Results of Modified Minimally Invasive Hallux Valgus Surgery, Factors for the First Metatarsal Shortening, and Patients’ Satisfaction

<b>Background</b>: Hallux valgus is a prevalent foot deformity conventionally treated with open surgical techniques, which carry risk of complications due to extensive soft tissue dissection. Minimally invasive surgeries (MISs) as alternatives offer comparable outcomes, reduced pain, and faster recovery; however, their challenges include the risk of shortening of the first metatarsal. This study aimed to assess the efficacy of our modified MIS hallux valgus correction technique and investigate the factors that affect first metatarsal shortening. <b>Methods</b>: Twenty-nine feet treated with modified MIS hallux valgus surgery between 2017 and 2022 were included with an average follow-up of 29 months. Clinical outcomes were evaluated with the Manchester-Oxford Foot Questionnaire (MOXFQ), Foot Function Index (FFI), and visual analog scale for pain. Radiographic evaluations included the intermetatarsal angle (IMA), hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), first metatarsal length, and sesamoid grade. <b>Results</b>: Functional and radiographic outcomes were significantly improved (<i>p</i> < 0.0001 and <i>p</i> < 0.001, respectively). Significant correlations between patient satisfaction and the MOXFQ, FFI, and VAS scores were found, with no significant correlations between patient satisfaction and radiographic outcomes. Non-purchasing of the lateral cortex of the proximal osteotomy site was identified to increase risk of first metatarsal shortening (odds ratio [OR] = 22.09, <i>p</i> = 0.0064). <b>Conclusions</b>: Our modified MIS for hallux valgus correction showed favorable radiographic and functional outcomes. Proximal lateral cortex purchasing should be targeted to reduce postoperative shortening of the first metatarsal.