Non pedicular fixation techniques for the treatment of spine

scoliosis Non pedicular fixation

1. Non- pedicular Fixation Techniques For The Treatment Of Spinal Deformity Dr Sabique Junior resident Moderator – Dr Balaji Zacharia Associate professor Dept of Orthopaedics GMC Kozhikode

2. INTRODUCTION Review advantages, disadvantageous and complications with non- pedicular fixation techniques of spine Comprehensive literature search in pubmed , scopus , web of science database (1990-2019) 10 methods of non- pedicular fixation

3. Non- Pedicular fixation techniques In-Out-In Screws Fusion Mass Screws Fusion Mass hooks Sublaminar Wires Sublaminar Bands Laminar Hooks Transverse Process Hooks Transverse process Wires Transverse process Bands Spinous process Tethering

4. 1,600 titles and abstracts pertaining to nonpedicular fixation 213 articles met inclusion criteria

5. Pedicle

6. Pedicular screw fixation screw placements into the vertebrae is first described by King   as early as 1944 Pedicle screw fixation was reported by Michele and Krueger in 1949 In 1959 Boucher first described pedicle screw fixation for posterior spinal fusion Since then its used in various constructs

7. Traumatic fractures with instability Stabilization after neural decompression for tumor / infection Deformity correction

8. favoured angle screw :polyaxial mode for engagement with the rod and a monoaxial mode for segmental derotation . screw with no locking cap Reduction screw

9. some points to note.. The respective facet joint space and the middle of the transverse process are the most important reference points for pedicle screw insertion Medial to the medial wall of the pedicle lies the dural sac.

10. Inferior to the medial wall is the nerve root . It is more dangerous to penetrate the pedicle medially or inferiorly as it may damage these structures

11. Limitations The safe placement of pedicle screws can be complicated by distorted and variable anatomy in cases of severe spinal deformity or skeletal dysplasia pedicles on the concave side of thoracic curves are narrower than on the convex side There is 3 times more chance of misplacement of pedicle screw in an abnormal pedicle compared to normal(21%versus 7%) Wide surgical exposure

12. complications Neurologic spinal cord / nerve root Dural tear – CSF leak / Fistula Vascular injury Pleural injury

13. “In patients with thoracic AIS , concave-side d pedicle screws at T5-T9 were associated with the highest risk of spinal cord injury , while convex-side d pedicle screws at T4-T9 were associated with the highest risk of pleural injury ” 9. Sarlak AY, Buluç L, Sarisoy HT, Memis¸o ˘ glu K, Tosun B. Placement of pedicle screws in thoracic idiopathic scoliosis: a magnetic resonance imaging analysis of screwplacement relative to structures at risk. Eur Spine J. 2008 May;17(5):657-62. Epub 2008 Feb 27

14. Pedicle fracture Long fusion construct – junctional problems Screw breakage Screw loosening and construct failure

15. “Prevalence of osteoporosis among patients with AIS is much higher than in the general pediatric population and may increase the risk of pedicle screw loosening and construct failure 10 ” 10. Li XF, Li H, Liu ZD, Dai LY. Low bone mineral status in adolescent idiopathic scoliosis. Eur Spine J. 2008 Nov;17(11):1431-40. Epub 2008 Aug 28.

16. PROXIMAL JUNCTIONAL KYPHOSIS Increase of more than 10°–20°in the proximal junctional angle (PJA). Cobb angle between the lower endplate of upper instrumented vertebrae (UIV) and upper end plate of two vertebrae above (UIV+2 )

17. Proximal junctional failure is defined as the presence of a symptomatic kyphosis with pain, neurological deficit and deformity with or without associated failure of the upper fixation Abrupt biomechanical transition between a rigidly fixed long-fusion construct and a relatively mobile, noninstrumented spine contributes to the development of proximal junctional kyphosis and proximal junctional failure 57,58 58. Aubin CE, Cammarata M, Wang X, Mac- Thiong JM. Instrumentation strategies to reduce the risks of proximal junctional kyphosis in adult scoliosis: a detailed biomechanical analysis. Spine Deform. 2015 May;3(3):211-8. Epub 2015 Apr 23.

18. Why Non- Pedicular fixation techiques ? Dysplastic pedicles are relatively common among scoliosis Provides a strong fixation in osteoporotic bone Minimize Junctional problems

19. 1. In-Out-In Screws Extra Pedicular screws placed more laterally than pedicle screws, through the transverse process, lateral aspect of the pedicle, rib, and vertebral body Trajectory is far away from spinal cord Used in upper and middle thoracic spine where pedicles are relatively small

20. Insertion point – Tip of Transverse process just medial to posterior side of rib EXTRAPEDICULAR SCREW PEDICULAR SCREW

21. Advantages Larger safety zone for screw placement – screw with greater length and diameter can be used Greater bone-screw contact – engages 4-5 cortices Similar reduction in ROM compared to transpedicular screw Higher pull-out strength

22. Kwan et al. – studied 2020 transpedicular screw in 140 patients reports that critical perforation rate of 2.2%, including 2 symptomatic medial perforations , 6 screws abutting the right lung , and 4 screws abutting the aorta 14. Kwan MK, Chiu CK, Gani SM, Wei CC. Accuracy and safety of pedicle screw placement in adolescent idiopathic scoliosis patients: a review of 2020 screws using computed tomography assessment. Spine (Phila Pa 1976). 2017 Mar;42(5):326-35.

