The palmaris longus muscle: its anatomic variations and functional morphology.

The functional morphology and evolution of the superficial forearm flexor, the palmaris longus, have long fascinated kinesiologists, physical anthropologists and anatomists alike. The anomalies, agenesis, variations and polymorphic presentation of the muscle, coupled with its biomechanical role in the performance of flexion and supination through distal articulations in the upper limb, have formed the base for many studies found in medical literature. We present data from published sources, along with our observations on the kinetics of palmaris longus, drawn from a series of dissections done on 30 cadavers. Complete agenesis was seen in four limbs. Reversal in the muscle-tendon orientation was seen in two limbs and duplication in one limb. The functional dynamics of the muscle and the clinical implication of its modifications in humans are discussed. We believe that every surgeon must be aware of the variations, since this, otherwise unimportant muscle, provides a very useful graft in tendon surgery.