The socioeconomic impact of musculoskeletal infections

Periprosthetic knee infections treated with irrigation and debridement: outcomes and preoperative predictive factors

The role of irrigation and debridement (I&D) in the treatment of periprosthetic joint infections (PJI) of the knee remains controversial. Our purpose was to identify the success rate and factors determining outcome of I&D in those patients. Clinical characteristics of 78 patients with PJI of the knee treated with I&D were retrospectively reviewed. Implant retention at final follow-up was achieved in 43 patients (55.1%). Logistic regression analysis revealed that duration of symptoms >5days and thyroid disease were independent predictors of I&D failure. Patients with methicillin-resistant staphylococcal infections had a success rate of 45.5% and significantly lower odds of success compared to patients with negative cultures. In selected patients, I&D is a reasonable option in the context of acute PJI of the knee.

Irrigation and debridement for periprosthetic infections of the hip and factors determining outcome

PURPOSE

Our purpose was to identify the success rate and factors predicting outcome of irrigation and debridement (I&D) in patients with deep periprosthetic joint infection (PJI) of the hip.

METHODS

We retrospectively reviewed clinical characteristics of patients with deep PJI after primary/revision total hip arthroplasty (THA) between January 2000 and May 2013 treated with I&D. Implant retention was the outcome of interest. Sixty patients (29 men and 31 women; mean age 64.9 years) were identified. Mean follow-up was 59 months (range, 12-168).

RESULTS

The implants were retained in 42 patients (70%). Failure of I&D treatment correlated with duration of symptoms >five days (p <0.001) and obesity [body mass index (BMI) ≥ 30)] (p = 0.0289). Treatment outcome was affected by the type of pathogen (p = 0.0482), with patients with methicillin-resistant staphylococci having significantly lower odds of success.

CONCLUSIONS

I&D can be a feasible option in THA patients presenting with acute deep PJI. Duration of symptoms >five days, isolation of methicillin-resistant staphylococci and obesity should be taken into consideration in pre-operative decision making.

Evaluation of implant sonication as a diagnostic tool in implant-associated infections

Infections of implants pose a severe problem in the field of orthopedic surgery, because they can cause bone degradation with subsequent loosening of the implant. The discrimination between septic implant loosening and aseptic loosening can be a challenge, and hence novel diagnostic methods have been introduced to improve the detection of bacteria. Because a major problem is their firm adherence to implants due to biofilm formation, sonication has been introduced, followed by identification of bacteria by culture or genetic methods. In this study, we compared the results obtained after sonication pretreatment with those of microbiological testing of tissue samples and histopathological evaluation of the same tissue. Furthermore, we related the results obtained following sonication to the clinical diagnosis of septic or aseptic implant loosening, respectively. Sonication of explanted devices also enhances the likelihood of detecting bacterial growth in patients who were considered "aseptic" based on the clinical evaluation.

Adherence of S. epidermidis on different metals. A comparative in vitro study

AIM

Staphylococcus epidermidis is the most common cause of orthopedic infections. Adhesion and biofilm formation on orthopedic implant surfaces play an important role in the physiopathology of these infections. The aim of our study was to evaluate the adhesion of S. epidermidis on the surface of metals usually used in orthopedics.

METHODS

Previously sterilized circular metal plates of titanium (Ti), porous titanium (p-Ti), cobalt chromium (CoCr) and stainless steel (SS) were hung completely submerged in a liquid medium with a known concentration of S. epidermidis (RP62A). They were incubated for 1 h or 24 h at 36°C. After incubation, each plate was washed with PBS and sonicated during 5 minutes in 10 mL of saline. Different dilutions were performed and 100 µL from each sample was cultured on agar plates.

RESULTS

26 metal plates were incubated for 1 h and other 55 metal plates for 24 h. The lowest bacterial count (cfu/mm2) at 1 h was observed in CoCr plates while in p-Ti it was 6 times higher. At 24 h the highest bacterial count was observed in SS plates while the lowest in Ti. However, these differences were not statistically significant.

CONCLUSIONS

After 1 h and 24 h of exposure, the lowest adherence was observed in CoCr and Ti plates, respectively. However, bacterial attachment occurred with all materials. It is necessary to further investigate new materials able to avoid bacterial attachment.

