History and systematic review of wear and osteolysis outcomes for first-generation highly crosslinked polyethylene

Abstract

Background: Highly crosslinked polyethylene (HXLPE) was introduced to reduce wear and osteolysis in total joint arthroplasty. While many studies report wear and osteolysis associated with HXLPE, analytical techniques, clinical study design and followup, HXLPE formulation and implant design characteristics, and patient populations differ substantially among investigations, complicating a unified perspective.

Questions/purposes: Literature on first-generation HXLPE was summarized. We systematically reviewed the radiographic wear data and incidence of osteolysis for HXLPE in hip and knee arthroplasty.

Methods: PubMed identified 391 studies; 28 met inclusion criteria for a weighted-averages analysis of two-dimensional femoral head penetration rates. To determine the incidence of osteolysis, we estimated a pooled odds ratio using a random-effects model.

Results: Weighted-averages analyses of femoral head penetration rates in HXLPE liners and conventional UHMWPE liners resulted, respectively, in a mean two-dimensional linear penetration rate of 0.042 mm/year based on 28 studies (n=1503 hips) and 0.137 mm/year based on 18 studies (n=695 hips). The pooled odds ratio for the risk of osteolysis in HXLPE versus conventional liners was 0.13 (95% confidence interval, 0.06-0.27) among studies with minimum 5-year followup. We identified two clinical studies of HXLPE in TKA, preventing systematic analysis of outcomes.

Conclusions: HXLPE liner studies consistently report lower femoral head penetration and an 87% lower risk of osteolysis. Reduction in femoral head penetration or osteolysis risk is not established for large-diameter (>32 mm) metallic femoral heads or ceramic femoral heads of any size. Few studies document the clinical performance of HXLPE in knees.

Fig. 1

The review was performed systematically and included a detailed analysis of 44 hip articles and two knee articles.

Fig. 2

This forest plot illustrates the variation in reported penetration rates of HXLPE in different studies used to calculate the weighted average of 0.042 mm/year.

Fig. 3

This forest plot illustrates the variation in reported penetration rates of conventional UHMWPE in different studies used to calculate the weighted average of 0.137 mm/year.

Fig. 4

This forest plot illustrates the variation in the standardized difference in mean of the 2D linear penetration rates of crosslinked and conventional polyethylene liners. Across every study, the difference in means consistently favors crosslinked over conventional polyethylene.

Fig. 5

The odds ratio for osteolysis (conventional versus HXLPE) was 0.131 across nine studies. Note an odds ratio of less than 1 implies a lower risk of osteolysis for HXLPE relative to conventional UHMWPE. PE = polyethylene.