The technical issue of whether one or two screws are needed has been addressed in various studies [25, 115, 188].Although there is a theoretical advantage of prevent- ing rotation with two screws, there is no increased strength for bending move- ments and no difference in successful bony fusion. Although two screws are theo- retically desirable, fixation with one screw is sufficient with adequate technique [115, 188] ( Case Study 1 ). Apfelbaum et al. [25] compared anterior screw fixation for recent and remote odontoid fractures in 147 patients at two institutions (138 Type II, 9 Type III). Anterior screw fixation was performed either within 6 months of injury or more than 18 months after injury. At a mean follow-up of 18 months, the fusion rates were 88% and 25%,respectively. These results indicate that remote dens fractures do not favorably respond to anterior screw fixation. An alternative technique for augmentation or salvage procedures of failed anterior screw fixation is an anterior atlantoaxial screw fixation ( Fig. 16e, f ). Dislocated Type II and Type IIA fractures are indications for surgery In cases with remote dens fractures, dens non-union, os odontoideum or elderly patients with osteoporosis, a posterior approach is more likely to be suc- cessful. The classical treatment is a posterior instrumented fusion according to abc d Case Study 1 This 51-year-old male patient fell from his mountain bike and complained about neck pain. On admission, the patient was neurologically intact (ASIA E). Standard anteroposterior and lateral ( a) radiographs demonstrated a Type II odontoid fracture. The sagittal CT reconstruction confirmed the diagnosis of the fracture at the base of the odontoid process ( b). Repositioning and anterior stabilization with a single screw was performed. Follow-up radiographs ( c, d) demonstrated an anatomical reduction of the fracture and bony healing. 858 Section Fractures ab cd ef gh Figure 17. Posterior atlantoaxial stabilization techniques Posterior C1/2 fusion according to a, b Brooks and c, d Gallie. e, f Transarticular atlantoaxial screw fixation according to Magerl [113] with additional wire cerclage and fusion with a bicortical bone graft. g, h Alternative screw-rod fixation according to Harms [96]. Cervical Spine Injuries Chapter 30 859 Gallie or Brooks (Fig. 17a–d). The drawback of these fusion techniques is the lack of primary stability increasing the rate of non-union. Posterior atlantoaxial transaxial screw fixation and fusion ( Fig. 17e, f) according to Magerl [113] pro- vides the highest chance of successful fusion. Harms et al. [96] have described an alternativefixationmethodfortheatlantoaxialjointcomplex,i.e.,aposterior atlas and axis screw-rod fixation and fusion ( Fig. 17g, h)(Case Study 2). In a recent review [5], 8 papers describe a total of 147 patients who underwent poste- rior cervical fixation and fusion for Type II dens fractures and 29 patients treated similarly for Type III fractures. The overall fusion rate for fractures managed with surgical fixation and fusion was 87% (Type II) and 100% (Type III), respec- tively. Management in the Elderly Patient Posterior instrumented fusion is indicated for Type II fractures in the elderly The management of odontoid fractures in the elderly patient remains controver- sial. Ryan and Taylor [167] described 30 patients 60 years and older with Type II odontoid fractures. The fusion success rate in patients older than 60 years treated with external immobilization was only 23%. Similarly, Andersson et al. [24] described 29 patients 65 years and older with odontoid fractures managed by surgical and non-surgical means. In their series, six (86%) of seven patients achieved successful fusion after posterior cervical C1–C2 arthrodesis. Patients treated with anterior odontoid screw fixation had a fusion rate of 20% and patients managed with external immobilization alone had a fusion rate of 20%. Pepin et al. [152] reported their experience with 41 acute odontoid fractures and found that halo immobilization was poorly tolerated in patients 75 years and older. They suggested that early C1–C2 fixation and fusion was appropriate in this group. In a recent review [5], three case series argued against surgical fixa- tion in the elderly patient whereas seven other case series favor surgical fixation in this age group. One case-control study by Lennarson et al. [125] provides Class II medical evidence for surgical treatment of elderly patients. This study exam- ined 33 patients with isolated Type II odontoid fractures treated with halo vest immobilization. The authors found that patients older than50 years had a signifi- cantly increased failure rate of fusion in a halo immobilization device (21 times higher) when compared to patients younger than 50 years. Other factors such as medical conditions, sex of the patient, degree of fracture displacement, direction of fracture displacement, length of hospital stay, or length of follow-up did not influence outcome. Traumatic Spondylolisthesis of the Axis Traumatic fractures of the posterior elements of the axis may occur after hyper- extension injuries as seen in motor vehicle accidents, diving, and falls or judicial hangings [172, 210]. Therefore, the term “hangman’s fracture” was coined by Schneider in 1965 [172]. Garber [85] described eight patients with “pedicular” fractures of the axis after motor vehicle accidents and used the term “traumatic spondylolisthesis” of the axis. Classification The classification scheme of Effendi [70] has gained widespread acceptance for the classification of these injuries. Effendi et al. [70]described three types of frac- tures which are mechanism based ( Fig. 18). 