Morphologic analysis of the distal humerus with special interest in elbow implant sizing and alignment

This study determined the relationship between the medullary canal axis and the flexion-extension axis of the distal humerus as they relate to implant selection and design for elbow arthroplasty. Computed tomography scans of 40 fresh-frozen cadaveric specimens were analyzed with computer-aided design software. The anterior offset and cubital angle were measured between the 2 axes, and the cross-sectional area and diameter were measured for the medullary canal at various intervals. The anterior offset of the flexion-extension axis from the medullary canal axis was proportional to the length of canal used to determine the stem axis. No correlation was established among the width of the articular surface, anterior-posterior canal curvature, and cubital angle. These findings suggest that modular implants that allow for the variability in the natural anterior bow and articular offset of the distal humerus may enhance proper restoration of the flexion-extension axis of the elbow.