Anatomic localization of motor points of wrist flexors

The aim of this study was to determine the location of the motor points and the intramuscular branches of the wrist flexors in relation to bony landmarks.

Sixteen limbs from eight adult cadavers were anatomically dissected. The motor branch points of the flexor carpi radialis and flexor carpi ulnaris muscles and the proximal limit points and the distal limit points in relation to a reference line connecting the medial epicondyle and the pisiform bone or one connecting the medial epicondyle and the base of the second metarcarpal bone were identified.

For the flexor carpi radialis muscles, the motor branch points were located at a distance of 27% ± 6% of the reference line, whereas the proximal limit points and the distal limit points were located at a distance of 21% ± 5% and 37% ± 8% of the reference line. For the flexor carpi ulnaris muscles, the corresponding data were 32% ± 8%, 23% ± 6%, and 43% ± 9%.

The results may assist in enhancing accuracy when localizing points for neuromuscular blockade of the wrist flexors. The optimal area for flexor carpi radialis muscle injection is at a quarter point and that for flexor carpi ulnaris muscle injection is at one-third point along each reference line from the medial epicondyle.