Cross-linked Compared with Historical Polyethylene in THA: An 8-year Clinical Study

Abstract

Wear particle-induced osteolysis is a major cause of aseptic loosening in THA. Increasing wear resistance of polyethylene (PE) occurs by increasing the crosslink density and early reports document low wear rates with such implants. To confirm longer-term reductions in wear we compared cross-linked polyethylene (irradiation in nitrogen, annealing) with historical polyethylene (irradiation in air) in a prospective, randomized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years (mean, 8 years; range, 7-9 years). The insert material was the only variable. The Harris hip score, radiographic signs of osteolysis, and polyethylene wear were recorded annually. Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed (five patients died, three were lost to followup). At 8 years, the wear rate was lower for crosslinked polyethylene (0.088 ± 0.03 mm/year) than for the historical polyethylene (0.142 ± 0.07 mm/year). This reduction (38%) did not diminish with time (33% at 5 years). Acetabular cyst formation was less frequent (39% versus 12%), affected fewer DeLee and Charnley zones (17% versus 4%), and was less severe for the cross-linked polyethylene. The only revision was for an aseptically loose cup in the historical polyethylene group. Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis, showing no signs of aging at mid-term followup.

The John Charnley Award: An Accurate and Sensitive Method to Separate, Display, and Characterize Wear Debris: Part 1: Polyethylene Particles

“…With the introduction of highly wear-resistant crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE), the overall volume of wear debris in THA has decreased compared to conventional polyethylene (PE) from more than 15 mm 3 /million cycles to less than 1 mm 3 /million cycles, particularly in THAs [9,37]. The reduction in overall PE wear rates has resulted in an associated and substantial reduction in the rates of osteolysis, with several clinical studies reporting no incidence at 5 to nearly 10 years' followup [10,13,19,20,27,32,39]. Furthermore, wear particles of specific shapes, such as fibrils or needles, that elicit higher cellular reaction [14,15,49] have been minimized.…”

Is Routine Mid-term Total Hip Arthroplasty Surveillance Beneficial?

“…Higher failure rates also have been associated with acetabular component malposition, younger age, and male gender [6,21,29]. Although mid-term followup of cross-linked polyethylene bearings suggests that clinically important periprosthetic osteolysis will be rare during the first decade after THA [3,9,17], longer followup is needed to determine that early results will be sustained into the second decade. Surgeons recognizing that components with a track record of concern may consider closer clinical and radiographic followup.…”

Use of Morphometry to Quantify Osteolysis after Total Hip Arthroplasty

“…The measurement of the area of osteolysis on radiographs has not been achieved easily [9,12]. Our aims were (1) to develop the concept of a morphometric grid to provide a simple tool for measuring the area of osteolytic lesions and (2) to test the reliability of this tool to measure osteolytic lesions seen on radiographic films when used by a representative range of observers.…”

“…However, the associated cost of CT or MRI and increased radiographic exposure for the patient (CT) preclude their use in routine screening. The addition of Judet oblique views to plain AP pelvic radiographs will improve sensitivity of detection from 41% to 73% and enable the observer to more precisely define the location of a lesion [5,12,40]. Consequently, it still is recommended that radiographic assessment be used in arthroplasty review [22,39,40].…”