Long-term use of opioids and neuropathic medication after diaphyseal humerus fractures with or without nerve injury: a nationwide register-based cohort study of 4,185 patients

Background and purpose: Diaphyseal humerus fractures may lead to prolonged pain medication use. We aimed to study pain medication use after such fractures, focusing on nerve injury.Methods: Using Swedish register data (2007–2015), we identified individuals with diaphyseal humerus fractures. High use of opioids and neuropathic pain medication (≥ 60% of days covered/year; 2-month post-fracture washout) was evaluated in 5 groups: the general population (reference) and fractures treated nonoperatively or surgically, with and without nerve injury. Relative risks (RRs; 95% confidence intervals [CIs]; crude and adjusted [aRR] models; adjusted for age, sex, country of birth, income, and cohabitation status; and for previous high use of pain medication during the first year when analyzing the second year) were estimated in Cox proportional hazards regression models.Results: We identified 4,185 individuals with diaphyseal humerus fractures (3.7% with nerve injury; 23% surgically treated). In the first year, opioid use was higher among surgically treated fractures with nerve injury (aRR 17.6, CI 11.0–28.3) and without nerve injury (aRR 9.5, CI 8.2–10.9) than in the general population. In the second year, opioid use declined across most groups but remained elevated among nonoperatively treated fractures with nerve injury (aRR 8.3, CI 2.6–26.1). Neuropathic pain medication use increased in the first year, with no elevated use in the second. Adjustment did not change overall patterns. Women, older adults, lower-income individuals, and those living alone showed higher medication risk use.Conclusion: Patients with a diaphyseal humerus fracture were associated with a substantial burden of pain medication use, particularly for opioids during the first year post-injury in surgically treated fractures with nerve injury (RR 17.6) and a persistent risk in the second year among nonoperatively treated fractures with nerve injury (RR 8.3). Demographics and socioeconomic factors strongly relate to medication use, highlighting the need for careful early pain management and monitoring for prolonged medication use in exposed groups.