23. 2. FUSION MASS SCREWS Indicated in Revision spinal deformity surgery inserted coronally and medially across the posterolateral fusion mass to achieve stable fixation

24. Intraoperative photograph of freehand placement of fusionmass screws in revision surgery for kyphoscoliosis in a patient with neurofibromatosis.

25. 3. Fusion mass Hooks Safe and effective in revision cases In a retrospective case series using this multiple-hook technique, 6 of 8 adult patients with spinal deformity had favorable outcomes 19 . Despite the limited sample size and duration of follow-up, the deformity correction was well maintained in most of the patients. 19. Liu N, Wood KB. Multiple-hook fixation in revision spinal deformity surgery for patients with a previous multilevel fusion mass: technical note and preliminary outcomes. J Neurosurg Spine. 2017 Mar;26(3):368-73. Epub 2016 Dec 9

26. A:  Burring the placement site for a hook on the fusion mass.  B:  Preparing a tunnel to accommodate the hook.  C and D:  The claw formation is made up of two hooks facing toward each other. 

27.  Preoperative CT image ( A ) and radiograph ( B ) of patient who was diagnosed with a flat-back deformity show the massive fusion mass from a previous spinal fusion in 1978. She underwent an anterior-posterior combined corrective surgery wherein multiple hooks were used to fixate the previous fusion mass between T-10 and L-2. On radiographs obtained 30 months postoperatively ( C and D )

28. 4. Sublaminar Wires 1977, Eduardo Luque introduced a growth-guidance construct using rods and sublaminar wires for segmental spinal fixation in children with scoliosis – “ Luque trolley” Designed to guide spine growth while maintaining correction.

29. A  and  B,  After division, wire is crimped on laminar surface of each side of spinous process

30. Subsequent studies have demonstrated that the Luque trolley fails to maintain spinal growth. However, more recent growth-guidance techniques(e.g., Shilla procedure, modern Luque trolley) have produced better clinical results 22-25. 22. McCarthy RE, McCullough FL. Shilla growth guidance for early-onset scoliosis: results after a minimum of five years of follow-up. J Bone Joint Surg Am. 2015 Oct 7;97(19):1578-84. 23. Ouellet J. Surgical technique: modern Luqu´e trolley, a self-growing rod technique. Clin Orthop Relat Res. 2011 May;469(5): 1356-67.

31. Advantages Superior correction of hypokyphosis Help to prevent Adjacent segment disease following lumbar spine fusion

32. Complications Spinal cord injury - upto 4.6% - transient paresthesia at a single nerve root level Delayed neurologic deficits due to epidural bleeding, cord edema or wire irritation Laminar cut through or fracture Wire breakage

33. Ultrahigh molecular weight polyethylene (UHMWPE) wires softer, flexible reduce the incidence of neurologic complications and construct failure. less osseous cutout, safer removal, and less friction while sliding along the rods fail by stretching unlike metal wires, which usually fail by abruptly snapping or breaking

34. 5. Sublaminar Bands Introduced in 2003 Deformity correction in both coronal and sagittal plane Universal clamp implant (Zimmer) Polyester band Metal clamp Locking screw https://youtu.be/99ypkimi47Y

35. Advantages Prevent development of proximal junctional kyphosis – UIV & UIV+1 Hybrid construct with pedicle screw sublaminar bands achieve superior correction in sagittal plane less risk of spinal cord injury compared to wires

36. Distribute stress over a larger area – greater reduction force , less chance of lamina fracture Hongo et al . found that sublaminar bands have a higher load to failure compared with wires, hooks, and transverse process bands 47 47. Hongo M, Ilharreborde B, Gay RE, Zhao C, Zhao KD, Berglund LJ, Zobitz M, An KN. Biomechanical evaluation of a new fixation device for the thoracic spine. Eur Spine J. 2009 Aug;18(8):1213-9. Epub 2009 Apr 29.

