Prophylactic antibiotics in hip and knee arthroplasty

Increased infection risk after hip hemiarthroplasty in institutionalized patients with proximal femur fracture

In patients undergoing hip hemiarthroplasty (HHA) secondary to proximal femur fracture, acute periprosthetic joint infection (PJI) is one of the most important complications. We have detected an increased risk of PJI in chronic institutionalized patients (CIPs), and a higher number of early postoperative infections are caused by Gram-negative bacteria (GNB), not covered by the current prophylaxis (cefazolin in noninstitutionalized patients (NIPs) and cotrimoxazole in CIPs). We sought to compare infection characteristics between NIPs and CIPs, analyzing predisposing factors, causative pathogens, and antibiotic prophylaxis-related microbiological characteristics. We performed a retrospective review of our prospective institutional database to identify all patients consecutively admitted for HHA to treat proximal femur fracture at our centre between 2011 and 2013. PJI was diagnosed in 21 of 381 (5.51%) patients, with 10 of 105 (9.52%) in the CIP group and 11 of 276 (3.99%) in the NIP group, and statistical significance was achieved. GNB accounted for PJI in 14 (66.67%) patients. We detected a single case of methicillin-resistant Staphylococcus aureus (MRSA) infection in the NIP group. We confirm a higher risk of acute PJI among institutionalized patients, commonly caused by Gram-negative microorganisms, which are not covered by the current prophylaxis. New prophylactic strategies should be investigated in order to reduce this problem.

Preventing Implant-Associated Infections by Silver Coating

Implant-associated infections (IAIs) are a dreaded complication mainly caused by biofilm-forming staphylococci. Implant surfaces preventing microbial colonization would be desirable. We examined the preventive effect of a silver-coated titanium-aluminum-niobium (TiAlNb) alloy. The surface elicited a strong, inoculum-dependent activity againstStaphylococcus epidermidisandStaphylococcus aureusin an agar inhibition assay. Gamma sterilization and alcohol disinfection did not alter the effect. In a tissue cage mouse model, silver coating of TiAlNb cages prevented perioperative infections in an inoculum-dependent manner and led to a 100% prevention rate after challenge with 2 × 10(6)CFU ofS. epidermidisper cage. InS. aureusinfections, silver coating had only limited effect. Similarly, daptomycin or vancomycin prophylaxis alone did not preventS. aureusinfections. However, silver coating combined with daptomycin or vancomycin prophylaxis thwarted methicillin-resistantS. aureusinfections at a prevention rate of 100% or 33%, respectively. Moreover, silver release from the surface was independent of infection and occurred rapidly after implantation. On day 2, a peak of 82 μg Ag/ml was reached in the cage fluid, corresponding to almost 6× the MIC of the staphylococci. Cytotoxicity toward leukocytes in the cage was low and temporary. Surrounding tissue did not reveal histological signs of silver toxicity.In vitro, no emergence of silver resistance was observed in several clinical strains of staphylococci upon serial subinhibitory silver exposures. In conclusion, our data demonstrate that silver-coated TiAlNb is potent for prevention of IAIs and thus can be considered for clinical application.

Prevention of Surgical Site Infections in Joint Replacement Surgery

Prosthetic joint infections (PJI), although rare, represent a serious complication of total joint arthroplasty as they pose not only a direct financial burden to the patient but also an indirect burden related to psychosocial impact that PJI incur on the patient. Treatment of PJI is complex and requires a combined surgical and medical approach. Patients are often subjected to multiple surgical procedures and prolonged courses of antimicrobial therapy. Therefore, all efforts should be directed toward maximizing the prophylactic measures in the peri-operative and post-operative phases in order to prevent the occurrence of surgical site infections. This article explores primarily the prophylactic measures that target the host and the operative theater environment. Implementation of such preventive measures requires a multi-disciplinary approach and is crucial for a successful outcome of the total joint arthroplasty.

Prophylactic antibiotics in elective hip and knee arthroplasty: an analysis of organisms reported to cause infections and National survey of clinical practice

Objectives

We wanted to investigate regional variations in the organisms reported to be causing peri-prosthetic infections and to report on prophylaxis regimens currently in use across England.

Methods

Analysis of data routinely collected by Public Health England’s (PHE) national surgical site infection database on elective primary hip and knee arthroplasty procedures between April 2010 and March 2013 to investigate regional variations in causative organisms. A separate national survey of 145 hospital Trusts (groups of hospitals under local management) in England routinely performing primary hip and/or knee arthroplasty was carried out by standard email questionnaire.

Results

Analysis of 189 858 elective primary hip and knee arthroplasty procedures and 1116 surgical site infections found statistically significant variations for some causative organism between regions. There was a 100% response rate to the prophylaxis questionnaire that showed substantial variation between individual trust guidelines. A number of regimens currently in use are inconsistent with the best available evidence.

Conclusions

The approach towards antibiotic prophylaxis in elective arthroplasty nationwide reveals substantial variation without clear justification. Only seven causative organisms are responsible for 89% of infections affecting primary hip and knee arthroplasty, which cannot justify such widespread variation between prophylactic antibiotic policies.

Cite this article: Bone Joint Res 2015;4:181–189.

Antimicrobial activity of bone cements embedded with organic nanoparticles

Infections after orthopedic surgery are a very unwelcome outcome; despite the widespread use of antibiotics, their incidence can be as high as 10%. This risk is likely to increase as antibiotics are gradually losing efficacy as a result of bacterial resistance; therefore, novel antimicrobial approaches are required. Parabens are a class of compounds whose antimicrobial activity is employed in many cosmetic and pharmaceutical products. We developed propylparaben nanoparticles that are hydrophilic, thus expanding the applicability of parabens to aqueous systems. In this paper we assess the possibility of employing paraben nanoparticles as antimicrobial compound in bone cements. The nanoparticles were embedded in various types of bone cement (poly(methyl methacrylate) [PMMA], hydroxyapatite, and brushite) and the antimicrobial activity was determined against common causes of postorthopedic surgery infections such as: Staphylococcus aureus, methicillin-resistant S. aureus, Staphylococcus epidermidis, and Acinetobacter baumannii. Nanoparticles at concentrations as low as 1% w/w in brushite bone cement were capable of preventing pathogens growth, 5% w/w was needed for hydroxyapatite bone cement, while 7% w/w was required for PMMA bone cement. No detrimental effect was determined by the addition of paraben nanoparticles on bone cement compression strength and cytocompatibility. Our results demonstrate that paraben nanoparticles can be encapsulated in bone cement, providing concentration-dependent antimicrobial activity; furthermore, lower concentrations are needed in calcium phosphate (brushite and hydroxyapatite) than in acrylic (PMMA) bone cements. These nanoparticles are effective against a wide spectrum of bacteria, including those already resistant to the antibiotics routinely employed in orthopedic applications, such as gentamicin.

