The prevalence of flexor digitorum superficialis and profundus muscle bellies beyond the proximal limit of the carpal tunnel: a cadaveric study.

A descriptive study was performed on 28 female (mean donor age, 64+/-21 years) and 26 male cadavers (mean donor age, 68+/-21 years) of mixed racial origin randomly sampled from 2 departments of anatomy. The objectives of the study were to determine the prevalence among the study population of the presence of flexor digitorum profundus and flexor digitorum superficialis muscle bellies within the proximal limit of the carpal tunnel and to investigate whether there were any sex, age, or stature differences in the study group. The female sample showed a 46% prevalence of muscle bellies in the tunnel versus only 7.8% for the male sample. The mean muscle belly distance from the proximal limit of the carpal tunnel in female cadavers was significantly smaller (p < .02) than in the male cadavers. The distribution of muscle belly distance from the tunnel, however, was found to be the same in both the male and female cadavers. In female cadavers, the majority of the mean muscle belly distances were significantly correlated with forearm length, while in the male cadavers, this was the exception rather than the rule.