Toxicity of antiseptics against chondrocytes: what is best for the cartilage in septic joint surgery?

Tolerability of N-chlorotaurine in comparison with routinely used antiseptics: an in vitro study on chondrocytes

BACKGROUND

Currently, povidone-iodine (PVP-I) and hydrogen peroxide (H2O2) are frequently used antiseptics in joint infections, but the cytotoxic effects of these solutions are already reported. N-chlorotaurine (NCT) shows a broad-spectrum bactericidal activity and is well tolerated in various tissues, but its effect on human chondrocytes is unknown. The purpose of this study was to assess the cytotoxic effect of NCT, PVP-I, and H2O2 on human chondrocytes compared to a control group in an in vitro setting to get first indications if NCT might be a promising antiseptic in the treatment of septic joint infections for the future.

MATERIAL AND METHODS

Chondrocytes extracted from human cartilage were incubated with various concentrations of NCT, PVP-I, and H2O2 for 5 and 30 min respectively. EZ4U cell viability kit was used according to the manufacturer's recommendations determining cell viability. To assess cell viability based on their nuclear morphology, cells were stained with acridine-orange and identified under the fluorescence microscope.

RESULTS

EZ4U kit showed after 5 and 30 min of incubation a significant decrease in cell viability at NCT 1%, NCT 0.1%, PVP-I, and H2O2, but not for NCT 0.001% and NCT 0.01%. Acridine-orange staining likewise presented a significant decrease in vital cells for all tested solutions except NCT 0.001% and NCT 0.01% after 5 and 30 min of incubation.

CONCLUSION

Our results demonstrate that NCT is well tolerated by chondrocytes in vitro at the tested lower NCT concentrations 0.01% and 0.001% in contrast to the higher NCT concentrations 1% and 0.1%, PVP-I (1.1%), and H2O2 (3%), for which a significant decrease in cell viability was detected. Considering that the in vivo tolerability is usually significantly higher, our findings could be an indication that cartilage tissue in vivo would tolerate the already clinically used 1% NCT solution. In combination with the broad-spectrum bactericidal activity, NCT may be a promising antiseptic for the treatment of septic joint infections.

Evaluation of the role of povidone‑iodine in the prevention of surgical site infections

Background

The occurrence of surgical site infections (SSIs) is associated with increased risk of mortality, development of other infections, and the need for reintervention, posing a significant health burden. The aim of this review was to examine the current data and guidelines around the use of antiseptic povidone‑iodine (PVP-I) for the prevention of SSIs at each stage of surgical intervention.

Methods

A literature search for selected key words was performed using PubMed. Additional papers were identified based on author expertise.

Results

Scientific evidence demonstrates that PVP-I can be used at every stage of surgical intervention: preoperative, intraoperative, and postoperative. PVP-I is one of the most widely used antiseptics on healthy skin and mucous membranes for preoperative surgical site preparation and is associated with a low SSI rate. For intraoperative irrigation, aqueous PVP-I is the recommended agent and has been demonstrated to decrease SSIs in a range of surgical settings, and for postoperative wound healing, there is a growing body of evidence to support the use of PVP-I.

Conclusions

There is a need for more stringent study designs in clinical trials to enable meaningful comparisons between antiseptic agents, particularly for preoperative skin preparation. The use of a single agent (PVP-I) at each stage of surgical intervention could potentially provide advantages, including economic benefits, over agents that can only be used at discrete stages of the surgical procedure.

Key message

Evidence supports the use of PVP-I at all stages of surgical intervention, from preoperative measures (including skin preparation, preoperative washing, and nasal decolonization) to intraoperative irrigation, through to postoperative wound management. However, there is a need for more stringent study designs in clinical trials to enable meaningful comparisons between antiseptic agents, particularly for preoperative skin preparation.

Postoperative Infection: Prevention, Diagnosis, and Treatment Guidelines for the Sports Surgeon

Postoperative infection remains a potentially devastating complication facing the sports medicine surgeon. Infection prevention begins with a thorough history and physical examination to identify patient specific risk factors and aid in risk stratification. Perioperative steroid injections should be used cautiously, with increased time prior to or following surgery being associated with lower infection risk. Sterile preparation with an alcohol containing solution is typically preferred, though there is limited evidence to identify which product is superior. Diagnosis can be challenging with a high index of suspicion needed to identify and appropriately manage patients. Treatment involves prompt irrigation and debridement with deep cultures. Antibiotic coverage should begin with empiric broad treatment and be tailored based on culture results. Early consultation with an infectious disease specialist is recommended to ensure appropriate antibiotic coverage and duration of treatment.

