Rehabilitation of the medial collateral ligament-deficient elbow: An in vitro biomechanical study

The purpose of th is study was to determine the relative contribution of mu scle activity and the effect of forearm position on the stability of the me dial collateral ligament (MCL)-deficient elbow. Simulated active and passiv e elbow flexion with the forearm in both supination and pronation was perfo rmed using a custom elbow testing apparatus. Testing was first performed on intact specimens, then on MCL-deficient specimens. Elbow instability was q uantified using an electromagnetic tracking device by measuring internal-ex ternal rotation and varus-vargus laxity of the ulna relative to the humerus . Compared with the intact elbow, transection of the MCL, with the arm in a vertical orientation, caused a significant increase in internal-external r otation during passive elbow flexion with the forearm in pronation, but for earm supination reduced this instability. Overall, following MCL transectio n the elbow was more stable with the forearm in supination than pronation d uring passive flexion. In the pronated forearm position simulated active fl exion also reduced the instability detected during passive flexion, with th e arm in a varus and valgus gravity-loaded orientation. The maximum varus-v algus laxity was significantly increased with MCL transection regardless of forearm position during passive flexion. We concluded that active mobiliza tion of the elbow with the arm in Vertical orientation during rehabilitatio n is safe in the setting of an MCL-deficient elbow with the forearm in a fu lly supinated and pronated position. Splinting and passive mobilization of the MCL-deficient elbow with the forearm in supination should minimize inst ability and valgus elbow stresses should be avoided throughout the rehabili tation period. Copyright (C) 2000 by the American Society for Surgery of th e Hand.