Flexor hallucis longus transfer for repair of chronic achilles tendinopathy

The flexor hallucis longus (FHL) tendon has been used to augment the repairs for chronic Achilles tendinopathy. Two common methods of FHL harvesting include a single incision (posterior) technique and a double incision (posterior and medial utility) technique. This cadaver study was designed to measure and compare the lengths of FHL tendon obtainable for reconstruction with each technique.

Fourteen fresh-frozen cadaver lower limbs were utilized for FHL harvest. The tendon was first exposed through the single posterior-medial incision approach adjacent to the Achilles. A second medial utility midfoot incision was then made and the FHL was marked at the level of Henry's knot with a suture, to approximate the level of potential harvest via a two-incision technique. The FHL was then harvested and delivered into the posterior wound. Single incision technique graft length was then measured from the tip of the calcaneal tuber to the level of transection. The remaining in situ tendon was then also measured between its level of transection and the more distal suture placed at Henry's knot. These two lengths were then combined to determine the total potential tendon graft length obtainable using a double incision technique.

The average length of the FHL tendon harvested through the single posterior incision technique measured 5.16 cm (range, 3.4-6.9 cm, SD = 1.29). The average total tendon graft length available using the double incision technique measured 8.09 cm (range, 5.1-11.1 cm, SD = 1.63). The difference between the lengths obtained from these two techniques was significant (p < .001).

These results demonstrate approximate FHL graft lengths obtainable by using either a single or double incision harvest technique and show that a significantly longer graft can be obtained using a double incision technique. Further data need to be obtained, however, to support whether the extra surgery and graft length obtained from a double incision technique are of any benefit in improving the ultimate functional outcome of these repairs.