Background Midcarpal instability is a term for a collection of poorly understood conditions where the proximal row of the carpus is unstable. The most common type of midcarpal instability is palmar midcarpal instability (PMCI). Treatment for PMCI includes nonoperative proprioceptive retraining of the wrist, splints, and strengthening. If this fails, various authors have suggested several different fusions, tenodesis procedures, or capsular shrinkage. There are no long-term case series in the literature. Objective The aim of this study is to assess the long-term results of arthroscopic capsular shrinkage when used for PMCI of the wrist. Methods A prospective cohort study of patients who underwent arthroscopic capsular shrinkage for PMCI was performed. Ethical board approval was given for this study. All patients were followed up and reviewed independently from the operating surgeon. Assessment included a structured questionnaire, disabilities of the arm, shoulder and hand (DASH) questionnaire, and clinical examination using a goniometer. PMCI was assessed objectively with the anterior drawer test and radiological imaging was only performed if clinically relevant to the residual symptoms. Results Thirteen patients (15 wrists) underwent arthroscopic capsular shrinkage for PMCI. Twelve patients (14 wrists) were available for clinical review with a follow-up rate of 92.3%. The mean time from index procedure to final review was 12 years (range: 10-14years). The symptoms of instability had completely resolved in nine wrists (7 patients). Only 2 of the 14 wrists had symptoms that were reproduced with a positive anterior drawer test. All other wrists were stable on objective assessment. The mean DASH score had improved from pre op of 34 to post op of 12.1 and at 12-year follow-up this had deteriorated minimally to 15.3. Assessment of the range of motion showed an average increase in range of flexion/extension by 22 degrees. Patient satisfaction was excellent. The patients rated that nine wrists were much better than presurgery, three as better, one unchanged, and one worse. Discussion/Conclusion There are no studies looking at the long-term natural history of treatments for PMCI. The lead author proposes a grading system for symptomatic PMCI that has been retrospectively applied to this cohort. It is a grading system from 1 to 4 and is based on a treatment algorithm. This is the first long-term study from any joint, where the results of capsular shrinkage have been maintained over time. In this series, we have not seen any deleterious effect from possible mechanoreceptor injury. We suspect that functioning mechanoreceptors are more relevant in the unstable joint, than the structurally stable joint. The authors propose that thermal capsular shrinkage is an effective and durable option for use in mild-to-moderate forms of PMCI.
Keywords: arthroscopic; capsular; instability; midcarpal; shrinkage.
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