The 2012 John Charnley Award: Clinical multicenter studies of the wear performance of highly crosslinked remelted polyethylene in THA

Abstract

Background: Highly crosslinked polyethylene (HXLPE) in THA was developed to reduce particle-induced periprosthetic osteolysis. A series of clinical studies were initiated to determine the clinical efficacy as judged by patient-reported scores, radiographic osteolysis, and wear analysis of one form of HXLPE.

Questions/purposes: The purposes of this series of studies were to (1) determine the wear rates of one form of HXLPE; (2) report long-term (7-10 years) patient-reported outcome measures; (3) assess the effect of femoral head size on wear; and (4) determine the incidence of periprosthetic osteolysis.

Methods: A single-center and two multicenter studies were conducted on 768 primary patients (head size 26-36 mm) undergoing THA at eight medical centers. Patient-reported outcome scores, radiographic grading for osteolysis, and radiographic wear evaluation were performed.

Results: Serial plain radiographs showed no periprosthetic osteolysis in the three studies. The average femoral head penetration rates did not correlate with time in vivo for patients with standard femoral head sizes. Although there was an indication of higher wear in patients with 36-mm diameter femoral heads, it was below the threshold for producing osteolysis.

Conclusions: The introduction of this HXLPE substantially improved the prognosis of patients after THA up to 13 years as judged by clinical scores, incidence of osteolysis, and polyethylene wear measurements.

Level of evidence: Level III, therapeutic study. See the Guideline for Authors for a complete description of levels of evidence.

Fig. 1

Comparison of the femoral head penetration over time in patients receiving conventional or HXLPE with conventional head sizes using the group regression method. Although the femoral head penetrated is a constant rate of 0.1 mm/year with conventional polyethylene, there was no correlation between femoral head penetration and time in the HXLPE group regardless of femoral head size.

Fig. 2

Steady-state wear plotted against time with regression lines for the early and late periods. There was no difference in the rate of femoral head penetration between the early and late time periods.

Fig. 3

The group regression graph of the multicenter large head series, Study 3. Although one analytical method indicated a difference in femoral head penetration rate for 36-mm femoral heads, there was no difference in the slope of the linear regression lines.