Hand Intrinsic Muscles

Sir William Osler stated that “variability is the law of life”, and in this chapter the variations of the intrinsic muscles of the hand are explored in detail. However, the chapter focuses on the observed variations of the intrinsic muscles of the hand. To facilitate the presentation of the various observed findings their descriptions will be subdivided into: origin; insertion; course and structure; numerical; and neurovascular variations. The implications of these variations are discussed to determine why this variability may prove to be clinically important. A multitude of variations have been observed and, while the clinical ramifications they present may lead to confusion, they are nonetheless relatively uncommon.The hypothenar eminence contains the muscles on the opposite side of the palm from the thenar muscles. There are four dorsal interossei. Anomalous insertion of the fourth lumbrical has been associated with camptodactyly.