, Volume 470, Issue 2, pp 462-470
Date: 09 Sep 2011

The Effect of Poly Sterilization on Wear, Osteolysis and Survivorship of a Press-fit Cup at 10-Year Followup

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access
Topic
Hip

Abstract

Background

During the mid-1990s when our institution was using a press-fit porous-coated cup without supplemental initial fixation for primary THA, the manufacturer transitioned from gamma irradiation to gas plasma for the terminal sterilization of their polyethylene liners.

Questions/purposes

At minimum 10-year followup, we asked whether the fixation achieved by solely relying on a press-fit would be durable and how different liner sterilization methods affected radiographic wear, osteolysis, and survivorship.

Patients and Methods

We retrospectively reviewed 373 patients who underwent 398 primary THAs with a press-fit porous-coated cup between March 1995 and December 1996. Mean age at time of surgery was 61.5 ± 13.3 years and mean followup was 10.4 ± 3.7 years. We determined reasons for revision, survivorship, femoral head penetration, osteolysis, and wear-related complications.

Results

Among 20 revisions involving any component, seven were associated with wear and osteolysis. Kaplan-Meier survivorship, using component revision for any reason as an end point, was 95.7% (95% confidence interval, 93.6%–97.9%) at 10 years. Noncrosslinked liners sterilized with gas plasma demonstrated a mean head penetration rate of 0.20 ± 0.09 mm/year compared with 0.13 ± 0.07 mm/year for liners sterilized with gamma irradiation in air and 0.09 ± 0.04 mm/year for liners sterilized with gamma-irradiation with barrier packaging without oxygen. THAs with increased volumetric wear tended to demonstrate larger osteolytic lesions (r = 0.40) and there tended to be less osteolysis among the liners sterilized with gamma-irradiation with barrier packaging without oxygen. However, there was no difference in survivorship among the sterilization groups and there has been no cup or stem loosening associated with osteolysis.

Conclusions

Durable biologic fixation through 10-year followup can be achieved by solely relying on an initial press-fit. Noncrosslinking gas plasma for terminal sterilization of the polyethylene liners was associated with greater head penetration rate than gamma irradiation.

Level of Evidence

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Two authors (CAE, CAEJr) have received or may receive payments or benefits from a commercial entity (DePuy Orthopaedics, Inc, a Johnson and Johnson company, Warsaw, IN, USA) related to this work. Two authors (CAE, CAEJr) receive royalties from DePuy, one (CAEJr) serves as a DePuy consultant, and one (CAE) owns Johnson & Johnson stock. The institution (AORI) of the authors (CAE, CCP, HH, SEB, RHH, CAEJr) has received funding from Inova Health Services (Fairfax, VA, USA), Medtronic Sofamor Danek, Inc (Minneapolis, MN, USA), and a cooperative agreement awarded and administered by the US Army Medical Research & Materiel Command (USAMRMC) and the Telemedicine & Advanced Technology Research Center (TATRC) under Contract Number W81XWH-05-2-0079.
Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.
This work was performed at Anderson Orthopaedic Research Institute and Inova Center for Joint Replacement at Mount Vernon Hospital.