification (CSRC) 292 CM, see See Center of mass (CM) Coflex Interlaminar Stabilization Device 240–241, 242 – See also See Interspinous process spacers Coil spring designs 3, Collagen 435 – type I 435, 441 – type II 441 – type IX 435 Complications 244, 380, 390 – access 403 – adverse reactions, see See Adverse reactions – major 232 – of cervical total disc replacement (CTDR) 157, 160 –– acute neurological 157 –– adjacent segment degeneration 160 –– approach-related 157 –– device-related 159 –– incidence of 160 –– intraoperative 157 –– migration 159, 159 –– overviews of 157, 160 –– patient positioning-related 157 –– postoperative 158 –– references for 160 –– risk factors for 160 –– risk reduction strategies 160 –– subsidence 159, 159 –– technical 159 –– vertebral body fractures 159 – of Charité disc 386 – of interspinous process spacers 244 – of lumbar total disc replacement (TDR) 380, 386, 390 –– adjacent segment degeneration 395 –– approach-related 390 –– device-related 233 –– dislocation 392 –– early postoperative 391 –– facet joint arthrosis 393 –– heterotopic ossification (HO) 394 –– infection-related 392 –– insertion-related 390 –– intraoperative 390 –– late postoperative 393 –– major 232 –– migration 392 –– subsidence 391 –– wear-related 394 – of prosthetic Disc Nucleus (PDN) 279 – of salvage procedures 390 Compressible spacers 240 – See also See Interspinous process spacers Compression, axial 79 Compressive preloads 56 – See also See Preloads Computed tomography (CT) 425 Constraints, ligamentous 178 Continuous loads 59 – See also See Loads Conventional motion patterns 61 – See also See Motion Coordinate systems 32, 33 COR, see See Center of rotation (COR) Corrosion, surface 164 Cosmic Posterior Dynamic System 214 – See also See Nonfusion stabilization – clinical results for 218 – contraindications for 217 – existing spondylodesis extensions 216 – for chronically recurring low back pain 215 – for discogenic pain 215 – for facet syndrome 215 – for recurrent disc herniation 215 – for symptomatic lumbar stenosis 215, 215 – indications for 215 – overviews of 193 – screws for 214, 214–216, 218 – spondylodesis with 215, 216 – surgical techniques for 217, 217, 218 Couple, force 34, 35 – See also See Force Creep tests 42 Cryoablation 281 CSF leakage, see See Cerebrospinal fluid (CDF) leakage CSRC, see See Clinical success related classification (CSRC) CT, see See Computed tomography (CT) CTDR, see See Cervical total disc replacement (CTDR) Cummins disc 125 D Da Vinci position 401, 402 Dacron tape DDD, see See Degenerative disc disease (DDD) Debris effects 164 – See also See Wear Deep vein thrombosis (DVT) 404 Deformation 86 Degenerative disc disease (DDD) 213, 281, 281, 441 449 | 20.02.15 - 13:31 Index Degrees of freedom (DOFs) 40, 46, 61 Delayed subsidence 380 Delayed-type hypersensitivity 110 Density 32 Design engineering 85 – See also See Biomaterials – future directions for 85 – overviews of 95 – references for 96 – selection criteria for 85 –– biocompatibility 85 –– ductility 85, 85 –– durability 85 –– load-deformation curves 86 –– load/applied load demands 85 –– material properties 85, 85, 86 –– premarket approval processes 87 –– preparation processes 85 –– regulatory controls 87 –– standardization 87 –– stress-strain curves 85, 85–86 –– structural aspects 85 –– toughness 85, 85 Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System 5, 240, 240, 241 – See also See Interspinous process spacers Device-related complications 159, 233 – See also See Complications DFIS, see See Dual fluoroscopic imaging system (DFIS) DIAM system, see See Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System Direct lateral lumbar interbody fusion (LLIF) approach 439 Direction 33 Disc height restorations 289 Disc replacement – future directions for 17 – historical perspectives of – overviews of 7, 18 – recent developments in – references for 18 – total –– See also See Total disc replacement (TDR) –– cervical 11, 11, 12 –– Food and Drug Administration (FDA) approval status 13 –– lumbar 9, 10–11 – vs arthroplasty – vs nucleus replacement Disc structures 441 – anatomy 441 –– annulus fibrosis 441 –– cartilaginous end plates 441 –– nucleus pulposus 441 – primary functions 441 Discectomy 90 – anterior cervical discectomy and fusion (ACDF) 90 –– goals of 90 –– historical perspectives of 90 –– indications for 98 –– rationales for 98 – microdiscectomy 432 Discocerv disc 135, 135, 136 – biomechanical testing for 136, 137, 137 – clinical results for 139, 140–141 – design of 135, 135 450 – sizes of 136 – surgical techniques for 138 Discogenic pain 215 Discs, prosthetic, see See Prosthetic discs Dislocation complications 381, 392 – See also See Complications Displacement-control protocols 54 DNA-ligand complexes 443 DOFs, see See Degrees of freedom (DOFs) Donor site morbidity 99 dsDNA, see See Double-stranded DNA (dsDNA) DSS, see See Wallis Posterior Dynamic Stabilization System (DSS) Dual fluoroscopic imaging system (DFIS) 426, 427 Dubois, Gill 3, Ductility 85, 85 Durability 85 DVT, see See Deep vein thrombosis (DVT) Dynamic Neutralization System for the Spine (Dynesys), see See Dynesys Dynamic Stabilization System Dynamic posterior instrumentation 20 – fusion grades 20 –– animal experiments 21, 22 –– human subjects 22 –– instrumentation removal effects 20 –– rigidity 21 –– stiffness 21 –– successful fusion definitions 20 –– uninstrumented fusion 20 – future directions for 28 – optimum strength of 22 –– adjacent segment degeneration (ASD) and 24 –– bone and fusion mass mechanical properties 22 –– fusion mass size-stiffness correlations 24, 25 –– fusion vs fracture healing 23, 23, 24 – overviews of 20, 28 – references for 28 – softer implants 26, 26 –– ideal dynamic stabilization devices 27 –– rationales for 27 Dynamic spacers 240 Dynamic stabilization – abnormal load distribution 185 – abnormal motion quality 186, 187 – abnormal motion quantity 185 – biomechanics 185 – devices –– CD Horizon Agile Dynamic Stabilization Device –– Coflex Interlaminar Stabilization Device –– Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System –– Dynesys Dynamic Stabilization System 3, 189, 228 –– Food and Drug AdministrationInvestigational Device Exemptions (FDA-IDE) trials 3–4 –– fulcrum-assisted soft stabilization (FASS) system 3, –– Graf ligament 2, –– hybrid –– interspinous process distraction (IPD) systems 2, 234 –– Leeds-Keio Tension Band System 4, –– NFlex –– Nitrol coil spring designs 3, –– Stabilmax NZ –– Transition Stabilization System 3, –– Wallis Posterior Dynamic Stabilization System (DSS) 4, –– X-Stop Spacer 4, – future