Load distribution between the radius and ulna through the forearm interosseous membrane: Effects of elbow flexion and Varus-Valgus alignment.

Abstract

The forearm interosseous membrane helps distribute load between the radius and ulna, yet the combined influence of elbow flexion and varus-valgus alignment on load transfer remains unclear. This study aimed to quantify interosseous membrane-mediated load transfer across elbow flexion angles under varus and valgus loading. Seven fresh-frozen cadaveric forearms were tested using a custom setup with tension/compression force sensors mounted to record loads transmitted through the radius and ulna. Specimens were positioned at multiple elbow flexion angles within 0-90° under controlled varus and valgus loading. The interosseous membrane load-transfer rate was calculated from synchronized force data, and conditions were compared statistically (Wilcoxon signed-rank test). The interosseous membrane load-transfer rate was significantly greater under varus than valgus loading (mean ± SD: 24.4 ± 14.8 % vs 10.1 ± 7.9 %, p < 0.001). Across the tested elbow flexion angles, flexion had no significant effect on the load-transfer rate in either alignment condition. Within the tested range, varus-valgus alignment, rather than elbow flexion angle, primarily determines the magnitude of interosseous membrane -mediated load transfer. These findings provide biomechanical insight relevant to understanding injury mechanisms and may inform alignment considerations during rehabilitation or immobilization.