CD3+ lymphocytosis in the peri-implant membrane of 222 loosened joint endoprostheses depends on the tribological pairing

Background and purpose - The most frequent cause of arthroplasty failure is aseptic loosening-often induced by particles. Abrasion material triggers inflammatory reactions with lymphocytic infiltration and the formation of synovial-like interface membranes (SLIM) in the bone-implant interface. We analyzed CD3 quantities in SLIM depending on articulating materials and possible influences of proven material allergies on CD3 quantities. Patients and methods - 222 SLIM probes were obtained from revision surgeries of loosened hip and knee arthroplasties. SLIM cases were categorized according to the SLIM-consensus classification and to the particle algorithm. The CD3 quantities were analyzed immunohistochemically, quantified, and correlated to the particle types. Results - Metal-metal pairings showed the highest CD3 quantities (mean 1,367 counted cells). CD3 quantities of metal-polyethylene (mean 243), ceramic-polyethylene (mean 182), and ceramic-ceramic pairings (mean 124) were significantly smaller. Patients with contact allergy to implant materials had high but not statistically significantly higher CD3 quantities than patients without allergies. For objective assessment of the CD3 response as result of a pronounced inflammatory reaction with high lymphocytosis (adverse reaction), a defined CD3 quantity per high power field was established, the "CD3 focus score" (447 cells/0.3 mm 2 , sensitivity 0.92; specificity 0.90; positive predictive value 0.71; negative predictive value 0.98). Interpretation - The high CD3 quantities for metal-metal pairings may be interpreted as substrate for previously described adverse reactions that cause severe peri-implant tissue destruction and SLIM formation. It remains unclear whether the low CD3 quantities with only slight differences in the various non-metal-metal pairings and documented contact allergies to implant materials have a direct pathogenetic relevance.