The cost of after-hours operative debridement of open tibia fractures

OBJECTIVES

The aim of this study was to evaluate the additional cost associated with performing after-hours operative debridement of open fractures within 6 hours of injury.

DATA SOURCES

The economic model is based on population estimates obtained from the National Trauma Database and the National Inpatient Sample on the number of open tibia fractures that occur annually in the United States and the number that present after-hours (between 6 PM and 2 AM) that undergo operative debridement within 6 hours. This model estimates incremental cost for after-hours surgery based on overtime wages for on-call personnel (nurses and surgical technicians) required to staff after-hours cases as published by the US Department of Labor and data from our own institution. As many level 1 hospitals are capable of performing after-hours cases without additional cost, a sensitivity analysis was performed to determine the effect of designated level of care of the trauma hospital.

DATA EXTRACTION AND SYNTHESIS

A total of 17,414 open tibia fractures were recorded in the National Inpatient Sample for 2009, and an estimated 7485 open tibia fractures presented after-hours, 4242 of which underwent operative debridement within 6 hours of presentation. Based on wage statistics from the US Department of Labor and our own institution, the estimated total additional cost for after-hours operative debridement of open tibia fractures within 6 hours is from $2,210,895 to $4,046,648 annually, respectively. For level 2 hospitals and below, the cost of performing after-hours operative debridement of open tibia fractures is calculated as from $1,532,980 to $2,805,846 annually.

CONCLUSIONS

The data indicated an increased overall financial cost of performing after-hours operative debridement of open tibia fractures. Given that there is minimal documented benefit to this practice, and with increased pressure to practice cost containment, elective delay of operative debridement of open fractures and/or transfer to a higher level of care trauma hospital may be an acceptable way to address these issues.

LEVEL OF EVIDENCE

Economic analysis level III. See instructions for authors for a complete description of levels of evidence.

Management strategies for infected total hip arthroplasty. A critical appreciation of problems and techniques

Infection is a devastating complication of total hip arthroplasty (THA). Risk factors have been recognised and prevention is possible. The nature of the disease is heterogeneous and for satisfactory management one has to weigh factors related to pathogen, host, local soft tissue, bone stock, surgeon experience and financial resources. Available data in the current literature is of poor quality and there is a lack of data comparing different techniques. Referral of patients to dedicated departments with the appropriate facilities may be more appropriate.

Biofilm Disrupting Technology for Orthopedic Implants: What's on the Horizon?

The use of orthopedic implants in joints has revolutionized the treatment of patients with many debilitating chronic musculoskeletal diseases such as osteoarthritis. However, the introduction of foreign material into the human body predisposes the body to infection. The treatment of these infections has become very complicated since the orthopedic implants serve as a surface for multiple species of bacteria to grow at a time into a resistant biofilm layer. This biofilm layer serves as a protectant for the bacterial colonies on the implant making them more resistant and difficult to eradicate when using standard antibiotic treatment. In some cases, the use of antibiotics alone has even made the bacteria more resistant to treatment. Thus, there has been surge in the creation of non-antibiotic anti-biofilm agents to help disrupt the biofilms on the orthopedic implants to help eliminate the infections. In this study, we discuss infections of orthopedic implants in the shoulder then we review the main categories of anti-biofilm agents that have been used for the treatment of infections on orthopedic implants. Then, we introduce some of the newer biofilm disrupting technology that has been studied in the past few years that may advance the treatment options for orthopedic implants in the future.

Interleukin-6 and other inflammatory markers in diagnosis of periprosthetic joint infection

PURPOSE

The purpose of this study was to evaluate the diagnostic value of interleukin-6 (IL-6) and other inflammatory markers including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count (WCC) in diagnosis of PJI.

METHODS

The study group included 40 patients (21 males, 19 females) admitted for surgical intervention after knee or hip arthroplasties. Patients were subjected to careful history taking, thorough clinical examination and pre-operative laboratory investigations including serum IL-6, CRP, WCC and ESR. Peri-implant tissue specimens were subjected to microbiological culture and histopathological examination.

