by P. Campbell Ph.D., J. Mirra M.D., and Harlan C. Amstutz, M.D.
Abstract
There is a general conception that resurfacing arthroplasty causes femoral head osteonecrosis and subsequent failure of the implant. This study histologically analyzed 25 resurfaced femoral heads up to 12 years post-operatively and found that osteonecrosis was not induced by the procedure.
Introduction
Materials and Methods
Results
Discussion
Acknowledgement
References
Introduction
Surface replacement arthroplasty developed from the cup arthroplasty concept that was introduced clinically in the 1950's. While the early cup arthroplasties mostly failed due to component loosening, the advent of cement fixation was a significant improvement and by the late 1970's surface replacements were used in England, Italy, Japan and the United States. However, short-term failures due to component loosening or technical errors such as incorrect positioning, poor fixation or inadequate component design led to a decline in clinical use [1]. Retrieval analyses of failed surface replacements showed that the majority of medium to long-term failures could be attributed to ultra high molecular weight polyethylene (UHMWPE) particle-induced bone resorption [2 , 3]. The large diameter components used in surface replacement arthroplasty, often in young and active patients, exacerbated the wear rate of the UHMWPE cups and osteolytic lesions were often rapid and extensive. Despite this explanation of the failure mechanism of surface replacements, there is a general conception within the orthopaedic community that resurfacing damages the femoral head blood supply, causing osteonecrosis (ON) and eventual failure. In light of the introduction of metal-on-metal surface replacements to prevent UHMWPE-induced osteolysis, the aims of this study were to assess the viability of femoral heads after resurfacing and to determine the role of ON in their failure.
Materials and Methods
Twenty-five revised, resurfaced femoral heads were studied by histological analysis. The clinical details of the patients included in the study are provided in Table 1. All of the specimens were from primary arthroplasty cases, except one that was a revision of a prior surface replacement Two cases had been treated with a femoral osteotomy, prior to arthroplasty. At revision, the femoral components were resected from the femur and were cut coronally through the middle third of the femoral head to yield 3mm thick sections. The cemented cobalt chrome THARIES cases were decalcified and processed for paraffin sections and were stained with Haematoxylin and Eosin. The cementless titanium PSRs were processed in poly-methyl-methacrylate for ground histology. These were thinned to approximately 0.5mm and stained with 2% aqueous Toluidine Blue. Several complete femoral head sections were examined from each case using a transmitted light microscope fitted with a polarizer to enhance the visualization