37. Complications Intraoperative clamp failure Laminar fracture – overtensioning Dural injury Posterior prominence of proximal instrumentation Aseptic soft tissue reaction with granuloma

38. 6. Laminar Hooks Laminar position is ideal for hook placement and has strongest purchase of any hooks Indicated when pedicles are too small or concave for screw placement

39. Improve fixation strength of pedicle screw within osteoporotic bone may offer fixation strength similar to that of pedicle screws in osteoporotic bone 51 May prevent proximal junctional kyphosis in patients with low bone mineral density 56 51. Hackenberg L, Link T, Liljenqvist U. Axial and tangential fixation strength of pedicle screws versus hooks in the thoracic spine in relation to bone mineral density. Spine ( Phila Pa 1976). 2002 May 1;27(9):937-42. 56. Metzger MF, Robinson ST, Svet MT, Liu JC, Acosta FL. Biomechanical analysis of the proximal adjacent segment after multilevel instrumentation of the thoracic spine: do hooks ease the transition? Global Spine J. 2016 Jun; 6(4):335-43. Epub 2015 Aug 21.

40. Laminar hook insertion. Laminar hooks may be placed facing rostrally or caudally. For placement of a rostral -facing hook, a small laminotomy of the superior portion of the lamina below the level of fixation may be required (  A  ). Because of the width of the lumbar laminae , it is often possible to affix a rostrally directed hook to the lamina of a vertebral body in conjunction with a pedicle screw (  B  ). This configuration aids resistance to screw pullout in cantilever beam constructs without incorporating additional motion segments (  C  ). Caudally directed hooks are placed following a laminotomy of the inferior portion of the lamina above the level of fixation. Caudally facing hooks cannot be placed on the same vertebra as a pedicle screw because of the apposition of the screw and hook connectors.

41. Complications Neurologic injury Hook migration Hook loosening and or displacement may occur in upto 16.7%cases 53-55 53. Been HD, Kalkman CJ, Traast HS, Ongerboe de Visser BW. Neurologic injury after insertion of laminar hooks during Cotrel-Dubousset instrumentation. Spine ( Phila Pa 1976). 1994 Jun 15;19(12):1402-5.

42. 7. Transverse Process Hooks Transverse process hooks at the UIV provide a more gradual transition to normal motion compared with pedicle screws in long fusion constructs 57,58 . 57. Thawrani DP, Glos DL, Coombs MT, Bylski - Austrow DI, Sturm PF. Transverse process hooks at upper instrumented vertebra provide more gradual motion transition than pedicle screws. Spine ( Phila Pa 1976). 2014 Jun 15;39(14): E826-32.

43. hook inserted in a downgoing manner around the superior portion of the transverse process.

44. 8.Transverse Process wire 9.Transverse Process Bands Passed underneath the transverse processes of the thoracic spine near the costovertebral junction

45. Advantages Lateral location – Can be placed more safely and distracted with greater force compared with sublaminar counterparts 64 assist in derotation of the spine 64. Strickland BA, Sayama C, Briceño V, Lam SK, Luerssen TG, Jea A. Use of subtransverse process polyester bands in pediatric spine surgery: a case series of 4 patients with a minimum of 12 months’ follow-up. J Neurosurg Pediatr. 2016 Feb;17(2):208-14. Epub 2015 Oct 30.

46. Limitations congenital anomalies - hypoplastic or conjoined transverse processes Transverse process fracture and lamina fracture Poor bone density in old patients

47. 10. Spinous Process Tethering Produce a more gradual transition of segmental stiffness and motion at the proximal ends of constructs – prevent PJK

48. Rate of proximal junctional kyphosis was significantly lower in the tether group compared with the non-tether group (26.7% compared with 45.3 %) 67 Incidence of proximal junctional failure was also lower in the ligament-augmentation group (4% compared with 18 %) Safaee MM, Deviren V, Dalle Ore C, Scheer JK, Lau D, Osorio JA, Nicholls F, Ames CP. Ligament augmentation for prevention of proximal junctional kyphosis and proximal junctional failure in adult spinal deformity. J Neurosurg Spine. 2018 May;28(5):512-9. Epub2018 Feb 23. 67. Buell TJ, Buchholz AL, Quinn JC, Bess S, Line BG, Ames CP, Schwab FJ, Lafage V, Shaffrey CI, Smith JS. A pilot study on posterior polyethylene tethers to prevent proximal junctional kyphosis after multilevel spinal instrumentation for adult spinal deformity. Oper Neurosurg (Hagerstown). 2019 Feb 1; 16(2):256-66.

49. Summary Non pedicular fixation techniques preferred in certain cases of spinal deformity Sublaminar bands and laminar hooks may provide stronger fixation in osteoporotic bone. Sublaminar bands and laminar hooks, spinous process tethers, and transverse process hooks may prevent the development of proximal junctional kyphosis and proximal junctional failure

50. Non- pedicular techniques is often limited by their reliance on intact posterior elements and high rates of failure in patients with lowbone mineral density Despite all the challenges, Pedicle screws remain the anchor of choice in deformity correction because of their ability to engage all 3 columns of the spine, safe correction in all 3 planes , and allow a ease multilevel construct assembly.

51. THANK YOU ALL

52. Reference JBJS reviews Campbell’s operative orthopaedics Clinical key - Elsevier Idiopathic scoliosis – HSG treatment guide Youmans and winn Neurological surgery Journal of Neurosurgery