Subtalar Fusion for Correction of Forefoot Abduction in Stage II Adult-Acquired Flatfoot Deformity.

BACKGROUND Correction of talonavicular uncoverage (TNU) in adult-acquired flatfoot deformities (AAFD) can be a challenge. Lateral column lengthening (LCL) traditionally is utilized to address this. The primary study objective is examining stage II AAFD patients and determining if correction can be achieved with subtalar fusion (STF) comparable to LCL. METHODS Following institutional review board approval, retrospective chart review performed identifying patients meeting criteria for stage IIB AAFD who underwent either STF with concomitant flatfoot procedures (but not LCL) to correct TNU, or who underwent LCL as part of their flatfoot reconstruction. Patients indicated for STF had one or more of the following: higher body mass index (BMI), were older, had greater deformity, lateral impingement pain, intraoperative spring ligament hyperlaxity. Patients without 1-year follow-up or compete records were excluded. All other patients were included. A total of 27 isolated STFs identified, along with 143 who underwent LCL. Pre-/postoperative radiographic parameters obtained as well as PROMIS (Patient-Reported Outcomes Measurement Information System) and FAOS (Foot and Ankle Outcome Score) scores. Radiographic and patient reported outcomes both preoperatively and at 1-year follow-up evaluated for both groups. RESULTS STF patients were older (P < .05), with higher BMIs (P < .004). STF had significantly worse TNU (P < .001) than LCL patients, and average change in STF TNU was larger than LCL change postoperatively (P = .006), after adjusting for age, BMI, gender. PROMIS STF improvement reached statistical significance in Physical Function (P 0.011), for FAOS Pain (P 0.025) and Function (P = 0.04). CONCLUSIONS STF can be used in appropriately indicated patients to correct flatfoot deformity without compromising radiographic or clinical, correcting not only hindfoot valgus, but also talonavicular uncoverage (TNU) and corresponding medial arch collapse. LEVELS OF EVIDENCE Level III: Retrospective chart review comparison study (case control).