860 Section Fractures Figure 18. Traumatic spondylolisthesis (hangman’s frac ture) Type I: isolated hairline fractures of the ring of the axis with minimal displacement of the body of C2. These injuries are caused by axial loading and hyperextension. Type II: displacement of the anterior fragment with disruption of the disc space below the axis. These injuries are a result of hyperextension and rebound flexion. Type IIA: displacement of the anterior fragment with the body of the axis in a flexed position without C2–C3 facet dislocation. Type III: displacement of the anterior fragment with the body of the axis in a flexed position in conjunction with C2–C3 facet dislocation. These injuries are caused by primary flexion and rebound extension. In the series reported by Effendi [70], Type I fractures were the most prevalent (65%) while Type II (28%) and Type III fractures(7%)werelesscommon.In 1985, Levine and Edwards [127] modified Effendi’s classification scheme by add- ing a subtype Type IIA (flexion/distraction injury). However, not all axis frac- tures can be classified according to this scheme [39]. Fujimura et al. [83] used radiological criteria to classify axis body fractures into: avulsion, transverse, burst, or sagittal fracture. Treatment Most fractures heal within 12 weeks of external immobilization Most patients with traumatic spondylolisthesis reported in the literature were treatedwithcervicalimmobilizationwithgoodresults[5].Importantly,thereis no Class I or Class II evidence that addresses the management of traumatic spon- dylolisthesis of the axis [5]. Fractures of the axis body can mostly be treated non- operatively [5, 91]. Most traumatic spondylolisthesis heals with 12 weeks of cer- vical immobilization with either a rigid cervical collar or a halo immobilization device. Surgical stabilization is an optioninTypeIIandIII fractures Surgical stabilization is a preferred treatment option in cases with: severe angulation (Effendi Type II) disruption of the C2–C3 disc space (Effendi Type II and III) inability to establish or maintain fracture alignment with external immobili- zation Axis body fractures are usually treated conservatively Surgical options for unstable traumatic spondylolisthesis include anterior C2/3 interbody fusion with anterior plate fixation ( Case Introduction) and posterior techniques such as direct screw fixation of the posterior arch [117]. In the series by Effendi et al. [70], 42 of 131 patients with hangman’s fractures were treated surgically (10 anterior C2–C3 fusion and 32 posterior fusion). All were success- fullystabilizedatlatestfollow-up.InthestudybyFrancisetal.[78],only7of123 patients with hangman’s fractures were treated surgically (4 anterior C2–C3 fusion, 2 posterior C1–C3 fusion, and 1 posterior C2–C4 fusion). The authors report that 6 of the 7 patients demonstrated a C2–C3 angulation of more than Cervical Spine Injuries Chapter 30 861 abc d e f gh i j Case Study 2 This 47-year-old male patient fell from a donkey at the age of 12 years. Neurologi- cal symptoms started at the age of 26 years. He recently presented with signs of chronic central cord compression, spasticity and gait difficulties (ASIA D). The sagittal CT reconstruction ( a) dem- onstrates a pseudarthrosis of the odonto- id process. The MRI ( b)showsthecom- pression of the spinal cord at the level of the pseudarthrosis. Flexion/extension ra- diographs (c, d) were taken during the operation and demonstrate the impor- tant atlantoaxial instability. Dorsal fusion of C1/C2 was performed according to the technique of Harms [96]; in addition lami- nectomy of C1 was performed. The intra- operative radiographs ( e, f)showthere- position and the position of the hardware as well as the needles used for the intraoperative neurological monitoring ( e). The postoperative CT scan demonstrates the reposition of the odontoid process in the anteroposterior view ( g) and lateral view (h), the position of the pedicle screw in C1 ( i) and C2 (j), as well as the laminectomy of C1 (i). 