THE ANATOMY OF THE RECURRENT BRANCH OF THE MEDIAN NERVE

One hundred one fresh-frozen cadavers were dissected under loupe magni fication to spatially define the origin of the recurrent branch of the median nerve and to define its course with respect to the distal edge of the transverse carpal ligament (TCL). The spatial orientation, num ber, and course of the recurrent branch was carefully determined. Cali pers were used to measure the distance between the recurrent branch an d the TCL. Histologic analysis of the fascia surrounding the recurrent nerve was performed. The recurrent branch of the median nerve was cla ssified into 3 types. Type I passed through the TCL; it is rare, occur ring in 7% of the specimens. Type ii nerves (74%) passed distal to the TCL through separate obliquely oriented fascia that originated on the TCL and inserted on the undersurface of the palmar aponeurosis. Type III (19%) passed distal to the TCL, but did not pass through the obliq uely oriented fascia. The distance from the distal edge of the TCL was significantly different between the 3 types, Ninety-nine percent of r ecurrent branches originated either from the central portion of the me dian nerve or just radial to it. There were no ulnar origins. Four cad avers (4%) had more than 1 recurrent branch. The variability in the li terature on the anatomy of the recurrent branch can be accounted for b y failure to properly identify the TCL as being separate from the obli quely oriented fascia distal to the TCL through which the nerve freque ntly penetrates. Histologic analysis confirmed a difference between th e TCL and these oblique fibers that can surround the recurrent nerve. This study concludes that the transligamentous branch (type I) is unco mmon and the reported high incidence of branches passing through the T CL can be explained by mistakenly combining recurrent nerve types I an d It. Copyright (C) 1998 by the American Society for Surgery of the Ha nd.