Intra-operator repeatability of skin marker derived segment measures and gait kinematics in healthy pigs

There is a lack of biomechanical research into locomotor pathology in pigs despite orthopaedic problems being a major concern for the industry. This study evaluates the intra-operator repeatability of marker placement in pigs undergoing biomechanical investigation. Three pigs were fitted twice per day on five consecutive days with skin markers over anatomical landmarks; data were captured with a 3D optoelectronic system and 10 markers were used here for segment length and gait parameter calculation. There were significant differences between front and hind leg and proximal and distal segment length repeatability. Repeatability showed a similar extent and location variability to human and other quadruped studies. The source of the greatest segment differences was the femoral segment in the hind leg. Segmental differences at the shoulder and elbow joint were limited in this application. For all segments, except the femoral, differences above 0–10 mm were observed at or less than 7% of the marker applications, which may be an acceptable level of disagreement. Gait parameter repeatability generally confirmed the segment length findings and resembled intra-operator achievement in horses. Implications in pigs will depend on the effect size of clinical conditions with an impact on gait parameters. Future studies should determine such effects by recruiting subjects with known clinical conditions whilst controlling for other confounding factors.