Combined Subtalar and Naviculocuneiform Fusion for Treating Adult Acquired Flatfoot Deformity With Medial Arch Collapse at the Level of the Naviculocuneiform Joint.

Background:: A challenge in treating acquired flatfoot deformities is the collapse of the medial arch at the level of the naviculocuneiform (NC) joint. Triple fusions, being a treatment option, may lead to problems such as increased foot stiffness. We thus established a method that combines subtalar (ST) fusion with NC fusion while preserving the Chopart joint. We analyzed the radiographic correction, fusion rate, and patient satisfaction with this procedure.

Methods:: 34 feet in 31 patients (female, 23; male, 8; age 67 [45-81] years) were treated with a ST and NC joint fusion. In 15 cases, a medial sliding-osteotomy was additionally necessary to fully correct hindfoot valgus. The following radiographic parameters were measured on weightbearing radiographs preoperatively and at 2 years: talo-first metatarsal angle, talocalcaneal angle, calcaneal pitch, talonavicular coverage angle and calcaneal offset. Fusion was radiologically confirmed.

Results:: All parameters, except the calcaneal pitch, showed a significant improvement. Fusion was observed after 1 year in all but 2 cases (94.1%). One nonunion each occurred at the ST and NC joint without needing any subsequent treatment. One patient developed avascular necrosis of the lateral talus with need for total ankle replacement after 1 year. All patients were satisfied with the obtained results.

Conclusion:: Our data suggest that a combined fusion of the ST and NC joint was effective and safe when treating adult acquired flatfoot with collapse of the medial arch at the level of the NC joint. Although the talonavicular joint was not fused, its subluxation was significantly reduced.

Level Of Evidence:: Level IV, case series.