Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 39 ppt

ab Figure 14. Landmarks for occipital screw insertion a Posterior view. b Axial view. nar control for optimal screw placement. The medial border of the C2 pedicle (2–5 mm axial diameter) should be palpated with a dissector or a nerve hook. The screw is positioned as medially as possible to avoid injuries to the vertebral artery, which lies immediately laterally. The entry point for screw insertion is about 3 mm cranial to the lower edge of the C2 inferior facet. Usually, there is a small groove at the transition of the inferior facet to the lamina which serves as a landmark for the entry point. The drill is angled to aim at the arch of C1 in a strictly sagittal plane. The screw should pass just below the posterior border of the C1/2 joint. In some cases, the craniocaudal angulation can only be achieved Injuries to the spinal cord or vertebral artery are rare if the technique is applied if the drill is significantly inclined. Rather than dissecting all the posterior mus- cles,wepreferonlytoexposethespinefromC1toC3andchooseapercutaneous insertion of the drill usually at the level of C7–T1 with a tissue protector. Injuries to the vertebral artery or spinal cord are rare if the technique is performed prop- erly [22, 27]. Atlantoaxial Pedicle Screw Fixation The 2nd cervical nerve is at risk when exposing the C1/2 joint An alternative to the transarticular screw fixation is a stabilization of the spine with pedicle screws which are connected with rods [29, 64] ( Fig. 15d–g). The screw entry point in C2 is more lateral (4–5 mm) than the transarticular screw trajectory. The drill is directed 20°–35° cranially and 15°–20° medially. The entry point in C1 is below the lamina and 2–3 mm lateral to the medial edge of the C1, which can be palpated with a dissector. The screw is aimed about 10°–15° medially and 15°–20° cranially. Care has to be taken not to injure the C2 exiting nerve root (greater occipital nerve). Anterior Atlantoaxial Transarticular Screw Fixation A second alternative is an anterior transarticular screw fixation [59]. The screw entrypointis5mmbelowtheC1/2jointlineinthegrooveformedbythebasisof 362 Section Surgical Approaches 52 53 Figure 15. Landmarks for upper cervical spine screw insertions Posterior atlantoaxial transarticular screw fixation: a posterior view; b lateral view; c axial view. Atlantoaxial pedicle screw fixation: d posterior view; e lateral view; f axial view at C2. Anterior atlantoaxial transarticular screw fixation: g anterior view; h lateral view; i axial view. the dens and the lateral mass (Fig. 15h–j). The screw trajectory is angled 25° later- ally and cranially. However, the exposure of the entry point is not easy because it is far up in the cervical spine. During exposure great care has to be taken not to injure the: hypoglossus nerve superior laryngeal nerve Lateral Mass Screw Fixation There are two commonly used techniques for screw placement in the lateral mass of the lower cervical spine. The screw entry point according to Roy-Camille [50] is in the center of the lateral mass and the trajectory is directed 10° outwards rect- angulartotheposteriorcortex.AccordingtotheMagerl technique, the screw’s insertion point lies 2 mm medial and cranial to the facet center. The screw trajec- tory is parallel to the facet joints and angled 20°–25° outwards ( Fig. 16a–c). Magerl’s method exhibits longer screw lengths and is therefore biomechanically Surgical Approaches Chapter 13 363 ab c de f Figure 16. Landmarks for lower cervical spine screw insertions Lateral mass screw fixation: a posterior view; b lateral view; c axial view. Pedicle screw fixation: d posterior view; e lat- eral view; f axial view. superior to the Roy-Camille method [50]. Some studies have reported that the Magerl method is less likely to damage the neurovascular structures [51]. Lower Cervical Spine Pedicle Screw Fixation This screw insertion technique is reserved for the most experienced spine surgeons Pedicle screw fixation in the lower cervical spine is demanding and reserved for the most experienced spine surgeons [38]. The risk potential of spinal