Risk factors for first metatarsal fracture in minimally invasive hallux valgus surgery

Aims: Minimally invasive hallux valgus (HV) correction techniques, including minimally invasive chevron and Akin osteotomy (MICA) and metaphyseal extra-articular transverse and Akin osteotomy (META), offer favourable outcomes but are associated with unpredictable first metatarsal fractures. This study identifies predictive factors for first metatarsal fractures following minimally invasive HV surgery. Methods: This retrospective case-control study analyzed 370 patients (499 feet) who underwent minimally invasive HV correction between November 2017 and August 2024 at a tertiary orthopaedic centre. Cases from the learning curve, revision procedures, and patients lost to follow-up were excluded. Patients were classified according to the presence or absence of a first metatarsal fracture, and logistic regression analysis was conducted to determine the associated risk factors. Results: First metatarsal fractures occurred in 5.4% (27 of 499 feet), with type II fractures being most common (40.7%). On multivariable logistic regression, both older age and simultaneous bilateral surgery were independently associated with fracture. The odds of fracture increased by 8.6% per year of age (OR 1.086 (95% CI 1.032 to 1.150); p = 0.003) and were higher in patients undergoing bilateral versus unilateral surgery (OR 4.02 (95% CI 1.75 to 9.80); p = 0.001). Bone mineral density of the femur and lumbar spine was not associated with fracture risk. Conclusion: Advanced age and bilateral surgery are key predictive factors for first metatarsal fractures following minimally invasive HV correction. Tailoring surgical and postoperative strategies, especially in elderly patients, may help mitigate fracture risk. Further research should explore metatarsal-specific bone density, surgical biomechanics, and younger patient cohorts.