Morphological study of synovial changes in two-stage reconstructions of the infected hip and knee arthroplasties

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 IX‑A with histopathological infection eradication and type IX‑B with histopathological infection persistence.

Periprosthetic joint infection: current concepts and outlook

Periprosthetic joint infection (PJI) is a serious complication occurring in 1% to 2% of primary arthroplasties, which is associated with high morbidity and need for complex interdisciplinary treatment strategies.

The challenge in the management of PJI is the persistence of micro-organisms on the implant surface in the form of biofilm. Understanding this ability, the phases of biofilm formation, antimicrobial susceptibility and the limitations of host local immune response allows an individual choice of the most suitable treatment.

By using diagnostic methods for biofilm detection such as sonication, the sensitivity for diagnosing PJI is increasing, especially in chronic infections caused by low-virulence pathogens.

The use of biofilm-active antibiotics enables eradication of micro-organisms in the presence of a foreign body. The total duration of antibiotic treatment following revision surgery should not exceed 12 weeks.

Cite this article: EFORT Open Rev 2019;4:482-494. DOI: 10.1302/2058-5241.4.180092

Synovial Fluid Aspiration Should Not Be Routinely Performed during the Two-Stage Exchange of the Knee

Purpose

Detection of infection persistence during the two-stage exchange of the knee for periprosthetic joint infection is challenging. Synovial fluid culture (SFC) and synovial white blood cell count (SWBCC) before joint reimplantation are widespread diagnostic means for this indication. The sensitivity and specificity of SFC and of SWBCC for infection persistence before planned reimplantation were evaluated.

Methods

94 two-stage exchanges of the knee with synovial fluid aspiration performed after a drug holiday of at least 14 days and before reimplantation or spacer exchange (planned reimplantation) were retrospectively analyzed. Only cases with at least 3 intraoperative samples at planned reimplantation were included. SFC and SWBCC were compared to pathogen detection (SFC_(culture)/SWBCC_(culture)) and to histopathological signs of infection persistence (SFC_(histo)/SWBCC_(histo)) from intraoperative samples at planned reimplantation. For SFC, the sensitivity and specificity were calculated. For SWBCC, the optimal cut-off value with its sensitivity and specificity was calculated with the Youden-Index.

Results

Sensitivity and specificity of SFC_(culture) were 0.0% and 98.9%. Sensitivity and specificity of SFC_(histo) were 3.4% and 100%. The optimal cut-off value for SWBCC_(culture) was 4450 cells/μl with a sensitivity of 50.0% and a specificity of 86.5%. The optimal cut-off value for SWBCC_(histo) was 3250 cells/μl with a sensitivity of 35.7% and a specificity of 92.9%.

Conclusion

The detection of infection persistence remains challenging and a consented approach is lacking. The results do not warrant the routine performance of SFC during the two-stage exchange at the knee. SWBCC can be used to confirm infection persistence at high cut-offs, but they only occur in few patients and are therefore inappropriate for the routine use.

Low intrapatient variability of histomorphological findings in periprosthetic tissues from revised metal/ceramic on polyethylene joint arthroplasties

The type of tissue response to implant by-products can be determined by examination of periprosthetic tissues. However, little is known about the most suitable location for tissue sampling. The main goal of this study was to evaluate the extent of variability in tissue response in relation to location of tissue sampling, implant fixation, age and sex in total joint arthroplasties with metal-on-polyethylene or ceramic-on-polyethylene bearing pairs. We processed 236 histology slides from 21 patients and focused on the association between the location of tissue samples and histological features. The presence of the synovial hyperplasia showed a significant association with the particular sampling site. A higher density of high endothelial cell venules was seen in the samples from around the joint, and polyethylene particles were more abundant in noncemented TJA but both findings did not show statistically significant association with the sampling site. The results showed a relatively small variance in the tissue response to prosthetic by-products among tissues sampled from the same patient. Our findings indicate that tissue samples retrieved from similar distance from around the TJA during the revision operation show comparable results of histological analysis. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2008-2018, 2018.

