The Thenar Index: An Objective Assessment and Classification of Thenar Atrophy Based on Static Hand Imprints and Clinical Implications

Abstract

The aims of this study were to test the effectiveness of the subjective clinical evaluation and to search for any possibility of constituting an objective assessment system for the diagnosis of thenar atrophy based on static hand imprints. Static hand imprints were obtained from normal subjects (group A, n = 116) and carpal tunnel syndrome patients with thenar atrophy (group B, n = 26). Thenar index and the bilateral thenar index ratio were defined. Cutoff values were considered by analyses with receiver operating characteristic curves. No statistically significant difference could be demonstrated in thenar index values of dominant and nondominant hands between genders and age groups (p > 0.05). A statistically significant difference was observed between severity groups in group B (p < 0.05). There was a statistically significant difference between thenar index and bilateral thenar index ratio values of groups A and B (p < 0.05). Cutoff values were considered a thenar index of 31 and a bilateral thenar index ratio of 0.8, which revealed acceptable specificity (95.3 percent) and sensitivity (77.4 percent). A new quantitative classification for thenar atrophy severity is proposed. Understanding the true onset and natural progression of thenar atrophy can only be anticipated with the aid of an objective assessment system. Currently, this method should be regarded as a system for patient records and comparison for presurgical and postsurgical data. The authors believe that the thenar index classification has some merit for future use. It seems that additional objective and scientific evaluation systems and novel approaches are still needed to demystify the true nature of carpal tunnel syndrome.