Femoral Head Penetration Rates of Second-Generation Sequentially Annealed Highly Cross-Linked Polyethylene at Minimum Five Years

Abstract

Background: Highly cross-linked polyethylene (HXLPE) liners in total hip arthroplasty (THA) have demonstrated decreased wear rates, resilience to cup orientation, and reduced osteolysis compared to conventional polyethylene. Sequential irradiation and annealing below the melting temperature is unique compared to most HXLPE which is irradiated and remelted. This study purpose was to provide minimum five-year femoral head penetration rates of sequentially annealed HXLPE in primary THA. Methods: A retrospective review of a prospectively collected database identified 198 consecutive, cementless primary THAs utilizing sequentially annealed HXLPE (X3 ™ , Stryker, Mahwah, NJ). Operative technique was standardized. Radiographs were analyzed utilizing the Martell method with minimum five-year and one-year radiographs as baseline to minimize the initial bedding-in period. Results: Seventy-seven hips with minimum five-year follow-up were analyzed. Mean steadystate linear and volumetric head penetration rates were 0.095 mm/year and 76 mm 3 /year. Volumetric head penetration was significantly less for 32mm compared to 36mm (p=0.028). In addition, less head penetration was observed for ceramic 32mm heads at nearly half the rate compared to CoCr 36mm heads (p≥0.092). No correlations existed between penetration rates and age, BMI, UCLA Activity Level, polyethylene thickness, cup inclination or anteversion (p≥0.10). No radiographic osteolysis was observed. Conclusion: Surprisingly, linear head penetration rates of sequentially annealed HXLPE were nearly identical to the osteolysis threshold for conventional polyethylene and greater than reports of irradiated and remelted HXLPE. Further, this data corroborates reports that HXLPE is resilient to cup orientation and demographic variables. Longer term follow-up is recommended.

Sequentially Irradiated and Annealed Highly Cross-Linked Polyethylene: Linear Vector and Volumetric Wear in Total Hip Arthroplasty at 10 Years

“…This process was then repeated, and findings were averaged. For analyses presenting negative wear rates, the number was converted to zero in a method similar to that of Deckard and Meneghini [20] to avoid false reductions in rates. The rate (mm per year) was determined by taking the overall magnitude and dividing the number by the patient's length of follow-up.…”

New polyethylenes in total hip arthroplasty

“…Lastly, the results for the so-called second-generation HXLPEs, developed by introducing sequential annealing or vitamin E, have not yet demonstrated superiority over first-generation HXLPE. 43,44 Moreover, in a recent radiostereometric study, Thoen et al 45 were able to detect lower wear rates for vitamin E liners compared with moderately cross-linked polyethylene at five years, although relevant clinical advantages have not become evident yet.…”

Recent update on crosslinked polyethylene in total hip arthroplasty

“…The 10-year survivorship was 98.3%. Deckard and Meneghini [15], using both ceramic and cobalt-chrome heads, from 32 to 40-mm diameters, found surprisingly higher wear rates of sequentially annealed PE (0.095 mm/year, with minimum 5-year follow-up), close to the 0.1 mm/year which is known as the osteolysis threshold.…”