Radiographic Assessment of Bilateral Asymmetry in the Upper Extremities of Living Humans

Objective Injuries resulting from trauma or tumor resection may cause length alterations in the bones of the upper extremities (UE) requiring reconstruction. Direct contralateral bone is often used to determine the appropriate length for reconstruction but fails to account for potential asymmetry. Given the paucity of data assessing asymmetry in living populations and the need for accurate length approximation, we developed a study evaluating UE long bone asymmetry using radiographic imaging in living subjects. Methods Bilateral X-ray images previously obtained for traumatic injury or chronic osseous conditions were retrospectively collected for adult subjects (ages 18-81). After screening, 61 patients met the inclusion criteria: 28 radii, 29 ulnae, and 19 humeri. Three serial measurements were taken, and the median was used for subsequent analysis. Wilcoxon signed-rank tests were performed to assess differences in contralateral bone lengths. Bootstrapping was utilized to obtain sample sizes of 200, 500, and 1000 for each bone. Results The difference in mean absolute length was 27.0 mm for the humerus, 8.6 mm for the radius, and 7.5 mm for the ulna. Neither the left side nor the right side was significantly longer for any bone. In 57.9% (11/19) of patients, the right humerus was longer than the left; in 60.7% (17/28), the right radius was longer than the left; and in 48.3% (14/29), the right ulna was longer than the left. All other measurements showed the left was longer than the right. Wilcoxon signed-rank tests did not find significant differences between contralateral pairs in any direct measurement group. In bootstrap samples, significant differences in length (p ≤ 0.05) were seen in all samples (n = 200, 500, and 1000) for both humerus and radius but only the 1000 sample group for the ulna. Conclusions Direct contralateral measure may be an appropriate method of length estimation for the humerus, radius, and ulna in post-industrial humans.