Palmar Midcarpal Instability: The Results of Treatment with 4-Corner Arthrodesis

Purpose: Palmar midcarpal instabitity (PMCI) is one type of nondissociative carpal instability. The optimal treatment for PMCI is uncertain. The purpose of this investigation was to evaluate the results of capitate-lunate-triquetrum-hamate (4-corner) arthrodesis for PMCI, Methods: Over a 10-year period 8 patients were treated with 4-corner arthrodesis for PMCI. The instability was diagnosed clinically and confirmed with cineradiography. The symptomatic instability began in all patients after a notable trauma; 6 of the patients were injured at work and 2 were injured in a motor vehicle accident. Patients were evaluated at an average of 34 months after surgery, Results: Seven of the 8 patients were satisfied with the surgery and 6 of 8 patients had no pain or mild pain. Both patients injured in motor vehicle accidents returned to all preinjury activities. Four of the 6 workers' compensation patients returned to work, 3 at full duty and 1 in a restricted position. Two patients, both with workers' compensation, did not return to their pre-injury jobs. One had occasional moderate pain and the other had chronic pain. The average wrist flexion/extension arc of motion decreased with surgery from 135° to 75°. The average grip strength increased significantly with surgery from 20 kg to 32 kg; however, grip strength remained significantly lower than the opposite side strength of 54 kg. Conclusions: Four-corner arthrodesis is a reasonable option for PMCI. Compared with previous reports of soft tissue reconstruction 4-corner arthrodesis may provide a more reliable solution for this difficult problem.