Objective: Stenosing tenosynovitis of the thumb flexor tendon sheath is also known as trigger thumb. It is an inflammatory process that involves the flexor tendon sheath at the A1 pulley. Successful percutaneous or open treatment of trigger thumb depends on the ability of the clinician to properly predict the location of the A1 pulley. Longitudinal anatomic landmarks can facilitate safe treatment for the trigger thumb while circumventing injury to the neurovascular bundles.
Methods: Fourteen fresh cadaveric hands were dissected to identify surface landmarks corresponding to the oblique course of the flexor pollicis longus tendon at the level of the A1 pulley.
Results: The longitudinal landmarks for the A1 pulley of the thumb are the palpable hook of the hamate and the midline of the thumb interphalangeal (IP) crease. Other bony prominences, such as the pisiform bone did not serve as effective landmarks while the thumb was in an abducted position.
Conclusion: we encourage the use longitudinal anatomic landmarks to predict the location of the thumb A1 pulley. The hook of the hamate and the midline at the palmar interphalangeal crease are reliable landmarks for safe release of the A1 pulley while avoiding inadvertent injury to adjacent structures.