862 Section Fractures 11 degrees. All seven patients achieved bony stability. A number of case series of hangman’s fractures offer similar experiences with surgical management [5]. Combined Atlas/Axis Fractures The occurrence of the fractures in combination often implies a more significant structural and mechanical injury. Combination fractures of the C1–C2 complex arerelativelycommon[7].Inreportsfocusingprimarilyonodontoidfractures, the occurrence of a concurrent C1 fracture in the presence of a Type II or Type III odontoid fracture has been reported in 5–53% of cases. Odontoid fractures have been identified in 24–53% of patients with atlas fractures. In the presence of a hangman’s fracture, the reported incidence of a C1 fracture ranges from 6% to 26% [7]. A higher incidence of neurological deficit is associated with combined atlas and axis fractures. The atlas–Type II odontoid combination fracture seems to be the most common combination injury subtype, followed by atlas–miscella- neous axis, atlas-Type III odontoid, and atlas–traumatic spondylolisthesis frac- tures. Treatment The axis fracture characteristics commonly dictate the management Reports of combined atlas/axis fractures are relatively rare and no treatment guidelines but only recommendations can be derived from the literature [7]. Treatment of combined atlas-axis fractures is based primarily on the specific characteristics of the axis fracture. External immobilization is recommended for most combined atlas/axis fractures. Combined atlas–Type II odontoid fractures with an atlantodental interval of more than 4 mm and atlas–traumatic spondylo- listhesis injuries with angulation of more than 10 degrees should be considered for surgical stabilization and fusion. The surgical technique must in some cases be modified as a result of loss of the integrity of the ring of the atlas. In most cir- cumstances, the specifics of the axis fracture will dictate the most appropriate management of the combination fracture injury. The integrity of the ring of the atlas must often be taken into account when planning a specific surgical strategy using instrumentation and fusion techniques. In cases where the posterior arch of C1 is not intact, both incorporation of the occiput into the fusion construct (occipitocervical fusion) and posterior C1–C2 transarticular screw fixation and fusion have been successful [7]. Classification and Treatment of Subaxial Injuries In contrast to atlas and axis, the vertebrae and articulations of the subaxial cervi- cal spine (C3–C7) have similar morphological and kinematic characteristics. However, important differences in lateral mass anatomy and in the course of the vertebral artery exist between the mid and lower cervical spine. Approximately Eighty percent of all cervical injuries affect the subaxial spine 80% of all cervical spine injuries affect the lower cervical spine and these injuries are often associated with neurological deficits [17, 22, 32, 182]. The variety and heterogeneity of subaxial cervical spinal injuries require accurate characteriza- tion of the mechanism and types of injury to enable a comparison of the efficacy of operative and non-operative treatment strategies. Cervical Spine Injuries Chapter 30 863 Classification The Allen and Ferguson classification system [16] has been the most commonly used scheme to differentiate and characterize subaxial vertebral injuries. Based on 165 cases, Allen and Ferguson [16] described common groups for: compres- sive flexion, vertical compression, distractive flexion, compressive extension, distractive extension, and lateral flexion. A systematic classification of the lower cervical spine was proposed by Aebi et al. [12, 13] and modified by Blauth [30]. The classification is adapted from the AO/ASIF (Association for the Study of Internal Fixation) classification scheme, which is widely used for thoracolumbar fractures (see Chapter 31 ). The three main groups are shown in Table 8 and Fig. 19. Table 8. AO Fracture Classification of lower injuries Type A: compression injuries Type B: anterior and posterior element injury with distraction Type C: anterior and posterior element injury with rotation A1.1 B1.1 C1.1 impaction of the endplate with transverse disc disruption rotational wedge fracture A1.2 B1.2 C1.2 wedge impaction with Type A vertebral body fracture rotational split fracture A1.3 B1.3 C1.3 vertebral body collapse anterior subluxation rotational burst fracture A2.1 B2.1 C2.1 sagittal split fracture transverse bicolumn fracture B1 injury with rotation A2.2 B2.2 C2.2 coronal split fracture transverse disruption of the disc B2 injury with rotation A2.3 B2.3 C2.3 pincer fracture with Type A vertebral body fracture B3 injury with rotation A3.1 B3.1 C3.1 incomplete burst fracture hyperextension subluxation slice fracture A3.2 B3.2 C3.2 burst-split hyperextension spondylolysis oblique fracture A3.3 B3.3 C3.3 complete burst fracture posterior dislocation complete separation of the adjacent vertebrae Types, groups, and subgroups allow for a morphology-based classification of cervical fractures according to Aebi and Nazarian [13] and modified by Blauth et al. [30] Thefracturetypesarerelatedtospecific injury pattern, i.e.: injuries of the anterior elements induced by compression (Type A) injuries of the posterior and anterior elements induced by distraction (Ty pe B) injuries of the anterior and posterior elements induced by rotation (Type C) TypesBandCarethemost common fractures Types B and C are the most common fracture types (Table 9). Subaxial fracture-dislocation is frequently associated with neurological injury ( Table 10). 