Contributing factors for surgically treated Hallux Valgus: a nationwide population-based cohort study in Taiwan

Hallux valgus (HV) is a prevalent deformity of the first metatarsophalangeal joint that can progress from a cosmetic concern to a painful, function–limiting condition requiring surgical correction. However, population-based data focusing on severe HV in Taiwan remains limited. Therefore, this study aims to examine national trends and systemic disease associations among patients undergoing HV surgery. Data from the National Health Insurance Research Database of Taiwan (2008–2021) were analyzed. Severe HV was defined by receipt of corrective surgery (procedure codes 64132 and 64133). Exposures were claims-defined comorbidities (≥ 10 outpatient visits or ≥ 1 hospitalization), and individuals with prior HV surgery were excluded. A non-exposed cohort was assigned random index dates. Propensity-score matching (1:1) was applied, and hazard ratios (HRs) were estimated using Cox proportional hazards models. Of 25,767,574 individuals in the NHIRD, 2,392,429 with index dates outside 2008–2020, 9,065 with prior HV surgery, and 8 men in the breast cancer analysis were excluded, leaving 23,366,072 eligible individuals (3,377,791 with and 19,988,281 without the study comorbidities). After 1:1 propensity-score matching, the matched cohort comprised 6,755,582 individuals (3,377,791 per group) with excellent post-matching covariate balance. The annual prevalence of severe HV increased steadily over the study period and was consistently higher among women and older adults. Several comorbidities were associated with significantly higher risk of HV surgery, most notably anterior cruciate ligament (ACL) injury (adjusted HR 7.37, 95% CI 2.62–20.75), rheumatoid arthritis (RA; adjusted HR 5.31, 95% CI 3.52–8.00), Sjögren’s syndrome (adjusted HR 4.25, 95% CI 1.94–9.30), and osteoporosis (adjusted HR 3.52, 95% CI 2.90–4.27). Increased risks were also identified for obesity (adjusted HR 2.51, 95% CI 1.42–4.44), gout (adjusted HR 2.58, 95% CI 1.93–3.45), thyroid disease (adjusted HR 1.71, 95% CI 1.46–1.99), chronic obstructive pulmonary disease (COPD; adjusted HR 2.44, 95% CI 1.83–3.25), and breast cancer (adjusted HR 1.46, 95% CI 1.10–1.93). Severe HV requiring surgery was associated with multiple systemic comorbidities, suggesting that factors beyond a localized forefoot deformity may be involved. A surgery-based case definition identifies clinically meaningful disease but may be influenced by healthcare access and treatment preferences. These findings may inform risk-stratified counseling; however, causal relationships and the benefit of early preventive strategies require confirmation in prospective studies.