Palmar mid-carpal instability: My management algorithm

Abstract

Introduction Palmar mid-carpal instability (PMCI) is an uncommon form of non-dissociative carpal instability, seldom reported in Asian population. It is however an important cause of chronic ulnar wrist pain. Diagnosis can be difficult and high index of suspicion is mandatory. Pathomechanics and optimal treatment of PMCI remains uncertain worldwide. We analyze our unique diagnostic approach in Chinese patients for the proposed etiology and evaluate our management outcomes. Methods Between 1997 and 2010, 16 patients diagnosed PMCI were reviewed for their clinical, radiologic and arthroscopic features. All patients were initially managed conservatively with a disease specific anti-carpal supination splint; refractory cases were evaluated by arthroscopy and treated by arthroscopic thermal shrinkage using radio-frequency appliance as an interim or definite surgical intervention. Shrinkage was targeted at the ulnocarpal ligament at the radiocarpal joint and triquetro-hamate ligament at the mid-carpal joint. Shrinkage of dorsal radiocarpal ligament was not attempted to minimize potential complication. Non-responsive or recurrent cases were managed by a newly designed dorsal radio-carpal ligament reconstruction procedure using a pisiform-based split flexor carpi ulnaris (FCU) tendon graft. Clinical outcomes were evaluated at an average of 86 months. Results Seven male and 9 female patients of a mean age 33.9 were diagnosed PMCI. All except one presented with ulnar wrist pain in their dominant hands. The average duration of symptom was 14 months. Most patients reported minor wrist injury before development of symptoms. Fifty percent of patients were associated with generalized ligamentous laxity. Positive mid-carpal clunk test was most sensitive and specific to diagnose PMCI. Other common clinical features included: lax ulnar column, volar sagging of wrist, increased piso-styloid interval, wrist pain aggravated by passive hand supination and not by passive forearm supination, wrist pain upon resisted pronation, which could be partially alleviated by manually supporting the piso-styloid interval. Common arthroscopic findings were excessive joint space at triquetro-hamate interval and reactive synovitis over the ulnar compartments. Nine cases responded well to conservative treatments. Arthroscopic thermal shrinkage was performed in 4 patients with recurrence in 2 cases. Five patients received split FCU tendon graft for ligament reconstruction and all claimed satisfactory results and restored stability at a mean follow-up 86 months. Conclusion PMCI is not rare in Chinese population but can often be missed. Better understanding of its etiologies, pathomechanics and using systematic method of clinical evaluation helps to establish diagnosis, predict prognosis and management outcomes. Many cases are self-limiting and can be expected to improve over time under conservative treatment. Thermal shrinkage offers an interim and minimally invasive measure to control symptom. The new surgical method of dorsal radio-carpal ligament reconstruction with split FCU graft is relatively simple and provides reliable long-term relief of symptom.