[Histopathologic diagnostics in endoprosthetics: periprosthetic neosynovialitis, hypersensitivity reaction, and arthrofibrosis]

How Useful Is Preoperative Aspiration before Revision of Unicompartmental Knee Prostheses Because of Osteoarthritis in the Other Compartments?

AIM

Periprosthetic joint infections (PJIs) of unicompartmental knee arthroplasties (UKAs) can lead to secondary osteoarthritis of the other compartments. The objective of this study was to identify the frequency of PJIs in cases of UKA with progressed secondary osteoarthritis and the result of septic one-stage revision in these cases to verify the value of preoperative aspiration in cases of secondary osteoarthritis of UKA.

METHODS

We retrospectively reviewed 97 patients with a unicompartmental arthroplasty who underwent revision surgery to a total knee arthroplasty (TKA) between January 2013 and March 2021 because of subsequent osteoarthritis. Preoperative aspiration and sample collection during the revision surgery were employed to identify potential periprosthetic joint infections (PJIs). The post-revision period was monitored for septic complications over an average duration of 55.7 ± 25.2 months (24-113).

RESULTS

PJIs were identified in 5.2% of cases through preoperative aspiration. In all instances of PJIs, a one-stage septic revision was performed, and notably, none of these cases experienced septic complications during the follow-up period.

CONCLUSIONS

Preoperative aspiration is essential in order to exclude the presence of a PJI before performing revision surgery of UKA due to secondary osteoarthritis.

Graphic type differentiation of cell count data for diagnosis of early and late periprosthetic joint infection: A new method

BACKGROUND

Graphic type differentiation of cell count data of synovial aspirates is a new method for the diagnosis of early and late periprosthetic joint infection.

OBJECTIVE

The aim of the study was to analyse if the same 6 LMNE-types can be differentiated in the new Yumizen H500 cell counter as it was the case for the old cell counter ABX Pentra XL 80 of previous publications, to verify if the erythrocyte and thrombocyte curves of the new device give additional information and to calculate the difference of cell count in LMNE-type I and III (with abrasion) in the cell counter and in the manual counting chamber (Neubauer improved).

METHODS

450 aspirates of 152 total hip arthroplasties and 298 knee arthroplasties obtained for the diagnosis of periprosthetic joint infection were analysed with the Yumizen H500.

RESULTS

All LMNE-matrices of the 450 aspirates could assigned to one of the six LMNE-types. There were 76 LMNE-type I, 72 LMNE-type II, 14 LMNE-type III, 241 LMNE-type IV, 36 LMNE-type V and 12 LMNE-type VI. The erythrocyte and thrombocyte distribution curves were very helpful for differentiation of hematoma and infection. The cell count in the manual counting procedure was lower than in the cell counter: for the LMNE-type I (abrasion type) the median of the difference was 925/μL (median) and for the LMNE-type III (combined type of infection and abrasion) 3570/μL (median).

CONCLUSION

The described graphic type differentiation is a new and helpful method for differentiation of hematoma and early PJI as well as abrasion and late PJI.

Periprosthetic joint infection caused by kytococcus schroeteri: The first reported case and a review of the literature

Oftentimes, Gram-positive cocci are the cause for periprosthetic joint infections (PJI). Most of these infections include bacteria such as Staphylococcus aureus, Staphylococcus epidermidis or other coagulase-negative staphylococci. We here present the first case of a PJI caused by Kytococcus schroeteri. While being a Gram-positive coccus, it is very rarely the cause for infections in the human body. K. schroeteri is part of the micrococcus branch and often encountered as a symbiotic bacterium living on the skin. Regarding its pathogenic potential, not a lot is known since less than a few dozen human infections have been reported worldwide. Furthermore, many of the cases reported are either associated with implanted material, especially heart valves, or associated with patients whose immune response is deficient. Only 3 reports of osteoarticular infections are described so far.

