Anatomy of the intrinsic hand muscles revisited: Part II. Lumbricals

The authors discuss the anatomic variations and the precise origins and insertions of the lumbrical muscles, after dissecting 14 fresh cadavers (56 lumbrical muscles) and reviewing the scant published literature. They compare the findings with those of other investigators, and they describe the lumbrical muscle insertions discovered during the dissections. The authors conclude that descriptions of the origins and insertions of the lumbrical muscles have been oversimplified or not investigated at all, that lumbricals originate variably from the flexor digitorum profundus tendon and may even be bipinnate, and that three different major destinations exist for distal insertion of these intrinsic muscles: bone, volar plate, and extensor apparatus. Previous descriptions have focused only on the lumbrical continuation to the lateral band of the extensor mechanism.