ab cd e f Figure 8. Surgical anatomy for left-sided thoraco-phrenico-lumbotomy a Landmark for skin incision. b Superficial dissection. c Dissection of the rib for resection (see Fig. 6c). d The rib cartilage is split and marked with stay sutures. e The diaphragm is split about 2 cm medial to its rib insertion. f The medial and lat- eral crus of the diaphragm are transected and marked with stay sutures. The segmental vessels are ligated. The thoracic exposure is shown in Fig. 6d, e. 352 Section Surgical Approaches section. After repair of the diaphragma, the rib cartilage halves are refixed. The thorax is closed as described above. The abdominal wall is sutured in three sepa- rate layers (transverse, internal and external oblique muscles). Pitfalls and Complications Injuries to the thoracic duct canresultinachylothorax A frequent complication is to accidently open the peritoneal sac during dissec- tion of the diaphragma. This can be avoided when the preparation of the two body cavities is started from the abdominal site and the peritoneum freed from the diaphragma. When taking the diaphragma down to its insertion at the spine, care has to be taken not to injure the: greater splanchnic nerve ascending lumbar vein sympathetic trunk thoracic duct (rarely visible during preparation) A detailed discussion of the complications associated with this approach is included in Chapter 39 . Anterior-Lateral Retroperitoneal Approach to L2–L5 The anterolateral retroperi- toneal lumbar approach is easily applicable even in obese patients The anterior-lateral retroperitoneal approach to the lumbar spine has been an established operative technique since the early 1960s. This approach can be car- ried out also from the right side. The left sided approach, however, is favored because the inferior vena cava is less at risk. This approach is easy to perform even in obese patients because the abdomen is hanging to the side and the flank is exposed. Indications Indications for this approach are spinal disorders located between L2 and L5 ( Table 4): Table 4. Indications for a retroperitoneal lumbotomy (L2–L5) spinal deformities lumbar fractures/instabilities degenerative disorders tumors infections Patient Positioning For this approach the patient is positioned on the right side similarly to as per- formed for the thoraco-phrenico-lumbotomy ( Fig. 7a, b). Surgical Exposure Landmarks for Skin Incision We favor a mini-open approach to the lumbar spine, which necessitates image intensifier localization of the skin incision. With a 6- to 8-cm incision, a two-level fusion can be done without difficulty when using a retractor frame. The skin inci- sion is done in the fiber direction of the external oblique muscle ( Fig. 9a). Surgical Approaches Chapter 13 353 ab cd ef Figure 9. Surgical anatomy for the anterior-lateral retroperitoneal approach to L2–L5 a Landmarks for skin incision. b, c, d Transsection of the external oblique, internal oblique and transverse muscles. e Retraction of the psoas muscle exposing the vertebral column. f Medial retraction of the peritoneal sac exposing the large abdominal vessels. Ligation of the segmental vessel. Superficial Surgical Dissection A muscle splitting approach is preferred After the incision of the skin and the subcutaneous tissue, the three layers of the abdominal wall: external oblique muscle ( Fig. 9b) internal oblique muscle ( Fig. 9c) transversus muscle ( Fig. 9d) are separated in the direction of their fibers. 354 Section Surgical Approaches Deep Surgical Dissection With sponge sticks the peritoneal sac is mobilized in the medial direction to free the psoas muscle and the anterior spinal column. The peritoneal sac can be cov- ered with a moistened abdominal towel. The paravertebral sympathetic chain medial to the psoas muscle as well as the ureter need to be identified and retracted together with the peritoneum carefully in a medial direction. The psoas is mobilized from the spine and retracted posteriorly. The genitofemoral nerve which lies on the anteromedial side of the psoas muscle needs to be preserved. Care has to be taken not to injure the segmental or great vessels anteriorly while Take care with the iliolumbar vein when retracting the large vessels medially liberating the spine with sponge sticks. Special attention has to be paid to the ilio- lumbar vein at level L4–L5, which requires ligation if it limits the mobilization of the common iliac vein. In men, the psoas muscle can be very big and covers almost the whole lateral aspect of the vertebra. In these cases, a psoas splitting approach can be used to approach the intervertebral discs for a fusion [8]. The latter approach is less suited to a complete corpectomy. Wound Closure Each layer of the abdominal wall needs to be sutured separately. Suction drainage is usually not needed. Pitfalls and Complications Care has to be taken not to injure the: segmental vessels ascending lumbar vein iliac vein and artery genitofemoral nerve on the anteromedial side of the psoas muscle paravertebral sympathetic chain ureter (slightly attached to the peritoneum) A detailed description of the management of complications is outlined in Chap- ter 39 . Anterior Lumbar Retroperitoneal Approach Indications The anterior lumbar retroperitoneal approach is indicated for spinal pathology located between S1 and L3. The indications are similar to those for the lumbo- tomy with the exception that the approach exposes the spine at S1–L2 ( Table 4). Patient Positioning The patient is positioned supine with both arms abducted. The table can be slightly bent at the level of the pelvis. The positioning