The palmar fat pad is a reliable intraoperative landmark during carpal tunnel release

During endoscopic or open carpal tunnel release, a palmar fat pad is visualized immediately proximal to the distal end of the transverse carpal ligament (TCL). Visualization of the fat pad allows anticipation of complete release of the TCL without unnecessary distal dissection that could risk iatrogenic injury. This study defines the anatomic relationship of the distal edge of the TCL to the fat pad, the superficial palmar arch, and the motor branch of the median nerve.

Eighteen fresh-frozen cadaver hands were dissected, and the proximal aspect of the palmar fat pad, the distal edge of the TCL, the superficial palmar arch, and the motor branch of the median nerve were identified. An electronic caliper was used to measure distances between each structure along the axis of the radial border of the ring finger. A subset of 8 hands was radiographically imaged with fingers flexed and extended (wrist neutral) to determine if finger positioning influenced measurements between marked structures.

The proximal aspect of the palmar fat pad is 2.0 mm proximal to the distal edge of the TCL. The distal end of the TCL, as measured along the axis of the radial border of the ring finger is 12.7 mm from the most proximal aspect of the palmar arch and 6.5 mm from the nearest aspect of the motor branch. Flexing the fingers decreases the distance between the distal end of the TCL and the fat pad while not markedly affecting the distance between the TCL and the palmar arch or the motor branch.

The palmar fat pad is a reliable anatomic landmark during carpal tunnel release. When dividing the TCL from proximal to distal, visualization of the proximal aspect of the fat pad indicates that the distal edge of the TCL is within approximately 2 mm and indicates that distal dissection beyond this extent is unnecessary.