Abstract: Objective To investigate the risk factors of hip instability in elderly patients with femoral neck fracture after hemiarthroplasty (HA).Methods The medical records of 133 patients with femoral neck fracture who received HA treatment in the Department of Orthopedics of our hospital from January 2015 to October 2022 were retrospectively collected.According to whether the patients suffered hip dislocation after surgery,the patients were divided into dislocation group (n=35) and non-dislocation group (n=98).Demographic variables such as age,sex and body mass index (BMI) were recorded in the two groups.Complications such as diabetes,hypertension,heart disease and chronic obstructive pulmonary disease (COPD) were recorded.Prosthetic type,surgical approach,soft tissue repair type,blood loss and other surgical phase variables were recorded.Central marginal Angle (CEA),extraneous Angle (ABA),eccentricity,lower limb length difference (LLD),acetabular width,acetabular depth,and femoral head coverage (FCR) were measured on radiographs.Wald method was used to establish Logistic regression model to elucidate the risk factors of dislocation after HA.Results The proportion of COPD in the dislocation group was significantly higher than that in the control group (P<0.05),and there was no significant difference in baseline characteristics between the two groups (P>0.05).There was no significant difference between the two groups (P>0.05).There were no significant differences in CEA,ABA,LLD,acetabular width,eccentricity and FCR between 2 groups (P>0.05),but the acetabular depth and depto-width ratio in luxation group were significantly lower than those in control group (P<0.05).Gender,COPD,CEA,acetabular width-to-depth ratio and LLD were independent risk factors for hip instability after HA (P<0.05).Conclusion In this study,COPD,male,LLD,and small CEA and acetabular broad-to-depth ratio are independent risk factors for hip instability after HA,and therefore HA is not recommended for the treatment of femoral neck fractures in elderly patients with these conditions.

Key words: femoral neck fracture; hemiarthroplasty; hip dislocation; acetabular parameter