Protocol-Based Arthroplasty: Less Is More

As a result of reading this article, physicians should be able to: 1. State an argument for, and background information on, patient-centered arthroplasty protocols. 2. Describe specific recommendations for designing a simplified arthroplasty care pathway that is reproducible in other institutions. 3. Discuss cost-effectiveness research on the latest value-delivering protocols. 4. Recognize areas of continued research and opportunities for future improvement in protocol development. Total joint arthroplasty is a successful orthopedic procedure that is performed in high volume in the United States and internationally. As economic pressures continue to mount in the US health care system, it will become increasingly important to minimize cost and improve quality and value. At the authors' institution, a protocol-based arthroplasty model is used, in many ways based on simplification of the patient care pathway. The largely evidence-based protocol has its foundation in eliminating unnecessary dogmatic practices, enhancing the patient experience, and achieving cost-effectiveness. The authors believe that a model like this can be applied to joint arthroplasty practices across the country in the future to maximize the value delivered to patients.

Systematic review and meta-analysis of randomized controlled trials of antibiotics and antiseptics for preventing infection in people receiving primary total hip and knee prostheses

Infection rates in primary (first-time) major joint arthroplasty continue to be a significant issue. The effect of antibiotic and antiseptic prophylaxis on outcomes for this type of surgery has not been adequately reviewed. A systematic search of the main databases for randomized controlled trials (RCTs) evaluating antibiotics and antiseptics was conducted to evaluate the predetermined endpoints of infection, adverse events, costs, quality of life, and concentration levels of antibiotics. A meta-analysis using pooled effect estimates and fixed-effect and random-effect models of risk ratios (RR), calculated with 95% confidence intervals (CI), was utilized. Thirty (30) RCTs examined the effects of antibiotic and antiseptic prophylaxis on infections after primary total hip arthroplasty (THA) (total of 11,597 participants) and total knee arthroplasty (TKA) (total of 6,141 participants). For THA, preoperative systemic intravenous (i.v.) antibiotic prophylaxis may be effective in reducing the incidence of infection after THA from 6 months to ≥5 years. For TKA, there is no RCT evidence that antibiotics and/or antiseptics have any effect on infection rate. Preoperative systemic antibiotic prophylaxis in primary THA may be effective at reducing infection rate. There is no evidence that timing, route of administration, or concentration levels have an effect on reducing infections, adverse events, or costs in THA or TKA. Many of the trials included in this study were published in the 1980s and 1990s. Thus, it would be important to replicate a number of them based on current patient demographics and incidence of bacterial resistance.

Attitudes of Nigerian orthopaedic surgeons to the use of prophylactic antibiotics

PURPOSE

Inappropriate use of prophylactic antibiotics can increase the rates of surgical site wound infections, lead to the development of resistant organisms and to increased health care costs. Despite widespread knowledge of standard antibiotic prophylaxis protocols (SAPs) in implant surgeries, it is thought that many Nigerian surgeons do not comply. The purpose of this study was to determine the awareness of Nigerian orthopaedic surgeons of SAPs in implant surgeries and their compliance.

METHODS

This was an observational study done using a questionnaire to collect data from orthopaedic surgeons at the National Orthopaedic Association annual conference held at Lokoja, Nigeria in November 2013.

RESULTS

There were 66 respondents divided into 56 consultants and ten surgical residents. Most respondents were aware of standard guidelines for the use of prophylactic antibiotics (86.36 %). Many of them (63.63 %) did not know the average rate of infection following implant surgery in their institutions. Compliance with SAPs was found to be 30.3 %. Compliance was worse among surgeons between 41 and 50 years of age and consultants with between six and ten years of practice.

CONCLUSIONS

Most respondents are aware of standard antibiotic protocols, but do not comply with them. The study also suggests that surgeons with intermediate levels of experience and those between 41 and 50 years of age were most unlikely to comply.

Deep Infections after Endoprosthetic Replacement Operations in Orthopedic Oncology Patients

BACKGROUND

Numerous studies have described various complications after endoprosthetic reconstructive operations. However, there are limited reports that focus specifically on deep infections (e.g., deep incisional surgical site infections), which remain one of the most dreaded complications of these operations, with rates ranging from 10% to 17%. Thus, this study was undertaken to determine the deep infection rates and to analyze possible risk factors, clinico-pathologic characteristics, and treatment modalities of endoprosthetic infections.

METHODS

We reviewed retrospectively the records of 105 consecutive patients who underwent endoprosthesis replacements from January 2007 to September 2011, with a minimal follow-up period of 32 mo. Comparison was made between patients with and without endoprosthetic infections.

RESULTS

Thirteen of the 150 patients (12.38%) who underwent endoprosthetic operations developed deep infections. Ninety-seven (92.4%) patients presented with a primary bone/soft tissue tumor, 5 (4.8%) with bone metastasis, and 3 (2.9%) with non-tumor conditions. Distal femoral was the most common implant location (42%). The majority of the infections (6/13) occurred within 3 mo post-operation. An elevated C-reactive protein concentration or erythrocyte sedimentation rate were present consistently in all patients at time of diagnosis, whereas clinical presentations and leukocytosis were inconsistent in determining infection. Staphylococcus aureus and coagulase-negative staphylococci (CoNS) were the most common organisms isolated, with high numbers demonstrating methicillin-resistance. Overall, multi-drug resistance was noted in 52.6% of the isolated strains. Four risk factors were associated independently with deep infection by multivariable analysis (p<0.05) and these were proximal tibia endoprosthesis, pelvic endoprosthesis, pre-operative duration of hospitalization of more than 48 h, and additional surgical procedures performed after the initial endoprosthetic insertion. Overall, infection was eradicated successfully in 53.8% (7/13) of the patients. Two-stage revision successfully treated the infection in 80% (4/5) of the patients, whereas surgical debridement without a change of implant was successful in only 42.8% (3/7) of patients. Amputation was performed in three patients.

CONCLUSIONS

Patients undergoing endoprosthetic replacement for various orthopedic oncologic conditions have high infection rates. The present study allows early identification of such patients in view of the high morbidity associated with this condition. This report also highlights the high rate of multi-drug-resistant infections, especially methicillin-resistant strains of S. aureus and CoNS encountered, which complicates further the management of these patients.

