Diagnostic value of the CD 15 focus score in two-stage revision arthroplasty of periprosthetic joint infections : High specificity in diagnosing infect eradication.

INTRODUCTION: The purpose of this study is to use the CD15 focus score (FS) to determine the sensitivity and specificity of bacterial infection persistence in spacer-based two-stage revision arthroplasty. METHODS: The analysis comprises 112 cases that were subjected to revision due to the presence of infection upon replacement of a joint endoprosthesis. The histopathological data were collected in accordance with the synovial-like interface membrane (SLIM) classification and the CD15-FS and correlated with the microbiological data (MD). The quantifying evaluation of the CD15-FS was performed without knowledge regarding the microbiological data (MD). Correlation with the MD was performed after a 14-day cultivation period. RESULTS: With a single evaluation (1 focus, field area: 1.2 mm2) with a score value of 42, the CD15-FS showed a sensitivity for the eradication of infections of 0.64 and a specificity of 0.79 (PPV = 0.5; NPV = 0.87). With tenfold evaluation (10 foci, field area: 12 mm2) with a score value of 220, the sensitivity for the eradication was 0.68, the specificity 0.91 (PPV = 0.7; NPV = 0.89). No statistically significant correlation between the score values and the different infectious species could be detected. Based on the MD in 112 cases the rate of infection eradication was 75%. Polymethylmethacrylate-particles (PMMA) were detected in the perispacertissue in 64 cases (58%). No significant correlation could be established between microbiological pathogen detection and the presence of PMMA. CONCLUSION: In all cases (n = 112), periimplant synovial tissue (SLIM) with variable fibroblastic cellularity, capillary proliferation, leukocytic infiltration, fibrin deposition, new formation of woven bone and detection of PMMA particles was observed. These cases were classified as type IX perispacer synovialis/SLIM: type IX­A with histopathological infection eradication and type IX­B with histopathological infection persistence.

[Joint tumors: rare but important differential diagnoses of malignant and benign tumors as well as pseudotumors in rheumatology]. / Gelenktumoren: Seltene, aber wichtige Differenzialdiagnosen von malignen und benignen Tumoren sowie Pseudotumoren in der Rheumatologie.

This review article elucidates the differential diagnostics of malignant and benign joint tumors, pseudotumors of the joints and the peri-implant tissue, which are rare but important entities in rheumatology and orthopedic rheumatology. The tissue of origin includes the synovium, peri-implant tissue, peri-articular fibrous tissue and peri-articular osseous tissue. Pseudotumors can be viewed as independent but heterogeneous entities. These are essentially manifested as tumor-like depositions of crystals, calcareous deposits, vascular malformations, ectasia of the synovia and joint capsule tissue and pseudocysts. Other causes for pseudotumors are focal destructive inflammation (e.g. induced by foreign bodies), high grade synovitis and focal fibrinoid necrosis (i.e. rheumatoid nodules). Methodologically, these diagnostics are based on conventional standard staining methods, immunohistochemical analyses of formalin-fixed and paraffin-embedded materials and on molecular diagnostic procedures. The latter are of great importance in cases of benign and malignant joint tumors. The most important immunohistochemical markers with respect to joint tumors are S100, SM-actin, CD68, CD34, STAT6, clusterin, Muc­4, beta-catenin and MDM2-FISH. The following markers are recommended for the differential diagnostics and typing of periarticular tumor metastases in the pathology of rheumatic diseases: AE1/AE3, CK8, p63, TTF­1, TGB, PSA, androgen receptor, GATA, CD56, chromogranin, CDX­2, SAT-B2, SALL4, estrogen and progesterone receptors, CD45LCA, CD30, CD79a and S100. Necrosis, inflammatory infiltrations and reparative inflammatory changes may complicate the histopathological classification. Therefore, a correlation with clinical, microbiological and radiological data in the sense of interdisciplinary synergistic diagnostics may be required.