Wintertime surgery increases the risk of conversion to hip arthroplasty after internal fixation of femoral neck fracture.

Unlabelled: The study demonstrates that wintertime surgeries are associated with impaired fracture healing and increases the risk of conversion to hip arthroplasty after osteosynthesis of femoral neck fracture. Furthermore, the results raise the possibility of association between seasonal changes in vitamin D levels and impaired fracture healing of femoral neck fracture.

Introduction: Although the changes of vitamin D level and calcitropic hormones influencing bone metabolism are seasonal, the effect of seasons on hip fracture healing is unknown. We assessed the effects of seasonal periodicity on conversion to hip arthroplasty after primary osteosynthesis of femoral neck fracture.

Methods: This nationwide retrospective observational cohort study involved 2779 patients aged ≥ 60 years who underwent internal screw fixation for primary femoral neck fracture and were discharged in 2000. Cases requiring conversion to arthroplasty during the 8-year follow-up derived from the Hungarian health insurance database were registered. Risk factors assessed included sex, age, fracture type, season of primary surgery and surgical delay. Competing-risks regression analysis was used for data analyses.

Results: During the observation period, 190 conversions to hip arthroplasty (6.8%) were identified, yielding an overall incidence of 19.5 per 1000 person-years. The crude incidence rates of conversions after osteosynthesis in winter, spring, summer and fall were 28.6, 17.8, 16.9 and 14.7 per 1000 person-years, respectively. Besides younger age, female sex and intracapsular fracture displacement, wintertime primary osteosynthesis significantly increased the risk of conversion (fall vs. winter, hazard ratio (HR): 0.50, 95% confidence interval [95% CI 0.33-0.76]; spring vs. winter, HR: 0.63, [95% CI 0.44-0.92]; summer vs. winter, HR: 0.62, [95% CI 0.42-0.91]).

Conclusions: Our study demonstrate that wintertime primary osteosynthesis increases the risk of conversion surgeries. The results may help improving the outcome of primary fixation of femoral neck fractures.