Anatomical differences in the psoas muscles in young black and white men.

The anatomy of the psoas major muscle (PMA) in young black and white men was studied during routine autopsies. The forensic autopsies included 44 fresh male cadavers (21 black, 23 white) with an age span of 14 to 25 y. The range for weight was 66-76 kg and for height 169-182 cm. The PMA was initially measured in its entire length before measuring the diameter and circumference at each segmental level (L1-S1). At each segmental level, the calculated anatomical cross-sectional area (ACSA) was more than 3 times greater in the black group compared with the white (P < 0.001). The psoas minor muscle (PMI) was absent in 91% of the black subjects, but only in 13% of the white subjects. These data show that the PMA is markedly larger in black than white subjects. The marked race specific difference in the size of the PMA may have implications for hip flexor strength, spine function and race specific incidence in low back pathology, and warrants further investigation.