SummaryIntroductionWear particles produced from prosthetic joints may play critical roles in periprosthetic inflammatory reactions and osteolysis. The objective of this study was to quantify and compare the response to wear debris from different biomaterials at the bone–implant interface in a rat knee model.MethodsSixty rats were divided into titanium alloy (Ti–6Al–4V), cobalt chromium (Co–Cr), ceramic (Al2O3), ultrahigh molecular weight polyethylene (UHMWPE), and control (phosphate buffered saline) groups with 12 animals per group. A nonweight-bearing titanium rod was implanted into the right distal femur of each rat followed by intra-articular injections of the biomaterial particles to the surgical knees for up to 16 weeks. Micro-computed tomography scanning was performed monthly and at the time of sacrifice to determine bone densities around the bone–implant interface. Histological evaluations were executed to quantify local inflammatory reactions and osteoclastogenesis.ResultsCo–Cr particles resulted in the most severe reductions in bone density. UHMWPE and ceramic particles resulted in a rapid reduction in bone density followed by a recovery. Inflammatory pseudo-membranes were ubiquitously present close to the femoral condyle and pin insertion site. Ceramic particles significantly promoted periprosthetic tissue formation compared with the other groups (p < 0.05). Cathepsin K positive cells were dominantly present at the peri-implant site following challenges of metallic alloy and ceramic particles.ConclusionDifferent biomaterials in particulate form exert different forms of adverse effects in terms of the amount of osteolysis and inflammatory reactions on bone tissue at the bone–implant interface. It provides information for engineering more appropriate materials for arthroplasty components.

Exposure to BMP-2 causes a marked proliferation of previously quiescent cells within peripheral nerves. These cells simultaneously express KLF4, Sox2, Oct4, and c-Myc, the transcription factors that confer embryonic pluripotency. Work described in the companion paper reveals some of the differentiation capacity of the cells and their likely clinical significance. In addition, the effects of direct exposure of nerves to rhBMP-2 as described here should clearly illuminate the mechanism of BMP-2-related nerve complications. We would suggest that the use of this agent in proximity to known neural structures should only be done with extreme caution.

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Sporotrichosis is a mycotic infection caused by the Sporothrix schenckii species complex. It typically presents as a localized, mostly cutaneous or lymphocutaneous infection, but has been increasingly presenting as a disseminated infection in immunocompromised individuals, especially in HIV/AIDS patients. We also included a literature review of sporotrichosis in this patient population. The aim of this case report is to raise awareness about atypical presentations of sporotrichosis in an attempt to decrease the time to diagnosis, initiate treatment earlier when infection is suspected, and improve overall survival in vulnerable patient populations.