508 AJVR, Vol 68, No. 5, May 2007 B ack problems in horses are often characterized by signs of pain, stiffness, and reduced performance. 1 Physical examination of the equine vertebral column requires detailed palpation of soft tissue and bony struc- tures as well as assessment of segmental and regional spinal mobility. 2 Unfortunately, the clinical assessment of back pain and stiffness is mostly subjective. Objec- tive methods are needed for functional assessment of the vertebral column and evaluation of the therapeutic efficacy of rehabilitative approaches used to treat back problems in horses. Kinematic tools that quantify verte- bral mobility or stiffness have the potential to improve the diagnosis and management of vertebral injuries. Effects of vertebral mobilization and manipulation on kinematics of the thoracolumbar region Kevin K. Haussler, DVM, DC, PhD; Ashley E. Hill, DVM, MPVM, PhD; Christian M. Puttlitz, PhD; C. Wayne McIlwraith, BVSc, PhD Objective—To measure passive spinal movements induced during dorsoventral mobiliza- tion and evaluate effects of induced pain and spinal manipulative therapy (SMT) on passive vertebral mobility in standing horses. Animals—10 healthy adult horses. Procedures—Baseline vertical displacements, applied force, stiffness, and frequency of the oscillations were measured during dorsoventral spinal mobilization at 5 thoracolumbar intervertebral sites. As a model for back pain, fixation pins were temporarily implanted into the dorsal spinous processes of adjacent vertebrae at 2 of the intervertebral sites. Vertebral variables were recorded again after pin placement and treadmill locomotion. In a random- ized crossover study, horses were allocated to control and treatment interventions, sepa- rated by a 7-day washout period. The SMT consisted of high-velocity, low-amplitude thrusts applied to the 3 non–pin-placement sites. Control horses received no treatment. Results—The amplitudes of vertical displacement increased from cranial to caudal in the thoracolumbar portion of the vertebral column. Pin implantation caused no immediate changes at adjacent intervertebral sites, but treadmill exercise caused reductions in most variables. The SMT induced a 15% increase in displacement and a 20% increase in applied force, compared with control measurements. Conclusions and Clinical Relevance—The passive vertical mobility of the trunk varied from cranial to caudal. At most sites, SMT increased the amplitudes of dorsoventral dis- placement and applied force, indicative of increased vertebral flexibility and increased tol- erance to pressure in the thoracolumbar portion of the vertebral column. (Am J Vet Res 2007;68:508–516) ABBREVIATION SMT Spinal manipulative therapy The equine vertebral column is typically modeled as a bowstring bridge with fore and hind cantilevers repre- senting the head and neck (cranially) and sacrum and tail (caudally). 3 The structural and functional relationships of a segmental 3-point bending model suggest that maximal vertical displacements occur at the central portion and are reduced near the supports at either end. Findings of increased regional spinal mobility at T6-T13 in in vitro 4-6 and in vivo 7-9 studies support this hypothesis. However, the lumbosacral junction is also cited as the single inter- vertebral articulation with the highest amplitude of flexion and extension in the thoracolumbar portion of the verte- bral column. 4,9,10 To validate a proposed model of vertebral mobility in standing horses, we were interested in measur- ing peak vertical displacement at 5 intervertebral sites in the thoracolumbar portion of the vertebral column. Spinal manipulative therapy involves the applica- tion of manually applied forces with the intent of re- ducing pain and promoting joint mobility. 11,12 Spinal manipulative therapy is being used with increased fre- quency for the conservative management of back pain in horses. 2 Biomechanical assessment and quantification of manipulative techniques are critical to understanding the mechanical events that occur during a manipulative thrust. 13 Presently, there is limited objective evidence of the mechanical effects of SMT in horses. 14,15 Received September 25, 2006. Accepted December 11, 2006. From the Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853 (Haussler); and the Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences (Hill, McIlwraith), and Department of Me- chanical Engineering, College of Engineering (Puttlitz), Colorado State University, Fort Collins, CO 80523. Dr. Haussler’s present address is Gail Holmes Equine Orthopaedic Research Center, De- partment of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523. Supported by the Harry M. Zweig Memorial Fund for Equine Research, Cornell University, College of Veterinary Medicine. The authors thank Lisa M. Mitchell; Vince Soderholm; and Drs. Amy Snyder, Elisa Salas, and Elizabeth Carothers for technical assis- tance. Address correspondence to Dr. Haussler. Unauthenticated | Downloaded 08/20/22 04:04 AM UTC