RESULTS

The mean age of patients was 58.4 years (range, 38-72 years). Intra-operative cultures and histopathological examination revealed 11 patients had been infected (PJI) and 29 patients were aseptic failure of prosthesis. Four presumed markers of infection were tested preoperatively: ESR, CRP, WCC, and IL-6. ESR (p = 0.0001), CRP (p = 0.004), WCC (0.0001), and IL-6 (p = 0.0001) were significantly higher in patients with septic revision than those with aseptic failure of the prosthesis. Serum IL-6 (>10.4 pg/ml) reportedly had a sensitivity of 100%, a specificity of 90.9%, a PPV of 79%, a NPV of 100%, and accuracy of 92.5%.

CONCLUSIONS

The present study demonstrated that IL-6 has been found to be the most accurate laboratory marker for diagnosing PJI when compared to ESR, CRP, and WCC. IL-6 above 10.4 pg/ml and CRP level above 18 mg/L will identify all patients with PJI and the combination of CRP + IL-6 is an excellent screening test to identify all such patients (sensitivity 100%, NPV 100%).

The macrophage inflammatory proteins MIP1α (CCL3) and MIP2α (CXCL2) in implant-associated osteomyelitis: linking inflammation to bone degradation

Bacterial infections of bones remain a serious complication of endoprosthetic surgery. These infections are difficult to treat, because many bacterial species form biofilms on implants, which are relatively resistant towards antibiotics. Bacterial biofilms elicit a progressive local inflammatory response, resulting in tissue damage and bone degradation. In the majority of patients, replacement of the prosthesis is required. To address the question of how the local inflammatory response is linked to bone degradation, tissue samples were taken during surgery and gene expression of the macrophage inflammatory proteins MIP1α (CCL3) and MIP2α (CXCL2) was assessed by quantitative RT-PCR. MIPs were expressed predominantly at osteolytic sites, in close correlation with CD14 which was used as marker for monocytes/macrophages. Colocalisation of MIPs with monocytic cells could be confirmed by histology. In vitro experiments revealed that, aside from monocytic cells, also osteoblasts were capable of MIP production when stimulated with bacteria; moreover, CCL3 induced the differentiation of monocytes to osteoclasts. In conclusion, the multifunctional chemokines CCL3 and CXCL2 are produced locally in response to bacterial infection of bones. In addition to their well described chemokine activity, these cytokines can induce generation of bone resorbing osteoclasts, thus providing a link between bacterial infection and osteolysis.

Analysis of parameters influencing the release of antibiotics mixed with bone grafting material using a reliable mixing procedure

Local infections arising from fracture fixation, defect reconstruction or joint replacement can cause extreme pain and impaired healing, lead to revision operations, prolong hospital stay and increase costs. Treatment options including prophylaxis are afforded by the use of grafts and biomaterials loaded with antibiotics. These can produce local therapeutic concentrations with a reduced systemic concentration and reduced systemic side-effects. Patient-specific loading of osteogenic graft materials with antibiotic could be an important option for orthopaedic surgeons. A local therapeutic concentration must be available for the desired duration and cytotoxic effects must be kept within an acceptable range. The present study investigates a simple and reliable mixing procedure that could be used for the perioperative combination of antibiotic powders and solutions with bone grafting materials. The potential influence of concentration and sampling regime on the release kinetics of gentamicin, tobramycin and vancomycin was studied over a period of 56days and potency and cytotoxicity were evaluated. In all treatment groups, gentamicin and tobramycin were completely released within 3days whilst vancomycin was released over a period of 14days. The results clearly show that the main parameter influencing release is the molecular weight of the drug. Growth of Staphylococcus aureus was inhibited in all 3 treatment groups for at least 3days. Cell viability and alkaline phosphatase activity of primary osteoblast-like cells were not significantly affected by the antibiotic concentrations obtained from the elution experiments. Bone grafting is an established component of surgery for bone defect filling and for biological stimulation of healing. Patient-specific enhancement of such procedures by incorporation of antibiotics for infection prevention or by addition of cytokines for promotion of impaired healing or for treatment of critical size defects will be a relevant issue in the future.

Posttraumatic and postoperative osteomyelitis: surgical revision strategy with persisting fistula

INTRODUCTION

Posttraumatic and postoperative osteomyelitis (PPO) with bacteria colonisation during trauma and associated surgery is an increasing clinical problem. This study investigated the treatment of PPO by surgical revision including irrigation, debridement, and temporary hardware maintenance. In addition, a drainage was inserted as persisting fistula to control osteomyelitis until fracture healing was achieved. Trauma- and osteomyelitis-related factors that influenced the study outcome were determined.

