The Volar Base of the Third Metacarpal Is Not a Palpable Landmark in the Palm.

Various techniques have been described to identify the topographical projection of the thenar branch of the median nerve (TBMN). This study explores two hypotheses: (1) There is a palpable landmark overlying the volar base of the third metacarpal, and (2) this landmark is the transverse carpal ligament, not the third metacarpal base itself. Using four upper extremities from two cadavers, manual palpation was performed to identify and mark the palpable landmark overlying the volar base of the third metacarpal using a radiopaque marker. The distance between the palpable landmark and the volar base of the third metacarpal was measured using fluoroscopy. Anatomic dissection was then performed to identify the basis of the landmark. The palpable landmark was confirmed to be the distal end of the transverse carpal ligament in all specimens. Therefore, there is a palpable landmark beneath the palmar skin overlying the volar base of the third metacarpal, and it is the distal edge of the transverse carpal ligament, not the metacarpal base.