A preliminary study on the application of deep learning methods based on convolutional network to the pathological diagnosis of PJI

OBJECTIVE

This study aimed to establish a deep learning method based on convolutional networks for the preliminary study of the pathological diagnosis of prosthetic joint infections (PJI).

METHODS

We enrolled 20 revision patients after joint replacement from the Department of Orthopedics, the First Medical Center, General Hospital of the People's Liberation Army, from January 2021 to January 2022 (10 of whom were confirmed to be infected against 2018 ICM criteria, and the remaining 10 were verified to be non-infected), and classified high-power field images according to 2018 ICM criteria. Then, we inputted 576 positive images and 576 negative images into a neural network by employing a resNET model, used to select 461 positive images and 461 negative images as training sets, 57 positive images and 31 negative images as internal verification sets, 115 positive images and 115 negative images as external test sets.

RESULTS

The resNET model classification was used to analyze the pathological sections of PJI patients under high magnification fields. The results of internal validation set showed a positive accuracy of 96.49%, a negative accuracy of 87.09%, an average accuracy of 93.22%, an average recall rate 96.49%, and an F1 of 0.9482. The accuracy of external test results was 97.39% positive, 93.04% negative, the average accuracy of external test set was 93.33%, the average recall rate was 97.39%, with an F1 of 0.9482. The AUC area of the intelligent image-reading diagnosis system was 0.8136.

CONCLUSIONS

This study used the convolutional neural network deep learning to identify high-magnification images from pathological sections of soft tissues around joints, against the diagnostic criteria for acute infection, and a high precision and a high recall rate were accomplished. The results of this technique confirmed that better results could be achieved by comparing the new method with the standard strategies in terms of diagnostic accuracy. Continuous upgrading of extended training sets is needed to improve the diagnostic accuracy of the convolutional network deep learning before it is applied to clinical practice.

A New Graphic Type Differentiation of Cell Account Determination for Distinguishing Acute Periprosthetic Joint Infection from Hemarthrosis

Aims: This study evaluates the value of a new graphic representation of cell count data of synovial fluid in the diagnosis of acute periprosthetic joint infection (PJI). Methods: A total of 75 patients with revisions of 48 primary total knee and 27 hip arthroplasties within the first six weeks after surgery were analyzed with cultivation of the synovial fluid and determination of its cell count as well as microbiological and histological analyses of the periprosthetic tissue obtained during the revision surgery using the ICM classification. The synovial fluid was additionally analyzed for graphic representation of the measured cells using LMNE-matrices. Results: A total of 38 patients (50.7%) had an infection. The following types of LMNE matrices could be differentiated: the indeterminate type (IV) in 14.7%, the infection type (II) in 5.3%, the hematoma type (V) in 33.3%, and the mixed type (VI; infection and hematoma) in 46.7%. Differentiation of LMNE types into infection (types II and VI) and non-infection (types IV and V) resulted in a sensitivity of 100%, a specificity of 97.3%, and a positive likelihood ratio of 37.0. The cell count measurement showed a sensitivity of 78.9%, a specificity of 89.2%, and a positive likelihood ratio of 7.3 at a cut-off of 10,000 cells. The percentage of polymorphonuclear leukocytes showed a sensitivity of 34.2%, a specificity of 100%, and a positive likelihood ratio of >200 at a cut-off of 90%. Conclusion: The graphic representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between genuine early periprosthetic infections and postoperative hemarthrosis.

The Graphical Representation of Cell Count Representation: A New Procedure for the Diagnosis of Periprosthetic Joint Infections

