A Novel Interpositional Arthroplasty Technique for Chronic, Painful Thumb Metacarpophalangeal Joint Instability—A Case Report

Background/Objectives: Chronic injuries of the radial collateral ligament (RCL) of the thumb metacarpophalangeal (TMCP) joint are becoming an increasingly common clinical challenge. In cases without degenerative changes, surgical treatment with ligament reconstruction may be effective. However, coexisting cartilage damage significantly worsens treatment outcomes and may necessitate arthrodesis, which limits joint mobility and carries a high risk of complications. In the present case, an alternative surgical approach was employed—combining RCL reconstruction using a palmaris longus (PL) tendon with interpositional arthroplasty. The aim of this report is to present an innovative method for treating chronic TMCP instability with focal cartilage damage through simultaneous ligament reconstruction and interpositional grafting using autologous tissue. Methods/Case presentation: A 60-year-old male manual laborer presented with chronic TMCP joint instability and pain impairing daily activities and preventing him from working. Intraoperatively, cartilage damage to the head of the first metacarpal was identified. Radial collateral ligament reconstruction was performed using the Glickel technique with the PL tendon, incorporating two modifications: (1) advancement of a capsuloligamentous flap as an interpositional graft, and (2) additional reinforcement of the dorsal capsule with a tendon strip.