The Cemented All-Polyethylene Acetabular Cup: Factors Affecting Survival With Emphasis on the Integrated Polyethylene Spacer

Four hundred seven primary total hip arthroplasties were performed using a cemented, direct compression molded all-polyethylene acetabular component. Based on a double-blinded randomization schedule, one group received acetabular cups with cement spacers made from polyethylene integrated into the cup, whereas the other group received the same acetabular cups with the polyethylene spacers removed. Patients were followed up for an average of 6.5 years. During this follow-up period, there were 3 revisions for acetabular cup loosening and 40 acetabular cups that had a global radiolucent line at least 1 mm wide. Acetabular cups with polyethylene spacers were found to have a significantly higher initial rate of failure (P < .0380) when compared with cups without cement spacers. Yet, polyethylene spacers resulted in a significantly thicker and more uniform cement mantle in zones 1, 2, and 3 (P < .0001). Cups initially placed at an angle of 45.0° to 50.5° had the highest survival rate compared with all possible angle ranges (P < .0158).