Synovial Membrane

The technique follows the general steps of the original technique described by Guimberteau^{9 (link)} with modifications that avoid division of the ulnar artery, making it more attractive to hand surgeons. Through a Bruner incision, the remnants of the FPL are resected from the digital canal in the thumb, preserving the oblique pulley if present, and otherwise reconstructing the annular pulley. The FDS of the fourth finger is exposed from the distal forearm to the proximal interphalangeal joint level through a zigzag incision. The branch of the ulnar artery to the common carpal synovial sheath is identified and preserved (Fig. 1). The tendon and its investing synovial tissue are elevated based on this vascular branch. The FDS IV tendon is cut proximally at the myotendinous junction and distally at the proximal interphalangeal joint level. Care is taken not to disrupt the synovial tissue around the tendon. Injuries of the synovial sheath are sutured with 8/0 nylon. A sublimus sling is performed in the donor fourth finger to avoid a swan-neck deformity. The pedicled tendon flap is transferred to the thumb, deep to the median nerve, without dividing the ulnar artery (Fig. 2). The distal end of the FDS is pulled through the digital canal with a tendon passer. Care is taken not to strip the synovial envelope of the tendon when passing under the oblique pulley. If an annular pulley is reconstructed, the tension is adjusted to avoid overconstriction of the vascularity of the synovial sheath. Distal fixation is performed with a pull-out transosseous suture to the P2 and a proximal Pulvertaft repair is performed to the FPL at the distal forearm. Full flexion of the thumb with the wrist in neutral is needed to avoid undue tension on the vascular pedicle. If tension is a concern, the ulnar vascular bundle can be separated from the ulnar nerve and mobilized radially. The deep palmar branch of the ulnar artery does not need to be ligated. Enough mobilization is possible through ligation of more proximal minor branches. The volar carpal retinaculum is reconstructed with a retinacular flap (Fig. 3).
The hand is immobilized in a dorsal splint with the wrist in neutral position, the thumb metacarpal adducted, and the metacarpophalanx joint fully flexed. Passive range of movement exercises are started on postoperative day two. Protected active range of movement exercises are started postoperatively at week five and continued until week 12. After the 12th week, full active flexion is allowed (Fig. 4).