PATIENTS AND METHODS

67 consecutive patients with PPO were included. At onset of PPO, patients had incomplete fracture healing. Patients were subdivided by time of PPO occurrence (acute, subacute or chronic), initial soft tissue trauma, anatomical location, and initial fracture type (AO classification). The study outcome measures included radiographic and clinical follow-up.

RESULTS

59 patients could be followed for an average of 23 months after revision surgery. A bone healing was achieved by 89% of patients after 14.7 ± 13.4 weeks. Fractures of the lower extremity, open fractures and comminuted C-type fractures took significantly longer to achieve bone healing (p < 0.05 each). Time of PPO occurrence did not influence bone healing. After fracture consolidation, no re-infection was found.

CONCLUSIONS

This study showed high rates of bone healing, indicating that this strategy with persisting fistula should be considered as alternative treatment option in patients with PPO.

Conventional and molecular diagnostic strategies for prosthetic joint infections

An accurate diagnosis of prosthetic joint infection (PJI) is the mainstay for an optimized clinical management. This review analyzes different diagnostic strategies of PJI, with special emphasis on molecular diagnostic tools and their current and future applications. Until now, the culture of periprosthetic tissues has been considered the gold standard for the diagnosis of PJI. However, sonication of the implant increases the sensitivity of those cultures and is being increasingly adopted by many centers. Molecular diagnostic methods compared with intraoperative tissue culture, especially if combined with sonication, have a higher sensitivity, a faster turnaround time and are not influenced by previous antimicrobial therapy. However, they still lack a system for detection of antimicrobial susceptibility, which is crucial for an optimized and less toxic therapy of PJI. More studies are needed to assess the clinical value of these methods and their cost-effectiveness.

Antibiofilm agents and implant-related infections in orthopaedics: where are we?

Orthopaedics is currently the largest market of biomaterials worldwide and implant-related infections, although relatively rare, remain among the first reasons for joint arthroplasty and osteosynthesis failure. Bacteria start implant infection by adhering to biomaterials and producing biofilms, which represent a major reason for bacterial persistence, in spite of antibiotic treatment and host's defence. In the last two decades, a number of different antibiofilm agents have been studied and both in vitro and in vivo results appear now promising, even if their effective role in orthopaedics remains to be assessed. In this review, we introduce an original classification of antibiofilm agents, based on their mechanism of action and examine the available data concerning their possible application to orthopaedic implant-related infections. Molecules that interfere with biofilm production (biofilm prevention agents) include anti-adhesion compounds, quorum sensing inhibitors, non-steroideal anti-inflammatory drugs, and antimicrobial peptides; N-acetylcysteine and specific enzymes promise the greatest therapeutic possibilities by disrupting established biofilms (biofilm disrupting agents). The identification of antimicrobials able to bypass the biofilm barrier (biofilm bypassing agents), and antibiofilm vaccines are further strategies aimed to reduce the impact of biofilm-related infections, opening new pathways in controlling implant-related infections. However, this review shows that still insufficient knowledge is currently available as to regard the efficacy and safety of the investigated antibiofilm strategies to treat infection that involve bone tissue and biomaterials commonly implanted in orthopaedics, pointing out the need for further research in this promising field.

Infection following simultaneous bilateral total knee arthroplasty

Between 2000 and 2009, demographics, clinical characteristics, and infection details were compared among patients undergoing simultaneous BTKA (SBTKA), staged or UTKA. 2825 (16%) patients underwent SB, 1151 (6%) staged, and 13,983 (78%) UTKA. The overall infection rate following SBTKA (0.57%) was lower compared to staged (1.39%) or UTKA (1.1%) (P=0.01). The in-hospital infection rate was lower for the SB group (0.28% vs. 0.96% vs. 0.69%, respectively, P=0.01). The rate of late infections was comparable between the groups (0.32% vs. 0.43% vs. 0.43%, respectively, P=0.72). The rate of superficial infection was lower in the simultaneous cohort (0.28% vs. 1.04% vs. 0.87%; P=0.003). The overall rate of deep infection and reoperation for infection was similar among the groups. Among patients with late infection, age, gender, comorbidity score, time to infection, and most common organism isolated were not significantly different between the groups. Among infected patients after SB or staged TKA, 3 SB patients (18.75%), and 3 staged (20%) had bilateral involvement (P=1.0). Staged patients had more 2nd side infections, while simultaneous patients had more 1st side infections (P=0.02). Regression analysis showed that UTKA patients were 2.5 times more likely to develop in-hospital infection compared to SBTKA, while staged patients were almost 3.4 times more likely. Each additional hospital day increased the risk of late infection by 11.3%. SBTKA demonstrates an advantage over staged and maintains the safety profile of unilateral approaches with respect to infectious complications.