cord and vertebral artery injury is high [70]. The pedicle dimensions are not infrequently smaller than the screw [36]. Preoperative CT planning is recommended to rule out anatomical anomalies. Computer assisted surgery may reduce the rate of misplaced screws [35, 60] but does not compensate for lack of profound knowl- edge of the cervical anatomy and surgical experience [2]. The technique accord- ing to Abumi and Kaneda [1] chooses an entry point slightly lateral to the center of the lateral mass and inferior to the facet joint line ( Fig. 16d–f). The cortical bone at the entry point is opened with a burr and the hole is enlarged to bury the pedicle screw (3–4 mm). The screw trajectory is angled 25°–45° medially. A thin pedicle finder is used to dilate the pedicle under lateral image intensifier control. Perforations can be detected with a fine pedicle probe (feeler) ( Fig. 17). In experi- enced hands, the complication rate is low [2, 38]. Thoracic Spine Pedicle Screw Fixation Screw placement in the thoracic spine requires a detailed knowledge of the anat- omy of the thoracic spine. However, it can be done with a high safety margin 364 Section Surgical Approaches Figure 17. Surgical instruments for screw hole preparations a Fine awl. b Thin pedicle finder. c Thick pedicle finder. d Pedicle feeler. when the proper technique is applied [20]. The pedicle morphology of the thoracic and lumbar spine has been thoroughly investigated in several studies [49, 65–67, 73]. The landmarks for screw insertion T2–T11 are below the rim of the inferior facet. Sometimes it is necessary to osteotomize the lateral inferior part of the facet to clearly identify the base of the superior facet. The entry point is at the lateral bor- der. The screw trajectory is angled 20° medially and 10° caudally. When the extrape- dicular technique [14] is used, the entry point is slightly more lateral and the angle to the midline is higher ( Fig. 18a–c ) (see Chapter 3 ). This inside-out-inside tech- nique involves a reduced risk of injuring the medial border of the pedicle [14]. The entry point at T1 is slightly more medial and the screw trajectory is less angled to the midline. The entry point for the pedicle of T12 is at the level of the mammillary process, which is opened/removed with a rongeur ( Fig. 18d–f ). The screw trajectory is angled more medially similarly to the lumbar spine. The screws for adult patients usually have a diameter of 5 (lower thoracic spine) and 6 mm (lower thoracic spine) and have a length of 30–35 mm at T1 and 45–55 mm at T12, respectively. Our preferred technique ( Fig. 17 ) is to use a sharp fine awl to open the cortical bone at the entry point. This position is checked in the lateral plane using an image intensifier. A thin pedicle finder is used to probe the pedicle again under fluoro- Check for potential perforations with a fine pedicle feeler scopic guidance. A fine pedicle feeler is entered into the pedicle hole to verify that the cortical shell of the pedicle is intact particularly medially, inferiorly and anteri- orly. In the lower thoracic spine, a thicker pedicle finder is used to further widen the pedicle. In questionable cases, the screw is inserted somewhat deeper than the base of the pedicle, which can be checked in the lateral view with an image intensi- fier. The screw is then removed and the medial pedicle wall is palpated with the pedicle feeler. When the medial wall is intact the screw can be reinserted. Lumbar Spine Pedicle Screw Fixation The pedicle morphology of the lumbar spine has been accurately described in several studies [41, 49, 56, 62, 67, 74]. Surgical Approaches Chapter 13 365 abc de f Figure 18. Landmarks for thoracic pedicle screw insertions Thoracic pedicle fixation at the level of T6: a posterior view; b lateral view; c axial view. Note the alternative extrapedicu- lar screw position on the right side. Thoracic pedicle fixation at the level of T12: d posterior view; e lateral view; f axial view. Several techniques have been described. We prefer a more lateral insertion point with a larger angulation to the midline, which is also biomechanically more sta- ble than