Kinematic motion patterns of the cranial and caudal canine cervical spine.

OBJECTIVE To define the kinematic motion patterns of the canine cervical spine, with a particular emphasis on identifying differences between the cranial (C(2)-C(4)) and caudal (C(5)-C(7)) segments, and to determine the significance of coupled motions (CM) in the canine cervical spine. STUDY DESIGN Cadaveric biomechanical study. SAMPLE POPULATION Cervical spines of 8 Foxhounds. METHODS Spinal specimens were considered free of pathology based on radiographic, computed tomography, and magnetic resonance imaging examinations. All musculature was removed without damaging ligaments or joint capsules. Spines were mounted in a customized pure-moment spine testing jig, and data were collected using an optoelectronic motion capture system. Range of motion, neutral zone and CM in flexion/extension, left/right lateral bending and left/right axial rotation were established. Data were analyzed using mixed-effects maximum likelihood regression models. RESULTS Total flexion/extension did not change across the 4 levels. There was no difference between flexion and extension, and no CM was identified. Lateral bending was not different across levels, but tended to be greater in the cranial spine. Axial rotation was ∼2.6 times greater in the caudal segments. Lateral bending and axial rotation were coupled. CONCLUSIONS Kinematics of the cranial and caudal cervical spine differed markedly with greater mobility in the caudal cervical spine.