Lumbrical length changes in finger movement: a new method of study in fresh cadaver hands.

A new method of loading the lumbrical muscle in the cadaver hand, based on the bicycle brake cable concept, has been developed. The device can be inserted with the aid of tendon-tunneling forceps and sutured to the profundus tendon at the origin of the lumbrical muscle. Lumbrical function is stimulated by applying a force that approximates the attachment point on the profundus tendon to the lateral wing of the extensor expansion without predetermining which will move the origin, the insertion, or both. This preliminary study reports the use of this device in determining lumbrical length changes in five fresh cadaver hands as the index finger was passively moved through each of six standard finger positions. In the absence of other restraints lumbrical contraction causes the index finger to move from the claw position through the straight to the intrinsic position. The latter position represents maximum shortening.