Fig. 2

a A transverse US scan to measure the cross-sectional area (CSA) of the median nerve at the tunnel inlet, which was at the level of the distal wrist crease. The CSAs of the nerve at the middle of the tunnel at the level of the pisiform and the tunnel outlet at the level of the hamate hook were also measured. b The flattening ratio (FR) of the median nerve, calculated by dividing the transverse diameter of the nerve by the anteroposterior diameter