a straight anterior screw insertion. The pedicle entrance point is at the lateral border of the base of the superior articular process. The same technique is used as described for the insertion of thoracic screws. The screw trajectory is angled 20°–25° to the midline. In the sagittal plan the screws take a course paral- lel to the upper vertebral endplates ( Fig. 19a–c). A double sacral screw fixation provides a strong sacral anchorage Knowledge of the size and anatomy of the pedicle is required, but also an under- standing of the topography of nerve and vascular structures in relation to the pedi- cle is indispensable for safe pedicle placement. The nerve roots are located directly atthemedial-inferiorborderofthepedicle.Screwsshouldnotpenetratetheante- rior cortex except in cases in which this is absolutely necessary to enhance the pull- out resistance. The screws should not be in contact with an artery because pulsa- tion can cause vessel wall erosion and the formation of an aneurysm. Sacral and Iliac Screw Fixation The most frequent technique is screw placement in the first sacral pedicle located just below the L5/S1 facet angled medially 20° cranially toward the anterior cor- ner of the promontorium. Another alternative is to insert the screws at a 30°–45° lateral and cranial direction into the sacral alae ( Fig. 19d–g). Both screw posi- 366 Section Surgical Approaches ab c de f g hi j Figure 19. Landmarks for lumbosacral and iliac screw insertions Lumbar pedicle screw fixation at the level of L4: a posterior view; b lateral view; c axial view. Sacral screw fixation tech- niques (red convergent S1 screw, green divergent S1 screw, blue divergent S2 screw): d posterior view; e lateral view; f axial view at S1; g axial view at S2. Pelvic fixation in the iliac wing: h posterior view; i lateral view; j axial view. tions can be combined to enhance the sacral fixation [6, 62, 74]. The insertion point for the S2 screw is in the middle between the first and second dorsal foram - ina. The screws should be directed 5° caudally and 30° laterally [6]. The slightest risk of injury is from placement of S1 pedicle screws. Lateral screw placement car- ries a risk of injury to the internal iliac vein or the lumbosacral plexus. Anterior cortical penetration of the S2 segment could cause injury of the bowel [44, 52]. Surgical Approaches Chapter 13 367 In neuromuscular scoliosis, fixation to the pelvis is often required to treat pelvic obliquity or because of insufficient screw purchase at the sacrum. The original technique was introduced by Allan and Ferguson as the so-called Galveston tech- nique with insertion of a contoured rod into the iliac wing [3]. However, this technique has the disadvantage of resulting in a painful loosening of the rod in the iliac wing with time (“windshield wiper effect”). A modification is to use a screw instead of the contoured rod for pelvic fixation, which results in an excel- lentbonypurchase.Anevenstrongerfixation is the so-called MW sacropelvic fixation [5] (see Chapter 24 ). The pelvic screw fixation starts with decortication of the posterior superior iliac spine with a Luer. A pedicle finder is inserted and aimed 20°–40° laterally and caudally aiming at the iliac notch and superior to the acetabulum ( Fig. 19h–j). A pedicle feeler is used to check that the iliac cortical laminae have not been perforated. Simultaneously the length is determined. Usu- ally, 7–8 mm strong 80- to 100-mm-long screws can be inserted. Recapitulation Surgical planning. Preoperative planning and a profound knowledge of the surgical anatomy are the prerequisites to achieving the goals of surgery and helping to avoid serious complications. Ana- tomical dissection studies are extremely valuable and supplement in-depth study of textbooks on surgical anatomy. The surgeon must proactively consider potential extensions of the approach and must be familiar with this anatomy. Surgical approaches. Image intensifier or radio- graphic verification of the correct level is an abso- lute must. Wrong level surgery is one of the most frequent complications. The anteromedial ap- proach to the cervical spine approaches