Individual and combined effects of somatic and mental disorders on reoperation risk after hip fracture surgery: a nationwide danish cohort study of 110,625 patients.

PURPOSE: Surgical complications after hip fracture surgery are common, particularly among patients with comorbidities. We examined the risk of reoperation concerning individual comorbidity groups, their combinations, and overall comorbidity burden.

METHODS

Using nationwide Danish registry data, we identified all patients undergoing hip fracture surgery between 2004 and 2021. Comorbidities were analysed as: (1) 10 major comorbidity groups, (2) all pairwise combinations of the 10 groups, and (3) overall comorbidity burden based on the 10 groups. Reoperation risk was estimated with 95% confidence intervals (CI), treating death as a competing event.

RESULTS

We included 110,625 patients, with a mean age of 82.4 years (70% female). The most prevalent comorbidity groups were cardiovascular (54%), renal/haematological (24%), and metabolic (20%) disorders. The highest 30-day reoperation risks were observed in patients with mental disorders 4.8% (CI 4.3-5.3) and musculoskeletal disorders 4.7% (CI 4.2-5.3). Compared with patients without comorbidities, adjusted hazard ratios (aHRs) for reoperation were 1.53 (CI 1.27-1.83) for neurological/alcohol disorders and 1.40 (CI 1.15-1.70) for mental disorders. Several combinations were associated with a significantly increased reoperation risk, highest for mental and hepatic/gastrointestinal disorders, with an aHR of 2.27 (CI 1.20-4.32). The reoperation risk increased with comorbidity burden, reaching an aHR of 1.33 (CI 1.11-1.59) for patients with ≥ 5 comorbidities. Similar patterns were seen at 365 days.

CONCLUSION

Specific comorbidities, particularly mental, hepatic/gastrointestinal, neurological/alcohol, and musculoskeletal disorders, were associated with increased reoperation risk after hip fracture surgery. Risk was highest for certain comorbidity combinations, highlighting the prognostic value of comorbidity profiles beyond overall burden and supporting their use in stratified care.