should be done in a way to allow the application of a table mounted retractor system, which facilitates the spinal exposure ( Fig. 10). Surgical Approaches Chapter 13 355 Figure 10. Patient positioning for an anterior retroperito- neal approach A table mounted retractor facilitates the approach. Surgical Exposure Landmarks for Skin Incision Landmarks for the skin incision are the umbilicus, symphysis and iliac wings. The umbilicus frequently projects onto the L4 level. However, this landmark is largely variable and necessitates image intensifier control to allow for a minimal length skin incision. The skin incision lies usually in the midline. Approaches to the L3/4 disc space, however, necessitate extending the incision above the level of the umbilicus. In these cases, we recommend using a slightly parasagittal inci- sion ( Fig. 11a). Superficial Surgical Dissection After skin incision and dissection of the subcutaneous tissue, the anterior rectus sheath is exposed over a length of 6–8 cm and opened 2 cm lateral to the midline ( Fig. 11b). The underlying rectus muscle is retracted laterally exposing the poste- rior rectus sheath and the arcuate line ( Fig. 11c). The peritoneal sac is mobilized medially below the arcuate line. The peritoneal sac is adherent to the inferior sur- face of the posterior rectus sheath and needs to be liberated from it to allow fur- ther retraction. After liberation, the posterior rectus sheath is incised about 2 cm medial to the abdominal wall and the peritoneum can be further retracted over the midline ( Fig. 11d). Deep Surgical Dissection At depth, the bifurcation is often visible with a medial sacral artery and vein. Depending on the size of the vessels, a ligation is necessary. Coagulation at the disc level should be avoided to preserve the presacral sympathetic plexus. In males, damage to the sympathetic plexus may result in a retrograde ejaculation. The L5/S1 disc is exposed between the bifurcation ( Fig. 11e )byslightlymobiliz- ing the vessels to both sides. Manipulation at the bifurcation should be done very carefully (if needed) to avoid injuries to the vessels, which are difficult to repair. The ascending lumbar vein is at risk when retracting the common iliac vein medially The L4/5 disc space or levels above are exposed by retracting the left common iliac vein and artery to the contralateral side ( Fig. 11e). During this maneuver, great care has to be taken not to tear the ascending lumbar vein from the common iliac vein. We recommend exposing the ascending lumbar vein and ligating it before retracting the vessels to the contralateral side. The paravertebral sympa- thetic chain lies medial to the psoas muscle and should be mobilized laterally while the ureter together with the peritoneum is retracted medially. 356 Section Surgical Approaches a b cd e f Figure 11. Surgical anatomy of the anterior retroperitoneal approach a Landmarks for skin incision. b Exposure of the anterior rectus sheath. c Dissection of the posterior rectus sheath close to the abdominal wall (arcuate line). d Exposure of the anterior spinal column. e Deep surgical dissection at the L5/S1 level accessing below the bifurcation. f Deep surgical dissection at the L4/5 level retracting the common iliac artery and vein medially. Surgical Approaches Chapter 13 357 Wound Closure The posterior rectus sheath should be readapted if possible. Interrupted sutures are placed in the anterior rectus sheath using slowly dissolving sutures. We do not routinely use a suction drainage. Pitfalls and Complications Care has to be taken not to injure the: segmental vessels ascending lumbar vein common iliac vein and artery paravertebral sympathetic chain ureter (slightly attached to the peritoneum) Injury to the sympathetic chain can result in retrograde ejaculation in males Injuries of the sympathetic chain may result in retrograde ejaculation (in males) or a sympathectomy syndrome with disturbed capability for vasoconstriction. This may result in the feeling of a hot (ipsilateral) or cold (contralateral) leg or foot, respectively. Weakness of the abdominal wall particularly in multiparas can result in abdominal herniations and needs to be repaired. A detailed description of the management of complications is provided in Chapter 39 . Posterior Approach to the Thoracolumbar Spine The posterior approach has been the most commonly used access to the spine since the 1950s. The exposure is straightforward but the collateral damage to the muscle is not negligible [23, 24, 39, 40]. Wiltse et al. [68] and Fraser et al. [21] have therefore suggested a so-called “muscle splitting approach”whichcanbeused when midline exposure is not necessary for decompression, e.g. for posterolat- eral fusion of a spondylolisthesis. Minimal-access surgery is preferred whenever possible. The target level should be determined with image intensifier to expose the spine only as much as is needed. Indications There are a wide variety of indications for this approach (Table 5): Table 5. Indications for the posterior approach to the thoracolumbar spine spinal stenosis thoracolumbar fracture/instability disc herniation tumors painful motion segment degeneration infections spinal deformities Patient Positioning An unobstructed abdomen is key to successful decompressive surgery The patient is positioned prone on rubber foam blocks (Fig. 12a). Aheadrest with support for mouth, nose and eyes is used to avoid pressure sores ( Fig. 12b). It is important that the abdomen is freely hanging and not compressed ( Fig. 12c). This is particularly important for decompressive surgery where a compressed abdomen can result in congested epidural veins and result in excessive bleeding. 