English

Abstract

Psoas minor (PM) muscle belongs to the category of vestigial muscles. It is large in size in all those quadrupeds that brachiate and leap or run at very fast speed. None of these functions being required in bipedal, plantigrade man the muscle has receded during evolution; hence it is present only in 40-60% population. Apart from racial variations, a large number of morphological variations of this muscle have been described in the literature. The present study has been conducted in 20 cadavers. Psoas minor muscle was present bilaterally in 35% cases and unilaterally in 5% cases; overall incidence being 40%. Average length of fleshy belly was 7.85 cm that of tendon was 13.13 cm. Average maximum width of fleshy belly was 1.93 cm, and that of the tendon was 0.77cm. In most of the cases, muscle originated from the sides of bodies of T12 & L1 vertebrae & their intervening intervertebral disc. In few of them, origin extended to the sub diaphragmatic fascia & the medial arcuate ligament (Fig.1a). Tendon of PM flattened out at insertion on iliopectineal line & blended with iliopsoas fascia (Fig.2a, 3a). The expansion of tendon into this fascia might be serving some special functions, hitherto fore unappreciated. We also found Psoas accessorius (PA) muscle which was described for the first time by Joshi et al. (2010) 1 , in 15% cases unilaterally only on the left side. In one case, PA showed a bilamellar arrangement of muscle fibres.