Choice and doses of antibacterial agents for cement spacers in treatment of prosthetic joint infections: review of published studies

Animal Models of Orthopedic Implant-Associated Infections and Revisions

Orthopedic implant-associated infections such as prosthetic joint infections (PJIs) lead to devastating complications for patients and impose significant financial burdens on the healthcare systems. Although the primary orthopedic implant associated infection rate is relatively low (0.3-9%), the reinfection rate after implant revisions can be as high as 20% to 40%. To evaluate novel therapeutic strategies for preventing and treating infections associated with primary and revision implants, it is essential to develop appropriate animal models that closely emulate clinical realities. Here we discuss existing animal models developed for orthopedic implant revision surgeries including small animal models in rats and mice, and larger animal models in rabbits, sheep, and mini-pigs. While larger animal models offer the advantage of more closely mimicking human surgical procedures, implant dimensions, and infection treatment protocols, rodent models are more cost-effective and better suited for screening experimental prophylaxes and therapeutics. Existing animal revision models have focused on primary infections established by Staphylococcal aureus (S. aureus) and revisions involving both one-stage and two-stage procedures. Further development of smaller animal implant revision models that implement more clinically relevant surgical procedures and recapitulate polymicrobial infections could facilitate the discovery and more rigorous evaluation of novel implant coating prophylaxes and therapeutics for reducing reinfection rates following implant revisions.

Medicaid Insurance Is Associated With Increased Readmissions and Mortality After Surgery for Periprosthetic Joint Infection

BACKGROUND

Patients with Medicaid insurance are at an increased risk of postoperative complications following total knee arthroplasty and total hip arthroplasty (TJA); however, their outcomes following revision TJA for periprosthetic joint infection (PJI) requires further study.

METHODS

A retrospective query was conducted for adult patients undergoing implant explantation and antibiotic spacer placement for TJA PJI from the Premier Healthcare Database between December 1, 2016, and December 31, 2021. Patients were then grouped by Medicaid or non-Medicaid insurance status and were age matched through exact caliper matching. Multivariable regression models addressed potential confounding. Adjusted risks of 90-day postoperative complications were reported.

RESULTS

Of the 40,346 patients identified, 2,711 Medicaid patients were matched to 10,844 non-Medicaid patients on age (56.1 vs. 56.1 years, P = 1.000). Patients with Medicaid experienced higher risk of sepsis (adjusted odds ratio [aOR] = 1.20, P = 0.010), readmission (aOR = 1.12, P = 0.022), being discharged to a skilled nursing facility (aOR = 1.13, P = 0.031), and had longer length of stay (9.48 vs. 6.67 days, P < 0.001), compared with patients with non-Medicaid. Medicaid patients had a higher rate of inpatient mortality (0.81% vs. 0.48%, P = 0.038); however, the risk was similar after accounting for differences in comorbidities.

CONCLUSION

Following revision TJA for PJI, patients with Medicaid were at an increased risk for postoperative complication, including sepsis and readmission. They experienced a higher rate of inpatient mortality that may be driven by differences in comorbidities. Insurers and policy makers should consider this information to develop risk stratification-based payment strategies that take into account the healthcare burden of this high-risk patient population.

LEVEL OF EVIDENCE

IV.

Clinical practice guidelines for antimicrobial-loaded cements and beads in orthopedic trauma and arthroplasty

PURPOSE

Implants in orthopedic trauma and arthroplasty surgery establish a milieu conducive to biofilm formation. Antimicrobial-loaded cements (ABCs) and beads have become popular in treating acute and chronic orthopedic surgery-related infections. The growing incidence of antimicrobial resistance has necessitated the exploration of alternative antibiotic medications. This review aims to demonstrate meaningful clinical decision-making guidance for orthopedic surgeons in approaching the management of these complex infections.

METHODS

This study protocol was conducted following the PRISMA checklist and guidelines of the Cochrane Handbook for Systematic Reviews of Interventions. PubMed, Ovid MEDLINE, Web of Science, and other databases were queried using applicable search terms. Relevant dosing, efficacy, and elution profiles were reviewed and compiled from 74 articles published between 1976 and 2019. First-line and targeted therapies were identified against rare and resistant bacteria. Drug therapies not recommended due to excessive cytotoxicity or poor delivery kinetics were also elucidated.

RESULTS

This compilation describes thirty-two antibiotics and three antifungals that have successfully managed orthopedic surgery-related infections, including infections with numerous recalcitrant and multidrug-resistant species. Optimized ratios of carrier to antimicrobial are provided for each delivery method. The elution and efficacy profiles of the various antibiotics are described when available.

DISCUSSION/CONCLUSION

These recommendations offer the most up-to-date and comprehensive practice guidelines for using antimicrobials in cements and beads for treating orthopedic hardware-related infections. With the ever-evolving propensity of bacteria to develop antibiotic resistance, these recommendations are dynamic. Collaboration with medicine, infectious disease, and/or pharmacology teams is recommended to create institutional protocols for antibiotic-eluting implants and close comanagement to ensure efficacy and patient safety.

Does Combined Treatment with Tranexamic Acid and Vancomycin Affect Human Chondrocytes In Vitro?

Background: The aim of our study was to examine the combined effects of tranexamic acid (TXA) and vancomycin powder (VP) on chondrocytes in vitro. Despite the use of TXA and VP being linked to a reduced risk of extensive postoperative blood loss and periprosthetic joint infections (PJIs) in TKA, the possible cytotoxic side effects on periarticular cell types remain unclear. Methods: Human chondrocytes were harvested from hyaline cartilage and expanded in monolayer culture before being simultaneously exposed to different concentrations of TXA and VP for varying exposure times. Cell viability and proliferation were assessed using an ATP assay and an Annexin 5 assay, respectively, while changes in the relative expression of chondrogenic marker genes were examined using semiquantitative RT-PCR. Results: The simultaneous exposure of chondrocytes to TXA and VP for more than 48 h led to a reduction in both cell viability and proliferation rates. When exposing chondrocytes to the lowest examined concentrations of both TXA (10 mg/mL) and VP (3 mg/mL), the observed effects were delayed until 96 h. However, our study found no dependencies of the observed effects on the concentrations tested. Further, we found no effects on the expression of chondrogenic marker genes. Conclusions: Consequently, limiting the exposure time of chondrocytes to TXA and VP in an in vitro setting to 24 h may be considered safe and could help to further improve the understanding of the safe use of substances in vivo. However, further in vitro research is required to develop a comprehensive understanding of the effects of both VP and TXA on important periarticular cell types in TKA, including chondrocytes, osteocytes, and tenocytes.

High and Low Dosage of Vancomycin in Polymethylmethacrylate Cements: Efficacy and Mechanical Properties

INTRODUCTION

Prosthetic joint infections (PJIs) are difficult to treat and represent a significant burden to the healthcare system. Two-stage revision surgery with placement of an antibiotic-loaded cement spacer is currently the gold standard for treatment in the United States for late-onset infections. We evaluate the efficacy of varying doses of vancomycin added to antibiotic-containing acrylic cement spacers and discuss the biomechanical and antimicrobial properties of using high versus low doses of vancomycin in cement spacers in the hip and knee.

MATERIALS AND METHODS

Commercially available Copal cement containing either gentamicin and clindamycin (G + C) or gentamicin and vancomycin (G + V) was prepared with the manual addition of low (2 g) and high (6 g) doses of vancomycin. In vitro mechanical testing was then carried out according to ISO 5833 and DIN 53435, as well as inhibition zone assays against common PJI pathogens. Additionally, inhibition zone assays were conducted on two commercially available prefabricated spacers containing gentamicin: Copal Exchange G and Cemex Spacer-K.

