Introduction

The optimal total hip bearing for young, active patients remains elusive. Early implant designs used 20-year survivorship as a benchmark for success in an older population of patients. Younger arthroplasty patients have created concern over traditional survivorship data because of their increased activity, and thus higher propensity for wear. However, there is insufficient evidence-based data regarding which bearing is best for such patients. A surgeon’s determination of the optimal bearing surface in total hip arthroplasty can be influenced by patient demographics, patient preference, hospital restrictions, implant cost, and risk factors for a particular bearing surface.

Three commonly used bearing surfaces are metal on polyethylene, ceramic on ceramic, and metal on metal. All of these bearings are currently on the market and have distinct advantages, but each also has unique complications. Metal-on-metal bearings have concerns regarding increased serum ion levels and their long-term consequences. Adverse local tissue reactions (ALTR) have recently become additional concerns. With ceramic-on-ceramic bearings, there is a risk of ceramic fracture, noise, and occasional squeaking. Metal-on-plastic cross-linked polyethylene articulations raise concerns about in vivo oxidation, as well as diminished strength of the polyethylene caused by the radiation dose used to cross link. Therefore the prevention of periacetabular osteolysis in young patients remains a challenge. The best bearing to use in this young, active population remains an unanswered question because there is currently no evidence-based data to rely on.

Two-dimensional plain radiographs are used as an evaluation instrument to estimate osteolytic lesions. However, plain films often underestimate the amount of periacetabular osteolysis by as much as 25%. Therefore, the lack of sensitivity of our current evaluation instrument, (ie, plain radiographs) prevents clinicians from distinguishing which bearing is functioning best at this early, 5-year time period. Computed tomography (CT) has been shown to be a novel method of assessing periacetabular osteolysis in different bearing surfaces and may ascertain these osteolytic lesions at an earlier stage. These computerized, thin-cut CT scans coupled with artifact suppression software can provide an evaluation of osteolysis at an earlier stage, thus increasing the sensitivity of detection.

This study compared the prevalence of periacetabular osteolysis using CT in patients with metal-on-metal, ceramic-on-ceramic, and metal-on-cross-linked bearings at a minimum 5-year follow-up.

Materials and methods

A retrospective review of all primary total hips using metal-on-metal, ceramic-on-ceramic, or metal-on-cross-linked polyethylene bearing surfaces before 2005 was performed. To determine eligibility, each of these patients had their preoperative radiographs screened by 1 individual (TKF) to determine the presence of periacetabular osteolytic lesions. Patients with a cystic lesion on their preoperative radiograph either on the anteroposterior or lateral view were excluded from the study group. In addition, any patient with less than 5 years’ follow-up was excluded.

All patients who met the inclusion criteria were contacted by mail and/or phone for a follow-up CT scan. Our final sample included 72 hips in 68 patients: 24 metal-on-metal hips, 24 metal-on-cross-linked polyethylene hips, and 24 ceramic-on-ceramic hips. For the metal-on-metal group, the average follow-up was 79.9 months (range 62–90 months), 73.3 months (range 62–98 months) for the metal-on-cross-linked polyethylene group, and 65.5 months (range 55–78 months) for the ceramic-on-ceramic group.

Thin-cut CT scans with artifact suppression were used to evaluate the 72 hips. Axial, coronal, and sagittal views were inspected for osteolysis. Clinical variables that were evaluated included age, body mass index (BMI), and University of California, Los Angeles (UCLA) Activity Score.

The implant used in the metal-on-metal group was a DePuy (Warsaw, IN) cobalt chrome-on-cobalt chrome bearing. The metal-on-cross-linked polyethylene was a DePuy cobalt chrome femoral head on a Marathon polyethylene, and the ceramic-on-ceramic implants studied in this group were all alumina-on-alumina constructs from a variety of manufacturers. There were 18 Stryker (Mahwah, NJ) implants, 1 Wright Medical (Arlington, TN) implant, and 5 Smith and Nephew (Memphis, TN) implants.

An analysis of variance (ANOVA) to evaluate the difference between bearing type with regard to age, BMI, and UCLA Activity Score was performed.