Computed-tomography-based three-dimensional analysis of bilateral differences in phalanges

Three-dimensional analysis of bones, especially for preoperative planning of corrective osteotomy in fracture malunion, assumes that the bilateral extremities exhibit a symmetrical mirror image when projected onto each other. No studies are available for phalanges. Three-dimensional bone models of all phalanges of 20 healthy participants (40 hands) were created from computed tomography data. For each phalanx, the difference between the left and right sides were assessed with respect to axis of rotation, ulnoradial deviation, flexion-extension and bone length. The average absolute side difference was small, but with significant differences of extension-flexion (mean 1.1°), supination-pronation (mean 1.8°), ulnoradial deviation (mean 0.9°) and translation (mean 0.2 mm). All left proximal phalanges were significantly pronated in comparison to the right side. The differences are likely unimportant, especially in corrective osteotomy using advanced 3D techniques.