RESULTS

In biomechanical testing, Copal G + V with the addition of 6 g of vancomycin failed to meet the ISO standard. Copal G + C and Copal G + V with low and high dosages of vancomycin were all effective against the tested pathogens and displayed constant efficacy for a duration of 42 days. High doses of vancomycin showed significantly lower mechanical stability. Moreover, Copal Exchange G showed significantly larger inhibition zones across 42 days.

DISCUSSION

While higher concentrations of vancomycin appear to improve the antimicrobial efficacy of cement, they also reduce its mechanical stability. Despite its smoother surface, the Copal Exchange G spacer exhibits large inhibition zones after 1 day and maintains consistently large inhibition zones over 6 weeks. Thus, it may be preferred for use in two-stage revision surgery.

CONCLUSION

Copal Exchange G is more effective than Cemex Spacer K against S. aureus and E. coli. The manual addition of vancomycin to cement containing double antibiotics is very effective. The influence on ISO compression is low, the ISO bending modulus is increased, and ISO bending, DIN bending, and DIN impact, are reduced.

Articulating Spacers in Total Hip Arthroplasty: Surgical Technique and Outcomes

Although one-stage exchange arthroplasty is gaining popularity, two-stage exchange arthroplasty remains the gold standard for the treatment of periprosthetic joint infections. Use of an articulating spacer for this procedure offers an avenue for maintaining hip motion and controlled weight-bearing, allowing local antibiotic elution. However, there is no uniform consensus on the optimal surgical protocol for using articulating spacers. This review describes the surgical technique for undertaking a first-stage exchange arthroplasty using an articulating spacer and discusses the pertinent literature on key concepts relating to periprosthetic joint infections in total hip arthroplasty to guide effective surgical decision making in these patients.

3D-printed antibiotic-loaded bone cement spacers as adjunctive therapy for hip periprosthetic infection after arthroplasty: A clinical assessment

OBJECTIVE

To explore the effect of three-dimensional (3D) printing to create personalized antibiotic-loaded bone cement (ALBC) spacers to assist in treatment of periprosthetic infection after total hip arthroplasty (THA).

METHODS

The data of 40 patients with postoperative infection after THA were analysed retrospectively. The patients were divided into two groups: the 3D-printing group (age 47-78 years, n = 20) and the conventional group (age 57-78 years, n = 20). In stage I surgery, 3D-printed silicone moulds were used to create ALBC spacers for the 3D-printing group, while traditional manual methods were used to create spacers for the conventional group. After the infection was controlled, both groups underwent conventional hip revision surgery (stage II surgery). All patients were evaluated using the Harris Hip Score (HHS) (primary outcome) for hip function.

RESULTS

All 40 patients had follow-up data from 3 months after stage I surgery and 12 months after stage II surgery. The intergroup difference in HHS was 11.25 points [97.5% confidence interval (CI) 7.92-14.58; P < 0.01] at 3 months after stage I surgery, and 9.15 points (97.5% CI 4.82-13.48; P < 0.01) at 12 months after stage II surgery. The overall difference between the two groups was 9.55 points (97.5% CI 5.83-13.27; P < 0.01), which was significant (P < 0.05).

CONCLUSION

During the follow-up period, the hip function of the 3D-printing group was superior to that of the conventional group following the treatment of infections after THA.

Effect of Antibiotic Spacer Dosing on Treatment Success in Two-Stage Exchange for Periprosthetic Joint Infection

INTRODUCTION

In two-stage exchange for periprosthetic joint infection (PJI), adding antibiotics to cement spacers is the standard of care; however, little is known about optimal dosage. There is emphasis on using >3.6 g of total antibiotic, including ≥2.0 g of vancomycin, per 40 g of cement, but these recommendations lack clinical evidence. We examined whether recommended antibiotic spacer doses affect treatment success.

METHODS

This was a retrospective review of 202 patients who underwent two-stage exchange for PJI from 2004 to 2020 with at least 1-year follow-up. Patients were separated into high (>3.6 g of total antibiotic per 40 g of cement) and low-dose spacer groups. Primary outcomes were overall and infectious failure.

RESULTS

High-dose spacers were used in 80% (162/202) of patients. High-dose spacers had a reduced risk of overall (OR, 0.37; P = 0.024) and infectious (OR, 0.35; P = 0.020) failure for infected primary arthroplasties, but not revisions. In multivariate analysis, vancomycin dose ≥2.0 g decreased the risk of infectious failure (OR, 0.31; P = 0.016), although not overall failure (OR, 0.51; P = 0.147).

CONCLUSION

During two-stage exchange for PJI, spacers with greater than 3.6 g of total antibiotic may reduce overall and infectious failure for infected primary arthroplasties. Furthermore, using at least 2.0 g of vancomycin could independently decrease the risk of infectious failure.

Vacuum assisted closure and local drug delivery systems in spinal infections: A review of current evidence

Background

Spinal infections are still showing increased incidence throughout the years as our surgical capabilities increase, coupled with an overall aging population with greater number of chronic comorbidities. The management of spinal infection is of utmost importance, due to high rates of morbidity and mortality, on top of the general difficulty in eradicating spinal infection due to the ease of hematogenous spread in the spine. We aim to summarize the utility of vacuum-assisted closure (VAC) and local drug delivery systems (LDDS) in the management of spinal infections.

Methods

A narrative review was conducted. All studies that were related to the use of VAC and LDDS in Spinal Infections were included in the study.

Results

A total of 62 studies were included in this review. We discussed the utility of VAC as a tool for the management of wounds requiring secondary closure, as well as how it is increasingly being used after primary closure as prophylaxis for surgical site infections in high-risk wounds of patients undergoing spinal surgery. The role of LDDS in spinal infections was also discussed, with preliminary studies showing good outcomes when patients were treated with various novel LDDS.

Conclusions

We have summarized and given our recommendations for the use of VAC and LDDS for spinal infections. A treatment algorithm has also been established, to act as a guide for spine surgeons to follow when tackling various spinal infections in day-to-day clinical practice.

Articulating spacers: what are available and how to utilize them?

Periprosthetic joint infection (PJI) is the most devastating complication following total joint arthroplasty (TJA) and is posing a global healthcare challenge as the demand for TJA mounts. Two-stage exchange arthroplasty with the placement of antibiotic-loaded spacers has been shown to be efficacious against chronic PJI. This study aimed to review the key concepts, types, and outcome evaluations of articulating spacers in the two-stage exchange for PJI. Previous studies indicated that articulating spacers have been widely used due to better functional improvement and a comparable infection control rate relative to static spacers. Several types of articulating spacers are reportedly available, including hand-made spacers, spacers fashioned from molds, commercially preformed spacers, spacers with additional metal or polyethylene elements, new or autoclaved prosthesis, custom-made articulating spacers, and 3D printing-assisted spacers. However, limited evidence suggested no significant difference in clinical outcomes among the different subtypes of articulating spacers. Surgeons should be familiar with different treatment strategies when using various spacers to know which is the most appropriate.

Antimicrobials in polymethylmethacrylate: from prevention to prosthetic joint infection treatment: basic principles and risk of resistance

BACKGROUND

Excellent revisions about antibiotic-loaded bone cement (ALBC) have been recently published. In the present article, we review the principles and limitations of local antibiotic delivery in the context of recent advances in the pathogenesis of prosthetic joint infections (PJI), with particular attention paid to the potential association between ALBC and antimicrobial resistance.