Aim: This study was designed to answer the question whether a graphical representation increase the diagnostic value of automated leucocyte counting of the synovial fluid in the diagnosis of periprosthetic joint infections (PJI). Material and methods: Synovial aspirates from 322 patients (162 women, 160 men) with revisions of 192 total knee and 130 hip arthroplasties were analysed with microbiological cultivation, determination of cell counts and assay of the biomarker alpha-defensin (170 cases). In addition, microbiological and histological analysis of the periprosthetic tissue obtained during the revision surgery was carried out using the ICM classification and the histological classification of Morawietz and Krenn. The synovial aspirates were additionally analysed to produce dot plot representations (LMNE matrices) of the cells and particles in the aspirates using the hematology analyser ABX Pentra XL 80. Results: 112 patients (34.8%) had an infection according to the ICM criteria. When analysing the graphical LMNE matrices from synovia cell counting, four types could be differentiated: the type “wear particles” (I) in 28.3%, the type “infection” (II) in 24.8%, the “combined” type (III) in 15.5% and “indeterminate” type (IV) in 31.4%. There was a significant correlation between the graphical LMNE-types and the histological types of Morawietz and Krenn (p < 0.001 and Cramer test V value of 0.529). The addition of the LMNE-Matrix assessment increased the diagnostic value of the cell count and the cut-off value of the WBC count could be set lower by adding the LMNE-Matrix to the diagnostic procedure. Conclusion: The graphical representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between real periprosthetic infections with an increased leukocyte count and false positive data resulting from wear particles. This new approach helps to increase the diagnostic value of cell count analysis in the diagnosis of PJI.

Long-term outcome after implantation of a nickel-containing cemented hip stem on the right in a patient with type IV sensitization to nickel sulphate

Type IV allergies to nickel sulfate, potassium dichromate and/or cobalt chloride are supposed to be associated with aseptic loosening, pain or infections in patients with hip arthroplasty. However, there is debate on any causal relation between type IV sensitization to metals and any of these complications. We report on a patient with suspicion of pre-existing type IV sensitization to nickel sulfate and potassium dichromate who did not show any complications after hip arthroplasty.

Periprosthetic Infection in Joint Replacement

BACKGROUND

The volume of joint replacement surgery has risen steadily in recent years, because the population is aging and increasingly wishes to reserve a high functional status onward into old age. Infection is among the more common complications of joint replacement surgery, arising in 0.2% to 2% of patients, or as many as 9% in special situations such as the implantation of megaprostheses. The associated morbidity and mortality are high. It is thus very important to minimize risk factors for infection and to optimize the relevant diagnostic and therapeutic strategies.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, including current guidelines and expert recommendations.

RESULTS

The crucial diagnostic step is joint biopsy for the identification of the pathogenic organism, which succeeds with over 90% sensitivity and specificity. If the prosthesis is firmly anchored in bone, the pathogen is of a type that responds well to treatment, and symptomatic infection has been present only for a short time, then rapidly initiated treatment can save the prosthesis in 35-90% of cases. The pillars of treatment are thorough surgical care (radical débridement) and targeted antibiotic therapy. On the other hand, if the prosthesis is loose or the pathogen is of a poorly treatable type, the infection can generally only be cured by a change of the prosthesis. This can be performed in either one or two procedures, always in conjunction with systemic antibiotic therapy tailored to the specific sensitivity and resistance pattern of the pathogen.

CONCLUSION

The risk of infection of an artificial joint is low, but the overall prevalence of such infections is significant, as the number of implanted joints is steadily rising. Artificial joint infections should be treated by a standardized algorithm oriented toward the recommendations of current guidelines. Many of these recommendations, however, are based only on expert opinion, as informative studies providing high-grade evidence are lacking. Thus, for any particular clinical situation, there may now be multiple therapeutic approaches with apparently comparable efficacy. Randomized trials are urgently needed.

Diagnosing periprosthetic hip joint low-grade infection via arthroscopic neo synovium biopsies

BACKGROUND

There is currently a lack of consensus regarding the most effective diagnostic algorithm for cases of supposed low-grade infection after total hip arthoplasty (THA).

OBJECTIVE

The aim of this study was to assess reliability in the use of biopsies, obtained by hip arthroscopy, to detect a periprosthetic hip joint infection (PJI).

