Release of the A4 pulley to facilitate zone II flexor tendon repair.

During primary or delayed primary repair of the flexor digitorum profundus tendon, surgeons often face difficulty in passing the retracted tendon or repaired tendon under the dense, fibrous A4 pulley. The A4 pulley is the narrowest part of the flexor sheath, proximal to the terminal tendon. Disrupted tendon ends (or surgically repaired tendons) are usually swelling, making passage of the tendons under this pulley difficult or even impossible. During tendon repair in the A4 pulley area, when the trauma is in the middle part of the middle phalanx and the A3 pulley is intact, the A4 pulley can be vented entirely to accommodate surgical repair and facilitate gliding of the repaired tendon after surgery. Venting the pulley does not disturb tendon function when the other major pulleys are intact and when the venting of the A4 pulley and adjacent sheath is limited to the middle half of the middle phalanx. Such venting is easily achieved through a palmar midline or lateral incision of the A4 pulley and its adjacent distal or/and proximal sheath, which helps ensure a more predictable recovery of digital flexion and extension.