Total joint replacement for neglected posterior knee dislocation following septic arthritis after arthroscopy

This report presents the first case of a knee dislocation following septic arthritis after arthroscopy. A 65-year-old woman had an arthroscopy with irrigation and debridement (I&D) of the joint and microfracture for the chondral lesions. She had complaints of postarthroscopic infection but non-steroidal anti-inflammatory medication and local ice compression was recommended. She revisited her physician twice and at the last visit she had a large purulent effusion in her knee. The gram stain of the joint fluid aspirate demonstrated gram-positive cocci and the cultures grew methicilline-sensitive Staphylococcus aureus. She underwent arthroscopic assisted I&D and received intravenous antibiotics. I&D was repeated after two weeks. Intravenous antibiotherapy was continued for one more week and was changed to oral antibiotherapy for six weeks. At the third month visit's physical examination, a deformity at the knee was noticed and was referred to us for further treatment. A posterior knee dislocation with no neurovascular deficit was detected. The patient had a history of knee sprain but did not seek medical advice immediately. The blood samples showed no abnormality. The patient underwent a surgery with a cemented hinged revision total knee prosthesis following the exclusion of the active knee joint infection. Intraoperative frozen sections were also taken to exclude the active infection. The patient's knee is pain-free with full range of motion after 3 years. The objective of this report was to highlight the importance of early diagnosis, prompt appropriate treatment of septic arthritis following arthroscopy and the awareness of the knee dislocation as a rare dreadful complication of postarthroscopic infection particularly in elderly patients.

Azzopardi phenomenon in cystic pseudotumours associated with retrieved metal-on-metal arthroplasty

The Azzopardi phenomenon represents a morphologically well defined lesion characterised by a deposition of basophilic material in the vessel walls associated with several malignant tumours. We report on 4 cases (3 men and 1 woman) showing the Azzopardi effect in retrieved metal-on-metal arthroplasty unrelated to malignancy. All cases were revised for groin pain and radiological findings of so-called pseudotumours. The Azzopardi phenomenon was seen in cases with cystic pseudotumours characterised by superficial necrobiosis, proliferative desquamative synovitis, finding of metal and corrosion wear particles and cellular infiltration by macrophages. The lesions, which were recognized as bluish substance in the hematoxylin and eosin staining, demonstrated a positive Feulgen reaction. We report on the Azzopardi phenomenon in non-neoplastic cystic pseudotumours from retrieved metal-on-metal arthroplasties. Although clinical relevance of this finding remains unclear, further research is necessary to investigate the possible relationship of this lesion with deliberation of metal ions from metal and corrosion wear particles and their role in a broad spectrum of adverse reactions to metal debris.

[Revision arthroplasty : Histopathological diagnostics in periprosthetic joint infections]

BACKGROUND

Histopathological differences in synovia and synovial-like interface membrane (SLIM) patterns can be used to differentiate periprosthetic particle-induced reactions, bacterial infections (bacterial synovitis and osteomyelitis), mechanical-induced tissue alterations, adverse reactions to implant material, and arthrofibrosis (SLIM consensus classification).

AIM

Because of differences in treatment the diagnosis of a bacterial implant infection is very important. Histopathological tests and scoring systems are important diagnostic tools in identifying deep implant infections in patients with unclear clinical history as well as radiographic and laboratory studies.

RESULTS

Modern enzyme PCR-based methods, histochemical- and immune-histopathological techniques (CD3,CD15, CD68) are useful in identifying specific and nonspecific infections, as well as differentiating postsurgical changes from recurrent infections in patients with a spacer. In all histopathological scoring systems for bacterial infection, quantifying the number of neutrophil granulocytes in a defined number of high power fields is crucial.

DISCUSSION

Neutrophil granulocytes can be detected through histochemical methods and more specifically by immune-histopathological techniques and by various quantification systems (histopathological scores) leading to the diagnosis of bacterial peri-implant infection. One important function of histopathology, apart from diagnosing infection, is to rule out other mechanisms of implant failure, such as tumor infiltrations, particle-induced reactions, and adverse reactions to implant materials.