METHODS

From 2012 to 2016, diagnostic arthroscopy of the hip joint was performed in 20 patients with a supposed PJI following THA. In 10 of these patients, the THA was revised for various reasons after diagnostic arthroscopy. The microbiological and histological findings of the biopsies obtained by arthroscopy were compared to findings from intraoperative samples of the revision arthroplasty.

RESULTS

For arthroscopic biopsies, we detected a sensitivity of 1.00 (95% confidence interval [CI] 0.40-1.00), a specificity of 0.83 (95% CI 0.36-1.00), a positive predictive value of 0.80 (95% CI 0.28-1.00), and a negative predictive value of 1.00 (95% CI 0.48-1.00). The accuracy was 0.90.

CONCLUSIONS

The analysis of arthroscopic biopsies represents a helpful tool to verify or rule out a PJI in selected patients. Nevertheless, minimally invasive diagnostic tools (e.g., laboratory analysis and aspiration) should be utilized beforehand.

Implant allergy

Osteosynthesis materials or artificial joint replacement make part of clinical routine. In case of complaints mostly mechanical causes or infections are found. Metals like nickel, chromium and cobalt or bone cement components like acrylates and gentamicine may however potentially cause intolerance reactions to implants. Correspondingly, eczema, delayed wound/bone healing, recurrent effusion, pain or implant loosening have been described as manifestation of implant allergy. In contrast to the high incidence of cutaneous metal allergy, allergies associated with implants are rare. Diagnosis of metal implant allergy is based on excluding differential diagnoses – in particular infection – and on a combined approach of allergological diagnostics by patch test and histopathology of periimplant tissue. Risk factors for allergic sensitization to implants or triggering periimplant allergic reactions in the case of preexisting cutaneous metal allergy are unknown. Despite the risk of developing complications being unclear, titanium-based osteosynthesis materials are recommended for metal-allergic patients and the use of metal-metal couplings in arthroplasty is rather not recommended for such patients. If a regular, potentially applicable CoCr-polyethylene articulation is preferred, the patient has to be well informed and has to give his written consent.

The value of arthroscopic neosynovium biopsies to diagnose periprosthetic knee joint low-grade infection

INTRODUCTION

The diagnostic algorithm in cases of assumed low-grade infection after total knee arthroplasty is discussed controversial. The aim of this study was to evaluate the reliability of neosynovium biopsies via knee arthroscopies in predicting a periprosthetic knee joint infection (PJI).

METHODS

From 2010 to 2015, 56 consecutive patients received a diagnostic arthroscopy of the knee joint by reason of an assumed PJI. In 34 cases, a revision arthroplasty was performed after the diagnostic arthroscopy. The microbiologic and histologic results from neosynovium biopsies were compared to intraoperative findings of the consecutively performed revision arthroplasty.

RESULTS

The arthroscopic neosynovium biopsies had a sensitivity of 0.88 (0.47-1.0 95 % confidence interval), a specificity of 0.88 (0.7-0.98), a positive predictive value of 0.7 (0.35-0.93), and a negative predictive value of 0.96 (0.79-1.0). The accuracy was 0.88. We determined a higher sensitivity of neosynovium biopsies compared to C-reactive protein (p = 0.038) and white blood cell count (p < 0.001) in serum. The itemized evaluation of histologic results showed a significant higher sensitivity compared to microbiologic results (p = 0.045) and a higher accuracy.

CONCLUSIONS

The analysis of arthroscopic neosynovium biopsies can be helpful to verify or exclude a PJI in selected patients. Especially, histologic assessment showed a high accordance with final results. Level of evidence IV, retrospective study.

Outcome of total knee replacement following explantation and cemented spacer therapy

Background: Infection after total knee replacement (TKR) is one of the serious complications which must be pursued with a very effective therapeutic concept. In most cases this means revision arthroplasty, in which one-setting and two-setting procedures are distinguished. Healing of infection is the conditio sine qua non for re-implantation.

This retrospective work presents an assessment of the success rate after a two-setting revision arthroplasty of the knee following periprosthetic infection. It further considers drawing conclusions concerning the optimal timing of re-implantation.

