Assessment of thumb positioning in the treatment of ulnar collateral ligament injuries. A laboratory study.

In the treatment of ulnar collateral ligament injuries in the metacarpophalangeal joint of the thumb, a cast or splint is often molded with the thumb and hand positioned so the patient can return quickly to a particular sport or activity. However, it is unknown whether a given position of immobilization or whether an early rehabilitation program will compromise ligament healing by causing undue tension in the ligament. To better define acceptable positions for thumb immobilization and a safe range of motion, this laboratory study measured strain in the ulnar collateral ligament at different degrees of metacarpophalangeal joint flexion. Ligament strain was found to increase with increasing joint flexion; the most significant increases in strain occurred as the joint moved from 0 degree to 25 degrees of flexion, with the dorsal portion of the ligament demonstrating greater strain than the palmar portion. Based on these results, immobilization of the metacarpophalangeal joint in excessive flexion and unrestricted early rehabilitation exercises should be done with caution and guided by the grade of injury or the quality of repair.