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.