MAIN BODY

Recalcitrance of PJI is related to the ability of pathogens to adapt to particular environments present in bone tissue and protect themselves from host immunity in different ways. Accordingly, delivery of high local antimicrobial concentrations using ALBC is needed. Most relevant clinical data showing the efficacy of ALBC for PJI prophylaxis and treatment are reviewed, and we dissected the limitations on the basis of the recent findings from animal models and suggested that aminoglycosides, in particular, could not be the best option. One of the major concerns associated with ALBC is the emergence of resistance because of theoretical prolonged exposure to low antibiotic concentrations. We summarize the mechanisms for the selection of resistant microorganisms, and we critically reviewed the evidence from animal models and clinical data from observational and registry studies and concluded that there is no evidence to support this association.

CONCLUSION

While waiting for better evidence from well-designed clinical trials, ALBC shows a beneficial effect as a prophylaxis in arthroplasty, and to avoid the colonization of spacers used for two-stage revision in patients with PJI. Experimental models and clinical evidence suggest the need to achieve high local antimicrobial concentrations to obtain the highest prophylactic and therapeutic effect. The current evidence does not support the risk of increasing resistance with use of ALBC. In the future, it is necessary to evaluate new carriers and different antimicrobials to improve clinical outcomes.

Is the routine use of local antibiotics in the management of periprosthetic joint infections justified?

Periprosthetic joint infection (PJI) following total hip and total knee arthroplasty continues to be a leading cause of re-operation and revision arthroplasty. Not only is the treatment of PJI notoriously challenging, but success rates are variable. Regardless of the surgical strategy used, successful management of PJI requires a comprehensive surgical debridement focused at eradicating the underlying biofilm followed by appropriate antimicrobial therapy. Although systemic antimicrobial delivery continues to be a cornerstone in the treatment of PJI, many surgeons have started using local antibiotics to deliver higher concentrations of antibiotics directly into the vulnerable joint and adjacent soft tissues, which often have compromised vascularity. Available evidence on the use of topical powder, bone cement, and calcium sulphate carriers for local delivery of antibiotics during the initial treatment of PJI is limited to studies that are extremely heterogeneous. There is currently no level-1 evidence to support routinely using these products. Further, appropriately powered, prospective studies are needed to quantify the safety and efficacy of antibiotic-located calcium-sulphate carriers to justify their added costs. These products should not encourage surgeons to deviate from best practice guidelines, such as those recommended during the International Consensus Meeting on Musculoskeletal Infections.

The Antibiotic Cement Bead Rouleaux: A Technical Trick to Maximize the Surface Area to Volume Ratio of Cement Beads to Improve the Elution of Antibiotics

The use of antibiotic-impregnated cement as a local antibiotic delivery system is well-established as an adjunctive treatment for chronic osteomyelitis. Because the elution of antibiotics is a surface area phenomenon, the geometry of the cement is an important consideration. The antibiotic cement bead rouleaux technique is a simple and efficient method of bead fabrication that requires only 10 minutes of preparation time and readily available operating room supplies. The discoid structure of the beads provides 3 times the surface-area-to-volume ratio of a spherical bead, which facilitates antibiotic elution. Given the speed and ease of fabrication, along with optimized geometry, the antibiotic cement bead rouleaux is a useful addition to the surgeon's repertoire.

A comparison of low-dose teicoplanin-loaded spacer application vs. high-dose vancomycin-and-gentamicin-loaded spacer application in the treatment of periprosthetic knee infection

Background/purpose

In the current study, our aim was to compare the efficacy and biocompatibility of teicoplanin-loaded and vancomycin-and-gentamicin-loaded articulating spacers used in two-stage revision arthroplasty for eradication of periprosthetic knee joint infection.

Methods

In the current retrospective cohort study, there were 24 patients who were given 2 g or less antibiotics per 40 g of cement in the low-dose teicoplanin group, and 20 patients who were given a total of 3.6 g or more antibiotics per 40 g of cement in the high-dose vancomycin and gentamicin group. Two groups were compared statistically.

Results

There was no statistically significant difference in the treatment failure between the two groups (p = 0.488). No statistically significant differences were found in spacer fracture rates between the two groups (p = 0.802).

Conclusion

The current study has demonstrated that low-dose teicoplanin protocol is as effective and safe as high-dose vancomycin and gentamycin protocol.

Elution and Biomechanical Properties of Meropenem-Loaded Bone Cement

Objective

To investigate the biomechanical and elution properties of meropenem‐loaded bone cement.

Methods

Bone cement (Palacos LV) with 5% (2 g/4 0g), 10% (4 g/40 g), and 15% (6 g/40 g) meropenem; 5% (2 g/40 g) and 10% (4 g/40 g) vancomycin; and blank bone cement were prepared in a total of six groups named A2, A4, A6, B2, B4, and A0 (antibiotic‐free). 36 cylinder specimens (6‐mm diameter and 12‐mm height) of all six groups were molded for a compression test. After the compression test, because of mechanical properties below the ISO standard requirements, groups B2, B4 were not subjected to a bending test. So a total of 24 rectangular strip specimens (10‐mm width, 75‐mm length, and 3.3‐mm thickness) for groups A2, A4, A6 and A0 were molded for the bending test. Between‐group differences of compressive strength, bending strength and bending modulus were analyzed. The meropenem standard was prepared as a series of standard solutions to calculate the standard curve. At a constant temperature of 37 °C, separately, meropenem‐loaded bone cement cylinder specimens (12 mm in diameter and 17 mm in length) of A2, A4 and A6 were serially immersed in saline solution without stirring. The eluent drug concentration at 24, 48, 72 h and 6, 12, 24 days was measured and the drug concentration‐time curve of meropenem was constructed.

Results

With the exception of groups B2 and B4, all cements compressive strength values were well above the minimum requirement of the ISO 5833 standard (70 MPa). The compressive strength and bending strength values of group A4 were higher than those of group A0 (P < 0.05), but no difference was found between the A0, A2 and A6 groups (P > 0.05). There were no intergroup differences of bending modulus between the A0, A2, A4 and A6 groups (P > 0.05). A standard curve of meropenem was obtained and a regression equation was constructed: Y = 15.0265 X + 13.5218, r = 1.00. At 37 °C, the release of meropenem was rapid during the first 48 h for all A2, A4, A6 samples, and subsequent release continued to decrease.

Conclusion

When adding up to 15% (6 g/40 g) meropenem to the bone cement, the biomechanical properties were not reduced, and bone cement with 10% (4 g/40 g) meropenem had the best performance. At a constant temperature of 37°C, meropenem can be released from bone cement for up to 24 days.

Total knee arthroplasty in dialysis patients: Is it safe? A systematic review of the literature

Purpose

This systematic review characterizes the safety and efficacy of total knee arthroplasty (TKA) in end stage renal disease (ESRD) patients due to the unique challenges they face.

Results

The cumulative complication rate for 3684 patients on dialysis for ESRD after primary TKA was 25%(N = 925/3702), with incidence rates of 2.5%(N = 92/3702) for periprosthetic joint infection, 3.7%(N = 71/1895) for reoperations, and 2.5%(N = 90/3578) for mortality.

Conclusion

Patients on dialysis for ESRD face significant mortality rates after primary TKA, in addition to other major complications. Careful counseling regarding risks and benefits should be provided prior to TKA in this population.

