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Assessment of Forearm Rotational Control Using Four Upper Extremity Immobilization Constructs
Ayesha Rahman, MD, MSE; Nicole Montero-Lopez, MD; Richard Hinds, MD; Michael Gottschalk, MD; Eitan Melamed, MD; John T. Capo, MD
NYU Hospital for Joint Diseases, New York, NY

Introduction: Forearm immobilization techniques are commonly used in the management of distal radius, scaphoid, and metacarpal fractures. The purpose of our study was to compare the degree of rotational immobilization provided by a sugartong splint (SS), short arm cast (SAC), Munster cast (MC), and long arm cast (LAC) at the level of the distal radioulnar joint (DRUJ), carpus, and metacarpals.
Materials and Methods: Seven cadaveric upper extremity specimens were mounted to a custom jig with the ulnohumeral joint fixated in 90 of flexion (Figure 1). 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 motion (supination to pronation) referenced to the ulnar ex-fix pin. Baseline measurements followed by sequential immobilization with well-molded SS, SAC, MC, and LAC were obtained with 1.25, 2.5, and 3.75 ft-lbs of supination and pronation force directed through the metacarpal K-wire. Each condition was tested three times. Digital photographs were taken perpendicular to the ulnar axis to analyze the total arc of motion.
Results: All immobilization constructs demonstrated significantly improved rotational control at the DRUJ, carpus, and metacarpals compared to baseline motion (Tables 1-4). The most effective constructs from least to greatest allowed rotational arcs were LAC, MC, SAC, and SS. Above-elbow constructs (MC, LAC) demonstrated superior immobilization compared to below-elbow constructs (SAC) (p<0.001). Circumferential constructs (SAC, MC, LAC) were superior to the non-circumferential construct (SS) (p<0.001). 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. Extending immobilization proximal to the elbow did not confer additional stability.
Figure 1. Photograph of testing jig with distal radius, scaphoid, and metacarpal K-wires in place for pronosupination measurements.

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