Comprehensive surface-based morphometry reveals the association of fracture risk and bone geometry

Surface-based morphometry method is advantageous in its objectivity and increased capability in detecting focal morphological changes, but has not been applied in bone-related research. Orthopedics research in human has confirmed the association of the bone geometry in proximal femur and its fracture. In this study, surface-based morphometry is used to test the hypothesis that there is relationship between bone geometry and fracture risk of the proximal sesamoid bone (PSB) in forelimbs of Thoroughbred racehorses. The PSB surfaces were extracted from CT images of nonfractured forelegs (i.e., right foreleg in this study) of 6 racehorses with fractures in the contralateral (i.e., left) foreleg, and the right forelegs of 6 matched controls. Significant differences were detected at the abaxial margin of the medial PSB base which was found to be up to 3.5 mm more prominent in the fracture-group compared to the control-group. This study demonstrated a successful application of computational morphometry in bone. The detected anatomical differences may lead to a larger moment arm generated via the medial branch of the suspensory apparatus, increasing pressure on the sesamoid surface, and thus potentially predisposing to fracture. Findings from this pilot study not only increase the likelihood of accurate PSB fracture risk assessment, but also shed light on investigating the influence of sports and exercise on human athletes.