directions for – historical perspectives of – instability vs clinical instability 189 – lumbar spine 184 –– abnormal load theory 186, 186 ––– See also See Loads –– biomechanical experiments 186, 187 –– historical perspectives of 184 –– marble-on-soup-bowl concept 186, 187 –– overviews of 184, 186 –– pseudoarthrosis transition revisions 207 –– references for 187 –– stone-in-shoe concept 185 – minimally-invasive posterior 222 – nonfusion technology development – overviews of – pedicle screw-based posterior dynamic stabilization (PDS) systems 2, 189 –– biomechanical goals of 189 –– classification of 192 –– design of 189 –– devices 192 –– hybrid devices 194 –– indications for 191 –– interspinous process distraction devices 192 –– load sharing 190, 191 ––– See also See Loads –– motion preservation 189, 190 –– nonmetallic devices 192 –– overviews of 2, 189, 194 –– rationales for 190 –– references for 281 – principles of 222 – references for – vs feathered fusion – vs motion preservation stabilization – vs spontaneous fusion – vs total disc replacement (TDR) –– See also See Total disc replacement (TDR) – with Graf ligamentoplasty 196 –– anterior column support with 199 –– clinical outcomes of 198, 199–200 –– contraindications for 196 –– hybrid stabilization for 199 –– indications for 196 –– overviews of 196, 200 –– rationales for 196, 196 –– references for 200 –– surgical techniques for 197, 197, 198 Dynamic Stabilization System, see See Dynesys Dynamic Stabilization System Dynardi-Dynamic Artificial Disc System 308, 308 Dynesys Dynamic Stabilization System 3, 3, 202, 228 – clinical results for 203, 228 – disc regeneration with 203, 203, 204 – Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 228 –– adverse events 229 –– complications, device-related 233 –– complications, major 232 –– description of 228 –– design of 228 –– goals of 228 –– overviews of 228 –– patient accounting 230 –– patient assessments 229–230 –– patient evaluations 229 –– postoperative care 229 –– randomization/blinding 230 –– references for 229 –– results of 231, 231, 232 –– safety evaluations 233 –– secondary surgical interventions 233 –– statistical analyses 230 – functional model of 202, 202 – goals of 202 – hybrid stabilization with 205, 205 – indications for 202 – overviews of 3, 3, 4, 4, 202, 206, 228 – references for 206, 229 – surgical techniques for 202, 203 – technical aspects of 202 Dysphagia avoidance 99, 100 E Early postoperative complications 391 – See also See Complications ECM structures, see See Extracellular matrix (ECM) structures Elastomeric Disc Physio-L, see See Physio-L Elastomeric discs 408 – adjacent biomechanical environment preservation of 410 – biomechanical analyses of 411, 411 – Cadisc-L 409, 409 – classification of 410 – controlled-motion from 410 – cores of 409 –– fixed to metal end plate discs 410 –– secured without fixation discs 410 –– with metal end plates discs 410 – design features of 410 – Freedom Lumbar Disc (FLD) 409, 409, 413 – injection molding of 410 – mechanical shock absorption of 410 – microelectronic sensors of 410, 411 – motion analyses of 411 – Physio-L disc 412 – Theken eDisc 409–410 End plates, cartilaginous 441 Energy 32 Engineering design 85 – See also See Biomaterials – future directions for 85 – overviews of 95 – references for 96 | 20.02.15 - 13:31 Index – selection criteria for 85 –– applied load demands 85 –– biocompatibility 85 –– ductility 85, 85 –– durability 85 –– load demands 85 –– load-deformation curves 86 –– material properties 85, 85, 86 –– premarket approval processes 87 –– preparation processes 85 –– regulatory controls 87 –– standardization 87 –– stress-strain curves 85, 85–86 –– structural aspects 85 –– toughness 85, 85 Engineering stress 41 – See also See Stress-strain Environment preservation 410 Equilibrium 35, 36, 40 Evidenced-based outcomes 404 Existing spondylodesis extensions 216 Extracellular matrix (ECM) structures 441 F Facet joints 253 – anatomy of 253, 253, 254 – arthrosis of 383 – biomechanics of 253 – degeneration of 375 – facet syndrome 215 – finite element analyses (FEA) 78, 79 –– See also See Finite element analyses (FEA) – kinetics of 177 – overviews of 253, 256 – references for 256 – replacement of 247, 253 –– ACADIA Facet Replacement System 263, 264 ––– See also See ACADIA Facet Replacement System –– as stand-alone device 254 –– as total disc replacement (TDR) adjunct 255 –– for posterior dynamic reconstruction 256 –– overviews of 258, 264 –– rationales for 258 –– references for 264 –– Total Facet Arthroplasty System (TFAS) 262, 263, 263 ––– See also See Total Facet Arthroplasty System (TFAS) –– Total Posterior Solution (TOPS) System 259, 259, 260 ––– See also See Total Posterior Solution (TOPS) System –– wide compression and 256 Falena device 240–241, 243 – See also See Interspinous process spacers FASS system, see See Fulcrum-assisted soft stabilization (FASS) system Fatigue failures 222 FDA-IDE trials, see See Food and Drug Administration-Investigational Device Exemption (FDA-IDE) trials FE motion, see See Flexion-extension (FE) motion FEA, see See Finite element analyses (FEA) Feathered fusion FEM, see See Finite element modeling (FEM) Fernström Ball 281 Fibrosis 432 – See also See Annulus Finite element analyses (FEA) 75 – advantages of 80 – applications of 80 –– device design parameters 82, 82– 83 –– surgical technique analyses 81, 82 – element types 4, 78 –– comparisons of –– facet joints 78, 79 ––– See also See Facet joints –– intervertebral discs 78 –– ligaments 78 –– posterior elements 78 –– vertebral body elements 78 – finite element modeling (FEM) 75 –– approaches to 75 –– definition of 75 –– step (preprocessing) 75 –– step (analyses) 75 –– step (postprocessing) 75 –– validation of 79, 79, 80 – for Total Posterior Solution (TOPS) System 259 – overviews of 75, 83 – references for 83 Finite element modeling (FEM) 75 – approaches to 75 – definition of 75 – step (preprocessing) 75 – step (analyses) 75 – step (postprocessing) 75 – validation of 79, 79, 80 First-generation lumbar prosthetic discs 408 – accelerated adjacent segment degeneration and 408 – Charité 408 – facet joint pain and 408 – premises of 408 – ProDisk-L 408 Flat tire disc 216 Flexibility 32, 54, 55 FlexiCore disc 308, 309, 350, 387 Flexion-extension (FE) motion 46–48 – See also See Motion Flexuspine 415 Fluoroscopy 424 Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 3–4 – disc prostheses 152 – Dynesys Dynamic Stabilization System 228 –– See also See Dynesys Dynamic Stabilization System – future directions for 156 – goals of 152 – meta-analyses of 154, 