The Contribution of Medial Cuneiform Osteotomy to Correction of Longitudinal Arch Collapse in Stage IIb Adult Acquired Flatfoot Deformity

Abstract

Category: Midfoot/Forefoot Introduction/Purpose: Residual forefoot supination present after correcting the hindfoot in Stage IIb adult acquired flatfoot deformity (AAFD) can be addressed with a dorsal opening wedge medial cuneiform (Cotton) osteotomy. The amount of correction is generally judged clinically and there currently are no preoperative guides that can predict the size of graft needed. The aim of this study was to evaluate the relationship between the Cotton osteotomy graft size and other accessory flatfoot reconstructive procedures, and the amount of correction of longitudinal arch collapse. We hypothesized that correction of longitudinal arch collapse, as measured by the cuneiform articular angle (CAA), would primarily be influenced by the Cotton osteotomy performed. More specifically, we hypothesized that the size of the graft would have the largest effect on the CAA. Methods: Seventy-nine feet in 74 patients undergoing Cotton osteotomy as part of flatfoot reconstruction were reviewed retrospectively. Preoperative and minimum 40-week postoperative lateral weightbearing foot radiographs were compared to assess correction of longitudinal arch collapse as measured by 13 radiographic parameters, with particular emphasis on the CAA. Additional demographic and intraoperative variables analyzed for association with radiographic change included age, gender, body mass index (BMI), amounts and graft types of Cotton osteotomy and lateral column lengthening (LCL), and amount of medializing calcaneal osteotomy (MCO). Other concomitant procedures at the time of surgery, namely Achilles lengthening, flexor digitorum longus (FDL) transfer, spring ligament reconstruction, gastrocnemius recession, and excision of accessory navicular were also recorded. Ultimately, a multivariable linear regression model was developed to estimate the effect of Cotton osteotomy on change in the CAA, adjusting for patient and clinical variables. Results: Cotton osteotomy graft size was significantly associated with changes in the CAA (P < .001), calcaneal pitch (P = .03), lateral talo-navicular Cobb angle (P = .03), and lateral naviculo-medial cuneiform Cobb angle (P = .03). Multivariable linear regression models included age at surgery, gender, BMI, and the use of all concomitant procedures (LCL, Achilles lengthening, FDL transfer, gastrocnemius recession, and excision of accessory navicular) except for spring ligament reconstruction, since this was not associated with any of the four radiographic measurements. Cotton graft size was the only factor found to significantly predict a change in the CAA in the final linear regression model (P < .001, R2 = .27), with each millimeter of Cotton corresponding to a 2.1-degree decrease of the CAA (figure 1). Conclusion: Correction of longitudinal arch collapse, as measured by the CAA, was primarily influenced by graft size of the Cotton osteotomy in a linear fashion. The results also demonstrate that the procedure has a more distal effect in correction of longitudinal arch collapse and is of particular importance when the apex of deformity is at the medial cuneiform. Because the relationship between the Cotton osteotomy graft size and the CAA can be modeled linearly, we believe that preoperative measurement of the CAA can be a useful guide in helping surgeons to titrate the proper amount of longitudinal arch collapse correction intraoperatively.