Abstract
Introduction: Approximately 0.5 % of patients with metal on metal hip replacements develop post operative pain which is thought to be due to an immune reaction to metal wear particles, known as Aseptic Lymphocyte Dominated Vasculitis Associated Lesion (ALVAL). Treatment usually requires revision to a non metal on metal hip.. Is the development of ALVAL more likely in those patients with high wear rates?
Methods: Retrieved Metal on Metal (MOM) hip implants; periprosthetic tissue and blood samples were obtained from patients (n = 18) undergoing revision for unexplained pain at a mean of 2 years post operatively. The following variables were measured:
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linear wear rate (depth of the femoral head and acetabular socket wear patch/time from operation);
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the diagnosis and severity of ALVAL from histological sections of periprosthetic tissue (Wilhert grading system);
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pre-revision whole blood cobalt, and chromium levels using Inductively Coupled Plasma Mass Spectrometry.
All implants and tissue samples were analysed against control samples from patients undergoing revision of MOM hips for fractured femoral neck or impingement.
Results: Linear wear rates of retrieved implants, and blood levels of cobalt and chromium from patients with unexplained plain were greater than from control patients. Histolopathological analysis of tissue showed dense inflammatory infiltrates with healthy looking endothelial cells in all vessels from both patient groups.
Discussion and Conclusion: A painful MOM hip was associated with high wear rates and blood metal levels. The local inflammatory response was similar to “ALVAL”, ie lymphocyte dominated, but not exclusive to those patients with unexplained pain. We question whether ALVAL represents a vasculitis, or merely a classical lymphocyte driven inflammatory tissue response to metal debris particles.
Correspondence should be addressed to Mr Peter Howard, Editorial Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
