Morphological changes in the interosseous membrane of the forearm during forearm rotation.

[Purpose] Changes in forearm interosseous membrane dynamics during forearm rotation relative to the shoulder joint position remain poorly understood. The purpose of this study was to clarify interosseous membrane dynamics during forearm rotation in shoulder abduction and external rotation positions. [Participants and Methods] We conducted open magnetic resonance imaging on 17 healthy forearms in the prone position. Three limb positions were set for measuring the forearm rotation angle: intermediate, maximum pronation, and maximum supination. Images were obtained with the shoulder joint abducted at 90°and externally rotated at 90°. The forearm interosseous membrane angle was measured at three points: the apex of the forearm interosseous membrane, the radius, and the ulna. The measurement of the interosseous angle was repeated thrice. [Results] Sufficient intra-rater reliability was confirmed for the forearm interosseous membrane angle measurement. The interosseous membrane of the forearm showed a mean dorsal convex shape during forearm pronation (141.7° ± 0.83°), and the mean palmar convex shape during forearm supination (-141.6° ± 0.64°). [Conclusion] This study provides useful information for future research by quantifying the dynamics of the interosseous membrane of the forearm, which is an important soft tissue for forearm rotation. The establishment of a quantitative evaluation method for forearm interosseous morphological changes will help further elucidate forearm rotation movements during sports activities.