Dual antibiotic loaded bone cement in patients at high infection risks in arthroplasty: Rationale of use for prophylaxis and scientific evidence

In view of the demographic changes and projected increase of arthroplasty procedures worldwide, the number of prosthetic joint infection cases will naturally grow. Therefore, in order to counteract this trend more rigid rules and a stricter implementation of effective preventive strategies is of highest importance. In the absence of a “miracle weapon” priorities should lie in evidence-based measures including preoperative optimization of patients at higher infection risks, the fulfilment of strict hygiene rules in the operating theatre and an effective antibiotic prophylaxis regimen. Instead of a “one size fits all” philosophy, it has been proposed to adjust the antibiotic prophylaxis protocol to major infection risks taking into account important patient- and procedure-related risk factors. A stronger focus on the local application mode via use of high dose dual antibiotic-loaded bone cement in such risk situations may have its advantages and is easy to apply in the theatre. The more potent antimicrobial growth inhibition in vitro and the strong reduction of the prosthetic joint infection rate in risk for infection patients with aid of dual antibiotic-loaded bone cement in clinical studies align with this hypothesis.

One-Stage Exchange Arthroplasty for Fistulizing Periprosthetic Joint Infection of the Hip: An Effective Strategy

Background: Prosthetic hip infection (PHI) is a disastrous scenario after an arthroplasty. International guidelines contraindicate one-stage exchange arthroplasty for fistulizing chronic prosthetic hip infection (FCPHI), nevertheless few surgical teams, mostly from Europe, support one stage procedure for this indication.

Questions/Purposes: Analysis of infection recurrence and implant failure of a series of FCPHIs treated with one stage arthroplasty.

Patients and Methods: Sixty-six FCPHIs treated with one-stage exchange arthroplasty were prospectively followed up at least 2 years. Clinical, radiological and bacteriological signs suggestive of reinfection were sought, as well as implant failures and PHI related deaths.

Results: Thirty-four females and thirty-two males with median age of 69.5 years [61–77] and BMI of 26 kg/m² [22-31] were included. Fistulae were productive in 50 patients (76%). Staphylococcus was responsible for 45% of PHI and 21% were polymicrobial. Twenty-nine patients (44%) received preoperative antibiotic therapy. After a median 60-month follow-up [35–82], 3 patients (4.5%) presented reinfection (two new infections, one relapse) and 3 patients experienced implant failure (1 femoral fracture, 1 stem breakage, 1 recurrent dislocation). One death was related to PHI. After a minimum of 2 years, the infection control rate was of 95.3% (±0.02).

Conclusion: One-stage exchange arthroplasty for FCPHIs showed a good infection control rate similar to that of non-fistulizing PHI. Systematic preoperative microbiological documentation with joint aspiration and, in some specific cases, the use of preoperative antibiotic therapy are among the optimizations accounting for the success of the one-stage arthroplasty. In light of these results, and those of other studies, international recommendations could evolve.

Level of Evidence: Descriptive therapeutic prospective cohort study. Level of evidence: IV.

Does Intra-Wound Vancomycin Powder Affect the Action of Intra-Articular Tranexamic Acid in Total Joint Replacement?

The intra-articular use of tranexamic acid (TXA) has contributed to reduced blood loss in total joint arthroplasty (TJA). The purpose of this study is to assess the efficacy of simultaneously topical use of tranexamic acid and vancomycin powder within the TJA space. From 2016 to 2017, 219 consecutive total hip arthroplasties (THAs) and 272 total knee arthroplasties (TKAs) were performed in a tertiary care center, with a group of patients receiving intra-articular TXA and vancomycin, compared to patients receiving only TXA and to a control group that did not receive anything. Haemoglobin and hematocrit were measured preoperatively, on the first and third days. Transfusions and adverse events were recorded. Haemoglobin and hematocrit dropped significantly in all THA and TKA groups till the third day postoperatively, with a major reduction in the control group, compared to the other two treatment groups. Infections and thromboembolic events were similar in either group of the TJAs. In conclusion, the topical use of tranexamic acid mixed with the vancomycin powder within the joint space after the TJAs of the hip and knee did not alter the anti-fibrinolytic effect of TXA.

Hand-mixed vancomycin versus commercial tobramycin cement revisited: A study on mechanical and antibacterial properties

PURPOSE

Arthroplasty-related infection has grown worldwide. Revision procedures for infection are associated with longer operating time, superior amounts of blood loss, and substantial economic encumbrance. To overcome cost, many surgeons opt for hand-mixed vancomycin into the bone cement. The objective of this research was to assess the biomechanical strength and antibacterial properties of hand-mixed vancomycin bone cement at different concentrations with commonly used industrial preblended antibiotic bone cement and plain cement. The target was to determine the ideal concentration of antibiotics that can be used in the preparation of hand-mixed vancomycin cement that delivers maximum antibiotics concentration without compromising its biomechanical properties.

MATERIALS AND METHODS

Vancomycin-impregnated polymethyl methacrylate (PMMA) specimen was hand prepared in varying concentrations (1-4 g). The authors tested three-point bending strength to determine 'maximum bending load' and stiffness and its antibacterial activity by looking into the zone of inhibition on methicillin-resistant Staphylococcus aureus-impregnated agar plate. These were compared with the industrial preblended Simplex™ P with 1 g tobramycin.

RESULTS

This study exhibited that vancomycin-PMMA disk that contained higher concentration of antibiotics had significantly higher antibacterial activity. The control group (plain cement) and industrial PMMA with preblended antibiotic (tobramycin) showed stable mechanical strength, while the hand-mixed antibiotic cement (HMAC) had variable mechanical strength varying on the concentration of antibiotics used.

CONCLUSION

It was effectively concluded that HMAC is advantageous as a cement spacer; however, it is not recommended for primary arthroplasty and second-stage revision arthroplasty. The recommended maximum concentration of vancomycin based on this study is 2 g/pack (40 g) of cement. Industrial preblended antibiotic cement is superior to hand-mixed cement.

Point/Counterpoint: Static vs Articulating Spacers-Static Spacers for Resection Arthroplasty of the Knee

Antibiotic spacers play a significant role in the treatment of periprosthetic joint infections. They help maintain soft-tissue tension and provide delivery of high dose of antibiotics to the local tissue. The use of static or dynamic spacers is based on multiple factors including the extent of soft-tissue, ligamentous and bone compromise, overall patient function, comorbid conditions, and virulence of the organism. There is no difference in reinfection incidence between static vs dynamic spacers following two-stage reimplantation. Static spacers can be customized to treat all cases of periprosthetic total knee infections and offer intraoperative flexibility to vary the cement quantity and amount of antibiotics in the spacer to provide high-dose local delivery of antibiotics to address the dead space, bone loss, and soft-tissue compromise. Static spacers are especially advantageous in cases of extensor mechanism and ligamentous compromise where articulating spacers may not be able to provide adequate stability.

Unexpected synergistic and antagonistic antibiotic activity against Staphylococcus biofilms

Objectives

To evaluate putative anti-staphylococcal biofilm antibiotic combinations used in the management of periprosthetic joint infections (PJIs).

Methods

Using the dissolvable bead biofilm assay, the minimum biofilm eradication concentration (MBEC) was determined for the most commonly used antimicrobial agents and combination regimens against staphylococcal PJIs. The established fractional inhibitory concentration (FIC) index was modified to create the fractional biofilm eradication concentration (FBEC) index to evaluate synergism or antagonism between antibiotics.