Patients and methods: A total of 34 patients have been enclosed in this study from September 2005 to December 2013. 35 re-implantations were carried out following explantation of total knee and implantation of cemented spacer. The patient’s group comprised of 53% (18) males and 47% (16) females. The average age at re-implantation time was 72.2 years (ranging from 54 to 85 years). We particularly evaluated the microbial spectrum, the interval between explantation and re-implantation, the number of surgeries that were necessary prior to re-implantation as well as the postoperative course.

Results: We reported 31.4% (11) reinfections following re-implantation surgeries. The number of the reinfections declined with increasing time interval between explantation and re-implantation. Patients who developed reinfections were operated on (re-implantation) after an average of 4.47 months. Those patients with uncomplicated course were operated on (re-implantation) after an average of 6.79 months. Nevertheless, we noticed no essential differences in outcome with regard to the number of surgeries carried out prior to re-implantation. Mobile spacers proved better outcome than temporary arthrodesis with intramedullary fixation.

Conclusion: No uniform strategy of treatment exists after peri-prosthetic infections. In particular, no optimal timing can be stated concerning re-implantation. Our data point out to the fact that a longer time interval between explantation and re-implantation reduces the rate of reinfection. From our point of view, the optimal timing for re-implantation depends on various specific factors and therefore it should be defined individually.

Human xylosyltransferases--mediators of arthrofibrosis? New pathomechanistic insights into arthrofibrotic remodeling after knee replacement therapy

Total knee replacement (TKR) is a common therapeutic option to restore joint functionality in chronic inflammatory joint diseases. Subsequent arthrofibrotic remodeling occurs in 10%, but the underlying pathomechanisms remain unclear. We evaluated the association of xylosyltransferases (XT), fibrotic mediators catalyzing glycosaminoglycan biosynthesis, leading to arthrofibrosis as well as the feasibility of using serum XT activity as a diagnostic marker. For this purpose, synovial fibroblasts (SF) were isolated from arthrofibrotic and control synovial biopsies. Basal α-smooth muscle actin expression revealed a high fibroblast-myofibroblast transition rate in arthrofibrotic fibroblasts. Fibrotic remodeling marked by enhanced XT activity, α-SMA protein expression as well as xylosyltransferase-I, collagen type III-alpha-1 and ACTA2 mRNA expression was stronger in arthrofibrotic than in control fibroblasts treated with transforming growth factor-β1 (TGF-β1). Otherwise, no differences between serum levels of XT-I activity or common fibrosis markers (galectin-3 and growth differentiation factor-15 levels (GDF-15)) were found between 95 patients with arthrofibrosis and 132 controls after TKR. In summary, XT-I was initially investigated as a key cellular mediator of arthrofibrosis and a target for therapeutic intervention. However, the blood-synovial-barrier makes arthrofibrotic molecular changes undetectable in serum. Future studies on monitoring or preventing arthrofibrotic remodeling should therefore rely on local instead of systemic parameters.

Two-stage revision total knee arthroplasty in cases of periprosthetic joint infection: an analysis of 50 cases

OBJECTIVES

A periprosthetic joint infection (PJI) is a significant complication after total knee arthroplasty (TKA). Still there is no agreement on a perfect diagnosis and treatment algorithm. The aim of this study was to evaluate the success and revision rates after two-stage revision total knee arthroplasty (TKA) and factors that affect the success rate.

