Meeting Abstract

75.1  Wednesday, Jan. 6  Kinematics of the Forefoot in Minipigs (Artiodactyla: Suidae) CLIFFORD, A B; Brown University, Providence RI andrew_clifford@brown.edu

Unguligrade foot posture is one where the bones of the foot are elevated from the locomotor substrate, except for the hoofed distal phalanx. Most unguligrade animals (horses and artiodactyls) posses foot joints that are very ginglymal (hinge-like) and are interpreted to restrict movement during locomotion to a parasagittal plane. This study tests whether the motion in minipigs’ forefoot digits is restricted during locomotion and whether motion between foot bones changes in level walking versus downhill steps. XROMM (a novel bi-planar cinefluoroscopy data collection and analyzation procedure) was used to determine the 3-D positions of metacarpals, proximal phalanges, and ungual phalanges of a digit during stance. Level steps, 10cm downhill steps and 15cm downhill steps were compared using the same methods. Analysis of motion using bone models with anatomically-fixed x- (antero-posterior), y- (medio-lateral), and z- (long-axis) axes permitted description of bone rotations. In level steps, minipigs consistently used a small subset of poses at toe-on and toe-off conditions and underwent large antero-posterior rotation (APR), modest long-axis rotation (LAR), and small medio-lateral rotation (MLR). Rotation between consecutive bones yielded joint motion, and the bulk of this motion occurred at the combined interphalangeal joints rather than at the metacarpophalangeal joint. In downhill steps, poses at toe-off were identical to those in level steps while toe-on poses differed. APR and MLR decreased during stance as step height increased, while LAR maintained similar excursions. Most of the motion at joints of the digit is anatomically hinge-like, although there is a consistent MLR and LAR that makes motion of the foot non-parasagittal. Paradoxically, minipigs used straighter foot postures during downhill steps than in level walking.