Subtalar Arthrodesis with Flexor Digitorum Longus Transfer and Spring Ligament Repair for Treatment of Posterior Tibial Tendon Insufficiency

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Abstract
The surgical treatment of flexible pes planovalgus deformities resulting from Stage 2 posterior tibial tendon insufficiency is controversial and many techniques have been proposed. We retrospectively reviewed the results of subtalar arthrodesis combined with spring ligament repair/reefing and flexor digitorum longus (FDL) transfer to the navicular. There were sixteen patients (seventeen feet) with an average follow-up of 27 months (9–52). All deformities were passively correctable. The average age was 56 yrs (39–78). All patients had failed conservative management, 88% had previously been treated with orthotics, and 53% had lateral pain from subfibular impingement. Two patients were noted to have degenerative changes of the subtalar joint. Successful subtalar joint fusion occurred in all patients with an average time to radiographic union of 10.1 weeks (5–24). The average AOFAS hindfoot score and Maryland foot score postoperatively was 82 and 86 respectively. Standing radiographic analysis demonstrated an average improvement in the AP talo-1st metatarsal angle of 6° (24° preoperative, 18° postoperative). The talonavicular coverage angle improved an average of 17° (34° preoperative, 17° postoperative). The lateral talo-1st metatarsal angle improved an average of 10° (18° preoperative, 8° postoperative). The lateral talocalcaneal angle decreased an average of 21 o (55° preoperative, 34° postoperative). The distance of the medial cuneiform to the floor on the lateral radiograph averaged 12mm preoperatively and 18mm postoperatively (avg. improvement 6mm). The combination of the flexor digitorum longus tendon transfer and spring ligament repair with subtalar arthrodesis is an effective and reliable procedure which provides excellent correction of hindfoot valgus as well as forefoot abduction and restoration of the height of the longitudinal arch. These results compare favorably with flexor transfer combined with either calcaneal osteotomy or lateral column lengthening.