MATERIAL AND METHODS

50 consecutive two-stage revision TKAs were performed between January 2011 and December 2012. We retrospectively reviewed study patient's charts including demographics, prior surgeries, comorbidities, incidence of persistent infection and revisions. At the final follow-up examination the patient's satisfaction, pain level and disorders were evaluated. A successful clinical outcome was defined as a functioning prosthesis without wound healing disorders, no sinuses tracts or other clinical evidence of a persistent infection. Results : Re-implantation of prosthesis was performed in 47 cases; three patients received a septic arthrodesis. Twelve patients had a persistent infection despite two-stage re-implantation resulting in a success rate of 76.0%. In eight of these twelve patients an infecting germ was isolated during second-stage procedure. Three patients received another two-stage revision arthroplasty and one patient an above knee amputation. A revision was performed in 23 of 50 patients (46.0%). Factors that diminish the success rate were further operations after primary TKA (p = 0.048), prior revision arthroplasties after TKA (p = 0.045), nicotine abuse (p = 0.048), Charlson comorbidity index above a score of 2 (p = 0.031) and a mixed flora during first-stage procedure (p < 0.001). Age, sex, immune status, chronic anticoagulant use, rheumatoid arthritis, body mass index and the presence of multidrug resistant germs showed no significant effect on success rate (p > 0.05). Conclusion : We found that patients who required surgery after the primary TKA, had a higher Charlson comorbidity index or were found to have mixed flora during explantation. The treatment of PJI remains difficult, both for the patient and for the treating surgeons.

Use of chloroacetate esterase staining for the histological diagnosis of prosthetic joint infection

A heavy neutrophil polymorph infiltrate [>5 per high-power field (HPF) after examination of at least 5 HPF by Musculoskeletal Infection Society (MSIS) criteria] is characteristically seen in peri-implant tissues of infected prosthetic hip and knee joints. We determined whether chloroacetate esterase (CAE) staining facilitated the identification of neutrophil polymorphs in peri-implant tissues in cases of hip and knee arthroplasty infection and reassessed MSIS criteria in the light of our findings. Frozen and paraffin sections of peri-prosthetic tissues of 76 cases of failed hip and knee arthroplasties classified as septic or aseptic loosening microbiologically were analysed histologically by both haematoxylin-eosin and CAE staining. The extent of the neutrophil polymorph infiltrate was determined semiquantitatively and correlated with the microbiological and clinical diagnosis. CAE staining facilitated identification of neutrophil polymorphs in arthroplasty tissues. All cases of aseptic loosening contained fewer than two neutrophil polymorphs per HPF. CAE staining showed that in some cases of septic loosening, fewer than five neutrophil polymorphs per HPF (on average) are present in peri-prosthetic tissues. The histological criterion of more than two neutrophil polymorphs per HPF showed increased sensitivity and accuracy for the diagnosis of septic loosening. CAE is a useful stain that facilitates the identification of neutrophil polymorphs in both frozen and paraffin sections of peri-implant tissues. CAE staining shows that some microbiologically confirmed cases of septic loosening contain relatively few neutrophil polymorphs, indicating that the MSIS histological criterion of more than five neutrophil polymorphs per HPF is too high an index figure for the diagnosis of all cases of hip and knee arthroplasty infection.

Clinical and diagnostic challenges of metal implant allergy using the example of orthopaedic surgical implants: Part 15 of the Series Molecular Allergology

The focus of this review are allergic reactions to orthopaedic-surgical metal implants. The spectrum of metal implant associated potential allergic reactions encompasses eczema, impaired wound and fracture healing, infection-mimicking reactions, effusions, pain and loosening. Nickel, cobalt and chromium seem to be the predominant eliciting allergens. Despite the growing number of respective publications the topic „metal implant allergy“ remains a diagnostic challenge. Initially, differential diagnoses should always be excluded in cooperation with surgery collegues. It is recommended to perform a combined evaluation of medical history, clinical findings, patch testing and histology. The lymphocyte transformation test (LTT) can indicate metal sensitization, but it needs careful interpretation. Allergists can provide a substantial contribution to this interdisciplinary topic.