the anteri- or column through anatomical planes. Great care must be taken to retract the carotid artery laterally and not medially. Particularly, the recurrent laryn- geal and the superior laryngeal nerve are at risk dur- ing this approach. The posterior approach to the cervical spine can be associated with heavy bleed- ing. For exposure of the craniocervical junction, the muscle insertion at the spinous process of C2 should be detached with an osteoligamentous flap. The vertebral artery is at risk when exposing C1. A deleterious complication of thoracotomy is wrong site surgery. The neurovascular bundle below the rib must be preserved to avoid painful neuralgias. The parietal pleura should be closed whenever pos- sible. Correct placement of the chest tubes mini- mizes postoperative pulmonary complications. The thoraco-phrenico-lumbotomy gives an excellent exposure of the thoracolumbar junction but is ma- jor surgery. The dissection should start with the ret- roperitoneal abdominal approach to minimize peri- toneal tears. Corresponding stay sutures at both sides of the diaphragma incision facilitate repair when closing the wound. The thoracic duct is at risk when exposing the thoracolumbar junction but dif- ficult to identify during preparation. The anterolate- ral retroperitoneal approach to the lumbar spine L5–L2iseasilypossibleeveninobesepatients.A muscle splitting approach is recommended. In males, the psoas muscle can cover the whole lateral aspect of the anterior column. Rather than dissect- ing and retracting the psoas posterolaterally, a pso- as splitting approach is the preferred alternative for discectomy and interbody fusion. The anterior lum- bar retroperitoneal approach approaches the spine through anatomical planes. The liberation of the peritoneal sac requires a dissection of the poste- rior rectus sheath at the arcuate line. When retract- ing the common iliac vein medially to expose the L4/5 disc space, the ascending lumbar vein must be controlled and ligated prior to vessel retraction. The posterior thoracolumbar approach results in con- siderable collateral damage to the spinal muscles, which can be minimized by mini-access surgery and use of pinpointed retractors which are intermittent- ly released. The target level must be identified prior to surgery to avoid unnecessary and extensive de- tachment of back muscles. Landmarks for screw fixation. Occipital screw fixa- tion must be accomplished in the midline between the superior nuchal and inferior nuchal line where the bone is thick enough to bury a screw. Posterior transarticular atlantoaxial screw fixation puts the vertebral artery at risk laterally and the spinal cord medially. Atlantoaxial pedicle screw fixation is an 368 Section Surgical Approaches alternative but the 2nd cervical nerve is at risk when exposing the atlantoaxial joint. Lateral mass screws aresafewhenperformedwiththepropertech- nique. Cervical pedicle screws carry a high risk of neurovascular complications and are preserved for the most experienced spine surgeons. Thoracic and lumbar pedicle screws can be placed with minimal risk with detailed anatomical knowledge. The use of a fine awl to open the cortical bone (image guided verification in the lateral and possibly ante- roposterior plane), bluntly probing the pedicle and verification with a pedicle feeler, is a safe method for screw hole preparation. Sacral screws can be placed in a divergent direction at S1 and S2 as well as in a convergent direction at S1. A double sacral screw fixation provides a strong anchorage at the sacrum. For neuromuscular deformities with pelvic obliq- uity, an iliac screw provides a solid pelvic fixation. Key Articles These texthooks are recommended for a study of the surgical anatomy of the spine and surgical approaches: Bauer RF, Kerschbaumer F, Poisel S (ed) (1993) Atlas of spinal operations. Thieme, Stutt- gart Nazarian S (2007)Surgicalanatomyofthespine.In:AebiM,ArletV,WebbJ.AOSPINE manual: principles and techniques, vol. 1.Thieme,Stuttgart,pp131 – 239 Louis R (1983) Surgery of the spine. Surgical anatomy and operative approaches. Springer, Heidelberg Wat kins RG (2003) Surgical