Residual rotation of forearm amputation: cadaveric study

BACKGROUND: The purpose of this study was to investigate residual rotation of patients with forearm amputation and the contribution of involved muscle to residual rotation. METHODS: Testing was performed using five fresh-frozen cadaveric specimens prepared by isolating muscles involved in forearm rotation. Amputation was implemented at 25 cm (wrist disarticulation), 18 cm, or 10 cm from the tip of olecranon. Supination and pronation in the amputation stump were simulated with traction of involved muscle (supinator, biceps brachii, pronator teres, pronator quadratus) using an electric actuator. The degree of rotation was examined at 30°, 60°, 90°, and 120° in flexion of elbow. RESULTS: Average rotation of 25 cm forearm stump was 148° (SD: 23.1). The rotation was decreased to 117.5° (SD: 26.6) at 18 cm forearm stump. It was further decreased to 63° (SD 31.5) at 10 cm forearm stump. Tendency of disorganized rotation was observed in close proximity of the amputation site to the elbow. Full residual pronation was achieved with traction of each pronator teres and pronator quadratus. Although traction of supinator could implement residual supination, the contribution of biceps brachii ranged from 4 to 88% according to the degree of flexion. CONCLUSIONS: Close proximity of the amputation site to the elbow decreased the residual rotation significantly compared to residual rotation of wrist disarticulation. The preservation of pronosupination was 80% at 18 cm forearm stump. Although the pronator teres and the pronator quadratus could make a full residual pronation separately, the supinator was essential to a residual supination.