Cross-linked compared with historical polyethylene in THA: an 8-year clinical study.
Wear particle-induced osteolysis is a major cause of aseptic loosening in THA. Increasing wear resistance of polyethylene (PE) occurs by increasing the cross-link 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 cross-linked 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.


METHODS
Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Geerdink
Carel H
CH
Department of Orthopaedic Surgery, Atrium Medisch Centrum, Heerlen, The Netherlands. carelgeerdink@hotmail.com
Grimm
Bernd
B
Vencken
Wendy
W
Heyligers
Ide C
IC
Tonino
Alphons J
AJ
D000077:Acetabulum / Q000473:pathology; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D003432:Cross-Linking Reagents; D005260:Female; D006305:Health Status Indicators; D006621:Hip Joint / Q000473:pathology / Q000503:physiopathology; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000209:etiology / Q000473:pathology; D020959:Polyethylene / Q000737:chemistry; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D016896:Treatment Outcome
D003432:Cross-Linking Reagents; D020959:Polyethylene