Three-dimensional movements of the pelvis and the lumbar intervertebral joints in walking and trotting dogs.

Current knowledge of the physiological range of motion (ROM) in the canine axial system during locomotion is relatively limited. This is particularly problematic because dogs with back-related dysfunction frequently present for routine consultations. To collect detailed kinematic information and describe the three-dimensional motions of the pelvis and the lumbar spine (i.e. intervertebral joints S1/L7-L2/L1), we recorded ventro-dorsal and latero-lateral X-ray videos of three walking and trotting dogs and reconstructed their pelvic and intervertebral motions using X-ray reconstruction of moving morphology and scientific rotoscoping. Pelvic roll displayed a monophasic motion pattern and the largest ROM with on average 13° and 11° during walking and trotting, respectively. Pelvic yaw had the smallest ROM with on average 5° (walk) and 6° (trot). A biphasic pattern was observed for pelvic pitch with a mean ROM of 8°. At both gaits, the greatest intervertebral motions occurred either in S1/L7 or L7/L6. The intervertebral motions were mono- or biphasic in the horizontal and the transverse body planes and biphasic in the sagittal plane. Cranial to L6/5, the ROM tended to decrease from 3° to <1.5° in all three planes. Our results confirm that pelvic displacement and intervertebral joint movements are tightly linked with pelvic limb action at symmetrical gaits. The overall small movements, particularly cranial to L5, are consistent with the epaxial musculature globally stabilising the spine against the external and internal limb forces acting on the pelvis and the trunk during walking and trotting.