The role of microbial biofilms in prosthetic joint infections

Prosthetic joint infection (PJI) still remains a significant problem. In line with the forecasted rise in joint replacement procedures, the number of cases of PJI is also anticipated to rise. The formation of biofilm by causative pathogens is central to the occurrence and the recalcitrance of PJI. The subject of microbial biofilms is receiving increasing attention, probably as a result of the wide acknowledgement of the ubiquity of biofilms in the natural, industrial, and clinical contexts, as well as the notorious difficulty in eradicating them. In this review, we discuss the pertinent issues surrounding PJI and the challenges posed by biofilms regarding diagnosis and treatment. In addition, we discuss novel strategies of prevention and treatment of biofilm-related PJI.

Long term follow-up of successfully treated superficial wound infections following TKA

The relevance of wound complications in association with acute prosthetic joint infection (PJI) is well known. However, whether a successfully treated superficial infection can result in a chronic deep infection remains unclear. The aim of this study was to determine the prevalence, treatment and late complications of superficial wound infections following TKA. In a 3000 TKA prospective cohort, 45 superficial infections were diagnosed and treated successfully with antibiotic therapy along with or without surgical debridement. None of the cases developed deep chronic PJI at 70 months of follow-up. Three cases were in need of a TKA exchange due to aseptic loosening. A successfully treated superficial wound infection does not result in a chronic deep TKA infection.

Clinical Characteristics of Methicillin-resistant Staphylococcus aureus Infection for Chronic Periprosthetic Hip and Knee Infection

Purpose

Deep infection after hip and knee arthroplasty is a serious complication and is difficult to treat due to its toxicity. The aims of our study were to find out the differences of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) infection after hip and knee arthroplasty focusing on clinical course and laboratory findings.

Materials and Methods

We retrospectively reviewed 61 staphylococcal infection cases after hip and knee arthroplasty (MSSA in 25 patients, MRSA in 36 patients). Vital signs, laboratory tests, microbiology and clinical courses were analyzed. The average follow-up period was 3.8 years (range, 2 to 10.1 years).

Results

At initial visit, MRSA group showed significant higher erythrocyte sedimentation rate, C-reactive protein (CRP) and neutrophil percentage. The average duration for the normalization of CRP was longer in MRSA group (MRSA: 36.7±25.1 days, MSSA: 24.7±13.6 days; P=0.008). The mean interval between staging operation was longer in MRSA group (MRSA: mean 8.7 weeks [range, 6.4 to 21.4 weeks], MSSA: mean 6.8 weeks [range, 6 to 13.1 weeks]; P=0.012). MRSA group (13.9%) revealed higher recurrence rate than MSSA group (4%). Two patients (5.6%) from MRSA group expired by sepsis. One limb amputation (2.7%) was carried out in MRSA group.

Conclusion

MRSA infection after arthroplasty showed more toxic serologic parameter and poorer prognosis. Aggressive treatment should be considered for MRSA infection following arthroplasty.

Review article: Perioperative care in enhanced recovery for total hip and knee arthroplasty

Enhanced recovery pathways for total hip and knee arthroplasty can reduce length of hospital stay and perioperative morbidity. 22 studies were reviewed for identification of perioperative care interventions, including preoperative (n=4), intra-operative (n=8), and postoperative (n=4) care interventions. Factors that improve outcomes included use of pre-emptive and multimodal analgesia regimens to reduce opioid consumption, identification of patients with poor nutritional status and provision of supplements preoperatively to improve wound healing and reduce length of hospital stay, use of warming systems and tranexamic acid, avoidance of drains to reduce operative blood loss and subsequent transfusion, and early ambulation with pharmacological and mechanical prophylaxis to reduce venous thromboembolism and to speed recovery.

Drug elution from high-dose antibiotic-loaded acrylic cement: a comparative, in vitro study

High-dose antibiotic-loaded acrylic cement (ALAC) is used for managing peri-prosthetic joint infections (PJIs). The marked increase in resistant high-virulence bacteria is drawing the attention of physicians toward alternative antimicrobial formulations loaded into acrylic bone cement. The aim of this in vitro study was to determine the elution kinetics of 14 different high-dose ALACs. All ALAC samples showed a burst release of antibiotics in the first hour, progressively decreasing over time, and elution curves strictly adhered to a nonlinear regression analysis formula. Among aminoglycosides, commonly seen as the most appropriate antibiotics to be loaded into the bone cement, the highest elution rate was that of tobramycin. Among the glycopeptides, a class of antibiotics that should be considered to treat PJIs because of the prevalence of aminoglycoside resistance, vancomycin showed better elution than teicoplanin. Clindamycin, which can be associated with aminoglycosides to prepare ALACs and represents a useful option against the most common pathogens responsible for PJIs, showed the highest absolute and relative elutions among all the tested formulations. A noticeable elution was also detected for colistin, an antibiotic of last resort for treating multidrug-resistant bacteria. The current study demonstrates theoretical advantages in the preparation of ALAC for some antibiotics not routinely used in the clinical setting for PJIs. The use of these antibiotics based on the infecting bacteria sensitivity may represent a useful option for physicians to eradicate PJIs. In vivo testing should be considered in the future to confirm the results of this study.

Performance characteristics of broth-only cultures after revision total joint arthroplasty

BACKGROUND

Surgeons frequently obtain intraoperative cultures at the time of revision total joint arthroplasty. The use of broth or liquid medium before applying the sample to the agar medium may be associated with contamination and false-positive cultures; however, the degree to which this is the case is not known.

QUESTIONS/PURPOSES

We (1) calculated the performance characteristics of broth-only cultures (sensitivity, specificity, positive predictive value, and negative predictive value) and (2) characterized the organisms identified in broth to determine whether a specific organism showed increased proclivity for true-positive periprosthetic joint infection (PJI).

METHODS

A single-institution retrospective chart review was performed on 257 revision total joint arthroplasties from 2009 through 2010. One hundred ninety (74%) had cultures for review. All culture results, as well as treatment, if any, were documented and patients were followed for a minimum of 1 year for evidence of PJI. Cultures were measured as either positive from the broth only or broth negative. The true diagnosis of infection was determined by the Musculoskeletal Infection Society criteria during the preoperative workup or postoperatively at 1 year for purposes of calculating the performance characteristics of the broth-only culture.