[Revised consensus classification. Histopathological classification of diseases associated with joint endoprostheses]

The revised classification of the periprosthetic membrane (synovial-like interface membrane SLIM) encompasses all pathological alterations which can occur as a result of endoprosthetic replacement of major joints and lead to a reduction in durability of prostheses. This also includes the established consensus classification of SLIM by which aseptic and septic prosthetic loosening can be subdivided into four histological types and histopathological criteria for additional pathologies: endoprosthesis-associated arthrofibrosis, immunological/allergic alterations and osseous pathologies. This revision represents the foundation for the histopathological diagnostics of the total spectrum of diseases associated with joint prostheses, is a suitable basis for a standardized diagnostic procedure and etiological clarification of endoprosthesis failure and also as a data standard for endprosthesis registers, in particular for registers based on routine data (e.g. German endoprosthesis register).

[Prosthesis loosening]

Prosthesis loosening is becoming more and more important due to increasing numbers of primary arthroplasty. Especially in patients suffering from rheumatoid arthritis this is a major topic due to younger age and multiple affected joints. A carefully performed diagnostic regimen is essential for ruling out septic loosening of the prosthesis. Preoperative planning is crucial for revision surgery. Revision implants should be available as back-up. Revision arthroplasty is a technically and economically demanding procedure. Costs for revision surgery are much higher than for primary arthroplasty due to longer hospital stay, intensive care, microbiology, histology, diagnostic imaging, implants and antibiotics. Revision arthroplasty should be performed in highly specialized centers.

[Allergic reactions as differential diagnosis for periprosthetic infection]

Metallic orthopedic devices are composed of elements known to be skin sensitizers in the general population and metal-on-metal hip prostheses in particular have the theoretical advantage of producing less abrasive wear than metal-on-polyethylene prostheses. However, there is concern about the possibility of hypersensitivity reactions with typical elicitors, such as nickel, chromium or cobalt. These materials are also used for total knee arthroplasty (TKA) and may elicit an immune response the role of which is still unclear in the outcome of arthroplasty. The immune response is dominated by perivascular T and B lymphocyte tissue infiltration around the hip replacement. The infiltrates are mostly surrounded by so-called high endothelial venules. This reaction is associated with periprosthetic osteolysis and aseptic loosening of the prostheses. The differentiation of hypersensitivity and low-grade infection is initially a diagnosis by exclusion using aspiration cultures. The final diagnosis is only resolved by histological investigation of synovial tissue. A close cooperation between orthopedic surgeons, pathologists and microbiologists is necessary to diagnose specific cellular differences in hypersensitivity and infection in tissue investigations.

Metal hypersensitivity in total knee arthroplasty: revision surgery using a ceramic femoral component - a case report

We present a case involving the revision of a total knee arthroplasty with a metal femoral component using a ceramic implant due to metal hypersensitivity. A 58-year-old female patient underwent total knee arthroplasty (TKA) with a standard metal bicondylar knee system. She suffered from persistent pain and strong limitations in her range of motion (ROM) associated with flexion during the early postoperative period. Arthroscopic arthrolysis of the knee joint and intensive active and passive physical treatment, in combination with a cortisone regime, temporarily increased the ROM and reduced pain. No signs of low grade infection or other causes of implant failure were evident. Histology of synovial tissue revealed lymphoplasmacellular fibrinous tissue, consistent with a type IV allergic reaction. Allergometry (skin reaction) revealed type IV hypersensitivity against nickel-II-sulfate and palladium chloride. Revision surgery of the metal components was performed with a cemented ceramic femoral component (same bicondylar design) and a cemented titanium alloy tibial component. Postoperative evaluations were performed 10days, and 3 and 12months after the revision surgery. There was an increased ROM in flexion to 90° at the 12month follow-up. No swelling or effusion was observed at all clinical examinations after the revision surgery. No pain at rest and moderate walking pain were evident. The presented case demonstrates that ceramic implants are a promising solution for patients suffering from hypersensitivity to metal ions in total knee arthroplasty.