155 – overviews of 152, 156 – premarket approval processes 87 – references for 156 – regulatory controls and 87 – significant device risk category 152 – X-Stop interspinous systems 247 Force 32, 34 – See also See Biomechanics – definition of 34 – force couple 34, 35 – moment of force about a point 34, 35 Fracture healing vs fusion 23 Fragment herniations 432 – fragment-contained 432 – fragment-defect 432 – fragment-fissure 432 – no fragment-contained 432 Free-body analyses 36 Freedom Lumbar Disc 310, 310 Freedom Lumbar Disc (FLD) 409, 413 Frontal (xy) plane 32 FSUs, see See Functional spinal units (FSUs) Fulcrum-assisted soft stabilization (FASS) system 3, Functional spinal units (FSUs) 40, 41, 54 Fusion 20 – anterior cervical corpectomy and fusion (ACCF) 98 – anterior cervical discectomy and fusion (ACDF) 90 – direct lateral lumbar interbody fusion (LLIF) approach 439 – feathered – grades 20 –– animal experiments 21, 22 –– human subjects 22 –– instrumentation removal effects 20 –– stiffness/rigidity 21 –– successful fusion definitions 20 –– uninstrumented fusion 20 – indications for 213 G Gauge length 41 GDF-5, see See Growth-differentiation factor-5 (GDF-5) Gene guns 443 Genetic and molecular therapies 441 – disc structure and functions 441 –– anatomy 441 –– annulus fibrosis 441 –– cartilaginous end plates 441 –– nucleus pulposus 441 –– primary functions 441 – for degenerative disc repairs 441 – future directions for 445 – gene therapy 443, 443, 445 –– effectiveness of 444 –– safety of 444 –– viral vectors 443 ––– See also See Viral vectors – growth factor therapy 442 – intervertebral disc degeneration (IDD) 441, 442, 442 –– challenges of 441 –– definition of 441 –– mechanisms of 442, 442 –– prevalence of 441 – overviews of 445 – references for 445 Geometry, design 269 Global motion 46, 46 – See also See Motion Glycosaminoglycan side chains, anionic 441 Grades, fusion 20 – See also See Fusion – animal experiments 21, 22 – human subjects 22 – instrumentation removal effects 20 – rigidity 21 – stiffness 21 – successful fusion definitions 20 – uninstrumented fusion 20 Graf ligamentoplasty 196 – anterior column support with 199 – clinical outcomes of 198, 199–200 – contraindications for 196 – hybrid stabilization for 199 – indications for 196 – overviews of 2, 2, 196, 200 – rationales for 196, 196 – references for 200 – surgical techniques for 197, 197, 198 –– band placement 197, 198 –– implant placement 197, 197 –– operative precautions 198 –– patient positioning 197 –– surgical approaches 197 Graf pedicle screws 196, 196 Graf, Henry 2, 2, 196 Graft donor site morbidity 99 Growth factor therapy 442 – See also See Molecular and growth factor therapies Growth-differentiation factor-5 (GDF5) 442 Guns, Gene 443 H HA, see See Helical axis (HA) HAM, see See Helical axis of motion (HAM) Height restorations 289 Helical axis (HA) 172 Helical axis of motion (HAM) 48, 61 – See also See Motion – definition of 48 – envelope of 48, 48 – finite 52, 52, 53 – in lumbar spine 51, 52, 172 – nonfusion stabilization applications of 52 – spinning football representation of 48, 48 Herniations 432 – fragment-contained 432 – fragment-defect 432 – fragment-fissure 432 – no fragment-contained 432 Heterotopic ossification (HO) 122, 123, 154, 377, 377, 384 Hibbs, Russell A Hippocrates HO, see See Heterotopic ossification (HO) Horizontal (xz) plane 32 Hybrid devices Hybrid protocols 54 Hybrid stabilization 199 Hypoelastic material properties 78 Hysteresis 42, 44–45 I IDD, see See Intervertebral disc degeneration (IDD) Ideal dynamic stabilization devices 27 451 | 20.02.15 - 13:31 Index IDET, see See Intradiscal electrothermal therapy (IDET) IGF-1, see See Insulin-like growth factor-1 (IGF-1) Iliac crest bone graft donor site morbidity 99 Imaging techniques 424 – computed tomography (CT) 425, 425 – dual fluoroscopic imaging system (DFIS) 426, 427 – fluoroscopy 424 – for kinematic assessments 424 –– See also See Kinematics – magnetic resonance imaging (MRI) 426, 427 –– open vs dynamic 426, 426 –– three-dimensional (3D MRI) 425 – plain radiographs 424, 424 – radiostereometric analyses (RSA) 425 – X-ray 424 Infection-related complications 382, 392 – See also See Complications Inflammatory reactions, adverse 110 Injectables, polymeric 432 Injection molding 410 Insertion-related complications 390 – See also See Complications Instability vs clinical instability 189 Instantaneous axis of rotation (IAR) 48, 49–51, 172 – See also See Rotation Instantaneous core of rotation (ICR) 46 – See also See Rotation Instrumentation removal effects 20 Insulin-like growth factor-1 (IGF-1) 444 International System of Units (SI System) 32, 32 Interpedicular distance (IPD) tracking 173, 173, 174–175 Intersection, axes 32 Interspinous process distraction (IPD) systems 2, 234 – applications of 234 – classification of 234 – clinical results for 234, 234, 235–238 – Coflex Interlaminar Stabilization Device 234 – complications of 238 –– See also See Complications – contraindications for 238 – Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System 234 – Flexus 234 – free vs restricted flexion 234 – indications for 234 –– facetogenic back pain 234 –– neurogenic claudication with stenosis 234 –– spinal arthrodesis 234 – Interspinous Locker 234 – nonmetallic 234 – overviews of 234, 238 – references for 239 – rigid vs dynamic devices 234 – spacers 240 452 –– See also See Interspinous process spacers – Superion Interspinous Spacer 234 – Wallis Posterior Dynamic Stabilization System 234 – X-Stop 234, 247 –– biomechanical effects of 249 –– clinical results for 247 –– complications of 250 –– design of 247, 248 –– economic considerations for 249 –– indications for 250, 251 –– lumbar spinal stenosis and 247 –– overviews of 251 –– rationales for 248 –– reviews of 251 Interspinous process spacers 240 – classification of 240, 241 –– Aperius Percutaneous Lumbar Interspinous Decompression Spacer 240–241, 244 –– Coflex Interlaminar Stabilization Device 240–241, 242 –– Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System 240, 240, 241 –– Falena device 240–241, 243 –– Superion Interspinous Spacer 240–241, 244 –– Wallis Posterior Dynamic Stabilization System 240–241, 243 –– X-Stop Spacer 240–241, 243 – clinical results 240, 244 –– for dynamic (compressible) devices 240 –– for percutaneous/dynamic devices 244 –– for static noncompressible devices 243 – complications of 244 –– See also See Complications – contraindications for 240 – Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System 241 – goals of 240 – indications for 240 – overviews of 240, 245 – rationales