Contribution of First Tarsometatarsal Joint Fusion to Deformity Correction in the Treatment of Adult Acquired Flatfoot Deformity

CATEGORY: Midfoot/Forefoot; Other INTRODUCTION/PURPOSE: Severe adult-acquired flatfoot deformity (AAFD) is often associated with painful medial column collapse at the naviculocuneiform (NC) joint. The purpose of this study was to examine the role of first tarsometatarsal (1st TMT) fusion combined with subtalar fusion in correcting deformity at this joint. METHODS: We retrospectively analyzed 40 patients (41 feet) who underwent 1st TMT and subtalar (ST) fusion as part of a flatfoot reconstructive procedure. We assessed six radiographic parameters both preoperatively and at a minimum of 6 months postoperatively, including talonavicular (TN) coverage angle, lateral talo-first metatarsal angle, lateral talocalcaneal angle, calcaneal pitch, hindfoot moment arm, and a newly defined navicular-cuneiform incongruency angle (NCIA). Patient-Reported Outcomes Measurement Information System (PROMIS) clinical outcomes were assessed preoperatively and at a minimum 1 year follow-up. RESULTS: The NCIA demonstrated excellent interobserver reliability, with no significant change between pre- and postoperative measurements. All other radiographic parameters, except calcaneal pitch, demonstrated statistically significant improvement postoperatively (p <0.01). Overall, patients had statistically significant improvement in all PROMIS domains (p <0.01), except for depression. Worsening NC deformity was not associated with worse patient-reported outcomes. CONCLUSION: Our data suggests that when addressing collapse of the medial arch in patients with AAFD, fusion of the 1st TMT joint in combination with other procedures leads to acceptable radiographic and clinical outcomes. There was no change in deformity at the NC joint at short-term follow-up, and patients achieved significant improvement in multiple PROMIS domains. Based on our findings, deformity through the NC joint does not significantly impact clinical outcomes. In addition, the NCIA was established as a reliable radiographic parameter that can be used to assess NC deformity in the presence of talonavicular and/or 1st TMT fusion.