RESULTS

The sensitivity, specificity, positive predictive value, and negative predictive value were 19%, 88%, 13%, and 92%, respectively. The most common organism identified was coagulase-negative Staphylococcus (16 of 24 cases, 67%). Coagulase-negative Staphylococcus was present in all three true-positive cases; however, it was also found in 13 of the false-positive cases.

CONCLUSIONS

The broth-only positive cultures showed poor sensitivity and positive predictive value but good specificity and negative predictive value. The good specificity indicates that it can help to rule in the presence of PJI; however, the poor sensitivity makes broth-only culture an unreliable screening test. We recommend that broth-only culture results be carefully scrutinized and decisions on the diagnosis and treatment of infection should be based specifically on the Musculoskeletal Infection Society criteria.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Continuous release of gentamicin from gold nanocarriers

Antimicrobial activity of gentamicin can be extended through release from gold nanocarriers after conjugation.

Antibiotics are still the most effective agents used to fight bacterial infections. Antibiotics are quickly metabolised or excreted from the human body, thus they need to be frequently administered (a few times a day) and their half life is usually an important factor in the therapeutic choice. In order to render the administration less frequent, antibiotic release from a carrier can be employed. In this work we covalently bound gentamicin to gold nanoparticles capped with cysteine or glutathione as gold nanoparticles are biologically safe. The conjugates exhibited antimicrobial activity against both S. aureus and MRSA at concentrations as low as 0.1 mg NP per ml consistent with an antibiotic load of 1–2% w/w as determined through TGA. No antimicrobial activity was exhibited by the unconjugated nanoparticles. The release of gentamicin from the conjugates was monitor in buffer solutions at pH = 7 and the antibiotic concentration continued to increase over two days. This work demonstrates that gold nanoparticles can be employed as antibiotic carriers providing a continuous release of antibiotic over a few days. Glutathione appeared to be a better coupling agent than cysteine allowing a higher load of gentamicin resulting in lower inhibitory concentrations of the conjugates.

Clinical Implication of Diabetes Mellitus in Primary Total Hip Arthroplasty

Purpose

The purpose of this study was to investigate the effect of diabetes mellitus on primary total hip arthroplasty by comparing the clinical outcomes of patients diagnosed to have diabetes mellitus before the operation with those without diabetes.

Materials and Methods

A total 413 patients who underwent unilateral cementless total hip arthroplasty from June 2006 to May 2009 were recruited and divided into diabetic and non-diabetic groups. The comparative analysis between the two groups was made. We evaluated Harris hip score, postoperative complications such as wound problem, surgical site infection, other medical complication and length of stay in hospital as clinical parameters. Radiographic evaluations were also included to determine loosening, dislocation and osteolysis.

Results

Patients with diabetes had an increased incidence of orthopaedic complications including surgical site infection and mortality, but other medical complications were not increased in diabetic patients. All complications after primary total hip arthroplasty were associated with diabetes mellitus, but the degree of diabetes was not associated with complications.

Conclusion

Diabetes mellitus increases incidence of orthopaedic complications, particularly deep infection, after cementless primary total hip arthroplasty.

Surgical Site Infection After Arthroplasty: Comparative Effectiveness of Prophylactic Antibiotics: Do Surgical Care Improvement Project Guidelines Need to Be Updated?

BACKGROUND

Prophylactic antibiotics decrease surgical site infection (SSI) rates, and their timing, choice, and discontinuation are measured and reported as part of the Surgical Care Improvement Project (SCIP). The aim of this study was to assess the comparative effectiveness of the SCIP-approved antibiotics for SSI prevention.

METHODS

This retrospective cohort study utilized national Veterans Affairs (VA) data on patients undergoing elective hip or knee arthroplasty from 2005 to 2009. Data on prophylactic antibiotics were merged with VA Surgical Quality Improvement Program data to identify patient and procedure-related risk factors for SSI. Patients were stratified by documented penicillin allergy. Chi-square and Wilcoxon rank-sum tests were used to compare SSI rates among patients receiving SCIP-approved prophylactic antibiotics.

RESULTS

A total of 18,830 elective primary arthroplasties (12,823 knee and 6007 hip) were included. Most patients received prophylactic cefazolin as the sole agent (81.9%), followed by vancomycin as the sole agent (8.0%), vancomycin plus cefazolin (5.6%), and clindamycin (4.5%). Documented penicillin allergy accounted for 54.1% of cases involving vancomycin administration compared with 94.6% of cases involving clindamycin. The overall thirty-day SSI rate was 1.4%, and the unadjusted rate was 2.3% with vancomycin only, 1.5% with vancomycin plus cefazolin, 1.3% with cefazolin only, and 1.1% with clindamycin. Unadjusted analysis of penicillin-allergic patients revealed an SSI rate of 2.0% with vancomycin only compared with 1.0% with clindamycin (p = 0.18). For patients without penicillin allergy, the SSI rate was 2.6% with vancomycin only compared with 1.6% with vancomycin plus cefazolin (p = 0.17) and 1.3% with cefazolin only (p < 0.01).

CONCLUSIONS

Current SCIP guidelines address antibiotic timing but not antibiotic dosage. (The generally accepted recommendation for vancomycin is 15 mg/kg.) Although vancomycin is a narrower-spectrum antibiotic than either cefazolin or clindamycin, our finding of higher SSI rates following prophylaxis with vancomycin only may suggest a failure to use an appropriate dosage rather than an inequality of antibiotic effectiveness.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The expanding horizon of prosthetic joint infections

Prosthetic joint infection (PJI) is a serious and potentially devastating complication of arthroplasty. Prior arthroplasty, immunosuppression, severe comorbid conditions, and prolonged surgical duration are important risk factors for PJI. More than half of the cases of PJI are caused by Staphylococcus aureus and coagulase-negative staphylococci. The biofilm plays a central role in its pathogenesis. The diagnosis of PJI requires the presence of purulence, sinus tract, evidence of inflammation on histopathology, or positive microbiologic cultures. The use of diagnostic imaging techniques is generally limited but may be helpful in selected cases. The most effective way to prevent PJI is to optimize the health of patients, using antibiotic prophylaxis in a proper and timely fashion. Management of PJI frequently requires removal of all hardware and administration of intravenous antibiotics. This review summarizes and analyzes the results of previous reports of PJI and assesses the prevention and management of this important entity.

