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

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

A Prospective, Randomized Clinical Study Comparing Marathon Polyethylene and Enduron Polyethylene Acetabular Liners Used in Total Hip Arthroplasty

The purpose of the study is to determine whether crosslinked Marathon and standard Enduron polyethylene liners show differences in bone loss around the hip implant.

Several institutions report very low wear rates with highly crosslinked polyethylene based on early clinical data. However, since bone loss typically appears after 5-year follow-up, the reduction in the incidence and extent of bone loss among total hip replacement patients with crosslinked Marathon liners, compared to those with standard Enduron liners, has not been as dramatic as the wear reduction. Despite the substantial reduction in wear that we observed at 5-year follow-up, the patients' perceptions of their outcomes remained similar among the Marathon and Enduron groups. This study will evaluate outcome at a minimum of 10-years after surgery among the same group of patients whose outcome was previously reported at 5-year follow-up. At 10-year follow-up, we anticipate that the reduction in wear associated with Marathon polyethylene will be associated with significant reductions in bone loss when compared to the Enduron polyethylene.

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?"

Inclusion Criteria: (from original study) -Elective total hip replacement patient (from 10-year follow-up) Consented to the original study. Received a Duraloc 100 cup with either a crosslinked Marathon or standard Enduron liner. Received an AML/Solution or a Prodigy stem with 28mm cobalt chrome femoral head. Exclusion Criteria: (from original study) -None (from 10-year follow-up) Patient did not receive device as specified in inclusion criteria. Patient refused to consent to the 10-year follow-up.

Leung SB, Egawa H, Stepniewski A, Beykirch S, Engh CA Jr, Engh CA Sr. Incidence and volume of pelvic osteolysis at early follow-up with highly cross-linked and noncross-linked polyethylene. J Arthroplasty. 2007 Sep;22(6 Suppl 2):134-9. doi: 10.1016/j.arth.2007.04.006. Epub 2007 Jul 27.

Engh CA Jr, Stepniewski AS, Ginn SD, Beykirch SE, Sychterz-Terefenko CJ, Hopper RH Jr, Engh CA. A randomized prospective evaluation of outcomes after total hip arthroplasty using cross-linked marathon and non-cross-linked Enduron polyethylene liners. J Arthroplasty. 2006 Sep;21(6 Suppl 2):17-25. doi: 10.1016/j.arth.2006.05.002.