Epidemiology of non-unions following foot and ankle fractures: a nationwide analysis from 2014 to 2023

Non-unions are a common complication following fractures. Although fractures of the foot and ankle are frequent, reliable data on the incidence and epidemiology of non-unions in these regions are lacking. A nationwide retrospective analysis was conducted using inpatient data from the German Federal Statistical Office between 2014 and 2023. Fractures and non-unions of the foot and ankle were identified via ICD-10 coding, with two cohorts defined: fracture cases and non-union cases. Data were stratified by age and sex, and all co-coded secondary diagnoses were extracted and aggregated to identify the most frequent comorbidities. Temporal trends were assessed using linear regression, while age distributions were modelled with two-component Gaussian mixture models to capture distinct etiological subpopulations. Data processing, statistical analyses, and visualization were performed in R (Version 4.3) using Tidyverse packages. Between 2014 and 2023, 992,360 foot and ankle fractures and 20,268 non-unions of the foot and ankle were treated in hospitalized patients in German hospitals. Women were more frequently affected by both fractures and non-unions than men. The age distribution was bimodal, with peaks at 18–29 and 50–59 years in men, and at 50–79 years in women. The overall non-union rate was 2.0% and showed a declining trend over time. Age- and sex-specific differences were observed, with the highest non-union rate in women aged 40–49 years (3.2%). Comorbidities including obesity, allergies, depressive episodes, asthma, and sleep disorders were more prevalent in patients with non-unions compared to those with fractures. Non-unions following fractures of the foot and ankle remain rare and have declined steadily over the past decade. Age- and sex-specific differences underscore the need for targeted prevention strategies.