Results

Only gentamicin (MBEC 64 mg/L) and daptomycin (MBEC 64 mg/L) were observed to be effective antistaphylococcal agents at clinically achievable concentrations. Supplementation of gentamicin with daptomycin, vancomycin or ciprofloxacin resulted in a similar or lower MBEC than gentamicin alone (FBEC index 0.25-2). Conversely, when rifampicin, clindamycin or linezolid was added to gentamicin, there was an increase in the MBEC of gentamicin relative to its use as a monotherapy (FBEC index 8-32).

Conclusions

This study found that gentamicin and daptomycin were the only effective single-agent antibiotics against established Staphylococcus biofilms. Interestingly the addition of a bacteriostatic antibiotic was found to antagonize the ability of gentamicin to eradicate Staphylococcus biofilms.

Colistin-containing cement spacer for treatment of experimental carbapenemase-producing Klebsiella pneumoniae prosthetic joint infection

Carbapenemase-producing Enterobacteriaceae (CPE) are emerging multidrug-resistant bacteria responsible for invasive infections, including prosthetic joint infections (PJIs). Local administration of colistin may provide bactericidal concentrations in situ. This study evaluated the efficacy of a colistin-impregnated cement spacer, alone and in combination with systemic antibiotics, in a rabbit model of CPE-PJI. Elution of 3 MIU of colistimethate sodium (CMS) in 40 g of poly(methyl methacrylate) cement was studied in vitro. In vivo, 5 × 10⁸ CFU of KPC-producing Klebsiella pneumoniae (colistin and meropenem MICs of 1 mg/L and 4 mg/L, respectively) were injected close to a prosthetic knee. Surgical debridement and prosthesis removal were performed 7 days later, and rabbits were assigned to six treatment groups (11-13 rabbits each): drug-free spacer; colistin-loaded spacer; colistin intramuscular (i.m.); colistin i.m. + colistin spacer; colistin i.m. + meropenem subcutaneous (s.c.); and colistin i.m. + meropenem s.c. + colistin spacer. Systemic treatment was administered at doses targeting pharmacokinetics in humans, and rabbits were euthanised 7 days later to evaluate bacterial counts in infected bones. In vitro, CMS elution was low (<0.1% at 24 h) but reached a local concentration of ≥20 mg/L (>20 × MIC). In vivo, combinations of local and systemic colistin, with or without meropenem, were the only regimens superior to the control group (P ≤ 0.05) in terms of viable bacterial counts and the proportion of rabbits with sterile bone, with no emergence of colistin-resistant strains. Colistin-loaded cement spacer in combination with systemic antibiotics were the most effective regimens in this CPE-PJI model.

Antimicrobial peptide LL-37 is bactericidal against Staphylococcus aureus biofilms

Our current challenge in the management of prosthetic joint infection is the eradication of biofilms which has driven the need for improved antimicrobial agents and regimens. In this study, the antimicrobial peptide, LL-37, and silver nanoparticles (AgNPs) were investigated for their antimicrobial efficacies against Staphylococcus aureus (S. aureus), a microorganism commonly implicated in biofilm-related infections. These antimicrobials were compared to conventional antibiotics and combination treatments with rifampin. Using a Centers for Disease Control reactor, 24 h S. aureus biofilms were formed on cobalt-chromium discs and the anti-biofilm activity was determined by quantifying the amount of colony forming units following treatments. We found that LL-37 was the most efficacious antimicrobial agent with a more than 4 log reduction in colony counts. In comparison, silver nanoparticles and conventional antibiotics were not as efficacious, with a less than 1 log reduction in colony counts. Antimicrobial combination treatments with rifampin significantly increased the log reduction for AgNPs and gentamicin, although still significantly less than LL-37 in isolation. Furthermore, kinetic studies revealed the rapid elimination of S. aureus biofilm with LL-37. Collectively, the results of this study demonstrated that LL-37 was an effective agent against S. aureus biofilms and may have potential clinical applications in the eradication of biofilms and treatment of prosthetic joint infection.

An Unusual Complication after Infected Total Knee Arthroplasty

One-stage or two-stage revision total knee arthroplasty (TKA) in periprosthetic joint infections has been at the center of scientific debate for many years. As regards two-stage revision TKA, cement spacers have a good infection control rate with successful results reportable up to 96%, though some studies describe related spacer complications such as stiffness and loss of bone stock. We report a case of a fracture close to the antibiotic-loaded cement spacer in a 74-year-old female patient. Due to the blood tests and high risk of infection, we performed a hybrid external fixator. Six months after the surgery, X-rays did not show signs of fracture consolidation and nonunion was considered as an impending complication; therefore, the decision was made to perform tumor-like total knee arthroplasty. The postoperative evolution was satisfactory and return to daily activity without pain. At the 5-year follow-up, the patient showed a good score of 36-Item Short Form Health Survey and a range of motion from 0 to 90° without pain. The X-rays did not show signs of mobilization, dislocation, recurrence of infection, or other complications.

Antibiotic-laden Bone Cement in Primary and Revision Hip and Knee Arthroplasty

Antibiotic-laden bone cement (ALBC) has a number of different uses in primary and revision total joint arthroplasty. However, considerable controversy remains regarding how and when it is best used. The prophylactic use of low-dose ALBC in primary cemented total hip arthroplasty is well supported by the literature, conferring both clinical and economic benefits. In contrast, conclusive evidence on the clinical efficacy or economic benefit of the routine use of ALBC in primary total knee arthroplasty remains elusive. Given the currently available evidence, we cannot determine definitively whether the routine use of ALBC in primary total knee arthroplasty is justified, although selective use in patients with a high risk of infection seems warranted. The routine use of ALBC in revision total joint arthroplasty is well accepted, with good supporting evidence in studies of both aseptic and first-stage revision procedures. Although limited clinical evidence exists on the use of ALBC at the time of definitive component reimplantation after septic revision, the rationale for its use is strong.

In vitro study of new combinations for local antibiotic therapy with calcium sulphate - Near constant release of ceftriaxone offers new treatment options

INTRODUCTION

Local application of antibiotics provides high concentrations at the site of interest, with minimal systemic toxicity. Carrier materials might help manage dead space. Calcium sulphate (CaSO₄) has a dissolution time that only slightly exceeds the usually recommended duration of systemic antibiotic treatments. This in vitro study evaluates compatibility, release kinetics and antibacterial activity of new combinations of antibiotics with CaSO₄ as carrier material.

METHODS

CaSO₄ pellets added with 8% w/w antibiotic powder were exposed once in phosphate-buffered saline (PBS) solution and once in bovine plasma, in an elution experiment run over 6 weeks at 37 °C. Antibiotic elution was examined at various time points. Concentration was measured by liquid chromatography with tandem mass spectrometry. Antimicrobial activity was checked with an agar diffusion test.

RESULTS

Piperacillin-tazobactam, ceftazidime, cefepime, and meropenem showed fast reduction of concentration and activity. Flucloxacillin and cefuroxime remained present in relevant concentrations for 4 weeks. Ciprofloxacin, levofloxacin and clindamycin lasted for 6 weeks, but also at cell toxic concentrations. Ceftriaxone showed a near-constant release with only a small reduction of concentration from 130 to 75 mg/l. Elution profiles from PBS and plasma were comparable.

