Ligament fibre recruitment of the elbow joint during gravity-loaded passive motion: An experimental study

Background Knowledge of elbow collateral ligament length during passive motion is essential in understanding ligament physiology and pathology, such as tightness and instability. Methods Five anatomical unembalmed specimens were passively placed in six flexion positions together with three forearm rotations, using equipment with gravity as motion force. These 18 positions were recorded using CT-scan. Three-dimensional data of ligament insertions were obtained through anatomical millimetre sections. Ligament length was measured in each position. Findings In neutral rotation, the lateral collateral ligament was long between 0° and 30° as well as at 90°, and short between about 60° and 120° of flexion. In pronation, it was long at about 0° and between 60° and 120°, short at about 30° of flexion. In supination, it was long at about 30° and 90° and short between 120° and 150° of flexion. In any forearm rotation, the highest length of the anterior bundle of the ulnar collateral ligament was measured at about 90°, its smallest length between 120° and 150° of flexion, position at which the posterior bundle length was greatest. Interpretation At 60° of flexion, the collateral ligaments were slackened in any forearm rotations. Forearm rotation plays an indirect role in the posterolateral stability of elbow as it changes length of the lateral collateral ligament. This ligament can be tested passively at 90° of flexion in supination, the anterior bundle of the ulnar collateral ligament between 0° and 30° in neutral rotation and the posterior bundle between 120° and 150° in neutral rotation.