for 240 – references for 245 Intervertebral disc degeneration (IDD) 442, 442 – challenges of 441 – definition of 441 – mechanisms of 442, 442 – molecular and genetic therapies for 441 –– See also See Molecular and genetic therapies – prevalence of 441 Intradiscal electrothermal therapy (IDET) 281, 434, 434 Intraoperative complications 157 – See also See Complications IPD systems, see See Interspinous process distraction (IPD) systems IPD tracking, see See Interpedicular distance (IPD) tracking J Joints, facet, see See Facet joints K Keratin sulfate 441 Kineflex disc 309, 309, 350 – biomechanics of 364 – clinical outcomes for 364 – design of 363, 364 Kineflex-C disc 109 – clinical results for 110 – design of 109, 110 – Food and Drug AdministrationInvestigational Device (FDA-IDE) trials 110, 153 Kinematics 38 – application definitions 38 –– anatomical planes 39, 39 –– Cartesian coordinate system 38 –– center of mass (CM) 41 –– center of rotation (COR) 40, 41 –– coupled motion 40 –– degrees of freedom (DOFs) 40 –– dynamics 40 –– equilibrium 40 –– functional spinal units (FSUs) 40, 41 –– instantaneous axis of rotation (IAR) 41 –– instantaneous center of rotation (ICR) 40, 41 –– kinetics 40 –– loads 38 ––– See also See Loads –– motion 38 –– plane motion 40 –– rigid bodies 38 –– statics 40 – cervical spine motion 61 –– center of rotation (COR), definition of 61 –– center of rotation (COR), determinations of 66, 66 –– center of rotation (COR), post-disc replacement 67, 67 –– conventional physiologic motion patterns 61 –– coupled motion 61 –– degrees of freedom (DOFs) 61 –– distribution of motion 61, 62, 63, 63, 64 –– helical axis of motion (HAM) 61 –– instantaneous axis of rotation (IAR) 61 –– overviews of 61, 68 –– range of motion (ROM) 61 –– references for 68 –– rigid bodies 61 –– segmental motion 61 –– testing methods for 65 – definition of 40, 61 – hysteresis 42, 44–45 – lumbar spine 172 –– adjacent level effect (ALE) 172 –– fusion effects of 172 –– helical axis (HA) 172 –– instantaneous axis of rotation (IAR) 172 –– interpedicular distance (IPD) tracking 173, 173, 174–175 –– motion assessments 423 –– neutral zone (NZ) motion 172 –– overviews of 172, 176 –– parameters of 172 –– range of motion (ROM) 172 –– references for 176 – overviews of 38, 45 – references for 45 – response measurements 59 – stress-strain 41, 42–43 –– curves 42–43 –– engineering stress 41 –– gauge length 41 –– modulus of elasticity 42 –– plastic regions 42 – viscoelasticity 42, 44 –– creep tests 42 –– stress relaxation tests 42 Kinetics 177 – facets 177 – intervertebral disc 179, 179, 180 – ligamentous constraints 178, 178 – muscles 179 – overviews of 177, 181 – radiographic representation of 177, 177 – references for 181 Kirschner wires (K-wires) 423 L Late postoperative complications 393 – See also See Complications Lateral lumbar interbody fusion (LLIF) approach 439 Laws of motion 35 – See also See Motion Leeds-Keio Tension Band System 4, Length 32 Ligamentoplasty, Graf 196 – anterior column support with 199 – clinical outcomes of 198, 199–200 – contraindications for 196 – hybrid stabilization for 199 – indications for 196 – overviews of 196, 200 – rationales for 196, 196 – references for 200 – surgical techniques for 197, 197, 198 –– band placement 197, 198 –– implant placement 197, 197 –– operative precautions 198 –– patient positioning 197 –– surgical approaches 197 Ligamentous constraints 178 Liposomes 443 LLIF approach, see See Lateral lumbar interbody fusion (LLIF) approach Loads 55, 85 – abnormal load theory 186 – applied demands 85 – applied load demand 85 – continuous 59 – continuous vs stepwise (static) 59 – cyclic 59, 85 – load-control 54, 55 – load-deformation curves 86 – load-sharing 190, 191 – overviews of 38 – pedicle screw load analyses 260 – preloads 56 – static 59 – stepwise 59 – testing protocols for 55 – types of 55 – vectors 34 –– See also See Vectors Local tissue reactions, adverse 383 | 20.02.15 - 13:31 Index Long-term outcomes 374 – adjacent level degeneration 376, 376 – facet joint degeneration 375 – heterotopic ossification (HO) 377, 377 – long-term motion preservation 374 – overviews of 374, 378 – references for 378 – retrieval analyses for 377, 378 Loosening, atraumatic 167 Low-Back Outcome Scores 434 LP-ESP disc 310, 310 Lumbar spine 287, 288 – annulus repairs 432 – anterior exposure to 298 – degenerative 288 – dynamic stabilization of 184, 198 –– See also See Dynamic stabilization – facet joints, see See Facet joints –– anatomy of 253, 253, 254 –– biomechanics of 253 –– overviews of 253, 256 –– references for 256 –– replacement of 247, 254–256 – interspinous process distraction (IPD) systems 2, 234 –– X-Stop 247 – interspinous process spacers 240 – kinematics of 172 –– See also See Kinematics – kinetics of 177 – minimally-invasive spine surgery (MISS) for 437 – motion kinematic assessments 423, 433 – nonfusion stabilization 213 – normal 287 – nucleus replacement systems 281 – prosthetic discs 408 –– first-generation 408 –– next-generation 408 –– overviews of 408, 413 –– references for 414 – pseudoarthrosis transition revisions 207 – salvage procedures 390 – total disc replacement (TDR) 292, 415 –– See also See Total disc replacement (TDR) –– anatomy of 304 –– biomechanics of 287, 304 –– classification of 304 –– clinical results for 367 –– complications of 380, 386, 390 ––– See also See Complications –– definition of 305 –– design of 306 –– first-generation 307 –– FlexiCore 350 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 386 –– indications for 287 –– long-term outcomes for 374 –– M6-L disc 343 –– Maverick TDR 350 –– Mobidisc 350 –– multilevel 399 –– overviews of 305, 311, 367, 368 –– polymer-on-metal 339 –– posterior approach 415 –– references for 311 –– second-generation 309 –– status quo of 306 –– third-generation 311 M M6-C Artificial Cervical Disc 125 – advantages vs disadvantages of 133 – biomechanics of 125 –– cadaver studies 125, 126–127 –– center of rotation (COR) 126, 127 –– facet joint studies 127, 128–129 – clinical results for 128 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) pilot study 132, 132, 133, 133–134 –– initial study 128, 130–131 – design of 125, 125 – development of 125 – overviews of 133 – references for 134 – surgical techniques for 128 –– access considerations 128 –– device insertion 128, 130 –– implant sizing 128, 130 –– keel track cutting 128, 130 –– preparation 128 M6-L disc 310, 310, 343 Magnetic resonance imaging (MRI) 426, 427 – open vs dynamic 426, 426 – three-dimensional (3D MRI) 425 Magnitude 33, 55 Major complications 232 – See also See