CONCLUSION

CaSO₄ provides new possibilities in the local treatment of bone and joint infections. Ceftriaxone appears to be of particular interest in combination with CaSO₄. Release persists at clinically promising concentrations, and appears to have a depot-like slow release from CaSO₄, with only a small reduction in activity and concentration over 6 weeks. To the best of our knowledge, such a particular persistent release never was described before, for any antibiotic in combination with a carrier material for local application.

Prosthetic Joint Infections: an Update

PURPOSE OF REVIEW

Prosthetic joint infection (PJI) is a rare but serious complication that is frequently misdiagnosed. We aimed to highlight the nuances of PJI diagnosis and antimicrobial therapies and provide clarity in key areas of management.

RECENT FINDINGS

Current research in PJI centers on a potential role for diagnostic biomarkers, molecular techniques, and implant sonication to reduce culture-negativity rates. The optimal duration of antimicrobial therapy remains controversial. A high clinical index of suspicion for PJI combined with data from multiple preoperative and intraoperative tests enables timely diagnosis and treatment. Biomarkers, molecular methods, and implant sonication are currently adjunctive to traditional diagnostic techniques. Shorter courses of antimicrobial therapies as well as the role of chronic suppressive therapy need confirmation by randomized controlled trials. Existing practices for preoperative dental prophylaxis and treatment of asymptomatic bacteriuria warrant revision based on evidence arguing against risk for PJI.

Antibiotic elution from acrylic bone cement loaded with high doses of tobramycin and vancomycin

Two-stage revision treatment of prosthetic joint infection (PJI) frequently employs the use of a temporary bone cement spacer loaded with multiple antibiotic types. Tobramycin and vancomycin are commonly used antibiotics in cement spacers, however, there is no consensus on the relative concentrations and combinations that should be used. Therefore, the purpose of this study was to investigate the influence of dual antibiotic loading on the total antibiotic elution and compressive mechanical properties of acrylic bone cement. Varying concentrations of tobramycin (0-3 g) and vancomycin (0-3 g) were added either alone or in combination to acrylic cement (Palacos R), resulting in 12 experimental groups. Samples were submerged in 37°C saline for 28 d and sampled at specific time points. The collected eluent was analyzed to determine the cumulative antibiotic release. In addition, the cement's compressive mechanical properties and porosity were characterized. Interestingly, the cement with the highest concentration of antibiotics did not possess the best elution properties. Cement samples containing both 3 g of tobramycin and 2 g vancomycin demonstrated the highest cumulative antibiotic release after 28 d, which was coupled with a significant decrease in the mechanical properties and an increased porosity. The collected data also suggests that tobramycin elutes more effectively than vancomycin from cement. In conclusion, this study demonstrates that high antibiotic loading in cement does not necessarily lead to enhanced antibiotic elution. Clinically this information may be used to optimize cement spacer antibiotic loading so that both duration and amount of antibiotics eluted are optimized. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1078-1085, 2018.

Static antibiotic spacers augmented by calcium sulphate impregnated beads in revision TKA: Surgical technique and review of literature

Periprosthetic joint infection (PJI) is a serious complication in total knee arthroplasty (TKA) and represents one of the most common causes of revision. The challenge for surgeons treating an infected TKA is to quickly obtain an infection-free joint in order to re-implant, when possible, a new TKA. Recent literature confirms the role of local antibiotic-loaded beads as a strong bactericidal, allowing higher antibiotic elution when compared with antibiotic loaded spacers only. Unfortunately, classical Polymethylmethacrylate (PMMA) beads might allow bacteria adhesion, secondary development of antibiotic resistance and eventually surgical removal once antibiotics have eluted. This article describes a novel surgical technique using static, custom-made antibiotic loaded spacers augmented by calcium sulphate antibiotic-impregnated beads to improve the success rate of revision TKA in a setting of PJI. The use of calcium sulphate beads has several potential benefits, including a longer sustained local antibiotic release when compared with classical PMMA beads and, being resorbable, not requiring accessory surgical interventions.

The levels of vancomycin in the blood and the wound after the local treatment of bone and soft-tissue infection with antibiotic-loaded calcium sulphate as carrier material

AIMS

Calcium sulphate (CaSO₄) is a resorbable material that can be used simultaneously as filler of a dead space and as a carrier for the local application of antibiotics. Our aim was to describe the systemic exposure and the wound fluid concentrations of vancomycin in patients treated with vancomycin-loaded CaSO₄ as an adjunct to the routine therapy of bone and joint infections.

PATIENTS AND METHODS

A total of 680 post-operative blood and 233 wound fluid samples were available for analysis from 94 implantations performed in 87 patients for various infective indications. Up to 6 g of vancomycin were used. Non-compartmental pharmacokinetic analysis was performed on the data from 37 patients treated for an infection of the hip.

RESULTS

The overall systemic exposure remained within a safe range, even in patients with post-operative renal failure, none requiring removal of the pellets. Local concentrations were approximately ten times higher than with polymethylmethacrylate (PMMA) as a carrier, but remained below reported cell toxicity thresholds. Decreasing concentrations in wound fluid were observed over several weeks, but remained above the common minimum inhibitory concentrations for Staphylococcus up to three months post-operatively.

CONCLUSION

This study provides the first pharmacokinetic description of the local application of vancomycin with CaSO₄ as a carrier, documenting slow release, systemic safety and a release profile far more interesting than from PMMA. In particular, considering in vitro data, concentrations of vancomycin active against staphylococcal biofilm were seen for several weeks. Cite this article: Bone Joint J 2017;99-B:1537-44.

Analytical Evaluation of a Vancomycin Immunoassay in Synovial Fluid

In clinical laboratories performing routine activities, the need to answer the burning clinical question in emerging field may be limited by lack of technology support or assays accessibility. Commercially available methods, although originally validated for specific biological matrices, may be employed for other matrices, following appropriate guidelines such as Clinical and Laboratory Standards Institute (CLSI) EP 19. We investigated the use of a vancomycin assay with synovial fluid samples, in view of a possible employment in vancomycin release study. The standard of care of periprosthetic joint infection is a two-stage revision surgery with antibiotic-loaded bone cement implantation. Vancomycin, for its activity against gram-positive bacteria even multidrug-resistant staphylococci, is the most widely used antibiotic. Despite the widespread use of such devices, little is known about the in vivo elution in the joint space. Clinical laboratories equipped with a validated, affordable method to quantify vancomycin in synovial fluid, may support clinical research, and give an important contribution to the study of the pharmacokinetics of antibiotic release from bone cement matrix.

Comparison of the efficacy of static versus articular spacers in two-stage revision surgery for the treatment of infection following total knee arthroplasty: a meta-analysis

Background

The aim of this study was to compare the outcomes of static versus articular spacers in two-stage reimplantation for the treatment of infected total knee arthroplasty (TKA).

Methods

The literature regarding the articulating and static spacers for treating infected TKA were searched in PubMed, Embase, Cochrane Library, Chinese Periodical Full-Text Database of CNKI, and Wanfang database. Data were extracted according to the inclusion and exclusion criteria and analyzed by Review Manager 5.3.

Results

Ten studies were included to this meta-analysis (nine retrospective studies, one prospective study) according to the principle of PICOS. There was no significant difference regarding the eradication rate (P = 0.28) and the American Knee Society knee score (KSS) pain score (P = 0.11) between the articulating and static spacers in the two-stage revision surgery. There was no significant difference regarding quadriceps femoroplasty and tibial tubercle osteotomy between the two groups (P = 0.50). The knee range of motion (ROM), Hospital for Special Surgery (HSS) score, and KSS function score in the articulating group were significantly higher than those in the static group (P < 0.00001).

