This study used ultrasound imaging to establish the relationship of the median nerve and its deformation by accompanying structures within the carpal tunnel. The authors obtained cross-sectional images of the wrists of volunteers without carpal tunnel syndrome. Subjects performed full fist and motion of the long finger only. The displacement and deformation of the median nerve was quantified and analyzed.
Displacement distance of the median nerve was not statistically different with long finger only flexion compared with full fist flexion. There was variation in the displacement of the long finger FDS tendon with full fist compared with single tendon motion. The aspect ratio decreased and circularity increased with long finger only flexion. This demonstrates statistically significant increases in deformation of the median nerve with long finger only flexion compared with full fist. They advocate using this model to investigate flexor tendon displacement in the pathology of carpal tunnel syndrome.