Abstract: Objective To investigate the correlation between the level of preoperative hemoglobin(Hb) and postoperative hospital stay in the elderly patients undergoing primary hip arthroplasty(PHA). Methods The basic information and related clinical data of 137 patients aged ≥65 years who underwent PHA in Nanjing Meishan Hospital from 2016 to 2022 were retrospectively collected. Multivariate linear regression was used to analyze the correlation between postoperative hospital stay and preoperative Hb level. Non-linear relationship was assessed by generalized additive mixed model and threshold effect model. Piecewise regression was used to evaluate segmented effect of Hb on hospital stay. Results Multiple linear regression analysis showed a negative correlation between hospital stay and preoperative Hb level in PHA patients(β=－0.51, P=0.031). After adjusting confounding factors, the results of the generalized additive mixed model curve fitting showed a nonlinear relationship between Hb level and hospital stay, with an inflection point at Hb 95 g/L. When the level of Hb was <95 g/L, there was a negative correlation between Hb and hospital stay(β=－0.52, P=0.003); When the level of Hb was >95 g/L, the correlation between the two factors was not statistically significant(P=0.482). Conclusions The decrease of preoperative Hb level shows significant effects on hospital stay in the elderly patients undergoing PHA, and 95 g/L is the threshold of Hb for prolonging hospital stay in PHA patients.

Key words: aged, hip fracture, primary hip arthroplasty, hospital stay, hemoglobin, retrospective cohort study