Extensor tendon reconstruction for zones II and IV using local tendon flap: a cadaver study

To assess the feasibility of reconstructing extensor tendon segmental defects in zones II (over the middle phalanx) and IV (over the proximal phalanx) using local tendon flaps (LTFs), explore in these 2 zones the anatomical constraints that limit the use of the LTF as regards the maximum defect that could be reconstructed, and compare this flap with distant tendon grafts (DTG) reconstruction for similar size defects.

We dissected 33 fresh-frozen cadaver extensor tendons from the fingers of 9 fresh-frozen cadaver forearms. A 0.5-cm defect was created in each extensor tendon of 21 fingers: 12 in zone II and 9 in zone IV. In each of 12 additional fingers, we created a 1.0-cm defect in zone IV. In 25 fingers, LTFs measuring 0.5 and 1.0 cm in length were harvested from the extensor tendon proximal to each defect and were turned distally to reconstruct the respective 0.5- and 1.0-cm defects. In 8 fingers, palmaris longus tendon grafts measuring 0.5 and 1.0 cm in length were used to reconstruct the respective 0.5- and 1.0-cm defects. Limited kinematic analysis was performed on the repaired fingers by maximally flexing the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints in sequential fashion.

In zone II, repair was technically feasible using LTFs in all 9 of the 0.5-cm extensor tendon defects. Likewise, LTFs were feasible for zone IV to repair 6 of 8 and all 9 of the respective 0.5- and 1.0-cm extensor tendon defects. Two failed repairs occurred early in the study by suture gapping following LTF of 0.5 cm to repair extensor tendon defects in zone IV of a long and small finger during maximal flexion. We determined the anatomical constraints for the use of the LTFs. The maximum length of repairable defect using the LTF was 0.5 cm in zone II of the index, long, ring, and small fingers, and zone IV of the small finger. In zone IV of the index, long, and ring fingers, the largest defect that could be repaired was 1.0 cm. Similarly, DTGs were feasible in zone II to repair all 4 of the 0.5-cm defects and in zone IV to repair all 4 of the 0.5- and 1.0-cm extensor tendon defects.

In a cadaver model, both the LTF and the DTG are anatomically feasible and technically easy to perform. However, the LTF avoids a distant donor site, provides morphologically similar donor tendon that is readily accessible, and avoids morbidity that may be associated with the use of DTG. In this study, however, the LTF was limited in its use to zones II and IV of the extensor tendon.