Thumb metacarpophalangeal joint palmar plate chronic avulsion in children: diagnosis and treatment.

Introduction: Thumb metacarpophalangeal joint instability can have a considerable functional impairment. Acute injuries are usually overlooked in children due to the high pain threshold and the presence of ligamentous laxity. Chronicity of the injury results in failure of conservative treatment. Literature is poor in defining such injuries. The purpose of our study is to determine the clinical and radiological tools for the diagnosis of metacarpophalangeal joint instability and we propose a simple surgical technique for their management.

Methods: From 2015 till 2019, we present a case series of four patients with chronic post-traumatic thumb metacarpophalangeal joint instability. Patients were assessed for palmar plate avulsion clinically and radiologically using plain X-ray and sonography. Surgical repair through a palmar approach with direct repair of the palmar plate was done in all patients. Patient demographics, complications, and clinical outcomes were recorded.

Results: Mean follow-up was 22.5 months. At the latest follow-up the metacarpophalangeal joint was stable in all patients. They were all pain free except one patient suffered from temporary pain at the dorsum of the metacarpal due to prominence of the suture anchor, which disappeared at 1-year follow-up. They had improvement in pinch strength. Full range of motion was obtained and all the patients have returned to full activity without limitations.

Conclusion: Chronic post-traumatic thumb metacarpophalangeal joint instability results in functional impairment. Clinical suspicion and sonographic assessment can verify the diagnosis. Surgical repair with transosseous sutures or anchors yields satisfactory results in the paediatric age group with the preservation of normal range of motion.