Finger position alters the median nerve properties within the carpal tunnel: a pre-post MRI comparison study.

PURPOSE: The purpose of this study was to compare the properties of the median nerve and the flexor retinaculum within the carpal tunnel with Magnetic Resonance Imaging (MRI) under two conditions: (a) fingers extended, and (b) fingers in an isometric squeeze grip.

METHODS

Thirty-Four volunteers participated in this experimental study. The flexor retinaculum and median nerve characteristics were measured during both conditions using MRI.

RESULTS

The isometric squeeze grip condition resulted in significant palmar bowing of the flexor retinaculum (t = 7.67, p<.001), a significant flattening-ratio of the median nerve (t = 4.308, p<.001), and no significant decrease in the cross-sectional area of the median nerve (t = 2.508, p = 0.017).

CONCLUSION

The isometric squeeze grip condition resulted in anatomical deformations within the carpal tunnel, possibly explained by the lumbrical muscles incursion into the carpal tunnel during finger flexion.