Topographic anatomical landmarks for pulley system of the thumb.

PURPOSE: Knowledge of anatomical landmark to pulley system of the thumb is essential in successful treatment of trigger thumb release either by percutaneous or by minimally invasive technique. Though surgical release of trigger thumb is done commonly, there is paucity of data in the literature regarding its surface landmarks. The purpose of this study is to identify palmar surface anatomical landmarks to the pulley system of the thumb.

METHODS: Dissection was performed on 55 fresh frozen adult cadaveric thumbs. The palmar thumb creases were given names as the proximal-proximal crease (PPC) present at the metacarpophalangeal joint, the distal-proximal crease (DPC) over the middle of the proximal phalanx and the distal crease (DC) at interphalangeal joint. The distance between the proximal edges of each pulley to the three thumb creases and longitudinal length of A1, A2, oblique and Av pulley was measured using digital vernier caliper and was expressed in mean and standard deviation.

RESULTS: The proximal edge of A1 pulley was 1.98 ± 1.61 mm proximal to the PPC. The mean longitudinal length of the A1 pulley was measured to be 5.06 ± 0.87 mm, so the distal edge of the A1 pulley was calculated to lie 3.08 mm distal to PPC. The proximal edge of Av and oblique pulley was situated 7.78 ± 2.5 and 15.72 ± 3.22 mm distal to PPC, respectively. The proximal edge of A2 pulley was very nearer and 2.88 ± 1.79 mm proximal to DC.

CONCLUSION: The knowledge of anatomical skin surface landmarks is helpful in the percutaneous release or minimally invasive procedure. The PPC serves as a definite landmark for A1, Av and oblique pulley whereas it is the DC for A2 pulley.