Complications Marble-on-soup-bowl concept 186, 187 Marked subsidence 380 Mass 32, 41 Materials, see See Biomaterials Maverick device 308, 308, 387 Mean center of motion 48 – See also See Motion Measurement units 32, 32 Mechanical equilibrium 35 Mechanics, see See Biomechanics Mediators, anabolic 441 Mesh refinement 79 Metal-on-metal disc prostheses 104, 359 – cervical 104 –– adjacent segment disease (ASD) and 104 –– adverse inflammatory reactions to 110 –– CerviCore disc 106, 108–109 ––– See also See CerviCore disc –– Food and Drug Administration (FDA) status of 104, 106, 109–110 –– Kineflex-C disc 109, 110 ––– See also See Kineflex-C disc –– overviews of 104, 110 –– Prestige disc family 104, 104, 105– 106 ––– See also See Prestige disc family –– references for 110 –– surgical techniques for 106, 106, 107–108 – lumbar 359 Metal-on-poly disc prostheses 112 – Bryan Cervical Disc 118 –– See also See Bryan Cervical Disc – clinical results for 112 – contraindications for 112 – M6-C Artificial Cervical Disc 125 –– See also See M6-c Artificial Cervical Disc – Mobi-C 115, 148 –– See also See Mobi-C – overviews of 112, 116 – Porous Coated Motion (PCM) disc 115 –– See also See Porous Coated Motion (PCM) disc – ProDisc-C 112, 112, 113 –– See also See ProDisc-C – references for 116 – Secure-C 114, 114, 115 –– See also See Secure-C – symptomatic cervical spine disease (SCDD) and 112 Metallic burnishing 166 Microbubble-enhanced ultrasound 443 Microdiscectomy 432 Microelectronic sensors 411 Migration complications 159, 159, 381 – See also See Complications Minimally-invasive dynamic stabilization, see See Dynamic stabilization – posterior 222 Minimally-invasive spine surgery (MISS) 437 – definition of 437 – for lumbar spine 437 –– advantages vs limitations of 437 –– clinical results for 438 –– direct lateral lumbar interbody fusion (LLIF) approach 439 –– motion-sparing technologies 439, 439 –– muscle tissue preservation 437 –– overviews of 437, 439 –– posterior dynamic stabilization 437 –– references for 439 –– total disc replacement (TDR) 437, 437, 438 –– transforaminal lumbar interbody fusion (TLIF) 437 – roles of 437 Minns, R J MISS, see See Minimally-invasive spine surgery (MISS) Mobi-C 115 – clinical results for 115 – design of 115, 115 – Food and Drug Administration (FDA) status of 115 Mobidisc 308, 308, 350 Modic sign 216 Modulus of elasticity 42 Molecular and genetic therapies 441 – disc structure and functions 441 –– anatomy 441 –– annulus fibrosis 441 –– cartilaginous end plates 441 –– nucleus pulposus 441 –– primary functions 441 – for degenerative disc repairs 441 – future directions for 445 – gene therapy 443, 443, 445 –– effectiveness of 444 –– safety of 444 –– viral vectors 443 ––– See also See Viral vectors – growth factor therapy 442 – intervertebral disc degeneration (IDD) 441, 442, 442 –– challenges of 441 –– definition of 441 –– mechanisms of 442, 442 –– prevalence of 441 – overviews of 445 – references for 445 Moment 32 – of force about a point 34, 35 –– See also See Force – of inertia 32 –– mass 32 –– sectional 32 Motion, see See Kinematics – assessments 423 –– disc deformation, normal vs symptomatic 428, 428 –– facet motion, normal vs symptomatic 428, 429 –– imaging techniques 424 ––– See also See Imaging techniques –– in vivo techniques for 423, 430 –– Kirschner wires (K-wires) vs bone pins 423, 423, 424 –– motion capture 423 –– overviews of 423, 429 –– pre-/post-X-Stop surgeries 429, 429 –– range of motion (ROM), normal vs symptomatic 427, 428 –– references for 430 –– transducers 423, 423, 424 – assessments of 423 – conventional physiologic patterns 61 – coupled 48 – flexion-extension (FE) 46–48 – global vs relative motion 46 – helical axis of (HAM) 48, 48 –– See also See Helical axis of motion (HAM) – mean center of 48 – motion-preservation devices 435 – motion-sparing technologies 439, 439 – neutral zone (NZ) 172 – Newton‘s laws of 35 – plane 40, 46, 46 – pure rotation 46, 47 –– See also See Rotation – pure translation 46, 46 – quality of 46, 46 – segmental 61 – three-dimensional (3-D) 49 – uniform rotation 46, 47 MRI, see See Magnetic resonance imaging (MRI) Multilevel disc replacement 399 – biomechanical considerations for 400 – challenges of 401 – complications of 403 –– access complications 403 –– deep vein thrombosis (DVT) 404 –– subsidence 404, 404 – Da Vinci position for 401, 402 – degenerative cascade biomechanics and 400 – design goals for 401 – evidenced-based outcomes for 404 – for adjacent segments 403 453 | 20.02.15 - 13:31 Index – intraoperative techniques for 401, 402 – overviews of 399, 405 – patient selection for 399 – preoperative evidence-based analyses for 401 – previous disc replacements and 403 – radiographic imaging analyses for 399, 400 – references for 405 Multisegment spines 54 Muscle kinetics 179 Muscle tissue preservation 437 N NDI, see See Neck Disability Index (NDI) Neck Disability Index (NDI) 128 Neutral element decompression 120 Neutral zone (NZ) motion 172 – See also See Motion Newton‘s laws of motion 35 Next-generation prosthetic discs 408 – elastomeric 408 –– adjacent biomechanical environment preservation of 410 –– biomechanical analyses of 411, 411 –– Cadisc-L 409, 409 –– classification of 410 –– controlled-motion from 410 –– cores of 409 –– design features of 410 –– Freedom Lumbar Disc (FLD) 409, 409, 413 –– injection molding of 410 –– mechanical shock absorption of 410 –– microelectronic sensors of 410, 411 –– motion analyses of 411, 411 –– Physio-L disc 409, 412, 412, 413, 413 –– Theken eDisc 409, 409–410, 411 –– total elastomeric disc 410 – premises of 408 NFlex device 4, 194 Nitrol coil spring designs 3, No fragment-contained herniations 432 Noncompressible static devices 243 – See also See Interspinous process spacers Nonfusion stabilization 213 – Cosmic Posterior Dynamic System 214 –– clinical results for 218 –– contraindications for 217 –– existing spondylodesis extensions 216 –– for chronically recurring low back pain 215 –– for discogenic pain 215 –– for facet syndrome 215 –– for recurrent disc herniation 215 –– for symptomatic lumbar stenosis 215, 215 –– indications for 215 –– screws for 214, 214–216, 218 –– spondylodesis with 215, 216 –– surgical techniques for 217, 217, 218 – fusion indications 213 – instability vs clinical instability 213 454 – overviews of 213, 220 – references of 220 Nonfusion technology development Nonlinear elastic materials 42 Nonmetallic pedicle screw-based posterior dynamic stabilization (PDS) systems Nonreplicating cell transduction 443 NuBac 284, 284, 285, 285 – See also See Nucleus replacement systems Nucleus