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Chapter 6170Table 2: SLIM consensus classificationType I Wear-induced synovitis/SLIMType II Infection-induced synovitis/SLIMType III Mixed synovitis/SLIMType IV Indifferent (not wear-induced, not infection-induced) synovitis/SLIMType V Prosthesis-associated arthrofibrosisType VI Adverse local tissue reactions to implant wear particlesType VII Local osseous pathologiesTo properly assess periprosthetic tissue responses, the ‘synovial-like interface membrane’ (SLIM) consensus classification (Table 2) has proven to be an extremely useful system. For a ‘neo-synovitis’ to be classified as being wear-induced (Type I), more than 20% of the sample must be filled in with macrophages. In addition, multinucleated foreign-body giant cells can be found as well. In addition to these inflammatory cells, wear particles are present within the macrophages.(12–14)Evaluation of peri-articular tissues from both the DLC-coated and uncoated systems revealed an increase in macrophagic cells compared to the control group. However, in all samples, the total wear volume and linear wear were well below the gold standard and well below the rate of 1mm/year and 80mm³ volume at which osteolysis can occur. (5,15) This was also reflected in the low macrophage response, which averaged 3.8% of the total surface area in case of the DLC-coated system and 3.1% in the case of the uncoated system. The authors concluded that no wear induced ‘neo-synovitis’ was found in any of the samples. (Tables 3 and 4) Evaluation of peri-articular tissues from both the DLC-coated and uncoated systems revealed an increase in macrophagic cells compared to the tissues from the control group. On further analysis, Important to note is that the significantly increased number of macrophages in the coated system was influenced by one sheep, showing a significantly higher number of macrophages compared to the other samples. When the recorded data for this sheep was omitted, both mean (17) and SD (16.08) dropped sharply. In fact, there was no longer a significant difference (p = 0.71) in the amount of macrophages found between the two groups and the average infiltration rate dropped to 2.9%. Post-operative clinical Nikolas de Meurechy NW.indd 170 05-06-2024 10:14