Potent antimicrobial activity of bone cement encapsulating silver nanoparticles capped with oleic acid

Bone cement is widely used in surgical treatments for the fixation for orthopaedic devices. Subsequently, 2–3% of patients undergoing these procedures develop infections that are both a major health risk for patients and a cost for the health service providers; this is also aggravated by the fact that antibiotics are losing efficacy because of the rising resistance of microorganisms to these substances. In this study, oleic acid capped silver nanoparticles (NP) were encapsulated into Poly(methyl methacrylate) (PMMA)-based bone cement samples at various ratios. Antimicrobial activity against Methicillin Resistant Staphylococcus aureus, S. aureus, Staphylococcus epidermidis, Acinetobacter baumannii was exhibited at NP concentrations as low as 0.05% (w/w). Furthermore, the mechanical properties and cytotoxicity of the bone cement containing these NP were assessed to guarantee that such material is safe to be used in orthopaedic surgical practice. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 273–281, 2015.

Superficial wound closure complications with barbed sutures following knee arthroplasty

As quality measures may be increasingly used in knee surgery reimbursement, an important focus in outcome assessment will shift toward minimizing complications and increasing efficiency in knee arthroplasty reconstruction. The purpose of this study was to evaluate the efficacy of barbed, absorbable sutures in closure of the longitudinal surgical incision following knee arthroplasty, using post-operative complication occurrences. In 416 operations, primary outcomes assessed were deep infection, superficial infection, dehiscence, or stitch abscesses. Secondary outcomes included self-limiting eschar, severe effusion, arthrofibrosis, and keloid formation. Evaluation of overall primary outcomes showed a higher rate of wound complications using barbed sutures (P < 0.001). With increased rates of infection and overall closure related complications, this study shows that barbed suture use for superficial closure after knee arthroplasty should be avoided.

Quantifying the excess cost and resource utilisation for patients with complications associated with elective knee arthroscopy: a retrospective cohort study

BACKGROUND

Recent studies have demonstrated morbidity associated with elective knee arthroscopy. The objective of the current study was to quantify resource utilisation and costs associated with postoperative complications following an elective knee arthroscopy.

METHODS

We undertook a retrospective, longitudinal cohort study using routinely collected hospital data from Victorian public hospitals during the period from 1 July 2000 to 30 June 2009. A generalised linear model was used to examine relative cost and length of stay for venous thromboembolism, joint complications and infections. Log-transformed multiple linear regression and retransformation were used to determine the excess cost after adjustment.

RESULTS

We identified 166,770 episodes involving an elective knee arthroscopy. There were a total of 976(0.6%) complications, including 573 patients who had a venous thromboembolism (VTE) (0.3%), 227 patients with a joint complication (0.1%) and 141 patients with infections (0.1%). After adjustment, the excess 30-day cost per patient for venous thromboembolism was $USD +3227 (95% CI: $3211-3244), for joint complications it was $USD +2247 (95% CI: $2216-2280) and for infections it was $USD +4364 (95% CI: $4331-4397).

CONCLUSION

This is the first study to quantify resource utilisation for complications associated with elective knee arthroscopy. With growing attention focused on improving patient outcomes and containing costs, understanding the nature and impact of complications on resource utilisation is important.

Effects of using intravenous antibiotic only versus local intrawound vancomycin antibiotic powder application in addition to intravenous antibiotics on postoperative infection in spine surgery in 907 patients

STUDY DESIGN

A prospective randomized controlled trial.

OBJECTIVE

To assess the ability of local vancomycin powder in controlling postoperative infection in spine surgery.

SUMMARY OF BACKGROUND DATA

Despite improvements through the use of prophylactic systemic antibiotics, surgical site infections remain a significant problem in spine surgical procedures. Various retrospective and prospective studies have reported the efficacy of local application of vancomycin powder in reducing the infection in animal and human studies. However, there were no randomized control trials that reported on its efficacy.

METHODS

Prospective randomized controls of 907 patients with various spinal pathologies were treated surgically during a period of 18 months. The control group received standard systemic prophylaxis only, whereas the treatment group received vancomycin powder in the surgical wound in addition to systemic prophylaxis. Patient demographics, comorbidities, level of spinal pathology, estimated blood loss, nutritional status, and hemoglobin were recorded. Incidence of infection was the primary outcome evaluated.

RESULTS

There were 8 infections (1.68%) in the control group (6 instrumented and 2 noninstrumented, 6 deep and 2 superficial) with bacteria cultured in 3 (1 Escherichia coli and 2 Staphylococcus aureus). In the treatment group, 7 infections (1.61%) were observed (6 instrumented and 1 noninstrumented surgical procedures, 6 deep and 1 superficial) with bacteria cultured in 3 (1 Staphylococcus aureus and 2 Klebsiella). No adverse effects were observed from the use of vancomycin powder. Statistically no significant difference was seen in infection rate between the treatment group and control group.

CONCLUSION

The local application of vancomycin powder in surgical wounds did not significantly reduce the incidence of infection in patients with surgically treated spinal pathologies. The use of vancomycin powder may not be effective when incidence of infection is low.

Staphylococcus aureus colonization among arthroplasty patients previously treated by a decolonization protocol: a pilot study

BACKGROUND

Although testing and treatment for Staphylococcus aureus colonization before total joint arthroplasty (TJA) are well described and understood, the durability of decolonization has not been studied extensively.

QUESTIONS/PURPOSES

The purpose of this pilot study is to determine the percentage of arthroplasty patients with S. aureus colonization despite previous decolonization at the time of TJA.

METHODS

Over a 2-year period, all patients having TJA by one surgeon were screened and treated for nasal S. aureus. Of 634 patients, 139 had methicillin-sensitive S. aureus (15%) or methicillin-resistant S. aureus (6.6%) colonization before TJA. Fifty-eight of these 139 patients (42%) were retested at 3 to 30 months for persistent colonization by nasal culture. Data collection included age at time of TJA, type of TJA, and time from TJA to repeat testing. We performed no clonal analysis for strains.

RESULTS

Thirty-nine of the 58 patients (67%) decolonized before surgery were negative on retesting and 19 (33%) were again positive for S. aureus colonization. Of the 19 patients who retested positive for colonization, 17 (89%) were colonized by bacteria with unchanged antibiotic sensitivity.

CONCLUSIONS

We demonstrate that 33% (19 of 58) of postoperative arthroplasty patients test positive for S. aureus colonization at 3 to 30 months after surgery despite preoperative decolonization. Arthroplasty surgeons must be aware that a decolonization treatment does not guarantee that a patient will remain decolonized in the future. Although unchanged antibiotic sensitivity in 89% of these patients suggests a substantial role for persistence as opposed to eradication and repeat colonization, we were unable to retrospectively perform clonal analysis to confirm this conclusion. This group of patients demonstrating continued colonization with S. aureus after arthroplasty deserves further study, because it remains unclear whether there is a higher risk of late infection in this population.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

In vitro evaluation of TiO2 nanotubes as cefuroxime carriers on orthopaedic implants for the prevention of periprosthetic joint infections

CONTEXT

The prevention of periprosthetic joint infections requires an antibiotic prophylactic therapy, which could be delivered locally using titanium dioxide nanotubes as novel reservoirs created directly on the orthopaedic implant titanium surface.