approaches to the spine. Springer, Heidelberg References 1. Abumi K, Kaneda K (1997) Pedicle screw fixation for nontraumatic lesions of the cervical spine. Spine 22:1853–63 2. AbumiK,ShonoY,ItoM,TaneichiH,KotaniY,KanedaK(2000)Complicationsofpedicle screwfixationinreconstructivesurgeryofthecervicalspine.Spine25:962–9 3. Allen BL, Ferguson RL (1982) The Galveston technique for L rod instrumentation of the sco- liotic spine. Spine 7:276–284 4. Apfelbaum RI, Kriskovich MD, Haller JR (2000) On the incidence, cause, and prevention of recurrent laryngeal nerve palsies during anterior cervical spine surgery. Spine 25:2906–12 5. Arlet V, Marchesi D, Papin P, Aebi M (1999) The ’MW’ sacropelvic construct: an enhanced fixation of the lumbosacral junction in neuromuscular pelvic obliquity. Eur Spine J 8:229–31 6. Asher MA, Strippgen WE (1986) Anthropometric studies of the human sacrum relating to dorsal transsacral implant designs. Clin Orthop Relat Res:58–62 7. Berlemann U, Monin D, Arm E, Nolte LP, Ozdoba C (1997) Planning and insertion of pedicle screws with computer assistance. J Spinal Disord 10:117–24 8. Bertagnoli R, Vazquez RJ (2003) The Anterolateral TransPsoatic Approach (ALPA): a new technique for implanting prosthetic disc-nucleus devices. J Spinal Disord Tech 16:398–404 9. Bertalanffy H, Eggert HR (1989) Complications of anterior cervical discectomy without fusion in 450 consecutive patients. Acta Neurochir (Wien) 99:41–50 10. Burke JP, Gerszten PC, Welch WC (2005) Iatrogenic vertebral artery injury during anterior cervical spine surgery. Spine J 5:508–14; discussion 514 11. Burrington JD, Brown C, Wayne ER, Odom J (1976) Anterior approach to the thoracolum- bar spine: technical considerations. Arch Surg 111:456–63 12. Capener N (1954) The evolution of lateral rhachotomy. J Bone Joint Surg Br 36-B:173–9 13. Cauchoix J, Binet JP (1957) Anterior surgical approaches to the spine. Ann R Coll Surg Engl 21:234–43 14. Dvorak M, MacDonald S, Gurr KR, Bailey SI, Haddad RG (1993) An anatomic, radiographic, and biomechanical assessment of extrapedicular screw fixation in the thoracic spine. Spine 18:1689–94 Surgical Approaches Chapter 13 369 15. Ebraheim NA, Lu J, Biyani A, Brown JA, Yeasting RA (1996) An anatomic study of the thick- ness of the occipital bone. Implications for occipitocervical instrumentation. Spine 21:1725–9; discussion 1729–30 16. Ebraheim NA, Lu J, Brown JA, Biyani A, Yeasting RA (1996) Vulnerability of vertebral artery in anterolateral decompression for cervical spondylosis. Clin Orthop Relat Res:146–51 17. Ebraheim NA, Lu J, Skie M, Heck BE, Yeasting RA (1997) Vulnerability of the recurrent laryngeal nerve in the anterior approach to the lower cervical spine. Spine 22:2664–7 18. Eleraky MA, Llanos C, Sonntag VK (1999) Cervical corpectomy: report of 185 cases and review of the literature. J Neurosurg 90:35–41 19. Fang HS, Ong GB, Hodgson AR (1964) Anterior spinal fusion: The operative approaches. Clin Orthop Relat Res 35:16–33 20. Fisher CG, Sahajpal V, Keynan O, Boyd M, Graeb D, Bailey C, Panagiotopoulos K, Dvorak MF (2006) Accuracy and safety of pedicle screw fixation in thoracic spine trauma. J Neuro- surg Spine 5:520–6 21. Fraser RD, Gogan WJ (1992) A modified muscle-splitting approach to the lumbosacral spine. Spine 17:943–8 22. Gebhard JS, Schimmer RC, Jeanneret B (1998) Safety and accuracy of transarticular screw fixation C1-C2 using an aiming device. An anatomic study. Spine 23:2185–9 23. GejoR,KawaguchiY,KondohT,TabuchiE,MatsuiH,ToriiK,OnoT,KimuraT(2000)Mag- netic resonance imaging and histologic evidence of postoperative back muscle injury in rats. Spine 25:941–6 24. Gejo R, Matsui H, Kawaguchi Y, Ishihara H, Tsuji H (1999) Serial changes in trunk muscle performance after posterior lumbar surgery. Spine 24:1023–8 25. Gieger M, Roth PA, Wu JK (1995) The anterior cervical approach to the cervicothoracic junction. Neurosurgery 37:704–9; discussion 709–10 26. Grob D, Dvorak J, Panjabi M, Froehlich M, Hayek J (1991) Posterior occipitocervical fusion. A preliminary report of a new technique. Spine 16:S17–24 27. Grob D, Jeanneret B, Aebi M, Markwalder TM (1991) Atlanto-axial fusion