Assessment of Forearm Rotational Control Using 4 Upper Extremity Immobilization Constructs.

Abstract

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. 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. 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. 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.