The role of hydrogen peroxide in hip arthroplasty: A narrative review

Hydrogen peroxide has become more commonly used in hip arthroplasties due to high risk of periprosthetic infections. Its purported roles include irrigation, haemostasis, reduction of aseptic loosening and attachment of antibiotics. However, current literature does not provide conclusive evidence on the efficacy of hydrogen peroxide in preventing aseptic loosening, with some controversy around whether it in fact contributes to aseptic loosening. The complications of hydrogen peroxide across medicine are well distinguished; however, the risks within orthopaedic surgery and hip arthroplasties are not well known. Beyond cytotoxicity, the most dangerous reported risk associated with hydrogen peroxide in hip arthroplasties was an oxygen embolism in an unvented femoral canal and acrylic bone cement, consequentially leading to cardiac arrest. However, it may be inappropriate to solely attribute the oxygen embolism to the use of hydrogen peroxide and thus if used appropriately, hydrogen peroxide may have a justifiable role in hip arthroplasty surgery. In this narrative review, we present the current uses of hydrogen peroxide while evaluating its associated risks. We have summarised the key indications and aggregated recommendations to provide guidelines for the use of hydrogen peroxide in hip arthroplasty.

Vancomycin is toxic to human chondrocytes in vitro

INTRODUCTION

Vancomycin powder (VP) is a well-established topical antibiotic used in spinal surgery to prevent surgical site infections. More recently its extension to hip and knee arthroplasty was introduced. The aim of this study was to examine toxic effects of VP on the viability of human chondrocytes. Our hypothesis was that VP damages human chondrocytes in vitro with increasing concentration and length of exposure.

MATERIAL AND METHODS

Primary human chondrocytes were isolated and cultured from donated human knee joints. VP was added to these cultures with increasing concentrations (0-50 mg/ml) and length of exposure (0-336 h). Toxicity and viability were analyzed using LDH und XTT Elisa assays. Cell structure and determination of vital versus dead cells were visualized using light microscopy and fluorescence microscopy.

RESULTS

Light microscopy and fluorescence microscopy visualized defect cell structures and cell death proportional to increasing dose and length of exposure to VP. The analysis of LDH activity data showed toxic effects on chondrocytes as early as 2,5 min after exposure to VP. XTT activity data revealed a significant toxic threshold of a VP concentration above 12.5 mg/ml.

CONCLUSIONS

These results show that exposure to high VP concentrations yields to a damage of human chondrocytes in vitro. Chondrotoxicity is an immediate effect that is proportional to VP concentration. Therefore, the intraarticular use of high concentrations of vancomycin powder in the presence of native cartilage tissue must be considered critically.

Post-operative septic arthritis after arthroscopy: modern diagnostic and therapeutic concepts

PURPOSE

Septic arthritis is a significant complication following arthroscopic surgery, with an estimated overall incidence of less than 1%. Despite the low incidence, an appropriate diagnostic and therapeutic pathway is required to avoid serious long-term consequences, eradicate the infection, and ensure good treatment outcomes. The aim of this current review article is to summarize evidence-based literature regarding diagnostic and therapeutic options of post-operative septic arthritis after arthroscopy.

METHODS

Through a literature review, up-to-date treatment algorithms and therapies have been identified. Additionally, a supportive new algorithm is proposed for diagnosis and treatment of suspected septic arthritis following arthroscopic intervention.

RESULTS

A major challenge in diagnostics is the differentiation of the post-operative status between a non-infected hyperinflammatory joint versus septic arthritis, due to clinical symptoms, (e.g., rubor, calor, or tumor) can appear identical. Therefore, joint puncture for microbiological evaluation, especially for fast leukocyte cell-count diagnostics, is advocated. A cell count of more than 20.000 leukocyte/µl with more than 70% of polymorphonuclear cells is the generally accepted threshold for septic arthritis.

CONCLUSION

The therapy is based on arthroscopic or open surgical debridement for synovectomy and irrigation of the joint, in combination with an adequate antibiotic therapy for 6-12 weeks. Removal of indwelling hardware, such as interference screws for ACL repair or anchors for rotator cuff repair, is recommended in chronic cases.