with transarticu- larscrewfixation.JBoneJointSurgBr73:972–6 28. Grob D, Magerl F (1987) Surgical stabilization of C1 and C2 fractures. Orthopade 16:46–54 29. Harms J, Melcher RP (2001) Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine 26:2467–71 30. Hertel G, Hirschfelder H (1999) In vivo and in vitro CT analysis of the occiput. Eur Spine J 8:27–33 31. Hodgson AR, Stock FE (1956) Anterior spinal fusion: a preliminary communication on the radical treatment of Pott’s disease and Pott’s paraplegia. Br J Surg 44:266–75 32. Hodgson AR, Stock FE, Fang HS, Ong GB (1960) Anterior spinal fusion. The operative approach and pathological findings in 412 patients with Pott’s disease of the spine. Br J Surg 48:172–8 33. Hoski JJ, Eismont FJ, Green BA (1993) Blindness as a complication of intraoperative posi- tioning. A case report. J Bone Joint Surg Am 75:1231–2 34. Jung A, Schramm J, Lehnerdt K, Herberhold C (2005) Recurrent laryngeal nerve palsy dur- ing anterior cervical spine surgery: a prospective study. J Neurosurg Spine 2:123–7 35. Kamimura M, Ebara S, Itoh H, Tateiwa Y, Kinoshita T, Takaoka K (2000) Cervical pedicle screw insertion: assessment of safety and accuracy with computer-assisted image guidance. J Spinal Disord 13:218–24 36. Karaikovic EE, Daubs MD, Madsen RW, Gaines RW, Jr. (1997) Morphologic characteristics of human cervical pedicles. Spine 22:493–500 37. Kasodekar VB, Chen JL (2006) Monocular blindness: a complication of intraoperative posi- tioning in posterior cervical spine surgery. Singapore Med J 47:631–3 38. Kast E, Mohr K, Richter HP, Borm W (2006) Complications of transpedicular screw fixation in the cervical spine. Eur Spine J 15:327–34 39. Kawaguchi Y, Matsui H, Tsuji H (1996) Back muscle injury after posterior lumbar spine sur- gery. A histologic and enzymatic analysis. Spine 21:941–4 40. Kawaguchi Y, Yabuki S, Styf J, Olmarker K, Rydevik B, Matsui H, Tsuji H (1996) Back muscle injury after posterior lumbar spine surgery. Topographic evaluation of intramuscular pres- sure and blood flow in the porcine back muscle during surgery. Spine 21:2683–8 41. Krag MH, Weaver DL, Beynnon BD, Haugh LD (1988) Morphometry of the thoracic and lumbar spine related to transpedicular screw placement for surgical spinal fixation. Spine 13:27–32 42. Laine T, Schlenzka D, Makitalo K, Tallroth K, Nolte LP, Visarius H (1997) Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine 22:1254–8 43. Lee MJ, Bazaz R, Furey CG, Yoo J (2007) Risk factors for dysphagia after anterior cervical spine surgery: a two-year prospective cohort study. Spine J 7:141–7 44. Licht NJ, Rowe DE, Ross LM (1992) Pitfalls of pedicle screw fixation in the sacrum. A cadaver model. Spine 17:892–6 370 Section Surgical Approaches 45. Lieberman IH, Webb JK (1998) Occipito-cervical fusion using posterior titanium plates. Eur Spine J 7:308–12 46. Lo CY, Kwok KF, Yuen PW (2000) A prospective evaluation of recurrent laryngeal nerve paralysisduringthyroidectomy.ArchSurg135:204–7 47. Lu J, Ebraheim NA, Nadim Y, Huntoon M (2000) Anterior approach to the cervical spine: surgical anatomy. Orthopedics 23:841–5 48. Manfredini M, Ferrante R, Gildone A, Massari L (2000) Unilateral blindness as a complica- tion of intraoperative positioning for cervical spinal surgery. J Spinal Disord 13:271–2 49. Marchesi D, Schneider E, Glauser P, Aebi M (1988) Morphometric analysis of the thoraco- lumbar and lumbar pedicles, anatomo-radiologic study. Surg Radiol Anat 10:317–22 50. McCullen GM, Garfin SR (2000) Spine update: cervical spine internal fixation using screw and screw-plate constructs. Spine 25:643–52 51. MerolaAA,CastroBA,AlongiPR,MathurS,BrkaricM,VignaF,RiinaJP,GorupJ,HaherTR (2002) Anatomic consideration for standard and modified techniques of cervical lateral mass screw placement. Spine J 2:430–5 52. Mirkovic S, Abitbol JJ, Steinman J, Edwards CC, Schaffler M, Massie J, Garfin SR (1991) Ana- tomic consideration for sacral screw placement. Spine 16:S289–94 53. Miscusi M, Bellitti A, Peschillo S, Polli FM, Missori P, Delfini R (2007) Does recurrent laryn- geal nerve anatomy condition the choice of the side for approaching the anterior cervical