pulposus 441 Nucleus replacement systems 281 – classification of 281, 282 – clinical outcomes for 283 – complications of 285 – contraindications for 283 – DASCOR Disc Arthroplasty System 284, 284 – design of 281 – indications for 283 – NuBac 284, 284, 285, 285 – overviews of 273, 281 – Prosthetic Disc Nucleus (PDN) 283 – references for 273 – salvage procedures for 285 – surgical techniques for 282 NuCore Injectable Nucleus 432 NuNec 135 – biomechanical testing for 136, 138 – clinical results for 141, 142, 143, 143 – design of 135, 135 – sizes of 136 – surgical techniques for 139, 139 Nutritional supplements 441 NZ motion, see See Neutral zone (NZ) motion O Optimal balance 290 ORBIT-R disc 309, 309 Osmotic gradients 441 Ossification, see See Heterotropic ossification (HO) Osteolysis 383 Osteolysis, secondary 164 Oswestry Disability Index (ODI) 435, 439 Oxidation 164 P Paravirus family 444 Park, J Y 3, Passive constraints 179 Pathology treatments 433 – See also See Annulus repairs Patient positioning-related complications 157 – See also See Complications PCM disc, see See Porous Coated Motion (PCM) disc PDN, see See Prosthetic Disc Nucleus (PDN) PDS systems, see See Pedicle screwbased posterior dynamic stabilization (PDS) systems Pedicle screw-based posterior dynamic stabilization (PDS) systems 2, 189 – biomechanical goals of 189 – classification of 192 – – – – – design of 189 devices 192 hybrid devices 194 indications for 191 interspinous process distraction devices 192 – load sharing 190, 191 –– See also See Loads – motion preservation 190 – nonmetallic devices 192 – overviews of 2, 189, 194 – rationales for 190 – references for 281 PEEK discs, see See Polyether-etherketone (PEEK) and ceramic discs Peer-reviewed literature 91 Percutaneous/dynamic devices 244 – See also See Interspinous process spacers Persistent back pain 382 Physio-L 310, 310, 408 Plain radiographs 424, 424 Plane motion 40, 46, 46 – See also See Motion Planes, anatomical 32 Plastic regions 42 PLL, see See Posterior longitudinal ligament (PLL) Point of application 32, 33 Poisson‘s ratio 78 Polyether-ether-ketone (PEEK) and ceramic discs 135 – clinical results for 139 –– ceramic-on-ceramic discs 139, 140–141 –– PEEK-on-PEEK discs 141, 142, 143, 143 – development of 135 – Discocerv disc 135, 135, 136 –– biomechanical testing for 136, 137, 137 –– clinical results for 139, 140–141 –– design of 135, 135 –– sizes of 136 –– surgical techniques for 138 – NuNec disc 135 –– biomechanical testing for 136, 138 –– clinical results for 141, 142, 143, 143 –– design of 135, 135 –– sizes of 136 –– surgical techniques for 139, 139 – overviews of 135, 141 – preclinical biomechanical testing of 136 – spacers – surgical techniques for 138 –– ceramic-on-ceramic discs 138 –– PEEK-on-PEEK discs 139, 139 Polymer-on-metal discs 339 Polymeric injectables 432 Porous Coated Motion (PCM) disc 115 – clinical results for 116 – design of 115, 115 – Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 153 Positioning-related complications 157 – See also See Complications Positive Modic sign 216 Post-microdiscectomy treatments 432 Posterior approach 415 Posterior dynamic stabilization – for lumbar spine 437 – minimally-invasive 222 –– clinical outcomes for 225, 227 –– clinical results of 224 –– continued motion and 222 –– device design 222, 222, 223–224 –– device fatigue failures 222 –– overviews of 222, 227 –– references for 227 –– shared vs restricted motion loads 222 –– surgical techniques for 225, 226 Posterior Dynamic Stabilization System (DSS) 4, 222 – design of 4, 222, 222, 223–224 –– Posterior Dynamic Stabilization System-I (DSS-I) 222, 222 – overviews of 4, 227 – references for 227 Posterior elements 78 Posterior longitudinal ligament (PLL) 178, 432, 435 Postoperative complications 158 – See also See Complications – early 391 – late 393 Postoperative dysphagia 99 Postoperative radiculopathy 382, 382 Power 32 Preloads 56 – See also See Biomechanical testing – compressive 56 – definition of 56 – follower 57, 57 –– current 58 –– limitations of 58 –– path optimization for 58, 58 – muscle force replicating 57 – vertical 57 Premarket approval processes 87 Preparation processes 85 – See also See Biomaterials Pressure 32 Prestige disc family 104 – design of 104 – development of 104, 104 – Food and Drug Administration (FDA) status of 106 – Prestige I 104, 105 – Prestige II 104, 105, 105 – Prestige ST 152 – Prestige STLP 105, 106 – surgical techniques for 106, 106, 107–108 Proababolic factors 443 ProDisc II 387 ProDisc-C 112 – clinical results for 113 – design of 112, 112, 113 – Food and Drug Administration (FDA) status of 113, 114, 153 – preoperative evaluations and 112 – surgical techniques for 112, 113–114 ProDisc-L 307, 307, 334 – biomechanics of 334 – clinical results for 336 – design of 334, 334 – overviews of 337 – references for 337 – surgical techniques for 335, 336 Properties 85, 85, 86 – See also See Biomaterials Prophylactic antibiotic therapy 382 | 20.02.15 - 13:31 Index Prosthetic Disc Nucleus (PDN) 272 – anatomy for 267, 267 – biomechanics of 256 – clinical results for 278 – complications of 279 – design of 268, 272, 272 –– center of rotation (COR) 269 –– fixation 269 –– geometry 269 –– range of motion (ROM) 269 –– stiffness 269 –– strength 269 – failure of 270 – historical perspectives of 266 – indications for 267, 268, 268, 269 – overviews of 266, 270, 272, 279 – patient selection criteria for 273 – rationales for 256 – Raymedica PDN-SOLO 272, 272, 273 – references for 270, 279 – salvage of 270 – stepwise approach to 266 – surgical techniques for 270, 273, 274–275 –– anterior approach 276 –– clinical outcomes for 277 –– lateral approach 276 –– postlateral approach 276 Prosthetic discs, see See Total disc replacement (TDR) – cervical 110 –– Bryan Cervical Disc 118 –– M6-C 125 –– M6-C Artificial Cervical Disc 125 –– metal on metal 104 –– metal-on-poly 112 –– polyether ketone (PEEK) and ceramic 135 – lumbar 408 –– Charité 334 –– contraindications for 293 –– first-generation 408 –– FlexiCore 350 –– indications for 292 –– M6-L disc 343 –– Maverick TDR 350 –– metal-on-metal 350 –– Mobidisc 350 –– next-generation 408 –– overviews of 413 –– ProDisc-L 334 –– references for 414 Proteoglycans 435, 441 Protocols 54, 55 – See also See Biomechanical testing Pseudarthrosis 99 – avoidance of 99 – rates of 99 – risks of 99 – transition revisions 207 Pseudoplastic materials 42 Pseudotumor formation 383 Pure motion, see See Motion – rotation 46, 47 – translation 46, 46 Q QALs, see See Quality-adjusted life years (QALs) Quality-adjusted life years (QALs) 98 R