OBJECTIVE

In this study, the influence of several parameters that could impact the use of titanium dioxide nanotubes as cefuroxime carriers was investigated.

METHOD

Cefuroxime loading and release was studied for 90 min with three nano-topography conditions (nano-smooth, nano-rugged and nano-tubular), two cefuroxime loading solution concentrations (150 mg/mL and 25mg/mL) and two nano-tubular crystalline structures.

RESULTS

In all tested conditions, maximum amount of cefuroxime was obtained within 2 min. For both cefuroxime loading solution concentrations, nano-smooth samples released the least cefuroxime, and the nano-tubular samples released the most, and a six-fold increase in the concentration of the cefuroxime loading increased the amount of cefuroxime quantified by more than seven times, for all tested nano-topographies. However, the nano-tubes' crystalline structure did not have any influence on the amount of cefuroxime quantified.

CONCLUSION

The results demonstrated that the surface nano-topography and loading solution concentration influence the efficiency of titanium dioxide nanotubes as cefuroxime carriers and need to be optimized for use as novel reservoirs for local delivery of cefuroxime to prevent periprosthetic infections.

Is arthroplasty immediately after an infected case a risk factor for infection?

BACKGROUND

It is common practice in many centers to avoid performing a clean case in a room in which an infected procedure has just taken place. No studies of which we are aware speak to the necessity of this precaution.

QUESTIONS/PURPOSES

The purposes of this study were to identify (1) the risk of infection in a group of patients who underwent arthroplasties performed immediately after a first-stage arthroplasty for joint infection; and (2) the risk of superficial and deep infections in these patients compared with a matched group of patients who underwent arthroplasties not performed after an infected surgery.

METHODS

Eighty-three patients (85 arthroplasties) who underwent arthroplasties (primary or revision) immediately after patients with known infections underwent surgery in the same operating room (OR) were analyzed for 12 months after surgery to determine the incidence of infection. They were matched for demographic factors and surgery type with a control group of 321 patients (354 arthroplasties) who underwent surgery in an OR that had not just been used for surgery involving patients with infections. We compared the risk of superficial and deep infections between the groups.

RESULTS

Patients in the study group were not more likely to have infections develop than those in the control group. One patient in the study group (1.17%) and three in the control group (0.84%) had deep infections develop; the infection in the patient in the study group was caused by a different organism than that of the patient with an infection whose surgery preceded in the OR. Two superficial infections (2.35%) were detected in the study group and 17 (4.8%) were detected in the control group.

CONCLUSIONS

With the numbers available, we found that a deep infection was not more likely to occur in a patient without an infection after an arthroplasty that followed surgery on a patient with an infection than in one who had surgery after a clean case. Although sample size was a potential issue in this study, the results may serve as hypothesis generating for future studies.

LEVEL OF EVIDENCE

Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

A novel bone cement impregnated with silver-tiopronin nanoparticles: its antimicrobial, cytotoxic, and mechanical properties

Post-operatory infections in orthopedic surgeries pose a significant risk. The common approach of using antibiotics, both parenterally or embedded in bone cement (when this is employed during surgery) faces the challenge of the rising population of pathogens exhibiting resistance properties against one or more of these compounds; therefore, novel approaches need to be developed. Silver nanoparticles appear to be an exciting prospect because of their antimicrobial activity and safety at the levels used in medical applications. In this paper, a novel type of silver nanoparticles capped with tiopronin is presented. Two ratios of reagents during synthesis were tested and the effect on the nanoparticles investigated through TEM, TGA, and UV-Vis spectroscopy. Once encapsulated in bone cement, only the nanoparticles with the highest amount of inorganic fraction conferred antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA) at concentrations as low as 0.1% w/w. No other characteristics of the bone cement, such as cytotoxicity or mechanical properties, were affected by the presence of the nanoparticles. Our work presents a new type of silver nanoparticles and demonstrates that they can be embedded in bone cement to prevent infections once the synthetic conditions are tailored for such applications.

Perioperative antibiotic use for spinal surgery procedures in US children's hospitals

STUDY DESIGN

Retrospective cohort study using the Pediatric Health Information System database.

OBJECTIVE

To describe longitudinal patterns of prophylactic antibiotic use and determinants of antibiotic choice for spinal fusion surgical procedures performed at US children's hospitals.

SUMMARY OF BACKGROUND DATA

Surgical site infections (SSIs) account for a significant proportion of post-spinal surgery complications, particularly among children with complex conditions such as neuromuscular disease. Antimicrobial prophylaxis with intravenous cefazolin or cefuroxime has been a standard practice, but postoperative infections caused by organisms resistant to these antibiotics are increasing in prevalence. Studies describing the choice of antibiotic prophylaxis for pediatric spinal surgery are lacking.

METHODS

We included children 6 months to 18 years of age discharged from 37 US children's hospitals between January 1, 2006, and June 30, 2009, with (1) an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure code indicating a spinal fusion and (2) combinations of diagnosis codes indicating adolescent idiopathic scoliosis (AIS) (n = 5617) or neuromuscular scoliosis (NMS) (n = 3633). After identifying antibiotics ordered on the operative day, we described variation in broad-spectrum antibiotic use over time and measured associations between patient/surgery characteristics and antibiotic choice.

RESULTS

Prophylactic antibiotic choice varied across hospitals and over time. Broad-spectrum antibiotics were used in 37% of AIS and 52% of NMS operations. Seven (19%) hospitals used broad-spectrum coverage for more 80% of all cases. For NMS procedures, broad-spectrum antibiotic use was associated with patient characteristics known to be associated with high SSI risk. Use of vancomycin and broad gram-negative agents increased over time.

CONCLUSION

Broad-spectrum antimicrobial prophylaxis varied across hospitals and was often associated with known risk factors for SSI. These results highlight the need for future studies comparing the effectiveness of various prophylaxis strategies, particularly in high-risk subgroups. This research can inform the development of best practice for SSI prevention in spinal fusion procedures.

