1. Posterior Cervical Pedicle Screw versus 360° stabilization of the Subaxial Cervical Spine in a Multilevel Vertebral Body Failure Model. An In vitro Biomechanical Study Lukas Bobinski MD 1, Marc Levivier PhD MD 1, Roy Daniels MD 1 and John M. Duff MD, FACS 1 Hussain, Mir BS 2 ; Klocke, Noelle MS 2 ; Yandamouri, Soumya MS 2 ; Bucklen, Brandon PhD 2 1 Neurosurgery Service, Department of Clinical Neurosciences, CHUV, Lausanne, Switzerland 2 Globus Medical Inc., Audubon PA, USA

2. Conflict of interest: none CPS vs. 360° stabilization of the Subaxial Cervical Spine…

3. LMS pros: ▪Easy technique with low rate of radiculopathy (1.4%) ▪Risk for misplacement leading to revision 2.64% per patient ▪Very low risk for vascular injury LMS cons: ▪ Dependent on amount of bone and its quality of lateral mass ▪ Only posterior tension band- not three column fixation ▪ Can cause breakage of lateral mass during insertion (4-7%)

4. CPS vs. 360° stabilization of the Subaxial Cervical Spine… CPS pros: ▪Biomechanical far more stable construct with pull-out strength 2-4 times higher than LMS ▪More resistant in fatigue testing ▪Broken lateral mass can be instrumented-does not depend on amount or bone quality CPS cons: ▪ Steep learning curve ▪ Vascular injury: 0.61% ▪ Radiculopathy: 1.24% ▪ Screws misplacement minimal with use of navigation (1.2%) compared with classical technique (6.7%)

5. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Does CPS fixation suffice for 3 column stabilisation in multilevel vertebral body failure?

6. CPS vs. 360° stabilization of the Subaxial Cervical Spine… ▪10 fresh frozen cadaveric cervical spines (two groups of 5 specimens each) from C2 to Th1 ▪Each specimen tested to set a baseline ▪No history of spinal trauma, malignancy, deformity etc. ▪Radiological investigated to exclude fractures ▪All specimens prepared to mimic severe disruption with drilling though the vertebral bodies of C4-C6 and disruption of middle column ▪ Custom 6 degree of freedom spine motion simulator – Range of Motion (ROM) measured in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) – Load control protocol of ±1.5 Nm and 1.5° per second Material and Methods

7. 1-Intact ROM 2-(ROM) C4-C6 anterior fracture 3- (ROM) Posterior Instrumentation w/ C3&C7 using pedicle screws 4-Wear Simulator for 18000 cycles 5- (ROM) Posterior Instrumentation w/ C3&C7 using pedicle screws 1-Intact ROM 2-(ROM) C4-C6 anterior fracture + Corpetomy 3- (ROM) Posterior Instrumentation w/ C3-C7 using lateral mass screws + cage + plate 4-Wear Simulator for 18000 cycles 5- (ROM) Posterior Instrumentation w/ C3-C7 using lateral mass screws + cage + plate Group 2 Bilateral pedicle screws (C3&C7) Group 1 Bilateral lateral mass screws + spacer + plate (C3-C7) CPS vs. 360° stabilization of the Subaxial Cervical Spine…

8. Group 1: (5 cadaveric cervical spines) ▪360° reconstruction from C3- C7 ( corpectomy+ expandible cage + plate anteriorly) and lateral mass fixation on every level Group 2: (5 cadaveric cervical spines) ▪Cervical Pedicle Screws in highest (C3) and lowest (C7) points of anchoring connected with rods without cross-link

9. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Group 1: – Decreased motion to 8% in flexion-extension, 9% in lateral bending and 38% in axial rotation – After cycling test loading the range of motion increased: 21% FE, 14%LB and 48% AR – There were two specimens with screw loosening: one with both anterior and posterior C7 screws the other with all C7 screws Group 2: – Decreased motion to 32% in flexion-extension (FE), 10% in lateral bending (LB) and 42% in axial rotation (AR) – After cycling test loading the range of motion increased just slightly to: 38% FE, 14%LB and 44% AR – There were one screw toggling at C7 in one specimen

10. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Results

11. CPS vs. 360° stabilization of the Subaxial Cervical Spine… 360 ° reconstruction provides with very strong construct in severe cervical instability Despite less rigid initial fixation CPS provided with more consistent stability following cycling loading In selected cases of anterior column failure, posterior stabilization with CPS may be an option Conclusions

12. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Clinical example ABCD 15 years old male Skiing accident, with severe cervical trauma Central Cord Syndrome (ASIA C)

13. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Clinical example Two years follow-up Both anterior and posterior fusion No lost of alignment Normal neurological examination Unrestricted daily activity ABC ABC

14. CPS vs. 360° stabilization of the Subaxial Cervical Spine… ▪ Coe JD, Vaccaro AR, Dailey AT, et al. Lateral mass screw fixation in the cervical spine: a systematic literature review. J Bone Joint Surg Am 2013;95:2136-43 ▪ Nakashima H, et.al Complications of cervical pedicle screw fixation for non-traumatic lesions: a multicenter study of 84 patients J Neurosurg Spine 2012, 16:238-247 ▪ Katonis P, et. al Lateral Mass Screw Complications Analysis of 1662 Scews J Spinal Disord Tech 24: 7, 415-420 ▪ Yoshihara H, Passias PG, Errico TJ. Screw-related complications in the subaxial cervical spine with the use of lateral mass versus cervical pedicle screws: a systematic review. J Neurosurg Spine 2013;19:614-23 ▪ Kowalski JM, Ludwig SC, Hutton WC, et al. Cervical spine pedicle screws: a biomechanical comparison of two insertion techniques. Spine (Phila Pa 1976) 2000;25:2865-7 ▪ Richter M, Cakir B, Schmidt R. Cervical pedicle screws: conventional versus computer-assisted placement of cannulated screws. Spine (Phila Pa 1976) 2005;30:2280-7 ▪ Abumi K, Shono Y, Ito M, Taneichi H, Kotani Y, Kaneda K:Complications of pedicle screw fixation in reconstructive surgery of the cervical spine. Spine (Phila Pa 1976)25:962-969,2000 References

15. CPS vs. 360° stabilization of the Subaxial Cervical Spine… ▪ Kotani Y., Abumi K., Ito M., Minami A.:Improved accuracy of computer-assisted cervical pedicle screw insertionJ Neurosurg99 (3 suppl) 257-263 2003 ▪ Kast E, Mohr K, Richter HP, Börm W:Complicationsof transpedicular screw fixation in the cervical spine Eur Spine J 15:327-334 2006 ▪ Johnson TL, Kraikovic EE, Lautenschlager EP, Marcu BS:Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout stengths The Spine J 6:667-672, 2006 ▪ Jones EL, Heller JG, Silcox Hal, Hutton WC: Cervical pedicle screws versus lateral mass screws. Anatomic feasibility and biomechanical comparison. Spine (Phila Pa 1976) 1996;22:977-982 ▪ Kotani Y, Cunningham BW, Abumi K and McAfee PC:Biomechanical Analysis of Cervical Stabilisation Systems. An assesment of transpedicular screw fixation in the cervical spine. Spine (Phila Pa 1976)22:2529-2539, 199 ▪Ishikawa Y et al: Clinical accuracy of three-dimensional fluoroscopy-based computer- assisted cervicl pedicle screw placement: a retrospective comparative study of conventional versus computer-assisted cervical pedicle screw placement J Neurosurg Spine 13;606-611, 2010 ▪Ito Y et al: Clinical ccuracy of 3D fluorpscopy-assisted cervical pedicle screw insertion J Neurosurg Spine 9; 450-453, 2008 References

16. CPS vs. 360° stabilization of the Subaxial Cervical Spine… Thank you For your attention