In-hospital surgical site infections after primary hip and knee arthroplasty--incidence and risk factors

Data of hospitalizations for THA or TKA were analyzed for each year between 1998 and 2007 from the National Inpatient Sample. Demographics, comorbidities, incidence of morbidity and mortality, length of hospital stay (LOS), and overall cost were compared for infected and non-infected patients. Perioperative SSI rates were 0.36% for THA and 0.31% for TKA (412,356 and 784,335 patient entries, respectively). Patients with SSI had a significantly higher overall comorbidity burden, higher perioperative mortality rates, longer length of stay, and higher complication rates. Average cost of in-hospital care was double for SSI versus non-SSI patients. Independent risk factors for perioperative SSI included male gender, minority race, a diagnosis for cancer, liver disease, coagulopathies, fluid and electrolyte disorders, congestive heart failure, and pulmonary circulatory disease. Data relied on coded information and could not differentiate between superficial or deep infection, or capture patients readmitted for SSI, and therefore may have underestimated the true incidence of SSI.

Titanium-tethered vancomycin prevents resistance to rifampicin in Staphylococcus aureus in vitro

Rifampicin is currently recognized as the most potent drug against Gram positive implant related infections. The use of rifampicin is limited by the emergence of bacterial resistance, which is often managed by coadministration of a second antibiotic. The purpose of this study was to determine the effectiveness of soluble rifampicin in combination with vancomycin tethered to titanium metal as a means to control bacterial growth and resistance in vitro. Bacterial growth was inhibited when the vancomycin-tethered titanium discs were treated with Staphylococcus aureus inocula of ≤2×10⁶ CFU, however inocula greater than 2×10⁶ CFU/disc adhered and survived. The combination of surface-tethered vancomycin with soluble rifampicin enhanced the inhibitory effect of rifampicin for an inoculum of 10⁶ CFU/cm² by one dilution (combination MIC of 0.008 mg/L versus 0.015 mg/L for rifampicin alone). Moreover, surface tethered vancomycin prevented the emergence of a rifampicin resistant population in an inoculum of 2×10⁸ CFU.

Biofilm growth on implants: bacteria prefer plasma coats

PURPOSE

Bacterial biofilm formation on prostheses or devices used for osteosynthesis is increasingly recognized as cause of persistent infections, an entity known as implant-associated posttraumatic osteomyelitis. Biofilm formation is a very complex, multistep process with adhesion as the first and decisive step. The most prevalent pathogens found are staphylococci species, especially S. aureus, presumably due to a preference to non-biological materials, such as metal. Adherence is influenced by several factors, including the microenvironment, in which blood proteins from serum or plasma might influence adhesion and maybe biofilm formation. The aim of the present study was to test and to compare adherence of S. aureus and P. aeruginosa to different biological and non-biological surfaces in vitro. The question was addressed if coating of the surface by plasma or serum proteins influences bacterial adherence.

METHODS

Adherence of radiolabeled bacteria to different surfaces in the presence or absence or serum/plasma proteins was measured over time.

RESULTS

When testing adherence of S. aureus to plastic, titanium or to monolayers of epithelial cells (A549) or fibroblasts (Colo800) a clear-cut preference for non-biological surfaces, especially for titanium was seen. Using P. aeruginosa species a similar pattern without a significant difference was revealed. When mimicking the in vivo situation by pre-coating of titanium with human serum or plasma adherence was increased, especially when titanium was coated ("opsonized") by plasma.

CONCLUSIONS

Bacterial adherence to surfaces is determined by a variety of factors such as temperature, the presence of nutrients, the absence of host defense systems and the configuration of the covered surface. In vivo, adherence to non-biological surfaces is also influenced by the microenvironment, especially plasma proteins, promoting biofilm formation.