LEVEL OF EVIDENCE

IV.

Sodium hypochlorite is more effective than chlorhexidine for eradication of bacterial biofilm of staphylococci and Pseudomonas aeruginosa

PURPOSE

Periprosthetic infection is a common reason for surgical revision. Given the increasing resistance of bacteria to antibiotics (e.g., VRE, 4-MRGN) local antiseptic treatment is gaining in importance. However, no standard guideline-based treatment recommendation is yet available. The aim of this study was to investigate the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Furthermore, the toxicity of both antiseptics towards human chondrocytes was examined.

METHODS

Human chondrocytes were isolated, cultivated and treated with sodium hypochlorite and chlorhexidine. The viability of cultures was assessed by determination of cell count, XTT and MTT ELISAs, and fluorescent staining with propidium iodide. Bacterial strains of Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa were added to liquid media and incubated overnight. After determination of bacterial concentrations polyethylene (PE) devices were inoculated with bacteria for 48 h until biofilms formed. The devices were then washed, treated with antiseptics for 2 and 5 min and subsequently spread on agar plates.

RESULTS

Sodium hypochlorite is more effective than chlorhexidine in penetrating biofilms of S. aureus, S. epidermidis and P. aeruginosa. Both antiseptics are chondrotoxic, but sodium hypochlorite damages human chondrocytes less than chlorhexidine in vitro.

CONCLUSIONS

The findings confirm the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Both antiseptics can be recommended for the treatment of periprosthetic infections. The toxic effects of sodium hypochlorite and chlorhexidine towards chondrocytes may mean there is a risk of damage to cartilage tissue.

LEVEL OF EVIDENCE

Controlled experimental study.

Tranexamic acid is toxic on human chondrocytes, in vitro

The aim of this study was to examine toxic effects of tranexamic acid (TXA) on the viability of human chondrocytes. Our hypothesis was that TXA damages human chondrocytes. Chondrocytes were cultured from donated human knee joints. TXA was added to these cultures. Toxicity were analyzed by using LDH und XTT Elisa assays, light microscopy and fluorescence microscopy. The results show that TXA damages human chondrocytes in vitro. We cannot recommend the use of TXA in hemiarthroplasty of the hip or unicompartmental knee arthroplasty in higher concentrations.

Antimicrobial peptides derived from the cartilage.-specific C-type Lectin Domain Family 3 Member A (CLEC3A) - potential in the prevention and treatment of septic arthritis

OBJECTIVE

To investigate the antimicrobial activity of peptides derived from C-type Lectin Domain Family 3 Member A (CLEC3A), shed light on the mechanism of antimicrobial activity and assess their potential application in prevention and treatment of septic arthritis.

DESIGN

We performed immunoblot to detect CLEC3A peptides in human cartilage extracts. To investigate their antimicrobial activity, we designed peptides and recombinantly expressed CLEC3A domains and used them to perform viable count assays using E.coli, P.aeruginosa and S.aureus. We investigated the mechanism of their antimicrobial activity by fluorescence and scanning electron microscopy, performed ELISA-style immunoassays and transmission electron microscopy to test for lipopolysaccharide binding and surface plasmon resonance to test for lipoteichoic acid (LTA) binding. We coated CLEC3A peptides on titanium, a commonly used prosthetic material, and performed fluorescence microscopy to quantify bacterial adhesion. Moreover, we assessed the peptides' cytotoxicity against primary human chondrocytes using MTT cell viability assays.

RESULTS

CLEC3A fragments were detected in human cartilage extracts. Moreover, bacterial supernatants lead to fragmentation of recombinant and cartilage-derived CLEC3A. CLEC3A-derived peptides killed E.coli, P.aeruginosa and S.aureus, permeabilized bacterial membranes and bound lipopolysaccharide and LTA. Coating CLEC3A antimicrobial peptides (AMPs) on titanium lead to significantly reduced bacterial adhesion to the material. In addition, microbicidal concentrations of CLEC3A peptides in vitro displayed no direct cytotoxicity against primary human chondrocytes.

CONCLUSIONS

We identify cartilage-specific AMPs originating from CLEC3A, resolve the mechanism of their antimicrobial activity and point to a novel approach in the prevention and treatment of septic arthritis using potent, non-toxic, AMPs.