Evaluating the use of preoperative antibiotics in pediatric orthopaedic surgery

PURPOSE OF THE STUDY

To evaluate the rate of infection after minimally invasive procedures on a consecutive series of pediatric orthopaedic patients. We hypothesized that the use of preoperative antibiotics for minimally invasive pediatric orthopaedic procedures does not significantly reduce the incidence of surgical site infection requiring surgical debridement within 30 days of the primary procedure.

METHODS

We retrospectively reviewed 2330 patients having undergone minimally invasive orthopaedic procedures at our institution between March 2008 and November 2010. Knee arthroscopy, closed reduction with percutaneous fixation, soft tissue releases, excision of bony or soft-tissue masses, and removal of hardware constituted the vast majority of included procedures. Two groups, based on whether prophylactic antibiotics were administered before surgery, were created and the incidence of a repeat procedure required for deep infection was recorded. Statistical analysis was performed to determine significance, if any, between the 2 groups.

RESULTS

Chart review of the 2330 patients identified 1087 as having received preoperative antibiotics, whereas the remaining 1243 patients did not receive antibiotics before surgery. Only 1 patient out of the 1243 cases in which antibiotics were not given required additional surgery within 30 days of the primary procedure due to a complicated surgical site infection (an incidence of 0.0008%). No patients in the antibiotic group developed a postoperative infection within 30 days requiring a return to the operating room for management. Our data revealed no significant increase in the incidence of complicated infection requiring additional procedures when antibiotics were not administered before surgery.

DISCUSSION

Though prophylactic antibiotics have been shown to confer numerous benefits for patients undergoing relatively major operations, their use in cases of minimally invasive and/or percutaneous orthopaedic surgery is not well defined. Our data suggest that the use of prophylactic antibiotics may not be indicated for many less invasive procedures when performed in a low-risk pediatric population. Future studies are warranted to help establish evidence-based guidelines regarding the routine use of prophylactic antibiotics in this specific population, hopefully resulting in improved cost-effectiveness and safety while slowing the emergence of new drug-resistant organisms.

LEVEL OF EVIDENCE

Level III, retrospective comparative.

Bacterial colonization and resistance patterns in 133 patients undergoing a primary hip- or knee replacement in Southern Sweden

BACKGROUND AND PURPOSE

Prosthetic joint infections can be caused by bacteria derived from the patient's skin. The aim of the study was: (1) to determine which bacteria colonize the nose and groin in patients planned for primary hip or knee arthroplasty, (2) to determine the antimicrobial resistance patterns, and (3) to monitor changes in bacterial colonization and resistance patterns connected to surgery.

PATIENTS AND METHODS

2 weeks before scheduled primary hip or knee arthroplasty, culture samples were taken from the anterior nares and from the groin of 133 consecutive patients. At surgery, cloxacillin was given prophylactically and cement with gentamicin was used. 2 weeks after surgery, another set of samples were taken from 120 of these patients. Bacterial findings and resistance patterns were analyzed.

RESULTS

Preoperatively, 95% of the patients had coagulase-negative staphylococci (CNS) in the groin and 77% in the nose. The proportion of patients with a methicillin-resistant CNS in the groin increased from 20% preoperatively to 50% postoperatively (p < 0.001), and the proportion of patients with a gentamicin-resistant CNS in the groin increased from 5% to 45% (p < 0.001). 28% of the patients had Staphylococcus aureus in the nose preoperatively, and 7% in the groin. Methicillin-resistant Staphylococcus aureus (MRSA) was found in the nose of 1 patient.

INTERPRETATION

In southern Sweden, beta-lactams were effective against 99% of the Staphylococcus aureus strains and 80% of the CNS strains colonizing the patients undergoing primary hip or knee arthroplasty. Gentamicin protects against most CNS strains in cemented primary joint replacements.

Increasing the elution of vancomycin from high-dose antibiotic-loaded bone cement: a novel preparation technique

BACKGROUND

Antibiotic bone cement is commonly used in staged revision arthroplasty as well as the treatment of open fractures. Multiple factors affect antibiotic elution from bone cement. This study was performed to investigate the effect of two variables, the quantity of liquid monomer and the timing of antibiotic addition, on the ultimate elution of antibiotic from bone cement.

METHODS

Vancomycin-loaded Simplex P and SmartSet MV bone cement was prepared with three different methods: a common surgical technique, a mixing technique that doubled the amount of liquid monomer, and a novel technique that delayed antibiotic addition until after thirty seconds of polymerization. Cylinders of a standardized size were created from each preparation. The elution profiles of five cylinders from each preparation were measured over six weeks with use of high-performance liquid chromatography. Cylinders were tested in compression to quantify strength.

RESULTS

Delayed antibiotic addition resulted in significantly greater cumulative elution over six weeks (p < 0.0001), with minimal reduction in strength, compared with the other groups. Doubling the liquid monomer significantly reduced cumulative elution over six weeks compared with either of the other techniques (p < 0.0001). Vancomycin elution from Simplex P was 52%greater and vancomycin elution from SmartSet MV was 25% greater in the delayed-antibiotic-addition groups than it was in the corresponding standard surgical technique groups. The majority of the antibiotic was released over the first week in all groups. : High-dose-antibiotic bone cement prepared with delayed antibiotic addition increased vancomycin elution compared with the standard surgical preparation. Incorporating additional liquid monomer decreased vancomycin elution from high-dose-antibiotic cement. We recommend preparing high-dose-antibiotic bone cement with the delayed-antibiotic addition technique and not incorporating additional liquid monomer.

CLINICAL RELEVANCE

Both the relative volume of liquid monomer and the timing of antibiotic addition have substantial effects on the elution of antibiotic from bone cement.

Does a prefabricated gentamicin-impregnated, load-bearing spacer control periprosthetic hip infection?

INTRODUCTION

Treating deep infection following THA has been a challenge. While the standard treatment has remained a two-stage revision, spacer designs, incorporated antibiotics, and concentrations have varied. Since control of infection may relate to choice and concentration of antibiotics, it is important to report rates of control from various spacers.

QUESTIONS/PURPOSES

We therefore determined (1) the rate of infection control and (2) complications associated with a prefabricated, load-bearing, gentamicin-impregnated hip spacer in treating periprosthetic infections of the hip.

METHODS

We retrospectively reviewed 33 patients with periprosthetic THA infections treated with a prefabricated, partial load-bearing, gentamicin-impregnated hemiarthroplasty spacer. Thirty of the 33 patients underwent second stage reimplantation after a mean 15 weeks. We collected patient demographic data, laboratory values, infecting organism, size of spacer mold, antibiotic selection, complications, and infection control rates from two academic centers. Recurrent infection at last followup was determined by the presence of physical symptoms or signs or elevated serologic tests. The minimum followup was 24 months (mean, 43 months; range, 24-70 months).

