Aims: In vitro studies have demonstrated that phagocytosed metal wear particles can lead to osteolysis by osteoclast activation. While others have reported massive metallosis with no loosening of the implant. The incidence of metallosis has remained uncertain so far. The purpose of this prospective study was to assess the incidence of metallosis and explore the correlation between metallosis and the time to revision of total hip replacements, getting additional information of the role of metallosis in aseptic loosening.

Materials and Methods: 72 patients underwent revision of total hip arthroplasty at the authors department from 01/01/2001 to 31/12/2002. All of them were examined for metallosis macroscopically and biopsy was taken from the interfacial membrane for histological analysis. Two subgroups were created from revisions of both cemented and uncemented prostheses. First group was composed of cases if metallosis was either visible during the surgery or high amount of metal particles were found by histology (high-grade metallosis). The other group consisted of cases if metallosis was not visible intraoperatively and only a few metal particles were described by histology (low-grade metallosis). The survivorships of the prostheses were assessed by Kaplan-Meyer statistic analysis.

Results: High-grade metallosis could be detected in 10/42 revisions of cemented (23.8%), and in 12/30 cases of uncemented prostheses(40%). The time from implantation to revision was 88(36–144) months when metal-losis could be observed vs. 122(41–360) months in cases with no metallosis in the cemented group. However there was not significant difference in survival rate of the uncemented prostheses between the metallotic and non-metallotic groups. If only very few metal particles were found, high amount of polyethylene particles were described by histology.

Conclusion: The incidence of high-grade metallosis was higher around uncemented prostheses. The time to revision of cemented prostheses was significantly less if high-grade metallosis was found. Hence it seems like metallosis can have effect on aseptic loosening of cemented prostheses by the large number of metal particles which can make the progress of osteolysis faster resulting in shorter survivorship of the implant. If no high-grade metallosis, but a lot of polyethylene wear were found, then those particles could have the same inductive effect on aseptic loosening.

Periprosthetic bone loss after total joint arthroplasty is a major clinical problem resulting in aseptic loosening of the implant. Among many cell types, osteoblasts play a crucial role in the development of peri-implant osteolysis. In this study, we tested the effects of calcitriol (1α,25-dihydroxy-vitamin-D₃) and the bisphosphonate pamidronate on titanium-particle- and TNF-α-induced release of interleukin-6 and suppression of osteoblast-specific gene expressions in bone-marrow-derived stromal cells with an osteoblastic phenotype. We monitored the expression of procollagen α1[1], osteocalcin, osteonectin and alkaline phosphatase mRNAs by Northern blots and real-time reverse transcription and polymerase chain reaction analyses. The release of various cytokines was also analysed by ELISA.

We found that calcitriol or pamidronate could only partially recover the altered functions of osteoblasts when added alone. Only a combination of these compounds restored all the tested functions of osteoblasts. The local delivery of these drugs may have therapeutic potential to prevent or to treat periprosthetic osteolysis and aseptic loosening of implants.