Local Anesthetics' Toxicity toward Human Cultured Chondrocytes: A Comparative Study between Lidocaine, Bupivacaine, and Ropivacaine

OBJECTIVE

In orthopedic joint injection, the most frequently used local anesthetics are ropivacaine, bupivacaine, and 1% or 2% lidocaine. The aim of this study was to examine effects of these various anesthetics on the viability of human chondrocytes. Our hypothesis was that all local anesthetics tested damage human chondrocytes in vitro.

METHODS

Primary human chondrocytes were isolated and cultured from 6 donated human knee joints (mean age of donors 61.2 years). Local anesthetics were added to these cultures. Toxicity analysis was performed by visualization of cell structure using light microscopy. Determination of vital chondrocytes was performed by use of a Casy cell counter. Chondrocytes' cell death was examined by fluorescence microscopy and an XTT ELISA assay.

RESULTS

Light microscope and fluorescence microscope data revealed a defect cell structure and increased number of dead cells after addition of 1% or 2% lidocaine and bupivacaine but not ropivacaine. We were able to show an increased level of XTT activity after treatment with bupivacaine, 2% lidocaine or ropivacaine. The count of vital chondrocytes was significantly decreased after treatment with bupivacaine, 1% or 2% lidocaine, and ropivacaine.

CONCLUSIONS

The data show that treatment with local anesthetics induces cell damage of human chondrocytes in vitro. Ropivacaine seems to be a local anesthetic with the lowest toxic potential on human chondrocytes, a feature that may favor its preference for use in joint injection.

[Antibiotic strategies in trauma surgery : Treatment of implant-associated infections]

Implant-associated infections represent a serious complication following fracture management. Due to biofilm formation, an optimized treatment strategy is required to treat these infections. Interdisciplinary cooperation between trauma surgeon, infectious diseases specialist and microbiologist enables the deployment of a concerted surgical and antibiotic treatment concept, which significantly influences treatment success. Fracture healing and chronic osteomyelitis prevention are the primary treatment goals. In general, the eradication of infection is possible with surgical debridement, change or removal of the implant and adequate antibiotic therapy. In some cases, suppressive therapy until consolidation of fracture and later removal of the implant is an option.

Hydrogen peroxide in orthopaedic surgery - is it worth the risk?

Hydrogen peroxide (H₂O₂) is commonly used in orthopaedic surgery during cemented arthroplasty and wound washouts. Its purported roles include antisepsis, haemostasis, mechanical debridement, and optimising the cement-bone interface during cementing. However, despite its apparent harmless mechanism of action, H₂O₂ has been implicated in fatal and near fatal complications caused through oxygen emboli. We present a case of oxygen embolism and review the existing literature to highlight its potential risks and its lack of therapeutic value. We believe there is little role for its use in orthopaedic surgery.

Icariside II inhibits cell proliferation and induces cell cycle arrest through the ROS-p38-p53 signaling pathway in A375 human melanoma cells

Icariside II (IS) is a metabolite of icariin, which is derived from Herba Epimedii. In the present study, the antiproliferative effects of IS on A375 human melanoma cells were examined in vitro and a possible mechanism through the ROS-p38-p53 pathway is discussed. A cell WST-8 assay revealed that treatment with IS markedly reduced cell viability from 77 to 21% (25 and 100 µM, respectively), and cell counting demonstrated that IS treatment reduced cell proliferation. IS treatment also induced cell cycle arrest of A375 cells at the G0/G1 and G2/M transitions and inhibited the expression of cell-cycle related proteins, including cyclin E, cyclin-dependent kinase 2 (CDK2), cyclin B1 and phosphorylated cyclin-dependent kinase 1 (P-CDK1). In this study, it was determined that IS inhibits cell proliferation and induces cell cycle arrest through the generation of reactive oxygen species and activation of p38 and p53. These findings were further supported by the evidence that pretreatment with N-acetyl-L-cysteine, SB203580 or pifithrin-α significantly blocked IS-induced reduction of cell viability, increase of cell death and cell cycle arrest. In conclusion, IS inhibits cell proliferation and induces cell cycle arrest. Crucially, it was confirmed that these effects were mediated at least in part by activating the ROS-p38-p53 pathway.

