Canine Vertebral Screw and Rod Fixation System: Design and Mechanical Testing

Abstract

Objectives To develop the canine vertebral screw and rod fixation system (CVSRF) and to compare the biomechanical properties between CVSRF and the screw and polymethylmethacrylate (Screw-PMMA) technique for internal fixation of the vertebral column in dogs.

Methods The CVSRF consisted of vertebral screws with monoaxial side-loaded head, rods and specific inner screws connecting rod to the screw head. The CVSRF prototype was made from titanium alloy and manufactured by the rapid prototype machine. Vertebrectomy models were simulated by ultra-high-molecular-weight polyethylene blocks and tested with the CVSRF system (n = 8) and the Screw-PMMA technique (n = 8). The models were developed according to the American Society for Testing and Materials (ASTM F-1717–04). The biomechanical parameters were the compressive bending yield load, the compressive bending stiffness, the compressive ultimate load and the load displacement curve.

Results The mean values of the compressive bending yield load, compressive bending stiffness and compressive ultimate load of the CVSRF were significantly higher than those of the Screw-PMMA technique (p < 0.01). The load displacement curve of the CVSRF showed higher rigidity and durability than that of the Screw-PMMA technique.

Clinical Significance This mechanical study indicated that the CVSRF system can be used for canine vertebral stabilization and the biomechanical properties were better than those for the Screw-PMMA device.

Keywords

dog - canine - spine - pedicle screw and rod fixation - vertebral screw

• References

• 1 Jeffery ND. Vertebral fracture and luxation in small animals. Vet Clin North Am Small Anim Pract 2010; 40 (05) 809-828
• 2 Gaines Jr RW. The use of pedicle-screw internal fixation for the operative treatment of spinal disorders. J Bone Joint Surg Am 2000; 82-A (10) 1458-1476
• 3 Meij BP, Suwankong N, Van der Veen AJ, Hazewinkel HA. Biomechanical flexion-extension forces in normal canine lumbosacral cadaver specimens before and after dorsal laminectomy-discectomy and pedicle screw-rod fixation. Vet Surg 2007; 36 (08) 742-751
• 4 Teunissen M, van der Veen AJ, Smit TH, Tryfonidou MA, Meij BP. Effect of a titanium cage as a stand-alone device on biomechanical stability in the lumbosacral spine of canine cadavers. Vet J 2017; 220: 17-23
• 5 Smolders LA, Voorhout G, van de Ven R. , et al. Pedicle screw-rod fixation of the canine lumbosacral junction. Vet Surg 2012; 41 (06) 720-732
• 6 Tellegen AR, Willems N, Tryfonidou MA, Meij BP. Pedicle screw-rod fixation: a feasible treatment for dogs with severe degenerative lumbosacral stenosis. BMC Vet Res 2015; 11: 299
• 7 Stanford RE, Loefler AH, Stanford PM, Walsh WR. Multiaxial pedicle screw designs: static and dynamic mechanical testing. Spine 2004; 29 (04) 367-375
• 8 Kim YY, Choi WS, Rhyu KW. Assessment of pedicle screw pullout strength based on various screw designs and bone densities-an ex vivo biomechanical study. Spine J 2012; 12 (02) 164-168
• 9 Krenn MH, Piotrowski WP, Penzkofer R, Augat P. Influence of thread design on pedicle screw fixation. Laboratory investigation. J Neurosurg Spine 2008; 9 (01) 90-95
• 10 Yamaguchi K, Konishi H, Hara S, Motomura Y. Biocompatibility studies of titanium-based alloy pedicle screw and rod system: histological aspects. Spine J 2001; 1 (04) 260-268
• 11 Watine S, Cabassu JP, Catheland S, Brochier L, Ivanoff S. Computed tomography study of implantation corridors in canine vertebrae. J Small Anim Pract 2006; 47 (11) 651-657
• 12 Smit TH. The use of a quadruped as an in vivo model for the study of the spine - biomechanical considerations. Eur Spine J 2002; 11 (02) 137-144
• 13 Walker TM, Pierce WA, Welch RD. External fixation of the lumbar spine in a canine model. Vet Surg 2002; 31 (02) 181-188
• 14 Jacobs RR, Nordwall A, Nachemson A. Reduction, stability, and strength provided by internal fixation systems for thoracolumbar spinal injuries. Clin Orthop Relat Res 1982; (171) 300-308
• 15 Liu T, Zheng WJ, Li CQ, Liu GD, Zhou Y. Design and biomechanical study of a modified pedicle screw. Chin J Traumatol 2010; 13 (04) 222-228
• 16 Liu YK, Njus GO, Bahr PA, Geng P. Fatigue life improvement of nitrogen-ion-implanted pedicle screws. Spine 1990; 15 (04) 311-317
• 17 Cho W, Cho SK, Wu C. The biomechanics of pedicle screw-based instrumentation. J Bone Joint Surg Br 2010; 92 (08) 1061-1065
• 18 Hsu CC, Chao CK, Wang JL, Hou SM, Tsai YT, Lin J. Increase of pullout strength of spinal pedicle screws with conical core: biomechanical tests and finite element analyses. J Orthop Res 2005; 23 (04) 788-794