The Effect of Minimally Invasive Hallux Valgus Correction on Sesamoid Position and Rotation

Abstract

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Minimally invasive hallux valgus correction is increasing in popularity. Third generation minimally invasive chevron / Akin (MICA) techniques have low complication rates and high patient satisfaction. The MICA technique utilizes burrs to make percutaneous osteotomies of the distal first metatarsal and base of the first proximal phalanx. Deformity correction is achieved through lateral translation of the metatarsal head and closure of the Akin osteotomy. In open hallux valgus procedures, derotation of the first metatarsal and reduction of the sesamoids has shown to be essential to optimizing outcome. To our knowledge, the impact of the MICA technique on sesamoid and first metatarsal rotation has not been evaluated. In this study, we attempt to quantify the correction of metatarsal rotation and sesamoid rotation following MICA bunion correction. Methods: A cohort of patients undergoing minimally invasive hallux valgus correction at a single center were prospectively followed. All bunion deformities were corrected utilizing the MICA technique. Demographic information including age, sex, BMI, and laterality were collected. Concomitant procedures and any complications were recorded. All patients underwent a weight bearing CT scan and had weight bearing radiographs performed both before surgery and at a minimum of 6 months after surgery, after the osteotomy sites had healed. Weight bearing CTs were utilized to compare sesamoid station, sesamoid rotation, and metatarsal rotation (alpha angle). Radiographs were used to compare HVA, IMA, and sesamoid station pre and postoperatively. PROMIS scores were also collected from patients before surgery and at their most recent follow-up visit to assess the impact of minimally invasive bunion correction on patient outcomes. Results: Twelve patients, all female, with an average age of 49.8 +- 13.5 years were included. There were no major complications and all osteotomies healed. Hallux valgus angle (HVA) and intermetatarsal angle (IMA) improved significantly from 29.4 +- 5.00 and 13.6 +- 1.38 to 13.6 +- 7.13 and 5.92 +- 3.99 respectively (p<.05). Alpha angle did not significantly change pre and postoperatively (p=.715). Rotation of the fibular sesamoid (p=.011) was significantly different postoperatively, while tibial sesamoid rotation trended towards significance (p=.136). Average sesamoid station significantly improved on CT scan from 1.45 preoperatively to 0.5 postoperatively (p=.001). PROMIS scores did not differ significantly from pre to postoperatively. Conclusion: MICA correction of hallux valgus deformity offers powerful correction of the IMA and HVA. The MICA technique, using a translational chevron osteotomy, does not significantly change first metatarsal rotation but does lead to reduction of the sesamoids, as measured by sesamoid station and improved sesamoid rotation. While differences in PROMIS scores were not seen in this study, larger studies are required to delineate the relationship between patient outcome measures and degree of sesamoid reduction in MICA hallux valgus correction.