A QUALITATIVE AND QUANTITATIVE STUDY OF RETRIEVED FEMORAL HEADS IN 3 DIFFERENT TYPES OF RESURFACE HIP ARTHROPLASTIES

Tissue reactions and percentage of mineralized bone in three different types of retrieved femoral head hip resurface prostheses were studied in undecalcified ground sections without removing the metal. All of t he prostheses demonstrated soft tissue between the cement-implant and bone. There were some areas without soft tissue between bone and cemen t. This bone was often not normally stained, indicating a disturbed mi neralization. The soft tissue layer in the cemented prostheses was obs erved in different stages of necrosis, while the uncemented prostheses demonstrated a thick collagen membrane. One of the cemented groups de monstrated a gradual decrease of mineralized bone towards the cement. The uncemented implants revealed normal bone qualitatively and quantit atively when the bone bordering the prosthesis was excluded. Too high interfacial stresses were probably a major failure mechanism, especial ly in the rapidly failed noncemented prostheses. Negative long-term ef fects of the cement on the bone may have contributed to failure in the cemented resurface arthroplasties.