Complex Metacarpophalangeal Joint Dislocation (Kaplan's Lesion) of the Index Finger in a 5-year-old Patient: A Case Report.

Introduction: This report highlights a rare case of complex metacarpophalangeal (MCP) joint dislocation, commonly referred to as Kaplan's lesion. This type of dislocation typically results from a hyperextension injury and requires surgical intervention as closed maneuvers are unsuccessful in reducing the dislocation. Surgical reduction for complex MCP joint dislocations is commonly done through classic volar or dorsal approaches. This report presents a case of a complex MCP joint dislocation and the surgical approach taken to address the issue. Case Report: We present a case of a complex MCP joint dislocation in a 5-year-old male patient who sustained a hyperextension injury to his index finger. The patient underwent open reduction surgery using a volar approach due to the buttonholing of the phalangeal head through the volar plate and blockage between the flexor tendons and lumbrical muscle. Following the procedure, the joint was immobilized in a palmar splint at 30° flexion for 2 weeks before being allowed unrestricted mobilization. At the 4-week follow-up, the patient reported being pain-free and had regained nearly full range of motion in the index finger MCP joint. Conclusion: Although there are multiple techniques to address complex MCP dislocation, the classic volar approach is still considered an effective treatment option for pediatric patients with this injury. In such cases, open reduction through a volar approach can enable surgeons to access the joint and address complex dislocations, which are often difficult to manage with closed reduction alone. Consequently, this surgical approach can help achieve a successful reduction and restore the joint's functionality. Therefore, despite the availability of alternative approaches, the classic volar approach should still be considered as a viable option for treating complex MCP joint dislocations in the pediatric population.