The authors described an A4 pulley reconstruction technique using one slip of the flexor digitorum superficialis tendon insertion. The slip was transferred over the flexor digitorum profundus tendon and sutured to the contralateral superficialis slip insertion. This created a new pulley at the base of the original A4 pulley that could be adjusted to accommodate a flexor digitorum profundus repair of increased bulk. In a biomechanical study of 33 fingers, the repair effectively diminished excess tendon excursion due to bowstring. In addition, 94% of repairs maintained their integrity when a proximally directed force of 50 N was applied.
The A2 and A4 annular digital pulleys are considered to be the most important contributors to efficient digital flexion. Loss of more than 50% of either pulley may lead to flexor tendon bowstringing, loss of full finger flexion, and a finger flexion contracture. Reported techniques to reconstruct the A4 pulley include suturing autogenous tendon graft or extensor retinaculum around the middle phalanx, weaving graft material between the remaining intact edges of the A4 pulley, and transferring of one slip of the flexor digitorum superficialis tendon insertion. Power and Trail (JHS Br 2004) determined that flexor tendons are subject to forces up to 50 N during active range of motion; consequently, the pulley reconstruction technique described by these authors may potentially withstand the forces encountered with early active range of motion.