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Autologous chondrocyte implantation (ACI) is an effective method of treatment of chondral defects of the knee. ACI outcomes are influenced by patient-, knee-, and lesion-specific factors. We compiled subject-level data from current studies on ACI and quantitatively analyzed this data set for associations between patient-, knee-, and lesion-specific factors and the outcome of ACI surgery. A systematic review of studies investigating ACI treatment outcomes in the knee was performed. Only studies that published subject-level data were included. Data on patient and lesion characteristics, as well as clinical outcome scores, were collected. Thirteen studies (305 defects) were included in this review. These studies showed that ACI treatment improves clinical outcomes in different patient populations. However, subject-specific variables such as patient age, gender, body mass index, duration of preoperative symptoms, as well as defect size and location were not associated with International Knee Documentation Committee score or visual analog scale score changes (p > 0.05 for all). Covariate analysis showed that patient age was related to symptom duration prior to surgery (p = 0.009). ACI surgery has been shown to improve outcomes in patients with chondral lesions of the knee. Despite evidence in the literature showing that multiple patient-, knee-, and lesion-specific factors may influence treatment outcomes, our review shows that these factors, solely, do not affect outcomes. However, together, they may synergistically affect outcomes.

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Infection is a major cause of orthopedic implant failure. There are few studies assessing both tissue cell and bacterial adherence on common orthopedic implant materials in a co-culture environment. An in vitro co-culture model was created using K12 osteosarcoma cells and Staphylococcus aureus in a medium incubated over metal disks for 48 h. The results showed that, in the presence of S. aureus, there were fewer osteosarcoma cells attached to the disks for all substrata tested. There were significantly more osteosarcoma cells adhering to the cobalt chrome than the stainless steel and titanium disks. Overall, in the presence of osteosarcoma cells, there were more bacteria adhering to the disks for all the substrata tested, with significantly more bacteria adhering to the stainless steel disks compared to cobalt chrome and titanium disks. Scanning electron microscopy verified that osteosarcoma cells and bacteria were adherent to the metal disks after incubation for 48 h. Furthermore, the observation that more bacteria were in the co-culture than in the control sample suggests that the osteosarcoma cells serve as a nutrient source for the bacteria. Future models assessing the interaction of osteogenic cells with bacteria on a substratum would be improved if the model accounted for the role of the immune system in secondary bone healing.