Biomechanical model of distal articular humeral fractures-influence of bone density on the fracture threshold.

INTRODUCTION Working hypothesis: The distal humeral bone density influences supracondylar fracture threshold. The aim of this study was first to develop a reproducible model of intra-articular distal humeral fractures and second to establish a relationship between bone mineral density (BMD) and the fracture threshold of the humerus. MATERIALS AND METHODS An original model of the fracture was developed using ten sawbones. After obtaining a reproducible and clinically relevant fracture model, we tested 21 cadaveric distal humeri for which the BMD was known with a stainless-steel custom-made proximal ulna jig. Fractures were created using a servo hydraulic-testing machine in axial compression to simulate a fall onto an outstretched hand. Fracture lines, load to failure, and rigidity of the bone were recorded based on the stress-strain curves. RESULTS The fracture generation was reliable, reproducible, and clinically relevant (type B2). A significant correlation between the BMD and the fracture threshold was found. Mean threshold was 901.86 N/m2. Mean distal humerus BMD was 0.9097 g/cm2 (r = 0.7321). CONCLUSIONS We developed a reproducible articular fracture of the distal humerus model and found a correlation between the fracture threshold and bone mineral density.