Short-Term in Vivo Wear of Cross-Linked Polyethylene

• Published in: Journal of bone and joint surgery. American volume 2004-04, Vol.86 (4), p.748-751
• Main Authors: Heisel, Christian, Silva, Mauricio, dela Rosa, Mylene A, Schmalzried, Thomas P
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; Arthroplasty, Replacement, Hip - instrumentation; Biocompatible Materials - therapeutic use; Biological and medical sciences; Diseases of the osteoarticular system; Female; Hip Prosthesis; Humans; Male; Medical sciences; Middle Aged; Polyethylenes - therapeutic use; Prosthesis Design; Prosthesis Failure; Time Factors
• ISSN: 0021-9355; 1535-1386
• DOI: 10.2106/00004623-200404000-00012

BackgroundCross-linked polyethylene was developed to reduce volumetric wear in prosthetic joints. Hip simulator studies have shown promising results with regard to wear reduction. This study evaluated the short-term in vivo wear of a moderately cross-linked polyethylene.MethodsLinear head penetration, as an assessment of in vivo polyethylene wear, was measured in two groups of patients after total hip replacement. Twenty-four hips received a conventional polyethylene insert and thirty-four, a cross-linked polyethylene liner; both inserts were manufactured by the same company. Linear and volumetric wear rates were measured on radiographs with use of a validated computer-assisted technique and were adjusted for patient-related factors. Patient activity was assessed by a computerized two-dimensional accelerometer worn on the ankle.ResultsPatients with a conventional polyethylene insert showed a mean linear wear rate of 0.13 mm per year and a mean volumetric wear rate of 87.6 mm per year. The group with a cross-linked polyethylene liner showed a mean linear wear rate of 0.02 mm per year and a mean volumetric wear rate of 17.0 mm per year. Wear in the group with cross-linked polyethylene was 81% lower than that in the group with conventional polyethylene (p < 0.00001). Accounting for differences in patient activity, the adjusted wear rates per million cycles for a patient weight of 70 kg were 53 mm per million cycles for conventional polyethylene and 15 mm per million cycles for cross-linked polyethylene, a 72% reduction (p = 0.0002). No factor, other than the type of polyethylene, was found to influence the difference in wear rates between the two groups.ConclusionsThe results of this study are promising. The in vivo wear reduction with this cross-linked polyethylene is consistent with the predictions of hip simulator studies.Level of EvidenceTherapeutic study, Level II-1 (prospective cohort study). See Instructions to Authors for a complete description of levels of evidence.