spine? J Neurosurg Sci 51:61–4 54. Mullett JH, McCarthy P, O’Keefe D, McCabe JP (2001) Occipital fixation: effect of inner occipital protuberance alignment on screw position. J Spinal Disord 14:504 –6 55. Nolte LP, Visarius H, Arm E, Langlotz F, Schwarzenbach O, Zamorano L (1995) Computer- aided fixation of spinal implants. J Image Guid Surg 1:88 –93 56. Olsewski JM, Simmons EH, Kallen FC, Mendel FC, Severin CM, Berens DL (1990) Mor- phometry of the lumbar spine: anatomical perspectives related to transpedicular fixation. JBoneJointSurgAm72:541–9 57. Pait TG, Killefer JA, Arnautovic KI (1996) Surgical anatomy of the anterior cervical spine: thediscspace,vertebralartery,andassociatedbonystructures.Neurosurgery39:769–76 58. Raynor RB (1983) Anterior or posterior approach to the cervical spine: an anatomical and radiographic evaluation and comparison. Neurosurgery 12:7–13 59. Reindl R, Sen M, Aebi M (2003) Anterior instrumentation for traumatic C1-C2 instability. Spine 28:E329–33 60. Richter M, Cakir B, Schmidt R (2005) Cervical pedicle screws: conventional versus com- puter-assisted placement of cannulated screws. Spine 30:2280–7 61. Roberts DA, Doherty BJ, Heggeness MH (1998) Quantitative anatomy of the occiput and the biomechanics of occipital screw fixation. Spine 23:1100–7; discussion 1107–8 62. Roy-Camille R, Saillant G, Mazel C (1986) Internal fixation of the lumbar spine with pedicle screwplating.ClinOrthopRelatRes:7–17 63. Southwick WO, Robinson RA (1957) Surgical approaches to the vertebral bodies in the cer- vical and lumbar regions. J Bone Joint Surg Am 39-A:631 –44 64. Stulik J, Vyskocil T, Sebesta P, Kryl J (2007) Atlantoaxial fixation using the polyaxial screw- rod system. Eur Spine J 16:479–84 65. Vaccaro AR, Rizzolo SJ, Allardyce TJ, Ramsey M, Salvo J, Balderston RA, Cotler JM (1995) Placement of pedicle screws in the thoracic spine. Part I: Morphometric analysis of the tho- racic vertebrae. J Bone Joint Surg Am 77:1193–9 66. Vaccaro AR, Rizzolo SJ, Balderston RA, Allardyce TJ, Garfin SR, Dolinskas C, An HS (1995) Placement of pedicle screws in the thoracic spine. Part II: An anatomical and radiographic assessment. J Bone Joint Surg Am 77:1200–6 67. Weinstein JN, Rydevik BL, Rauschning W (1992) Anatomic and technical considerations of pedicle screw fixation. Clin Orthop Relat Res:34–46 68. Wiltse LL, Bateman JG, Hutchinson RH, Nelson WE (1968) The paraspinal sacrospinalis- splittingapproachtothelumbarspine.JBoneJointSurgAm50:919–26 69. Wolfe SW, Lospinuso MF, Burke SW (1992) Unilateral blindness as a complication of patient positioning for spinal surgery. A case report. Spine 17:600–5 70. Xu R, Kang A, Ebraheim NA, Yeasting RA (1999) Anatomic relation between the cervical pedicle and the adjacent neural structures. Spine 24:451–4 71. Yamaki K, Saga T, Hirata T, Sakaino M, Nohno M, Kobayashi S, Hirao T (2006) Anatomical study of the vertebral artery in Japanese adults. Anat Sci Int 81:100–6 72. Zeidman SM, Ducker TB, Raycroft J (1997) Trends and complications in cervical spine sur- gery: 1989–1993. J Spinal Disord 10:523–6 73. Zindrick MR, Wiltse LL, Doornik A, Widell EH, Knight GW, Patwardhan AG, Thomas JC, Rothman SL, Fields BT (1987) Analysis of the morphometric characteristics of the thoracic and lumbar pedicles. Spine 12:160–6 74. Zindrick MR, Wiltse LL, Widell EH, Thomas JC, Holland WR, Field BT, Spencer CW (1986) A biomechanical study of intrapeduncular screw fixation in the lumbosacral spine. Clin Orthop Relat Res:99–112 Surgical Approaches Chapter 13 371 . provides a strong sacral anchorage Knowledge of the size and anatomy of the pedicle is required, but also an under- standing of the topography of nerve and vascular structures in relation to the. the rate of misplaced screws [35, 60] but does not compensate for lack of profound knowl- edge of the cervical anatomy and surgical experience [2]. The technique accord- ing to Abumi and Kaneda. study of the surgical anatomy of the spine and surgical approaches: Bauer RF, Kerschbaumer F, Poisel S (ed) (1993) Atlas of spinal operations. Thieme, Stutt- gart Nazarian S (2007)Surgicalanatomyofthespine.In:AebiM,ArletV,WebbJ.AOSPINE manual: