Background: Injuries to the radial collateral ligament of the thumb metacarpophalangeal joint are less common than injuries to the ulnar side. Therefore, published data on this subject are scarce. An innovative method of radial collateral ligament repair is hereby presented, placing emphasis on the long-term results. This technically simple method was developed to allow for a biological joint stabilization based on functional and anatomical considerations. The key concept is to reestablish joint stability by spanning the tendinous portion of the insertion of the abductor pollicis brevis over the radial side of the metacarpophalangeal joint.Methods: Nine patients with rupture of the radial collateral ligament were treated by means of the abductor pollicis brevis-plasty. All patients suffered from subacute or chronic radial ligament insufficiency. To determine the subjective results of the repair, a score was developed grading the patient's ranking of the results achieved by the abductor pollicis brevis-plasty. All patients graded the results on a scale from 1 (excellent) to 6 (unacceptable).Results: Patients were operated on 37.1 +/- 14.6 days after trauma. Long-term examination was performed after 39 +/- 14.5 months. The patients showed a high satisfaction score of 1.7 +/- 0.5, with good mobility of the metacarpophalangeal 1 joint (range of motion, 52.2 +/- 6.7 degrees).Conclusion: Favorable results suggest that the abductor pollicis brevis-plasty is a suitable, safe, and technically feasible procedure for the operative treatment of chronic instability of the thumb metacarpophalangeal joint after radial hyperadduction trauma and complete rupture or deinsertion of the radial collateral ligament.