Behavior of the Subtalar Joint after Arthroereisis in Adult Acquired Flatfoot, Evaluation with WBCT

CATEGORY: Hindfoot INTRODUCTION/PURPOSE: Flatfoot is a common deformity in adult and pediatric populations, with a 5% incidence. It corresponds to a complex three-dimensional pathology characterized by peritalar subluxation (PTS) of the hindfoot, with a dynamic behavior during weight-bearing. This is how weight-bearing computed tomography (WBCT) has become a fundamental tool for optimizing staging in flatfoot deformities. The indication for arthroereisis is a symptomatic flexible flat foot or hindfoot valgus in the pediatric or adolescent population in most publications. There are no studies that evaluate the behavior of the subtalar joint and degree of three-dimensional correction achieved in adult patients who underwent arthroereisis for symtomatic flexible flatfoot. METHODS: After obtaining IRB approval, our prospectively collected surgical database was queried for patients undergoing arthroereisis for symptomatic flexible flatfoot. Patients were included if they had preoperative weight-bearing CT (WBCT). Patients were excluded if they had less than four months postoperative, had revision surgery, or declined to participate. Nine patients (15 feet) met the inclusion/exclusion criteria. All patients were brought back to the clinic for weight-bearing CT scan and to sign informed consent for the specific needs of this study. All measurements were performed by one of the authors in two time-frames (alignment of the hindfoot and talonavicular joint), separated for one month each. RESULTS: Median age of 39 years. 14 feet showed a significant correction of the evaluated parameters. The preoperative median Talonavicular Coverage angle and Posterior and Middle Facet Subluxation of the subtalar joint were 33°, 19° and 39° respectively in preoperative WBCT, and 18°, 10° and 27° respectively in postoperative WBCT. The t test showed p < 0.01 for the change between preoperative and postoperative angles. The incidence of sinus tarsi pain was 20%, 2 patients required removal of the implant, 1 of them bilateral, without loss of correction in control with WBCT at the final follow-up (6 months after extraction). CONCLUSION: The application of subtalar arthroereisis is a minimally invasive alternative and effective therapy for adult acquired flatfoot, which achieves an adequate three-dimensional correction observed with WBCT after surgery. No loss of correction was observed in patients who required implant removal.