Human osteoblast damage after antiseptic treatment

PURPOSE

Antiseptics are powerful medical agents used for wound treatment and decontamination and have a high potential for defeating joint infections in septic surgery. Both chlorhexidine and polyhexanide are frequently used in clinical practice and have a broad antimicrobial range, but their effect on human osteoblasts has not been sufficiently studied. Our objective was to investigate the toxic effects of polyhexanide and chlorhexidine on human osteoblasts in vitro to evaluate their clinical applicability in septic surgery.

METHODS

We isolated and cultivated human osteoblasts in vitro and assayed the toxic effects of chlorhexidine 0.1% and polyhexanide 0.04%, concentrations commonly applied in clinical practice. Toxicity analysis was performed by visualisation of cell structure, lactate dehydrogenase (LDH) activity and evaluation of vital cells. Toxicity was evaluated by microscopic inspection of cell morphology, trypan blue staining and determination of LDH release.

RESULTS

Damaged cell structure could be shown by microscopy. Both antiseptics promoted LDH activity after incubation with osteoblasts. The evaluation of vital osteoblasts showed a significant decrease of vital cells.

CONCLUSIONS

Both antiseptics induced significant cell death of osteoblasts at optimum exposure. We therefore recommend cautious use of polyhexanide and chlorhexidine in septic surgery to avoid severe osteoblast toxicity.

Cytotoxic Effects of Polyhexanide on Cellular Repopulation and Calcification of Decellularized Equine Carotids in vitro and in vivo

Purpose

Disinfection of biological implants is indispensable for clinical safety. Here, decellularized equine carotid arteries (dECAs) were disinfected by polyhexanide (PHX), an effective, well-tolerated and nontoxic wound disinfectant and evaluated as vascular grafts for their repopulation and local biocompatibility in vivo.

Methods

dECAs were terminally disinfected by a combination of 0.1% PHX and 70% ethanol (dECA_PHX-ET) or exclusively ethanol (dECA-ET) and subsequently implanted as arteriovenous shunts in sheep for 14 weeks. Repopulation was determined by immunohistochemistry for endothelial- (ECs) or smooth muscle cells (SMCs) using antibodies against CD31 and smooth muscle actin. Histological evaluation was performed on HE-stained sections. Cytotoxicity of dECAs was measured directly by seeding the scaffolds with L-929 fibroblasts, which were visualized by calcein staining. Indirect cytotoxicity was determined by WST-8 viability assay by incubation of L-929 with dECA extracts.

Results

dECA_PHX-ET completely lacked repopulation with ECs and SMCs, showed leukocyte infiltration, strong calcification and poor neovascularization indicating insufficient biocompatibility and inflammatory graft degeneration. PHX-treatment reduced cell viability to 33.2 ± 12.6% and disturbed cell growth at direct contact. In contrast, dECA_ET had no direct cytotoxic effect and only slightly influenced cell viability (82.9 ± 12.5%), showed a substantial repopulation by ECs and SMCs including neovascularization, and were only slightly calcified.

Conclusion

The disinfectant polyhexanide seems to exert severe cytotoxic effects when used for the processing of decellularized matrices and may result in degenerative graft deterioration. In contrast, dECAs exclusively disinfected with ethanol were well integrated. Thus, ethanol seems to be a more suitable tool for graft processing than polyhexanide.

Effects of indigo carmine on human chondrocytes in vitro

Joint infections following or accompanying superficious soft tissue infections are severe complication in orthopedic surgery. The use of intra-articular blue staining is a helpful method to visualize a fistula and to differentiate between superficial and intra-articular infections. Regarding this clinical implication data about the effects of indigo carmine, a frequently used blue staining substance, on cartilage is missing. The hypothesis of this study was that indigo carmine damages human chondrocytes in a time and concentration dependent manner. Human chondrocytes were isolated from donors with osteoarthritis who were treated with TKA. Cells were cultivated and treated with different concentrations of indigo carmine for 5 and 10 minutes. Morphologic damage was examined by light microscopy. Toxicity was quantified by counting vital cell number and lactate dehydrogenase (LDH) expression. Analysis by light microscopy showed defected cell structure and loss of cell number after treatment with 100% indigo carmine for 10 minutes. Treatment with 10% and 1% indigo carmine showed no significant cell defects and loss of cells. Counting vital cell number showed loss of vital cells after treatment with 100% and 10% indigo carmine for 10 minutes. LDH expression was significantly increased after treatment with 100% indigo carmine.Toxic effects were shown after treatment with indigo carmine. Therefore, it should be used in 1:100 dilution. This is both, sufficient for visualizing a fistula in a possible clinical application and could be protective for chondrocytes.