rAAVs, see See Recombinant adenoassociated viruses (rAAVs) Radiculopathy 90, 382, 382 Radiofrequency ablation 281 Radiostereometric analyses (RSA) 425 Range of motion (ROM), see See Motion – definition of 46 – of lumbar spine 172 – testing protocols for 54 Raymedica Prosthetic Disc Nucleus (PDN) 272 Recombinant adenoassociated viruses (rAAVs) 443 Recurrent disc herniation 215 Reference systems 46 Regenerative methods 435 – See also See Annulus repairs Regulatory controls 87 Reherniation prevention 432 Relative motion 46 – See also See Motion Replacement discs, see See Total disc replacement (TDR) Response measurements 59 Retrieval analyses 162 – atraumatic loosening 167 – backside wear 166 – biomechanical simulation studies 167 – bony outgrowths 167 – implant and surrounding tissue 162 – in animal models 167 – inflammatory responses 164 – limitations of 168 – loosening 167 – metallic burnishing 166 – modular inferior components 166 – overviews of 162, 169 – oxidation 164 – references for 169 – retrieval causes 162, 163 – secondary osteolysis 164 – surface damage corrosion 164 – third-body wear 166 – wear debris effects 164 – wear modes 22, 162 – wear particles 164 Retroviruses 443 Revision of spinal pseudarthrosis with transition 207 – dynamic stabilization for 207 –– See also See Dynamic stabilization – fusion assessments 210 – indications for 207, 207 – overviews of 207, 212 – patient selection for 208 – references for 212 – reoperation rates 211 – successful fusion definitions 207 – surgical techniques for 207, 208– 209, 211 Rigid bodies 38 Rigidity/stiffness 21 Risk reduction strategies 160 ROM, see See Range of motion (ROM) Root injuries 382 Rotation, see See Kinematics – axis of 47 – center (COR) 46 –– See also See Center of rotation (COR) – centroid of 48 – definition of 46 – instantaneous axis of (IAR) 48, 49–51 – instantaneous core of (ICR) 46 – uniform motion 46, 47 RSA, see See Radiostereometric analyses (RSA) S Safety evaluations 233 Sagittal (yz) plane 32, 46 Salvage procedures 390 Scalars 32 Secondary osteolysis 164 Secure-C 114 – clinical results for 115 – design of 114, 114, 115 – Food and Drug Administration (FDA) status of 115 Segmental mobility restorations 289 Segmental motion 61 Sense 33 Sequestrectomy, Williams 432 SF-36, see See Short Form (SF)-36 Health Survey Shopping cart sign 240 Short Form (SF)-36 Health Survey 128 SI System (International System of Units) 32, 32 Significant risk device classification 152 Simulation studies 167 Single vs multilevel disc arthroplasty 145 Softer implants 26, 26 – ideal dynamic stabilization devices 27 – rationales for 27 Spacers, interspinous process 240 – classification of 240, 241 –– Aperius Percutaneous Lumbar Interspinous Decompression Spacer 240–241, 244 –– Coflex Interlaminar Stabilization Device 240–241, 242 –– Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System 240, 240, 241 –– Falena device 240–241, 243 –– Superion Interspinous Spacer 240–241, 244 –– Wallis Posterior Dynamic Stabilization System 240–241, 243 –– X-Stop Spacer 240–241, 243 – clinical results 240, 244 –– for dynamic (compressible) devices 240 –– for percutaneous/dynamic devices 244 – complications of 244 – contraindications for 240 – goals of 240 – indications for 240 – overviews of 240, 245 – rationales for 240 – references for 245 Spinal fusion grades 20 – animal experiments 22 – human subjects 22 – instrumentation removal effects 20 – stiffness/rigidity 21 – successful fusion definitions 20 – uninstrumented fusion 20 Spinning football representation 48 Spondylodesis 215, 216 Spontaneous fusion 2, 384 Stability vs clinical instability 189 Stabilization, dynamic – abnormal motion quantity 185 – devices –– CD Horizon Agile Dynamic Stabilization Device –– Coflex Interlaminar Stabilization Device –– Device for Intervertebral Assisted Motion (DIAM) Spinal Stabilization System –– Dynesys Dynamic Stabilization System 3, 189, 228 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 3–4 –– fulcrum-assisted soft stabilization (FASS) system 3, –– Graf ligament 2, –– hybrid –– interspinous process distraction (IPD) systems 2, 234 –– Leeds-Keio Tension Band System 4, –– NFlex –– Nitrol coil spring designs 3, –– Stabilmax NZ –– Transition Stabilization System 3, –– Wallis Posterior Dynamic Stabilization System (DSS) 4, –– X-Stop Spacer 4, – for revision of spinal pseudarthrosis with transition 207 – future directions for – historical perspectives of – instability vs clinical instability 189 – lumbar spine 184 –– See also See Lumbar spine –– abnormal load theory 186, 186 –– biomechanical experiments 186, 187 –– historical perspectives of 184 –– marble-on-soup-bowl concept 186, 187 –– overviews of 184, 186 –– pseudoarthrosis transition revisions 207 –– references for 187 –– stone-in-shoe concept 185 – minimally-invasive posterior 222 – nonfusion technology development – overviews of – pedicle screw-based posterior dynamic stabilization (PDS) systems 2, 189 –– biomechanical goals of 189 –– devices 192 –– hybrid devices 194 –– indications for 191 –– interspinous process distraction devices 192 –– load sharing 190, 191 ––– See also See Loads –– motion preservation 190 455 | 20.02.15 - 13:31 Index –– nonmetallic devices 192 –– overviews of 2, 189, 194 –– rationales for 190 –– references for 281 – principles of 222 – references for – stability vs clinical instability 189 – vs feathered fusion – vs motion preservation stabilization – vs spontaneous fusion – vs total disc replacement (TDR) –– See also See Total disc replacement (TDR) – with Graf ligamentoplasty 196 –– anterior column support with 199 –– clinical outcomes of 198, 199–200 –– contraindications for 196 –– hybrid stabilization for 199 –– indications for 196 –– overviews of 196, 200 –– rationales for 196, 196 –– references for 200 –– surgical techniques for 197, 197, 198 Stabilization, nonfusion 213 – Cosmic Posterior Dynamic System 214 –– clinical results for 218 –– contraindications for 217 –– existing spondylodesis extensions 216 –– for chronically recurring low back pain 215 –– for discogenic pain 215 –– for facet syndrome 215 –– for recurrent disc herniation 215 –– for symptomatic lumbar stenosis 215, 215 –– indications for 215 –– screws for 214, 214–216, 218 –– spondylodesis with 215, 216 –– surgical techniques for 217, 217, 218 Stabilmax NZ device 3, 193 Standardization 87 – See also See Biomaterials Static loads 59 – See also See Loads Static noncompressible devices 243 – See also See Interspinous process spacers Staufer-Coventry scores 404 Stepwise loads 59 – See also See Loads Stiffness 21, 32 Stone-in-shoe