[Restoration of thumb flexion at the interphalangeal joint by transposition of the flexor digitorum superficialis tendon from the ring finger].

OBJECTIVE: Restoration of active thumb flexion at the distal joint. INDICATIONS: Loss of active flexion of the interphalangeal (IP) joint of the thumb if there is a transection of the flexor pollicis longus (FPL) tendon at the tendon channel of the thumb or thenar and direct suture is not possible but the tendon channel is intact, as alternative procedure to a free tendon graft if the transection is proximal to the tendon channel and the muscle of the FPL is contracted/injured or the FPL tendon is unharmed but the FPL muscle is partially or complete paralyzed. CONTRAINDICATIONS: Insufficiency of the FPL tendon channel, impairment of the superficial or deep flexor tendon of the ring finger, limited passive motion of the proximal and distal thumb joints, acute local general infection and non-compliance or incapacity of the patient. SURGICAL TECHNIQUE: The surgical technique depends on the necessity of transosseous refixation of the FDS IV at the base of the distal phalanx of the thumb or the possibility of woven sutures through the FPL proximal to the tendon channel. If the tendon channel is intact the distal part of the FPL tendon is shortened to 1 cm, the FDS IV tendon is cut distal to the chiasma of Camper, pulled through the carpal tunnel and moved into the channel of the FPL tendon and fixed transosseously through the base of the distal phalanx of the thumb. If the transection of the FPL tendon is located proximal to the tendon channel and muscle of the FPL is injured, FDS IV tendon will be woven using the Pulvertaft technique through the FPL tendon at the distal forearm. POSTOPERATIVE MANAGEMENT: Postoperative 6 weeks motion of thumb flexion without resistance in relieved position of the thumb through a thermoplast splint and 6 weeks of functional use of the hand with increasing weight bearing.
RESULTS: In this study 10 patients with FDS IV transposition to reconstruct an isolated rupture of the FPL tendon could be followed for an average of 4.1 years postoperatively. The active range of motion of the IP joint of the thumb averaged 65° (10-100°), 8/10 patients achieved an equal active and passive range of motion of the IP joint of the thumb, in 2 patients some flexion insufficiency remained, 9 patients could reach the fingertip of the small finger with the thumb and 1 patient lacked 3 mm. Contracture of the proximal thumb joint developed in two patients. After removal of the FDS IV tendon two patients developed contracture of the PIP joint of the ring finger. The grip force was reduced to 81 %, lateral grip to 83 % and pinch grip to 77 %. The DASH score averaged 18 (0-31) and 8/10 patients would choose to undergo this surgery again.