864 Section Fractures Figure 19. AO Fracture Classification of subaxial injuries According to the classification of AOSPINE (Blauth et al. [30], redrawn and modified). Table 9. Frequency of fracture types in subaxial injuries n= 448 Total percentage Percentage within the types Type A 66 14.7 % A1 13 2.9% 19– 7% A2 9 2.0 % 13.7 % A3 44 9.8 % 66.6% Type B 197 43.9 % B1 157 35.0 % 79.7% B2 4 0.9% 2.0% B3 36 8.0% 18.3% Type C 185 41.2 % C1 0 0% 0 % C2 184 41.0 % 99.5 % C3 1 0.2 % 0.5 % Based on an analysis of 448 cases by Blauth et al. [30] Cervical Spine Injuries Chapter 30 865 Table 10. Frequency of neurological deficits in subaxial injuries Types and groups Number of patients Neurological deficit Type A 66 42.4 % A1 13 15.3% A2 9 22.2% A3 44 54.5% Type B 197 64.4% B1 157 61.0% B2 4 75.0% B3 36 73.0% Type C 185 62.7% C1 0 0% C2 184 62.0 % C3 1 100% Total 448 60.7% Based on an analysis of 448 cases by Blauth et al. [30] Treatment Non-operative Management Most subaxial cervical injuries can be treated conservatively Most subaxial spine injuries can be successfully treated by conservative means (Philadelphia collar, Minerva cast or halo vest fixation). Treatment with traction and prolonged bedrest has been associated with increased morbidity and mor- tality and has widely been abandoned today. After reduction of dislocated frac- tures, more rigid fixation techniques (halo vest fixation, Minerva cast) appear to have better success rates than less rigid orthoses (collars, traction only). Operative Management Operative stabilization of unstable fractures (especially for Type B and Type C injuries) is gaining increasing acceptance because it facilitates aftertreatment without disturbing external supports. Indications for surgical treatment include ( Table 11)[11]: Table 11. Surgical indications for subaxial injuries irreducible spinal cord compression vertebral subluxation of 20 % or more ligamentous injury with facet instability failure to achieve anatomical reduction (irreducible injury) spinal kyphotic deformity more than 15° persistent instability with failure to maintain reduction vertebral body fracture compression of 40% or more ligamentous injury with facet instability Most subaxial spine injuries can be treated by an anterior approach Both posterior (Fig. 20) and anterior (Fig. 21) cervical fusion techniques usually result in spinal stability for most patients with subaxial injuries. The outcome of anterior vs. posterior fracture fixation has been addressed in various recent publications [14, 77, 97, 119, 133, 162, 192]. The studies include only small case series (21 patients [77] to 35 patients [119]) and the methodology allows the clas- sification of the studies using only Class III and Class IV [97, 192] evidence. Aebi et al. [14] were one of the first groups to suggest that most lower cervical spine fractures can successfully be treated by an anterior approach even in the case of distraction and rotation injuries with posterior element involvement. Today, lit- erature reviews indicate that anterior fixation of fractures of the lower cervical 866 Section Fractures ab c d Figure 20. Posterior fracture stabilization a, b Lateral mass screw fixation according to the technique of Magerl [113]. The screw is directed from the medial upper quadrant of the facet joint 20 –25° laterally and 30 –40° cranially. Polyaxial top-loading screws facilitate rod placement. c, d After decortication of the posterior elements, a posterior fusion is added and a cross-connector used (when appro- priate) to increase construct stability. spine is now the preferred treatment approach. Failures of this technique which may result in reoperations are rare (0–6%) [119, 133]. Anterior fusion should not be performed without plate fixation Anterior fusion should not be performed without plate fixation (Fig. 21), because it is associated with an increased likelihood of graft displacement and the development of late kyphosis, particularly in patients with distractive Type B and Type C injuries [11]. Similarly, posterior fusion that uses wiring techniques is more likely to result in late displacements with kyphotic angulation when compared to posterior Cervical Spine Injuries Chapter 30 867 . mechanism and types of injury to enable a comparison of the efficacy of operative and non-operative treatment strategies. Cervical Spine Injuries Chapter 30 863 Classification The Allen and Ferguson. modified as a result of loss of the integrity of the ring of the atlas. In most cir- cumstances, the specifics of the axis fracture will dictate the most appropriate management of the combination. incorporation of the occiput into the fusion construct (occipitocervical fusion) and posterior C1–C2 transarticular screw fixation and fusion have been successful [7]. Classification and Treatment of Subaxial