[Joint endoprosthesis pathology. Histopathological diagnostics and classification]

Prosthesis durability has steadily increased with high 10-year rates of 88-95%. However, four pathogenetic groups of diseases can decrease prosthesis durability: (1) periprosthetic wear particle disease (aseptic loosening) (2) bacterial infection (septic loosening) (3) periprosthetic ossification, and (4) arthrofibrosis. The histopathological "extended consensus classification of periprosthetic membranes" includes four types of membranes, arthrofibrosis, and osseous diseases of endoprosthetics: The four types of neosynovia are: wear particle-induced type (type I), mean prosthesis durability (MPD) in years 12.0; infectious type (type II), MPD 2.5; combined type (type III) MPD 4.2; and indeterminate type (type IV), MPD 5.5. Arthrofibrosis can be determined in three grades: grade 1 needs clinical information to be differentiated from a type IV membrane, and grades 2 & 3 can be diagnosed histopathologically. Periprosthetic ossification, osteopenia-induced fractures, and aseptic osteonecrosis can be histopathologically diagnosed safely with clinical information. The extended consensus classification of periprosthetic membranes may be a diagnostic groundwork for a future national endoprosthesis register.

Comparative Study of Clinical and Radiological Outcomes of Unconstrained Bicondylar Total Knee Endoprostheses with Anti-allergic Coating

Background:

Hypersensitivity reactions to implant materials have become more important in total knee replacement (TKR). The purpose of this retrospective comparative study was to evaluate the clinical and radiological outcomes of unconstrained bicondylar total knee prostheses with and without anti-allergic titanium(niobium)nitrite (Ti(Nb)N) coating.

Methods:

Twenty-four patients (25 TKRs) underwent a preoperative clinical evaluation and then a postoperative evaluation after 26.2 months in the allergy group treated with coated implants (n=13 implants) and after 24.5 months in the control group treated with uncoated implants but identical geometry (n=12) using HSS, WOMAC and SF-36 scores. Radiological evaluations were performed using standard anterior-posterior (a.p.) and lateral X-rays.

Results:

During follow-up two patients of the allergy group had to undergo revision surgery due to non-implant-related reasons. A comparative analysis of both study groups showed a significant difference in the HSS scores at both evaluation time points (MW test p≤0.050); these findings are remarkable since the control group had a significantly lower score preoperatively (54.0 vs 65.0 points) and a significantly higher score (82.5 vs 75.0 points) postoperatively. The preoperative and postoperative WOMAC and SF-36 scores were comparable in both groups (MW test p≥0.052), although the postoperative increase in the score for the allergy group was lower. The radiological results were comparable in both groups and were unlikely to influence the results.

Conclusions:

This clinical study demonstrates the restricted outcome in postoperative function and quality of life in the allergy group compared to the control group.

[Replacement of infected knee and hip endoprostheses]

Infections occur in 0.5-5% of cases after implantation of an endoprosthesis and represent one of the most severe complications of artificial joint replacements. Approximately 300,000 primary implantations for hip and knee prostheses are carried out in Germany annually with a corresponding number of early and late infections. This means that approximately 4,000-6,000 cases are to be expected annually. Periprosthetic infections normally lead to a significant loss of function and quality of life for patients and the complex remediation is costly. Therefore, preventive measures, such as perioperative prophylaxis with antibiotics, maintaining highly sterile conditions during operations and an expedient selection of patients are of substantial importance. The basic principles of an adequate restoration include identification of the pathogen, local eradication of the infection mostly after removal of the prosthesis, pathogen-oriented systemic and local antibiotic therapy and finally re-implantation of the revision prosthesis under infection-free conditions. The standard procedure for revision surgery is a two-phase replacement with maintenance of an infection-free interval before renewal of the prosthesis. The use of single-phase or multi-phase strategies, as well as the selection of cemented or cement-free revision, varies between centers as a definitive evaluation is not yet available.The most important parameters for successful treatment of periprosthetic infections have been identified as the earliest possible diagnosis, radical surgical cleansing with an adequate antibiotic therapy and successful restoration has been reported in approximately 80% of cases. Because of the complex therapy regime, treatment in specialized centers is generally recommended especially under the aspect of a demanding patient monitoring.