Flexor digitorum longus tendon harvest length utilising a limited operative exposure: A cadaveric study

Flexor digitorum longus (FDL) is a commonly used donor tendon for transfer to substitute for a dysfunctional tibialis posterior in the management of adult acquired flatfoot deformity. The tendon transfer is attached to the navicular bone via a drill hole. Interference-fit screws are an alternative means of securing a transferred tendon allowing for a shorter length of graft and less extensive dissection. The aim of this cadaveric study was to investigate the length of FDL tendon harvest required for transfer and to determine if this length of tendon can be obtained without formal dissection to the Knot of Henry.

The FDL tendon was exposed in 8 cadaveric specimens via a medial hindfoot incision. The tendon was divided proximal to the Knot of Henry. The lengths of the skin incisions and the length of the FDL tendon harvest were measured. No specialist tendon harvesting instruments were used. The average length of the skin incision was 9.0cm (95% confidence intervals 8.0-10.0cm). The average length of the harvested FDL tendon was 6.7cm (95% confidence intervals 6.4-7.0cm).

This study demonstrates that the FDL tendon can be safely and adequately harvested via a limited exposure. The average length of FDL tendon harvest via this approach compares favourably with other descriptions of approaches. This shorter graft length is more than adequate, allowing at least 2cm for fixation by interference screw to a tunnel in the navicular bone.