New insights into the origin of the lumbrical muscles of the foot: tendinous slip of the flexor hallucis longus muscle.

Abstract

The aim of this study was to clarify the origins of the lumbricals of the foot toward a better understanding of its precise action in the gait. The lumbricals in the foot were investigated in 66 specimens of embalmed Korean adult cadavers. The first lumbrical arose as two muscle bellies from both the tendon of the FDL and the tendinous slip of the FHL in 83.3 %, and as one muscle belly from the tendon of the FDL or the tendinous slip of the FHL in 16.7 %. These two muscle bellies subsequently merged to form the muscle belly of the first lumbrical. The second lumbrical arose from the tendinous slips of the FHL for the second and third toes as well as the tendon of the FDL in all specimens. The third lumbrical arose from the tendinous slips of the FHL for the third and fourth toes in 69.7 %, and the fourth lumbrical arose from the tendinous slip of the FHL for the fourth toe in 18.2 %. Some deep muscle fibers of the fourth lumbrical arose from the tendinous slip of the FHL for the second toe in 4.5 %, for the third toe in 28.8 %, and for the fourth toe in 15.2 %. The results of this study constitute new anatomical knowledge regarding the origin of the lumbricals, and provide insight into their specific role in production of gait. These findings will be useful for various types of surgery, biomechanics research, and rehabilitation programs.