[References to avoid complications in releases of the trigger thumb: a cadaveric study]

The aim of this cadaveric study was to demonstrate the utility of some visible landmarks in the hand in avoiding probable complications during percutaneous or open releases performed for the trigger thumb associated with flexor tendon tenosynovitis.

In this cadaveric study, we dissected 20 thumbs of 10 fresh cadavers (10 males; mean age 46 years; range 31 to 62 years) from the interphalangeal to the metacarpophalangeal creases to expose all digital arteries, nerves, the flexor tendon, and the A1 pulley. The following distances were measured: from the proximal edge of the A1 pulley to the digital arteries and nerves, and to the interphalangeal and metacarpophalangeal creases of the thumb.

The proximal edge of the A1 pulley lies at a mean distance of 3.5 mm distal to the metacarpophalangeal crease, and about 35 mm distal to the interphalangeal crease. These values may be helpful during percutaneous releases in avoiding any injury to the radial digital nerve, which crosses the flexor tendon proximal to the A1 pulley. On the other hand, care should be taken for the ulnar digital nerve during open releases, which is at a higher risk than the radial digital nerve due to its closer proximity to the A1 pulley, the mean distances being 1.95 mm and 3.40 mm, respectively.

These data are helpful in avoiding injuries to the digital nerves, which imply that the digital nerve on the ulnar side of the A1 pulley is more vulnerable during open releases, while the radial digital nerve proximal to the metacarpophalangeal crease is more vulnerable during percutaneous attempts. Complications can be avoided if the interphalangeal and palmar creases are taken into consideration.