358 Section Surgical Approaches a b c Figure 12. Patient positioning for a posterior thoracolumbar approach a Rubber foam blocks supporting the patient in prone position. b Headrest. c Positioning of the patient with free hang- ing abdomen. Surgical Exposure Landmarks for Skin Incision The landmarks for the posterior approach are: spinous processes posterior superior iliac spine iliac wings The line drawn between the bilateral posterior superior iliac spine usually pro- jects to the disc level of L4–L5 ( Fig. 13a). However, this is unreliable and image intensifier control is necessary in every case. Surgical Approaches Chapter 13 359 ab cd Figure 13. Surgical anatomy of the posterior thoracolumbar approach a Landmarks for skin incision. b Superficial surgical dissection. c Deep surgical dissection. d Muscle retraction with pin- pointed retractors to minimize muscle damage. Note the decortication at L4–S1 on the left side as preparation of the bone graft bed. Superficial Surgical Dissection After the incision of the skin in the midline above the spinous processes and the dissection of the subcutaneous layers, the thoracolumbar fascia is incised with a cautery knife ( Fig. 13b). The paraspinal musculature is subperiosteally detached from the spinous process and the laminae. Sponges are used to push the paraspi- nal muscles laterally and control bleeding by densely packing the created space between the spinous process and the muscle ( Fig. 13c). Care has to be taken not to injure: facet joint capsules Deep Surgical Dissection In spinal fusion cases, the posterolateral bed has to be prepared for the bone graft. Therefore, the multifidus muscle must be detached from the laminae, facet 360 Section Surgical Approaches Pin-pointed retractors minimize soft tissue damage joint and transverse process (Fig. 11d).Whiledissectingthetransverseprocess, the periarticular vessels which cross around the facet joint and transverse pro- cess usually tend to bleed and need to be controlled by electrocautery. We prefer to use pinpointed rather than rack type retractors because it causes less tissue damage. The retractors should be released intermittently ( Fig. 11d). Wound Closure The thoracolumbar fascia needs to be closed over suction drains. The fascia needs to be sutured tightly either by close interrupted or running sutures. Pitfalls and Complications The posterior access is usually a safe approach to the spine. In slim patients, how- ever, the interlaminar window at L5/S1 can lie very superficially and can be injured with the cautery knife causing an unintended durotomy. Landmarks for Screw Inser tion Computer assisted surgery provides a false security in inexperienced hands Screw fixation has become a standardized technique throughout the entire spine. However, the prerequisite for a safe screw insertion is critically dependent on a profound knowledge of the surgical anatomy. Preoperative planning of the screw trajectories with CT scans is mandatory if an altered anatomy (e.g. in spinal deformities) is expected. Computer assisted surgery [7, 42, 55, 60] does not com- pensate for insufficient knowledge of the anatomy and can even be dangerous in inexperienced hands. Cervico-occipital Spine Screw Placement of the Occiput Screw insertion must be below the external occipital protuberance Screw fixation of the occiput should be in the area with the thickest bone, which is in the midline between the superior nuchal and inferior nuchal line [54] ( Fig. 14). Above the superior nuchal line, injuries to the intracranial sinus must be expected. There is a wide variation in thickness of the occipital bone [61]. The maximum thickness of the occipital bone ranges from 11.5 to 15.1 mm in males and from 9.7 to 12.0 mm in females and is found at the level of the external occipi- talprotuberance[15].FixationcanbedoneusingaY-plate[26]orbilateraltita- nium plates [45]. The screws are inserted either in the midline or 2–3 mm para- sagittally, respectively. The parasagittal cortical bone is substantially thinner and ranges between 3 and 7 mm [30]. The screw holes can be prepared using a drill guide (2.5 mm) with an adjustable drill penetration depth. Initially the depth is set at 4 mm and is increased incrementally until the distal cortex is penetrated. In areas of the occiput which are thicker than 7 mm, unicortical fixation is as strong as bicortical fixation [61]. The standard screw diameter is 3.5 mm and sometimes requires pre-taping. In case of a cerebrospinal fluid flow from the hole, insertion ofthescrewsufficestoclosetheleak. Posterior Atlantoaxial Transarticular Screw Fixation The vertebral artery is at risk laterally and the spinal cord medially Atlantoaxial transarticular screw fixation [27, 28] is a frequent stabilization tech- nique for degenerative and traumatic disorders ( Fig. 15a–c). Although lateral image intensifier control is sufficient, we recommend using a simultaneous bipla- Surgical Approaches Chapter 13 361 . respectively. Weakness of the abdominal wall particularly in multiparas can result in abdominal herniations and needs to be repaired. A detailed description of the management of complications is. critically dependent on a profound knowledge of the surgical anatomy. Preoperative planning of the screw trajectories with CT scans is mandatory if an altered anatomy (e.g. in spinal deformities) is. thickness of the occipital bone [61]. The maximum thickness of the occipital bone ranges from 11.5 to 15.1 mm in males and from 9.7 to 12.0 mm in females and is found at the level of the external