846 AJVR • Vol 77 • No. 8 • August 2016 C ervical intervertebral disk herniation with asso- ciated spinal cord injury is a common condition in dogs. 1,2 The conventional ventral slot procedure is the most commonly performed surgical treatment for decompression of the spinal cord following cervical intervertebral disk herniation. 3,4 However, common concerns associated with this surgical procedure in- clude postsurgical instability and subluxation caused, in part, by removal of the dorsal and ventral por- tions of the annulus fibrosus of the disk, disruption of the nucleus pulposus and longitudinal vertebral ligaments, and creation of a bone defect in adjoin- ing vertebral bodies. 5–7 To determine the effect of various surgical procedures on the stability and stiff- ness of the cervical portion of the vertebral column, biomechanical tests have been performed on VMUs Effects of conventional and slanted ventral slot procedures on the biomechanical behavior of the C5-C6 vertebral motion unit in dogs Haisheng Yang PhD Nicolaas E. Lambrechts BVSC, MMED VET Michael Lehner BS Gremah M. Adam BS Rebecca A. Packer MS, DVM Trevor W. Moore DVM Russell P. Main PhD Received May 21, 2015. Accepted October 30, 2015. From the Departments of Basic Medical Sciences (Yang, Packer, Main) and Veterinary Clinical Sciences (Lambrechts, Packer, Moore), College of Veterinary Med- icine, the Weldon School of Biomedical Engineering, Col- lege of Engineering (Lehner, Main), and the Department of Biological Sciences, College of Science (Adam), Pur- due University,West Lafayette, IN 47907. Dr.Yang’s pres- ent address is Department of Pediatric Surgery, Shriners Hospital for Children, McGill University, Montreal, QC H3G 1A4, Canada. Drs. Lambrecht and Packer’s present address is Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523. Address correspondence to Dr. Main (rmain@purdue. edu). OBJECTIVE To compare the effects of conventional and slanted ventral slot procedures on the biomechanical behavior of the C5-C6 vertebral motion unit (VMU) in dogs. SAMPLE 14 vertebral columns (C4 through C7) from canine cadavers. PROCEDURES Specimens were assigned to a conventional or slanted ventral slot group (n = 7/group). For each specimen, the C5-C6 VMU was tested in ventral and dor- sal bending and positive and negative axial torsion before and after surgery. Range of motion (ROM), stiffness, and energy absorption were compared be- tween the 2 groups. RESULTS Both procedures signifcantly increased the ROM and stiffness and signifcant- ly decreased the energy absorption of the C5-C6 VMU in ventral and dorsal bending. Both procedures also increased the ROM in positive and negative axial torsion. In negative torsion, total stiffness and stiffness over the maxi- mum ROM tested decreased less for the slanted slot procedure than for the conventional slot procedure. There were no signifcant differences between procedures for any of the other biomechanical outcomes examined. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the biomechanical response of the C5-C6 VMU to the conventional and slanted ventral slot procedures was not signifcantly different, especially when considering postsurgical instability induced by both procedures. This was most likely due to disruption of the nucleus pulposus and dorsal annulus fbrosus of the disk with both procedures. On the basis of these fndings, neither procedure appeared biomechanically superior. Com- parative clinical studies are warranted to further evaluate the 2 procedures. (Am J Vet Res 2016;77:846–853) obtained from cadavers. 4,8,9 These biomechanical ex- periments have shown that the conventional ventral slot procedure substantially increases the ROM of surgically treated VMUs, compared with the ROM of intact, untreated specimens. The slanted ventral slot procedure has been pro- posed as an alternative to the conventional ventral slot procedure. It was developed with the intention of reducing postsurgical instability by preserving the ventral annulus fibrosis and ventral longitudinal liga- ments. 10,11 However, the effects of this procedure on VMU stiffness and ROM are unknown, and the assump- tion of improved postsurgical stability compared with the conventional ventral slot procedure is untested. Acquiring comparative data regarding biomechanical behavior of the cervical portion of the vertebral col- umn following each of these surgical procedures is im- portant in determining the most appropriate surgical approach for veterinary patients. Thus, the purpose of the study reported here was to compare the effects of ABBREVIATIONS ROM Range of motion VMU Vertebral motion unit Unauthenticated | Downloaded 09/26/22 04:12 AM UTC