Classification of First Metatarsal Osteotomy Healing Following Minimally Invasive Hallux Valgus Surgery

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Minimally invasive or percutaneous surgery (MIS) for hallux valgus correction has seen increased adoption due to a growing evidence base of positive clinical and radiographic outcomes following surgery. However, no standardised or validated radiographic classification exists to evaluate the first metatarsal osteotomy healing following MIS hallux valgus surgery. The aim was to develop a new radiographic classification system for assessing bone healing following MIS distal transverse osteotomy for hallux valgus. Methods: A four-domain radiographic classification system based on callus formation, AP osteotomy line, lateral osteotomy line, and remodelling for MIS osteotomy healing was developed and tested on a cohort of 27 feet who underwent percutaneous transverse osteotomy for hallux valgus correction. Patients had simultaneous postoperative WBCT and standard radiographs following surgery. Five surgeons reviewed anonymized radiographs to evaluate interobserver reliability. WBCT was used to confirm union status and classification interpretation. Results: The classification system demonstrated substantial interobserver reliability for lateral osteotomy line (Fleiss kappa = 0.671, 95% CI: 0.505-0.814) and AP osteotomy line assessment (Fleiss kappa = 0.664, 95% CI: 0.459-0.811), with moderate agreement for callus formation (κ = 0.465) and remodelling (κ = 0.439). The classification showed strong correlation with WBCT findings, with an optimal threshold of 8 points identified to differentiate union from non-union, achieving an overall classification accuracy of 85.2%. Receiver operating characteristic analysis indicated an area under the curve of 0.832. At the optimal threshold, the classification demonstrated 90.0% sensitivity and 71.4% specificity for detecting union. Conclusion: This new classification provides a reliable tool for assessing first metatarsal bone healing following MIS hallux valgus osteotomies, with substantial interobserver reliability. It offers a standardised approach for radiographic evaluation, supporting clinical decision-making and enhancing comparability across studies. Classification and scoring guide for percutaneous osteotomy healing on radiographs – the Percutaneous Osteotomy Healing Score