Prospective validation of mean metacarpophalangeal joint extension as a measure of diabetes-related fibrotic hand manifestations.
INTRODUCTION: Hand conditions in diabetes, namely, limited joint mobility (LJM), flexor tenosynovitis (FT), carpal tunnel syndrome (CTS), and Dupuytren disease (DD), share a common pathophysiological process involving pro-fibrotic inflammation in flexor structures. A unified, quantitative measure of disease severity across these conditions is lacking, limiting correlational research. We evaluated mean metacarpophalangeal (MCP) joint extension as a potential measure of severity. METHODS: We assessed 2,405 adults, including individuals with type 1 diabetes (n=291), type 2 diabetes (n=877), prediabetes (n=326), and non-diabetic controls (n=911). MCP extension was calculated as the average maximum passive extension of the second to fifth fingers, measured with a protractor. Validity was determined by correlating MCP extension with physician-rated severity (convergent) and hand grip strength and the Duruöz Hand Index (DHI, both divergent). Inter-rater reliability was tested in 128 individuals, and sensitivity to change was evaluated in 143 participants assessed at two time points. RESULTS: Mean MCP extension was significantly lower in individuals with all hand conditions (42.4° LJM, 42.8°FT, 39.9° DD, 51.7 °CTS) than in those without (58.6°, all p<0.05). MCP extension correlated with physician-rated severity (-0.5, p<0.01) and weakly with DHI (R2 = 0.03) and grip strength (R2 = 0.07). Inter-rater reliability was strong (ICC 0.72), and MCP extension demonstrated sensitivity to change, worsening over 8 months (SRM -0.61). CONCLUSION: Mean MCP extension is a valid, reliable, and responsive measure for assessing fibro-inflammatory hand conditions in diabetes. CLINICAL TRIAL REGISTRATION: https://ctri.nic.in/Clinicaltrials/login.php, identifier CTRI/2020/12/030057.
