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Abstract Aims Periprosthetic joint infection (PJI) is one of the most serious complications after total joint arthroplasty (TJA) but the characterization of the periprosthetic environment microbiome after TJA remains unknown. Here, we performed a prospective study based on metagenomic next-generation sequencing to explore the periprosthetic microbiota in patients with suspected PJI. Methods We recruited 28 patients with culture-positive PJI, 14 patients with culture-negative PJI, and 35 patients without PJI, which was followed by joint aspiration, untargeted metagenomic next-generation sequencing (mNGS), and bioinformatics analysis. Our results showed that the periprosthetic environment microbiome was significantly different between the PJI group and the non-PJI group. Then, we built a “typing system” for the periprosthetic microbiota based on the RandomForest Model. After that, the ‘typing system’ was verified externally. Results We found the periprosthetic microbiota can be classified into four types generally: “Staphylococcus type,” “Pseudomonas type,” “Escherichia type,” and “Cutibacterium type.” Importantly, these four types of microbiotas had different clinical signatures, and the patients with the former two microbiota types showed obvious inflammatory responses compared to the latter ones. Based on the 2014 Musculoskeletal Infection Society (MSIS) criteria, clinical PJI was more likely to be confirmed when the former two types were encountered. In addition, the Staphylococcus spp. with compositional changes were correlated with C-reactive protein levels, the erythrocyte sedimentation rate, and the synovial fluid white blood cell count and granulocyte percentage. Conclusions Our study shed light on the characterization of the periprosthetic environment microbiome in patients after TJA. Based on the RandomForest model, we established a basic “typing system” for the microbiota in the periprosthetic environment. This work can provide a reference for future studies about the characterization of periprosthetic microbiota in periprosthetic joint infection patients.

Abstract Background Periprosthetic joint infection is a serious complication after total joint arthroplasty. Despite that alpha-defensin was used as diagnostic test in the 2018 ICM (international consensus meeting) criteria, its position in the PJI diagnostic pipeline was controversial. Therefore, we performed a retrospective pilot study to identify whether synovial fluid alpha-defensin test was necessary when corresponding synovial fluid analysis (WBC count, PMN% and LE tests) was performed. Methods Between May 2015 and October 2018, a total of 90 suspected PJI patients who underwent revisions after TJA were included in this study. Based on the 2018 ICM criteria, the interobserver agreements between preoperative diagnostic results and postoperative diagnostic results and the interobserver reliability between preoperative diagnostic results and postoperative diagnostic results with or without synovial fluid alpha-defensin tests were calculated. After that, the ROC analysis, and the direct cost-effectiveness of adding alpha-defensin was performed. Results There were 48,16 and 26 patients in the PJI group, inconclusive group and non-PJI group, respectively. Adding the alpha-defensin tests into 2018 ICM criteria can’t change the preoperative diagnostic results, postoperative diagnostic results, and the concordance between preoperative and postoperative diagnostic results. Moreover, the Risk–benefit Ratio is over 90 per changed decision and the direct cost-effectiveness of alpha-defensin was more than $8370($93*90) per case. Conclusions Alpha-defensin assay exhibit high sensitivity and specificity for PJI detection as a standalone test based on the 2018 ICM criteria. However, the additional order of Alpha-defensin can’t offer additional evidence for PJI diagnosis when corresponding synovial fluid analysis was performed (synovial fluid WBC count, PMN% and LE strip tests). Evidence level Level II, Diagnostic study.

Objective: To investigate the biomechanical properties of porous bioactive bone cement (PBC) in vivo and to observe the degradation of PBC and new bone formation histologically., Methods: According to the weight percentage (W/W, %) of polymethylmethacrylate (PMMA) to bioglass to chitosan, 3 kinds of PBS powders were obtained: PBC I (50: 40:10), PBC II (40:50:10), and PBC III (30:60:10). The bilateral femoral condylar defect model (4 mm in diameter and 10 mm in depth) was established in 32 10-month-old New Zealand white rabbits (male or female, weighing 4.0-4.5 kg), which were randomly divided into 4 groups (n = 8); pure PMMA (group A), PBC I (group B), PBC II (group C), and PBC III (group D) were implanted in the bilateral femoral condylar defects, respectively. Gross observation were done after operation. X-ray films were taken after 1 week. At 3 and 6 months after operation, the bone cement specimens were harvested for mechanical test and histological examination. Four kinds of unplanted cement were also used for biomechanical test as control., Results: All rabbits survived to the end of experiment. The X-ray films revealed the location of bone cement was at the right position after 1 week. Before implantation, at 3 months and 6 months after operation, the compressive strength and elastic modulus of groups C and D decreased significantly when compared with those of group A (P < 0.05), but no significant difference was found between groups C and D (P > 0.05); the compressive strength at each time point and elastic modulus at 3 and 6 months of group B decreased significantly when compared with those of group A (P < 0.05). Before implantation and at 3 months after operation, the compressive strength and elastic modulus of groups C and D decreased significantly when compared with those of group B (P < 0.05); at 6 months after operation, the compressive strength of group C and the elastic modulus of group D were significantly lower than those of group B (P < 0.05). The compressive strength and elastic modulus at 3 and 6 months after operation significantly decreased when compared with those before implantation in groups B, C, and D (P < 0.05), but no significant difference was found in group A (P < 0.05). At 3 months after operation, histological observation showed that a fibrous tissue layer formed between the PMMA cement and bone in group A, while chitosan particles degraded with different levels in groups B, C, and D, especially in group D. At 6 months after operation, chitosan particles partly degraded in groups B, C, and D with an amount of new bone ingrowth, and groups C and D was better than group B in bone growth; group A had no obvious change. Quantitative analysis results showed that the bone tissue percentage was gradually increased in the group A to group D, and the bone tissue percentage at 6 months after operation was significantly higher than that at 3 months within the group., Conclusion: According to the weight percentage (W/W, %) of PMMA to bioglass to chitosan, PBCs made by the composition of 40:50:10 and 30:60:10 have better biocompatibility and biomechanical properties than PMMA cement, it may reduce the fracture risk of the adjacent vertebrae after vertebroplasty.