Analysis of the Effects of COVID-19 on Hip Fractures in Korea Without Lockdown: Interrupted Time Series Analysis Using a Nationwide Cohort

BACKGROUND: The purpose of this study was to investigate the change in the incidence rate, length of hospital stay (LOS), in-hospital mortality rate, and surgical method of hip fractures during the coronavirus disease 2019 (COVID-19) pandemic in South Korea where lockdown restrictions were not implemented. METHODS: We calculated the expected values of the incidence of hip fractures, in-hospital mortality and LOS of hip fracture patients in 2020 (COVID period) based hip fracture database of the Korean National Health Insurance Review and Assessment (HIRA) during a 9-year period from 2011 to 2019 (pre-COVID period). A generalized estimating equation model with Poisson distribution and logarithmic link function was used to estimate adjusted annual percent change (PC) of incidence rate and 95% confidence intervals (CIs). Then, we compared the annual incidence, in-hospital mortality rate and LOS in 2020 with the expected values. RESULTS: The overall incidence rate of hip fracture in 2020 was not significantly different from the expected value (PC, −5%; 95% CI, −13 to 4; P = 0.280). In women, the incidence rate of hip fracture in age groups over 70 years was smaller than the predicted value (P < 0.001). The in-hospital mortality rate was not significantly different from the expected value (PC, 5%; 95% CI, −8 to 19; P = 0.461). The mean LOS was larger than the expected value by 2% (PC, 2%; 95% CI, 1 to 3; P < 0.001). In intertrochanteric fracture, the proportion of internal fixation was smaller than the predicted value by 2% (PC, −2%; 95% CI, −3 to −1; P < 0.001), and that of hemiarthroplasty was larger than the predicted value by 8% (PC, 8%; 95% CI, 4 to 14; P < 0.001). CONCLUSIONS: In 2020, the incidence rate of hip fracture did not significantly decrease, and in-hospital mortality rate did not significantly increase compared to the expected rates, which were projected based on the HIRA hip fracture data from 2011 to 2019. Only LOS increased slightly.