In Vivo Wear Analysis of Third- versus Second-Generation Moderately Crosslinked Polyethylene Liners in Total Hip Arthroplasty.

BACKGROUND

Prior studies have reported low rates of wear associated with crosslinked polyethylene (XLPE) liners used in total hip arthroplasty, but no studies have compared the in vivo performance of second-generation and third-generation XLPE liners. The purpose of this study was to compare the in vivo wear profile and corresponding odds of developing osteolysis associated with second-generation and third-generation liners.

METHODS

Patients receiving a second-generation or third-generation XLPE liner during primary total hip arthroplasty were reviewed. Patients who had < three years of radiographic follow-up were excluded. A total of 58 third-generation and 51 second-generation liners were analyzed. Polyethylene wear was estimated using a semiautomated, edge-detection software analysis of anterioposterior pelvis radiographs. Radiographs were examined manually for osteolysis. Multivariable analysis was performed to estimate and compare the rates of wear. Odds ratios were calculated to estimate the relative odds of developing wear > 0.1 or > 0.05 mm/y.

RESULTS

The median linear wear of second-generation liners was 0.068 mm/year, and that of third-generation liners was zero mm/year. There were 20 (39%) second-generation and 13 (22%) third-generation liners that demonstrated wear > 0.1 mm/year. Osteolysis was radiographically observed in three second-generation liners and no third-generation liners. Multivariable analysis found second-generation liners, increased femoral head size, and increased acetabular abduction angle to be associated with increased wear. Liner type was not associated with wear > 0.1 or > 0.05 mm/year. Increased inclination angle was consistently associated with higher levels of wear across all analyses.

CONCLUSIONS

Third-generation liners exhibited lower wear than second-generation liners at a minimum 3-year follow-up, but were not associated with lower rates of osteolysis or wear exceeding 0.1 or 0.05 mm/year. Both XLPEs had surprisingly high proportions of liners with wear greater than > 0.1 mm/year. Component positioning appears to be more important than liner material when using contemporary XLPEs.