Conclusion

Articulating spacers can provide better ROM and knee function scores after revision surgery when compared to static spacer while not compromising the infection eradication rate, soft tissue contracture during exclusion period, and knee pain scores.

Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement

OBJECTIVES

Thermal stability is a key property in determining the suitability of an antibiotic agent for local application in the treatment of orthopaedic infections. Despite the fact that long-term therapy is a stated goal of novel local delivery carriers, data describing thermal stability over a long period are scarce, and studies that avoid interference from specific carrier materials are absent from the orthopaedic literature.

METHODS

In this study, a total of 38 frequently used antibiotic agents were maintained at 37°C in saline solution, and degradation and antibacterial activity assessed over six weeks. The impact of an initial supplementary heat exposure mimicking exothermically curing bone cement was also tested as this material is commonly used as a local delivery vehicle. Antibiotic degradation was assessed by liquid chromatography coupled to mass spectrometry, or by immunoassays, as appropriate. Antibacterial activity over time was determined by the Kirby-Bauer disk diffusion assay.

RESULTS

The heat exposure mimicking curing bone cement had minimal effect on stability for most antibiotics, except for gentamicin which experienced approximately 25% degradation as measured by immunoassay. Beta-lactam antibiotics were found to degrade quite rapidly at 37°C regardless of whether there was an initial heat exposure. Excellent long-term stability was observed for aminoglycosides, glycopeptides, tetracyclines and quinolones under both conditions.

CONCLUSIONS

This study provides a valuable dataset for orthopaedic surgeons considering local application of antibiotics, and for material scientists looking to develop next-generation controlled or extended-release antibiotic carriers.Cite this article: E. Samara, T. F. Moriarty, L. A. Decosterd, R. G. Richards, E. Gautier, P. Wahl. Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement. Bone Joint J 2017;6:296-306. DOI: 10.1302/2046-3758.65.BJR-2017-0276.R1.

Distribution characteristics of Staphylococcus spp. in different phases of periprosthetic joint infection: A review

Periprosthetic joint infection (PJI) is a devastating condition and Staphylococcus spp. are the predominant pathogens responsible, particularly coagulase-negative staphylococci (CoNS) and Staphylococcus aureus. The aim of the present systematic review was to evaluate the distribution characteristics of specific Staphylococcus spp. in different PJI phases, reveal the effect of pathogens' feature on their distribution and suggest recommendations for antibiotic treatment of Staphylococcal PJI. The present systematic review was performed using PubMed and EMBASE databases with the aim to identify existing literature that presented the spectrum of Staphylococcus spp. that occur in PJI. Once inclusion and exclusion criteria were applied, 20 cohort studies involving 3,344 cases in 3,199 patients were included. The predominant pathogen involved in PJI was indicated to be CoNS (31.2%), followed by S. aureus (28.8%). This trend was more apparent in hip replacement procedures. In addition, almost equal proportions of CoNS and S. aureus (28.6 and 30.0%, respectively) were indicated in the delayed phase. CoNS (36.6%) were the predominant identified organism in the early phase, whereas S. aureus (38.3%) occurred primarily in the late phase. In PJI caused by S. aureus, the number of cases of methicillin-sensitive Staphylococcus aureus (MSSA) was ~2.5-fold greater than that of methicillin-resistant Staphylococcus aureus (MRSA). MRSA occurred predominantly in the early phase, whereas MSSA was largely observed in the delayed and late phases. With regards to antibiotic treatment, the feature of various pathogens and the phases of PJI were the primary considerations. The present review provides useful information for clinical practice and scientific research of PJI.

Management of Prosthetic Joint Infection

Although uncommon, prosthetic joint infection is a devastating complication. This challenging condition requires a coordinated management approach to achieve good patient outcomes. This review details the general principles to consider when managing patients with prosthetic joint infection. The different medical/surgical treatment strategies and how to appropriately select a strategy are discussed. The data to support each strategy are presented, along with discussion of antimicrobial strategies in specific situations.

In-situ deposition of Cu2O micro-needles for biologically active textiles and their release properties

Metal/metal oxide containing fibres are gradually increasing in textile industrialization recently, owing to their high potential for application as antimicrobial textiles. In this study, the reducing properties of cellulose were applied to synthesize cuprous oxide in-situ. The direct formation of Cu₂O on viscose fabrics was achieved via quite simple technique in two subsequent steps: alkalization and sorption. Cu contents in fabrics before and after rinsing ranged between 45.2-86.4mmol/kg and 18.1-67.7mmol/kg, respectively. Uniform micro-needles of Cu₂O were obtained with regular size and dimensions of 1.60±0.20μm in length and 0.13±0.03μm in width. Release of Cu^1+/2+ ions from selected samples was studied in water, physiological fluid and artificial sweat. Copper containing fabrics exhibited a percent of 96.8-97.8% and 85.5-89.0% for reduction in microbial viability, which was tested for S. aureus (as gram positive bacteria), E. coli (as gram-negative bacteria) and C. albicans and A. niger (as fungal species), respectively after 24h contact time.

Antibiotic Elution from Hip and Knee Acrylic Bone Cement Spacers: A Systematic Review

Knowledge about the elution from antibiotic-loaded cement spacers is an indispensable premise for guarantee of clinical success. A systematic literature search was performed through PubMed. Search terms were “antibiotic elution” and “antibiotic release” in combination with “spacer,” “hip spacer,” and “knee spacer,” respectively. A total of 11 studies could be identified. Seven studies reported on the release of antibiotics after spacer implantation, three studies at spacer removal, and one study on both time points. Seven studies reported on hip spacers, one study on knee spacers, and three studies on both. In eight studies, custom-made spacers have been implanted and in three prefabricated ones. In the majority of the studies, the cement has been loaded with an antibiotic combination, mostly consisting of aminoglycoside (either gentamicin or tobramycin) and vancomycin. Measured concentrations exceeded the minimal inhibitory concentration of the particular pathogen organisms in each case. However, large discrepancies were observed with regard to the height of the antibiotic concentration depending on the antibiotic combination and the antibiotic ratio used. Current literature data indicate a sufficient elution of antibiotics after spacer implantation and at spacer removal, respectively. Future studies are required to optimize the local antibiotic therapy at the site of spacer implantation.

The use of spacers (static and mobile) in infection knee arthroplasty

Revision total knee arthroplasty (TKA) is the treatment of choice in patients with periprosthetic joint infection. It may be performed in either a single stage or two stages. In the latter option, between stages, an antibiotic-loaded spacer may be used to maintain a certain amount of joint stability and mobility after the infected implant is removed, adding an intra-articular concentration of antibiotics. There are two types of antibiotic-loaded cement spacers: static and dynamic. Static spacers basically create a temporary arthrodesis with antibiotic-loaded cement and usually are handmade within the surgical field. Dynamic spacers can be created intraoperatively by using different tools or may be prepackaged by the manufacturer; they allow range of motion between stages. In this article, the authors review the indications, surgical techniques, and results for static and dynamic spacers in two-stage revision TKA.

The Otto Aufranc Award: Modifiable versus nonmodifiable risk factors for infection after hip arthroplasty

BACKGROUND

Periprosthetic joint infections (PJIs) are associated with increased morbidity and cost. It would be important to identify any modifiable patient- and surgical-related factors that could be modified before surgery to decrease the risk of PJI.

