Continued Improved Wear with an Annealed Highly Cross-linked Polyethylene

Abstract

Background Highly cross-linked polyethylene (HXLPE), created by disrupting the molecular structure of polyethylene, then through the application of heat, encourages creation of new cross-links in the process, resulting in a material with improved wear resistance. The impetuses for this new technology were the unsatisfactory wear properties and subsequent osteolysis of noncross-linked polyethylene. A 72% reduction in wear using highly crosslinked polyethylenes (HXLPE) compared with conventional polyethylene at 5 years was described previously. The longest term followup studies on HXLPE range from 2 to 6 years. Questions/purposes We therefore addressed the following questions: (1) Does the improvement in wear observed at the earlier followup continue to 7 to 10 years? (2) What is the incidence of osteolysis in this group of patients and in the control group? Methods We retrospectively reviewed 38 prospectively followed patients who had 42 hips with an annealed HXLPE who were followed a minimum of 7 years (average, 8.6 years; SD = 1; range, 7-10.3 years). Wear and osteolysis were compared with those of a control group of 39 patients (40 hips) from a US Investigational Device Exemption (IDE) prospective, randomized study begun in 1996 with conventional polyethylene and followed for a minimum of 6 years (average, 7.5 years; SD = 1.1; range, 6-10.2 years). Linear head penetration was measured from AP radiographs at early, 1-year, 5-year, and most recent followups. Results At the average followup, annual linear wear was 0.031 mm (SD = 0.014) for the HXLPE and 0.141 mm (SD = 0.080) for the control group, a 78% reduction. No mechanical failure of the polyethylene was noted in either group. Incidence of osteolysis was 50% in the control group (all lesions confined to proximal Gruen Zones 1 and 7) compared with no cases in the investigational group. Conclusions We observed an improvement in wear and no mechanical failures with this annealed material.

Ceramic Bearings for Total Hip Arthroplasty Have High Survivorship at 10 Years

“…Periprosthetic osteolysis with conventional polyethylene is reportedly the most common reason for revision surgery with a revision rate as high as 12% at 10 years [18,19]. A recent report using a highly crosslinked polyethylene followed for 10 years showed no evidence of osteolysis [4]. In our study, at minimum 10 years, radiographic evidence for osteolysis is present in 26% of the control patients with only 3% being revised (Fig.…”

“…New alterative bearings with greater wear resistance have been developed with the promise to reduce wear debris and extend implant longevity [8,11]. These new low-wear bearings, which include highly cross-linked polyethylenes, metal on metal, and ceramic on ceramic, now have minimum 5-year results and have high survivorship [3,4,8,9,14,31].…”

Highly Crosslinked Polyethylene Does Not Reduce Aseptic Loosening in Cemented THA 10-year Findings of a Randomized Study

“…In a variety of studies with mean followup ranging from 5 to 8.6 years, wear rates have been lower than for conventional PE [5,10,34,38,46,52]. For uncemented THA, the low wear rates of XLPE have been accompanied by absent or low occurrence of periprosthetic osteolysis [4,30], supporting the PE particle theory.…”

Causes of Failure of Ceramic-on-Ceramic and Metal-on-Metal Hip Arthroplasties

“…The wear rate of highly crosslinked polyethylene is 23%-95% lower than conventional polyethylene [3,4,13], even for thinner liners, allowing for use of larger femoral heads, neutralizing the purported advantages of the hard bearings to a degree. However, these data emerged over time, as hard bearings became available in the marketplace and grew rapidly, peaking to about 40% use during THA by 2006 [1].…”