CHARACTERIZATION AND COMPARISON OF WEAR DEBRIS FROM FAILED TOTAL HIP IMPLANTS OF DIFFERENT TYPES

Particles of wear debris have been associated with loosening of implan ts and with osteolysis, but few studies have examined the relationship between characteristics of the implant and clinical variables and the concentration of particles isolated from periarticular tissues, We is olated and quantified particles of wear debris from orthopaedic implan ts in 123 tissue samples that had been obtained adjacent to a failed t otal hip prosthesis from eighty-eight patients, The concentration of t hese particles in the tissue and the size of the particles were then a nalyzed in relation to patient and implant-related variables, The numb er of particles ranged from 8.5 x 10(8) to 5.7 x 10(11) per gram of ti ssue (dry weight), More particles were found adjacent to failed titani um-alloy stems that had a cobalt-chromium-alloy modular head and faile d titanium-alloy-backed cups than were found adjacent to all-cobalt-ch romium-alloy prostheses. In addition, fewer particles were found adjac ent to implants with a twenty-eight-millimeter femoral head than were found adjacent to implants with other femoral head sizes, Univariate a nalysis also showed correlations between a high concentration of parti cles and fixation without cement, an implant that had been in situ for a long duration, a young patient age, and an initial clinical diagnos is of avascular necrosis, Biopsy specimens from the proximal femoral m embranes had higher concentrations than those from the joint capsules or the acetabular membranes, Although only five specimens were obtaine d directly from osteolytic lesions, the concentration of particles in those specimens was higher than that in biopsy specimens from other si tes, Although many univariate correlations were identified, stepwise c orrelation regression analysis showed that the composition of the impl ant and the size of the modular femoral head were most strongly relate d to the concentration of debris in tissue. CLINICAL RELEVANCE: The re sults of this study show that most failed hip implants are associated with billions of debris particles and that the concentration of these particles in tissue is related to several factors that are thought to be associated with the extent of implant wear, There are probably many factors that influence the production of orthopaedic wear debris. Som e are related to the design of the implant, Others, such as the level of activity, are related to the patient. Of the variables tested in th is study, the composition of the implant and the size of the modular h ead appeared to be most closely linked with the production of particle s, Our results do not necessarily reflect the extent of debris product ion by stable implants, but they suggest that the metallic composition of the femoral stem, the acetabular cup, and the modular head may hav e an important influence on the amount of wear debris.