A Novel Method for the Objective Assessment of Thenar Atrophy

Abstract

Purpose: Although thenar atrophy is caused by a variety of clinical conditions, it is commonly associated with carpal tunnel syndrome. Thenar atrophy has been mostly assessed subjectively. The purposes of the study are to test a simple, novel, objective and quantitative test for the assessment of thenar atrophy; and to correlate this test with subjective evaluation of thenar atrophy. Methods: The apparatus consisted of a box with a clear glass sheet on the top uncovered surface, with a digital camera placed in the base of the box. Group 1 included 106 healthy volunteers with a total of 212 hands. Group 2 was formed from 36 patients with a total of 72 hands with carpal tunnel syndrome. Thenar atrophy was classified subjectively as none, mild, moderate and severe. Patients and subjects were asked to press their hands facing down on the glass sheet and digital photos were taken. The technique relies on the fact that the area where pressure is exerted on the palm blanches. Photos were transferred to photo processing software. After enhancement the photos were transferred to an image analysis software. The thenar area (A) and the rest of the palm area (B) were measured. The thenar ratio was calculated as A divided by A plus B multiplied by hundred. Results: Hands with thenar atrophy had a statistically significant lower thenar ratio than healthy hands (19.9±6.7 vs 35.6±8.0; P value <0.0001). Subjective assessment of atrophy correlated with the thenar ratio. Conclusions: This method can be used as a simple objective test for the assessment and follow-up of thenar atrophy.