Transfer of the long flexor tendon into the extensor expansion can rebalance a flexible claw or hammer toe. Like all tendon transfers it is only appropriate when deformity can be fully passively corrected at both interphalangeal and MTP joints (Blackburn type 1 toe).
A dorsal curved incision gives access to the PIPJ and MTPJ and to the extensor apparatus. A short longitudinal plantar incision gives access to the flexor tendon for harvest. The digital neurovascular bundles are at risk during both harvest and passage fo the tendon.
If used for MTP stabilisation in a patient with a fixed PIPJ deformity, a PIPJ excision arthroplasty or fusion can be carried out by dividing or reflecting the extensor hood. Fixed hyperextension deformity at the MTPJ can be treated by the sequential release method described by Myerson (1990), Hossain (2002) and Boyer (2007). First the extensor tendons are released or Z-lengthened – make sure to release the short extensor. IF this does not correct the deformity the MTP capsule is released and then the collateral ligaments of the MTPJ. Most patients need a full release.
The flexor sheath is opened and the long flexor tendon is withdrawn as far as possible and divided distally. For a toe without valgus or varus deformity, the tendon is split longitudinally and passed round each side of the toe as close to the bone as possible to avoid damage to the neurovascular bundle. The toe is plantarflexed and the ends of the transferred tendon sutured to one another and to the extensor tendon.
Patients can walk on the toe with minimal protection. The toe can be gently mobilised after a few weeks – no data is available on different post-op regimes.
Transfer of the long flexor tendon into the extensor expansion (FET) can rebalance a flexible claw or hammer toe.
In both Barbari (1984) and Ozdolop (2006) series most patients got good correction of deformity with careful patient selection. Boyer and deOrio (2007) used the technique for both flexible and fixed deformity of the PIPJ, but added PIPJ in the 2/3 of patients with fixed deformities. Results were similar in both groups with a mean modified AOFAS score of 73/85 and 72% satisfied. However, 1/3 complained of stiffness, 1/3 of residual or recurrent deformity and nearly 50% of calluses. Bouche described FET in association with plantar plate repair and (Boyer) Weil osteotomy. Most patients got a good result but the incidence of floating toes was 5/15.
Garcia-Gonzalez (2009) compared transfer of the FDL and FDS tendons in a finite-element model; there was little difference in the correction achieved or the stresses in the resultant model.