Long harvest of flexor hallucis longus provides grafts that are more suitable for large Achilles defects

Objetive: To compare the short (zone 1) and intermediate (zone 2) harvest zones of Flexor Hallucis Longus (FHL) tendon to a long harvest site at the interphalangeal joint of the hallux (zone 3). Methods: Fourteen fresh-frozen cadaveric lower limbs were used to measure the length of FHL tendon in zone 1, 2 and 3, tendon thickness, length of the calcaneal tunnel, percentage of tendon inside the tunnel, and relation between the base of the first metatarsal and medial plantar nerve. Results: In the short harvest, the mean length of the FHL tendon was 22.9 ± 4.5 mm with the ankle in neutral position, and 33.2 ± 4.1 mm with the ankle in 15 degrees of plantarflexion. Thickness of FHL was 6.2 ± 0.8 mm. The mean length of the calcaneus osseous tunnel was 44.1 ± 4.2 mm and the mean length of the tendon traversing the bone tunnel was 21 ± 3.2 mm, while covering on average 48.5% of tunnel length. The FHL length at the intermediate harvest was 48.9 ± 5.7 mm with a mean distance of 24 ± 4.8 mm between the base of the first metatarsal to the medial plantar nerve. The FHL length was the longest at the long harvest with 128.6 ± 7.1 mm. Conclusion: The short harvest provided FHL grafts that covered only 48.5% of the calcaneal tunnel. The long harvest provides longer FHL grafts that are suitable for large Achilles defects where augmentation with the remaining FHL tendon may be needed. Level of evidence V.