Assessment of Forearm Rotational Control Using 4 Upper Extremity Immobilization Constructs

Background: Forearm immobilization techniques are commonly used to manage distal radius, scaphoid, and metacarpal fractures. The purpose of our study was to compare the degree of rotational immobilization provided by a sugar-tong splint (STS), short arm cast (SAC), Munster cast (MC), and long arm cast (LAC) at the level of the distal radioulnar joint (DRUJ), carpus, and metacarpals. Methods: Seven cadaveric upper extremity specimens were mounted to a custom jig with the ulnohumeral joint fixated in 90° of flexion. Supination and pronation were unrestricted. K-wires were placed in the distal radius, scaphoid, and metacarpals using fluoroscopic guidance to measure the total arc of rotation referenced to the ulnar ex-fix pin. Baseline measurements followed by sequential immobilization with well-molded STS, SAC, MC, and LAC were obtained with 1.25, 2.5, and 3.75 ft-lb of supination and pronation force directed through the metacarpal K-wire. Each condition was tested 3 times. Digital photographs were taken perpendicular to the ulnar axis to analyze the total arc of motion. Results: The most effective constructs from least to greatest allowed rotational arcs were LAC, MC, SAC, and STS. Above-elbow constructs (MC, LAC) demonstrated superior immobilization compared with below-elbow constructs (SAC) ( P < .001). Circumferential constructs (SAC, MC, LAC) were superior to the noncircumferential construct (STS) ( P < .001). There were no significant differences between the MC and LAC in all conditions tested. Conclusions: Both circumferential and proximally extended immobilization independently improved rotational control of the wrist. However, extending immobilization proximal to the epicondyles did not confer additional stability.