Study Comparing Marathon Polyethylene and Enduron Polyethylene Acetabular Liners Used in Total Hip Arthroplasty

The incidence of clinically significant osteolysis was based on the number of unrevised THAs (total hip arthroplasties) with at least 1.5 square centimeters of pelvic and/or femoral osteolysis. Osteolysis was defined as an area of localized loss of trabecular bone or cortical erosion that was not apparent on the pre-operative or immediate postoperative radiograph. To obtain lesion sizes, the defects were outlined on the anteroposterior pelvic radiograph and the area of the lesion was measured using Martell's Hip Analysis Suite software. Lesions were considered clinically important if the total area of osteolysis around a hip replacement was at least 1.5 square centimeters.

A single reviewer, who was blinded to the type of polyethylene liner, evaluated femoral head penetration among all unrevised hips with minimum 9-year radiographic follow-up using serial anteroposterior pelvic radiographs. Two-dimensional head penetration was determined for each follow-up radiograph relative to the immediate post-operative (nominal 6-week follow-up) reference view using Hip Suite Analysis version 8.0 with elliptical correction, a validated, computer-assisted technique. A linear wear rate was evaluated for each hip that had a minimum of three follow-up radiographs by using a least-squares linear regression to calculate the slope of the best-fit line for the wear vector magnitude versus time in situ data. The slope from this regression represented the steady-state linear wear rate. The steady-state linear wear rate data from all hips in a group was used to compute a mean polyethylene wear value.

The rate of reoperation was based on the number of reoperations in each group. Any additional surgery after a participant's initial hip replacement was considered a reoperation.

The Harris Hip Score measures outcome after hip replacement and is based on a scale from 0 (worst) to 100 (best).

Patient satisfaction was quantified by asking participants to respond "yes" or "no" to the question, "Are you satisfied with the results of your hip operation?"