Introduction: Recently, motions preserved lumbar fusion has been attempt to prevent the adjacent segment degeneration using semi-rigid instrumentations.The purpose of this study is comparing of segmented ROM at the implanted L4-L5 level and the cranial and caudal adjacent levels and of whole lumbar spine ROM after dynamic stabilizations, Bio-flex?R and Cosmic?R system.

Methods: Thirty patients with back pain and neurogenic claudication due to grade 1 spondylolisthesis at the level of L4-L5 were treated either with decompression and Bio-flex?R(n=17) or with decompression and Cosmic?R(n=13) and also were not performed discectomy at any level. All patients underwent neutral, flexion and extension radiographs before surgery and at 2 year follow-up postoperatively. ROM was assessed at the implantation level (L4-L5), the adjacent cranial/caudal levels (L3-L4/L5-S1), and at the whole lumbar spine with neutral lumbar lordosis (from L1 to S1). The radiologic results were analyzed using linear mixed model test and p value of less than 0.05 were considered statically significant.

Results: In both groups, there were significant reduction of the segmental ROM at implantation L4-L5 level (p=0.039 and 0.011). Postoperative whole lumbar ROM and ROM at adjacent cranial (L3-L4)/caudal (L5-S1) level did not change significantly compared with preoperative data in both groups. And between groups, there were not statistically significant differences in ROM changes.

Conclusions: According to our radiologic results, lumbar dynamic stabilizations using pedicle screws with a nitinol spring rod system and a hinged screw head system may decrease motion of instability level and both device systems may maintain the ROM of adjacent segments. We suggest that these outcomes may play a role in decrease the risk of ASD after dynamic stabilization at least 2 yrs follow-up.

Patient Care: It will be able to decrese the conventional fusion.

Learning Objectives: Participants should be able to describe the mechanism of dynamic stabilization.

References: Axelsson P, Johnsson R, Stromqvist B (2007) Adjacent segment hypermobility after lumbar spine fusion: no association with progressive degeneration of the segment 5 years after surgery. Acta Orthop 78:834-839 2. Bellini CM, Galbusera F, Raimondi MT, Mineo GV, Brayda-Bruno M (2007) Biomechanics of the lumbar spine after dynamic stabilization. J Spinal Disord Tech 20:423-429 3. Bozkus H, Senoglu M, Baek S, Sawa AG, Ozer AF, Sonntag VK, Crawford NR (2010) Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization. J Neurosurg Spine 12:183-189 4. Cakir B, Carazzo C, Schmidt R, Mattes T, Reichel H, Kafer W (2009) Adjacent segment mobility after rigid and semirigid instrumentation of the lumbar spine. Spine (Phila Pa 1976) 34:1287-1291 5. Fay LY, Wu JC, Tsai TY, Wu CL, Huang WC, Cheng H (2012) Dynamic stabilization for degenerative spondylolisthesis: Evaluation of radiographic and clinical outcomes. Clin Neurol Neurosurg 6. Gedet P, Haschtmann D, Thistlethwaite PA, Ferguson SJ (2009) Comparative biomechanical investigation of a modular dynamic lumbar stabilization system and the Dynesys system. Eur Spine J 18:1504-1511 7. Harrop JS, Youssef JA, Maltenfort M, Vorwald P, Jabbour P, Bono CM, Goldfarb N, Vaccaro AR, Hilibrand AS (2008) Lumbar adjacent segment degeneration and disease after arthrodesis and total disc arthroplasty. Spine (Phila Pa 1976) 33:1701-1707 8. Heo DH, Cho YJ, Cho SM, Choi HC, Kang SH (2011) Adjacent Segment Degeneration After Lumbar Dynamic Stabilization Using Pedicle Screws and a Nitinol Spring Rod System With 2-year Minimum Follow-up. J Spinal Disord Tech 9. Ilharreborde B, Shaw MN, Berglund LJ, Zhao KD, Gay RE, An KN (2011) Biomechanical evaluation of posterior lumbar dynamic stabilization: an in vitro comparison between Universal Clamp and Wallis systems. Eur Spine J 20:289-296 10. Kanayama M, Togawa D, Hashimoto T, Shigenobu K, Oha F (2009) Motion-preserving surgery can prevent early breakdown of adjacent segments: Comparison of posterior dynamic stabilization with spinal fusion. J Spinal Disord Tech 22:463-467