Evaluation of the material properties of the subsynovial connective tissue in carpal tunnel syndrome

Background The purpose of this study was to determine the material properties of the normal carpal tunnel subsynovial connective tissue in response to shear stress. Methods The shear modulus and maximum shear strength were measured with a custom-made micro-tester in 10 specimens of subsynovial connective tissue from 10 wrists in eight patients with idiopathic carpal tunnel syndrome and in 10 specimens from five fresh frozen cadavers without a history of carpal tunnel syndrome. Findings The mean shear modulus was 22.8 (SD 15.4) kPa for the patient group and 2.7 (SD 1.8) kPa for the control group. The mean maximum shear strength was 54.6 (SD 20.3) kPa for the patient group and 23.3 (SD 10.7) kPa for the control group. The values for the patient group were significantly higher than the control group (P < 0.05). Interpretation The material properties of subsynovial connective tissue are altered in patients with idiopathic carpal tunnel syndrome. The impact, if any, of these altered properties on carpal tunnel syndrome remains to be elucidated.