Osteoarthritis synovial fluid activates pro-inflammatory cytokines in primary human chondrocytes

PURPOSE

Two of the most common joint diseases are rheumatoid arthritis (RA) and osteoarthritis (OA). Cartilage degradation and erosions are important pathogenetic mechanisms in both joint diseases and have presently gained increasing interest. The aim of the present study was to investigate the effects of the synovial fluid environment of OA patients in comparison with synovial fluids of RA patients on human chondrocytes in vitro.

METHODS

Primary human chondrocytes were incubated in synovial fluids gained from patients with OA or RA. The detection of vital cell numbers was determined by histology and by using the Casy Cell Counter System. Cytokine and chemokine secretion was determined by a multiplex suspension array.

RESULTS

Microscopic analysis showed altered cell morphology and cell shrinkage following incubation with synovial fluid of RA patients. Detection of vital cells showed a highly significant decrease of vital chondrocyte when treated with RA synovial fluids in comparison with OA synovial fluids. An active secretion of cytokines such as vascular endothelial growth factor (VEGF) of chondrocytes treated with OA synovial fluids was observed.

CONCLUSIONS

Significantly increased levels of various cytokines in synovial fluids of RA, and surprisingly of OA, patients were shown. Activation of pro-inflammatory cytokines of human chondrocytes by synovial fluids of OA patient supports a pro-inflammatory process in the pathogenesis of OA.

[Joint infections. Known facts and new trends]

Acute septic arthritis is a surgical emergency because rapid septic destruction of articular cartilage can lead to impairment or even loss of joint function. Diagnosis consists of patient history, clinical examination, laboratory results, (sonography- guided) joint aspiration and radiography. Emergency therapy is based on arthroscopic or open joint debridement and lavage combined with systemic antibiotic therapy. No data are available for the recommendation of local antibiotics but antiseptic solutions are not recommended because of cartilage damage. New trends in diagnostics are positron emission tomography/computed tomography (PET/CT), urine sticks for analysis of joint fluid and molecular pathology. Chronic joint empyema is more diagnostically demanding and is difficult to treat. In cases of necrotic and infected articular cartilage, joint resection has to be performed for quiescence of infection. Options following successful treatment of empyema are arthroplasty, arthrodesis or permanent resection.

Hydrogen Peroxide – A Party Trick from the Past?

Hydrogen peroxide solutions are found in almost every operating theatre and are used by many surgical specialties, often with little knowledge of their inherent risk. We reviewed the literature and evidence related to the use of hydrogen peroxide in surgery. We found little evidence supporting the use of hydrogen peroxide solutions intraoperatively, a large number of reports of sometimes-fatal oxygen embolism and other evidence of tissue toxicity. We conclude that the use of hydrogen peroxide as an antiseptic has no direct benefit, but is associated with significant risk, and therefore should be reconsidered.

Preferred use of polyhexanide in orthopedic surgery

In orthopedic and trauma surgery, the most frequently used antiseptic is polyhexanide. Its favored application is based on prepossessing tissue compatibility in contrast to various antiseptics and a high antimicrobiological effect. Recent studies showed toxic effects of this antiseptic on human chondrocytes. The aim of this study was to further analyze the toxic and apoptotic effects of polyhexanide on primary human chondrocytes. The hypothesis of this study was that polyhexanide induces apoptosis on human chondrocytes. Primary human chondrocytes were isolated and cultured from human donors with osteoarthritis of the knee who underwent total arthroplasty and had no indication of infection. Polyhexanide at a standard concentration of 0.04% was added to the monolayer cultures. Early and late apoptotic cells were analyzed by flow cytometric detection of annexin V, active caspases, and 7AAD, and by fluorescence microscopy using annexin V and propidium iodide staining. Flow cytometric analysis demonstrated an increase of annexin V and active caspases expression of human chondrocytes after incubation with polyhexanide. Fluorescence microscopy demonstrated a high number of annexin V positive and propidium iodide negative early apoptotic cells. The data show that polyhexanide promotes apoptosis on primary human chondrocytes in vitro, which may indicate the use of polyhexanide in septic joint surgery.