concept 185 Strain, see See Stress-strain Stress-strain 41, 42–43 – See also See Kinematics – curves 42–43, 85, 85–86 – engineering stress 41 – gauge length 41 – modulus of elasticity 42 – overviews of 32 – plastic regions 42 Structural aspects 85 – See also See Biomaterials Subluxation 381 Subsidence 159, 159, 380, 380, 391 Successful fusion definitions 20 Superion Interspinous Spacer 240– 241, 244 456 – See also See Interspinous process spacers Surface damage corrosion 164 Symptomatic annular tears 433 – See also See Annulus repairs Symptomatic disc rehernaitions 432 Symptomatic stenosis 215, 215 T T3D2, see See Uniaxial two-node truss elements (T3D2) Tape, Dacron TDA (total disc arthroplasty), see See Total disc replacement (TDR) TDR, see See Total disc replacement (TDR) Tears, symptomatic 433 – See also See Annulus repairs Technical complications 159 – See also See Complications Temperature 32 Tension Band System 4, Testing, biomechanical 54 – See also See Biomechanical testing – activities of daily living (ADLs) and 54–55 – apparatus for 54 – for cervical disc arthroplasty evaluations 70 –– overviews of 73 –– references for 74 – functional spinal units (FSUs) vs multisegment spines 54 – goals of 54 – limitations of 59 – overviews of 54, 59 – protocols for 54, 55 –– continuous vs stepwise loads 59 –– cyclic loads 59 –– displacement-control protocols 54 –– flexibility protocols 55 –– hybrid protocols 54 –– kinematic response measurements 59 –– load types 55 –– load-control protocols 54, 55 –– magnitudes 55 –– preloads 56 ––– See also See Preloads –– range of motion (ROM) and 54, 55 –– static loads 59 – references for 59 TFAS, see See Total Facet Arthroplasty System (TFAS) TGF-ß, see See Transforming growth factor-ß (TGF-ß) Theken Disc 408 Theken eDisc 409–410 Third-body wear 166 Three-dimensional Cartesian coordinate system 32, 33 TIMP-1, see See Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) 444 Tissue reactions, adverse 383 TLIF, see See Transforaminal lumbar interbody fusion (TLIF) TOPS System, see See Total Posterior Solution (TOPS) System Torque 32 Total disc arthroplasty (TDA), see See Total disc replacement (TDR) Total disc replacement (TDR) 2, – cervical (CTDR) 110 –– biomechanical aspects of 90 –– Bryan Cervical Disc 118 –– ceramic 135 –– disadvantages of 100 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials of 152 –– indications for 98 –– M6-C 125 –– metal-on-metal 104 –– metal-on-poly 112 –– overviews of 98, 101 –– polyether-ether-ketone (PEEK) 135 –– rationales for 98 –– references for 102 –– retrieval analyses for 162 – lumbar 292, 415 –– advancements in 408 –– anatomy of 304 –– biomechanics of 287, 304 –– case studies of 293 –– Charité 334 –– classification of 304 –– clinical results for 364, 367 –– clinical success related classification (CSRC) 292 –– complications of 380, 386, 390 –– contraindications for 293 –– definition of 305 –– design of 305, 408 –– elastomeric 408 –– first-generation 307, 307, 308–309 –– FlexiCore 350 –– Flexuspine 415 –– Food and Drug AdministrationInvestigational Device Exemption (FDA-IDE) trials 386 –– indications for 292 –– long-term outcomes of 371 –– M6-L 343 –– Maverick TDR 350 –– metal-on-metal 350, 359 –– minimally-invasive spine surgery (MISS) 437 ––– See also See Minimally-invasive spine surgery (MISS) –– Mobidisc 350 –– multilevel 399 –– overviews of 305, 311, 367, 368 –– Physio-L 408 –– polymer-on-metal 339 –– posterior approach 415 –– references for 311, 371 –– salvage procedures 390 –– second-generation 309, 310 –– status quo of 306 –– Theken disc 408 –– third-generation 311 – vs dynamic stabilization –– See also See Dynamic stabilization Total Facet Arthroplasty System (TFAS) 262 – clinical outcomes for 262 – design of 262, 262, 263, 263 Total Posterior Solution (TOPS) System 259, 259, 260 – biomechanical analyses for 260, 261 – clinical outcomes for 260, 262 – design of 259 – finite element analyses (FEA) for 259 – motion segment analyses for 260 – pedicle screw load analyses 260 Toughness 85, 85 – See also See Biomechanics Transforaminal lumbar interbody fusion (TLIF) 437 Transforming growth factor-ß (TGFß) 357 Transgene expression of growth factors (TGFs) 444 Transition Stabilization System 3, 3, 192 Translation 32 Translation motion 46, 46 – See also See Motion Two-node truss elements (T3D2) 78 U U.K Bristol Artificial Cervical Joint 104 UHMWPE, see See Ultrahigh molecularweight polyethylene (UHMWPE) Ultrahigh molecular-weight polyethylene (UHMWPE) 112, 114, 118, 125 Ultrazonix Spine Minimal-Invasive Disc System 435 Uniaxial two-node truss elements (T3D2) 78 Uniform rotation motion 46, 47 Uninstrumented fusion 20 Unit vectors 33 – See also See Vectors Units of measure 32, 32 V Validation 79, 79, 80 – See also See Finite element modeling (FEM) VAS scores, see See Visual analog scale (VAS) scores Vectors 32 – See also See Biomechanics – analyses of 34 – definitions of 32, 33 – loads 34 –– See also See Loads – unit 33 – viral 443 –– See also See Viral vectors Velocity 32 Vertebral body elements 78 Vertebral body fractures 159, 381, 381 Viral vectors 443 – See also See Molecular and genetic therapies – adenoassociated viruses (AAVs) 444 – adenoviruses 443 – definition of 443 – effectiveness of 444 – retroviruses 443 – safety of 444 Viscoelasticity 42, 44 – creep tests 42 – stress relaxation tests 42 Visual analog scale (VAS) scores 401, 434–435 Volume 32 | 20.02.15 - 13:31 Index W Wallis Posterior Dynamic Stabilization System (DSS) 4, 4, 240–241, 243 Walsh, W K Wear 166, 383 – debris effects 164 – modes 22, 162 – particles 164 – third-body 166 – wear-related complications 394 –– See also See Complications Wide decompression 256 Williams sequestrectomy 432 Work 32 X xy (frontal) plane 32 xz (horizontal) plane 32 X-ray techniques 424 X-Stop interspinous systems 247 X-Stop Spacer 4, 5, 240–241, 243 Xclose tissue repair system 433 XL TDR device 308, 309 Y Young‘s modulus 42, 78 yz (sagittal) plane 32 457 | 20.02.15 - 13:31 ... of the segment The complaints depend on the stage of the vertebral column degeneration In the first phase, with a reduction of the height of the vertebral disc and loss of the congruence of the. .. S170–S178 22 7 | 20 . 02. 15 - 13 :27 Restoration of the Lumbar Motion Segment 32 Clinical Results of IDE Trial of Dynesys for Dynamic Stabilization Alex Ha and Dilip K Sengupta 32. 1 Introduction 32. 2 .2 Study... quality of flexion and extension, supports the hypothesis that the kinematics of the DSS is complementary to that of the intact motion segment Therefore, the influence of the disc and the facet