Subtalar and Naviculocuneiform Fusion in Treating Adult Acquired Flatfoot Deformity with Medial Arch Collapse at the Level of the Naviculocuneiform Joint

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: A conflicting problem in treating acquired flatfoot deformities is the break-down of the arch at the naviculocuneiform (NC) joints. After having encountered problems with extended triple fusion, in particular increased stiffness of the foot, we established a rational to combine subtalar (ST) fusion with NC I-III fusion while preserving the talonavicular (TN) and calcaneo-cuboidal (CC) joint. Our hypothesis was that the break-down of the arch at the NC joint can be specifically addressed while sparing the Chopart Joint (TN and CC joint). This, in turn, will allow the patient to accommodate better to the ground while walking. The aim of the study was to analyze the radiographic correction and fusion rate, and to determine patient’s satisfaction with this procedure. Methods: Between 2009 and 2015, a consecutive series of 34 feet in 31 patients (female, 23; male, 8; age 67 [45-81] years) were treated by combining a fusion of the subtalar joint with a NC fusion. Both joints were exposed through a medial approach. Two 7.5mm-screws were used for ST fusion, and two 5.5mm-screws were used for NC fusion. In addition an anatomically contoured plate was used as a medio-plantar tension bending support of the NC joint. In 15 patients, an additional medial sliding-osteotomy was done to fully correct valgus misalignment of the hindfoot. The following measures were taken on standard weight-bearing radiographs including hindfoot alignment view preoperatively and at 2 years: the talus-first metatarsal angle, the talocalcaneal angle, the calcaneal pitch, the talonavicular coverage angle, the talus-first metatarsal angle, and calcaneal offset. Bony fusion was confirmed on plain radiographs. If no trabeculation was visible, a CT scan was performed. Results: All radiographic parameters, except the calcaneal pitch, showed a statistically significant improvement (Table 1). Solid fusion at the arthrodesis site was observed between 8 and 12 weeks in all but 2 cases (94.1%). One nonunion occurred at the ST joint and one at the NC joint. No interventions were necessary as both cases were asymptomatic. One patient developed an avascular necrosis of the lateral talus with need for a total ankle replacement after one year. All patients were satisfied with the results of this procedure and stated that they would undergo the surgery again. All patients were able to wear normal shoes without insoles. Conclusion: Our results show that a combined fusion of the subtalar and NC joint is an effective and safe technique in treating the adult acquired flatfoot with collapse of the medial arch at the level of the NC joint. The deformity was corrected in all three planes. Even though the TN joint was not fused, its subluxation was significantly reduced. Although our radiographic results are promising, a clinical follow-up study is necessary to quantify the clinical benefit of this procedure.