OBJECTIVETo investigate the decrease of bone mineral density in female patients, effects on acetabular displacement.

METHODSFrom October 2013 to November 2015, a total of 34 patients underwent total hip replacement in the Department of orthopedics, the Third Affiliated Hospital of Zunyi Medical College. The two groups of patients were female and the patients were treated with hip osteoarthritis. Based on the lowest value of preoperative dual energy X-ray bone mineral density (DXA), the patients were divided into normal group and low bone mineral density(-3.5<=T<=-1). There were 10 patients in the normal group, ranging in age from 55 to 64 years old, with an average of (58.00±4.22) years old. There were 24 patients in the low bone density group, ranging in age from 58 to 72 years old, with an average age of (65.71±8.19) years old. All the patients received a THA implant with ceramic-on-ceramic bearings(Depuy America). The lining system was Pinnacle cup. During the operation, the acetabular cup was maintained at abduction 45 degree and anteversion 15 degree. Analysis (RSA) of acetabular components in 3, 6, 12, and 24 months after surgery.

RESULTSThere was a statistically significant difference in cup migration between patients with normal BMD and those with low BMD. At 3 months, compare to the normal group, the low bone mineral density (BMD) occurred in the X axis (95% confidence interval, 0.01 to 0.31;=0.006) and Y (95% confidence interval 0.20 to 0.39;=0.003). The initial rotation occurs in a separate Z axis(95% confidence interval -0.26 to 0.81;=0.006).

CONCLUSIONSIt has produced that increaseed migration of uncemented cups in female patients with low systemic BMD in 3 months after surgery.