RESULTS

Twenty-eight of the 30 patients who underwent reimplantation remained infection-free at last followup: one patient became reinfected with a different organism secondary to wound problems; one became reinfected with the same organism, but was restaged with the mold used in this study, reimplanted, and subsequently remained free of infection. Two of the 33 patients had persistently elevated inflammatory markers at the completion of their first stage and were restaged with this mold; both underwent reimplantation and remained free of infection at latest followup. One of the 33 patients was satisfied and ambulatory with their spacer mold. There were no major complications.

CONCLUSION

Our data supported the use of a partial load-bearing, gentamicin-impregnated hemiarthroplasty spacer in treating deep periprosthetic THA infections.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Does dual antibiotic prophylaxis better prevent surgical site infections in total joint arthroplasty?

INTRODUCTION

It is unclear which antibiotic regimen provides the best prophylaxis against surgical site infection (SSI) in patients undergoing hip and knee surgery.

QUESTIONS/PURPOSES

Therefore, we determined whether dual antibiotic prophylaxis (1) reduced the rate of SSI compared to single antibiotic prophylaxis and (2) altered the microbiology of SSI.

METHODS

We retrospectively reviewed 1828 primary THAs and TKAs performed between September 1, 2008 and December 31, 2010. We divided patients into two groups: (1) those who received a dual prophylactic antibiotic regimen of cefazolin and vancomycin (unless allergy), or (2) received cefazolin (unless allergy) as the sole prophylactic antibiotic. There were 701 males and 1127 females with an average age of 56 years (range, 15–97 years). We limited followup to 1 year, presuming subsequent infections were not related to the initial surgery.

RESULTS

During this period, there were 22 SSIs (1.2%). The infection rates for dual antibiotic prophylaxis compared to a single antibiotic regimen were 1.1% and 1.4%, respectively. Of 1328 patients treated with dual antibiotic prophylaxis, only one (0.08%) SSI was culture positive for methicillin resistant Staphylococcus aureus (MRSA), while four of 500 patients (0.8%) receiving only cefazolin prophylaxis had culture positive MRSA infection at the time of reoperation.

CONCLUSION

The addition of vancomycin as a prophylactic antibiotic agent apparently did not reduce the rate of SSI compared to cefazolin alone. Use of vancomycin in addition to cefazolin appeared to reduce the incidence of MRSA infections; however, the number needed to treat to prevent a single MRSA infection was very high.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Is it time to include vancomycin for routine perioperative antibiotic prophylaxis in total joint arthroplasty patients?

In an effort to reduce methicillin-resistant Staphylococcus aureus (MRSA) and overall periprosthetic joint infections (PJI), we switched the perioperative prophylactic antibiotic during total knee arthroplasty and total hip arthroplasty from cefazolin to vancomycin in June 2008. We retrospectively reviewed the total and MRSA PJI in 5036 primary total joint arthroplasties, as well as the cure rate of PJI from January 2006 to June 2008 (Ancef Period) and June 2008 to December 2010 (Vanco Period). With vancomycin, total PJI was significantly reduced (1.0%-0.5%) and MRSA PJI (0.23%-0.07%). Periprosthetic joint infections that occurred were more successfully treated with irrigation and debridement only, not requiring spacer (76.9% vs 22.2%). The use of vancomycin as the perioperative prophylactic antibiotic for primary total joint arthroplasties appeared to be effective in decreasing the rate of PJI and may result, when they occur, in infections with less virulent organisms.

Characterization of daptomycin-loaded antibiotic cement

Antibiotics are commonly mixed with polymethylmethacrylate (PMMA) cement to suppress severe periprosthetic infections associated with total joint arthroplasty. The relationship between antibiotic concentration and the resulting elution kinetics remains unclear. The purpose of this study was to characterize the release of daptomycin from PMMA cement and the subsequent effects on mechanical properties.Varying concentrations of daptomycin and tobramycin were vacuum mixed in commercially available PMMA and subjected to an in vitro elution period. High-performance liquid chromatography was used to quantify the concentration of the amount of daptomycin eluted at predetermined time points. Samples were subjected to compressive loading to analyze the effect of antibiotic concentration on cement mechanical properties. Daptomycin elution increased when initial tobramycin concentration was increased. Furthermore, the addition of antibiotics increased the compressive strength of the cement in the postelution period. The binary addition of tobramycin with daptomycin antibiotics modifies the elution and mechanical properties of PMMA bone cement. Based on the findings of our study, 2 g of daptomycin and 3.6 g of tobramycin per 40-g packet of cement should be used to promote daptomycin elution without sacrificing PMMA mechanical properties.

Infection rates following hip and knee joint arthroplasty: large referral centre versus a small elective-only hospital

PURPOSE

The aim of this study was to investigate deep infection rates following hip and knee arthroplasty at a large referral hospital and to compare these rates with a smaller hospital where only elective surgery was performed. Both hospitals were administered by the same public institution.

METHODS

A search of the medical records was performed for all deep infections following elective primary hip and knee arthroplasty; revision procedures were excluded as were total hip replacement and hemiarthroplasty following trauma. To be considered, a deep infection cases must have had bacterial growth confirmed on deep tissue surgical specimens or on aspiration of the joint within 1 year of the index procedure.

RESULTS

There were 14 infections confirmed following 1,160 arthroplasties at the larger hospital and 1 infection for the elective-only hospital following 466 arthroplasties. Statistical analysis showed there was a 7.06 greater chance of having an infection at the larger campus compared with the smaller campus CI (1.3, 130.7). Although there was a trend towards a greater number of infections at the larger hospital, the result was not statistically significant (P = 0.06). We acknowledge there were some differences between the two study populations.

CONCLUSION

We found a trend towards, but not a statistically significant difference, between infection rates at the elective-only hospital compared to the larger institution. Given the low overall rate of infection, studies with improved statistical power are needed to determine whether there is a difference in infection rates at smaller elective-only hospitals versus larger hospitals providing elective and non-elective services. The reasons for the difference are likely to be multifactorial. We hypothesise that infection rates are increased in the larger hospital where there is more procedures, both clean and contaminated being performed in the operating theatres, as well as a greater number of inpatient beds and where the hospital admits non-elective cases via its emergency department.

LEVEL OF EVIDENCE

Level-two cohort study.