Direct plantar approach to Henry's knot for flexor hallucis longus transfer.

Background: Transfer of the flexor hallucis longus (FHL) tendon is an established method to replace a dysfunctional Achilles tendon. When using a single incision, the FHL tendon has to be transferred as a single stranded graft into the calcaneus and the distal FHL stump cannot be directly attached to the flexor digitorum longus tendon (FDL). Another concern with tendon retrieval is neurovascular damage. We report our results with a direct plantar approach for tendon harvest.

Methods: A direct plantar approach to the master knot of Henry with reattachment to its distal stump while protecting the medial plantar nerve was used allowing a double stranded FHL-transfer in 25 cases of a severely dysfunctional Achilles tendon in 24 consecutive patients. Patients were evaluated prospectively and at an average followup of 73 (range, 20 to 121) months.

Results: No wound healing problems and no lesion of the medial plantar nerve occurred. The subjective result was rated as excellent in 18 (72%), good in five (20%), and fair in one case (8%).The AOFAS hindfoot score averaged 95.4 (range, 61 to 100) points and the AOFAS hallux score averaged 97.6 (range, 87 to 100) points. No loss of plantarflexion force was observed in the big toe as compared to the contralateral side.

Conclusion: The plantar approach to Henry's knot allowed the use of a double stranded FHL transplant. The distal stump was attached to the FDL tendon to preserve flexion at the great toe without damaging to the medial plantar nerve.