QUESTIONS/PURPOSES

We sought to identify and quantify the magnitude of modifiable risk factors for deep PJIs after primary hip arthroplasty.

METHODS

A series of 3672 primary and 406 revision hip arthroplasties performed at a single specialty hospital over a 3-year period were reviewed. All deep PJIs were identified using the Centers for Disease Control and Prevention case definitions (ie, occurs within 30-90 days postoperatively, involves deep soft tissues of the incision, purulent drainage, dehiscence and fever, localized pain or tenderness). Univariate and multivariate analyses determined the association between patient and surgical risk factors and PJIs. For the elective patients, the procedure was performed on the day of admission ("same-day procedure"), whereas for the fracture and nonelective patients, the procedure was performed 1 or more days postadmission ("nonsame-day procedure"). Staphylococcus aureus colonization, tobacco use, and body mass index (BMI) were defined as patient-related modifiable risk factors.

RESULTS

Forty-seven (1.3%) deep PJIs were identified. Infection developed in 20 of 363 hips of nonsame-day procedures and 27 of 3309 same-day procedures (p=0.006). There were eight (2%) infections in the revision group. After controlling for confounding variables, our multivariate analysis showed that BMI≧40 kg/m2 (odds ratio [OR], 4.13; 95% confidence interval [CI], 1.3-12.88; p=0.01), operating time>115 minutes (OR, 3.38; 95% CI, 1.23-9.28; p=0.018), nonsame-day surgery (OR, 4.16; 95% CI, 1.44-12.02; p=0.008), and revision surgery (OR, 4.23; 95% CI, 1.67-10.72; p<0.001) are significant risk factors for PJIs. Tobacco use and S aureus colonization were additive risk factors when combined with other significant risk factors (OR, 12.76; 95% CI, 2.47-66.16; p=0.017).

CONCLUSIONS

Nonsame-day hip and revision arthroplasties have higher infection rates than same-day primary surgeries. These characteristics are not modifiable and should be categorized as a separate cohort for complication-reporting purposes. Potentially modifiable risk factors in our patient population include operating time, elevated BMI, tobacco use, and S aureus colonization. Modifying risk factors may decrease the incidence of PJIs. When reporting deep PJI rates, stratification into preventable versus nonpreventable infections may provide a better assessment of performance on an institutional and individual surgeon level.

LEVEL OF EVIDENCE

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

Local gentamicin delivery from resorbable viscous hydrogels is therapeutically effective

BACKGROUND

Local delivery can achieve the high antimicrobial concentrations necessary to kill biofilm-related microbes. Degradation times for resorbable carriers are too long. Hydrogels (gels of hydrophilic polymer in water) can degrade faster but release antimicrobials too quickly. We previously developed hydrogels based on the copolymer poly(N-isopropylacrylamide-co-dimethyl-γ-butyrolactone acrylate-co-Jeffamine® M-1000 acrylamide) (PNDJ) with delivery times of several days with complete degradation in less than 6 weeks.

QUESTIONS/PURPOSES

We asked: (1) What is the elution profile of gentamicin from PNDJ hydrogels? (2) Is gentamicin released from gentamicin-loaded PNDJ (G-PNDJ) hydrogel effective for treatment of orthopaedic infection? (3) Does local gentamicin delivery from G-PNDJ hydrogel cause renal dysfunction?

METHODS

(1) Two formulations of G-PNDJ, lower dose (1.61 wt%) and higher dose (3.14 wt%), five samples each, were eluted in buffered saline under infinite sink conditions. (2) Infections were induced in 16 New Zealand White rabbits by inserting a Kirschner wire in a devascularized radius segment and inoculating with 7.5×10(6) colony-forming units Staphylococcus aureus. At 3 weeks, débridement was performed and a new Kirschner wire was placed in the dead space. Treatment was randomized to higher-dose G-PNDJ or no hydrogel. No systemic antimicrobials were used. Positive culture and acute inflammation on histology were used to determine the presence of infection 4 weeks postdébridement. (3) 3.14 wt% G-PNDJ, 0.75, 1.5, or 3.0 mL, was injected subcutaneously in nine Sprague-Dawley rats, three of each dose. Serum gentamicin, blood urea nitrogen, and creatinine were measured on Days 1, 3, 7, 14, and 28.

RESULTS

(1) Gentamicin release was sustained over 7 days with the higher-dose formulation release profile similar to release from high-dose antimicrobial-loaded bone cement. (2) Four weeks postdébridement, infection was present in eight of eight no-hydrogel rabbits but zero of eight rabbits treated with G-PNDJ hydrogel (p<0.001). (3) Blood urea nitrogen and creatinine were transiently elevated (p<0.05) only for the two of three rats receiving the 3.0-mL dose on Days 3 and 7.

CONCLUSIONS

Gentamicin is delivered from PNDJ hydrogel with low systemic exposure and decreased treatment failure for orthopaedic infection. Transient renal dysfunction occurs at high doses. Biodistribution and toxicity testing are needed for G-PNDJ to be clinically usable.

CLINICAL RELEVANCE

Resorbable viscous hydrogels for local antimicrobial delivery may improve outcomes for one-stage management of implant infections when uncemented reconstructions are performed.

Antimicrobial distribution from local delivery depends on dose : a pilot study with MRI

BACKGROUND

Tissue distribution after local delivery has been quantified over a period of 5 hours on 7-T MRI in a rabbit model using gadolinium-labeled diethylenetriamine pentaacetic acid (Gd-DTPA) as an antimicrobial surrogate; however, it is unknown how the Gd-DTPA load in a local depot will affect the duration of high-concentration Gd-DTPA in local tissues after surgical débridement.

QUESTIONS/PURPOSES

We determined whether the Gd-DTPA load in bone cement affected its local tissue distribution over a period of 1 month after local delivery.

METHODS

A 1-cm3 soft tissue dead space was created in the quadriceps of seven rabbits and filled with gadolinium-loaded bone cement. At 7, 14, and 33 days, the volume of tissue with a Gd-DTPA concentration of more than 14 μg/mL was calculated from T1-weighted images using 7-T MRI. Differences in volumes of distribution were analyzed with ANOVA.

RESULTS

The volume of tissue with more than 14 μg/mL Gd-DTPA was much larger from higher gadolinium loads on Day 7 (p=0.02) (2121 mm3 for 10 g and 665 mm3 for 1 g) and smaller with time for the 10-g formulation (2121 mm3 on Day 7 and 1241 mm3 on Day 14).

CONCLUSIONS

Volume of distribution and duration of Gd-DTPA after local delivery increased with increasing load in the cement and decreased with time.

CLINICAL RELEVANCE

For local delivery, high antimicrobial concentrations would be expected in greater volumes of tissue, for longer durations, when higher antimicrobial loads are used.

Antibiotic-loaded synthetic calcium sulfate beads for prevention of bacterial colonization and biofilm formation in periprosthetic infections

Periprosthetic infection (PI) causes significant morbidity and mortality after fixation and joint arthroplasty and has been extensively linked to the formation of bacterial biofilms. Poly(methyl methacrylate) (PMMA), as a cement or as beads, is commonly used for antibiotic release to the site of infection but displays variable elution kinetics and also represents a potential nidus for infection, therefore requiring surgical removal once antibiotics have eluted. Absorbable cements have shown improved elution of a wider range of antibiotics and, crucially, complete biodegradation, but limited data exist as to their antimicrobial and antibiofilm efficacy. Synthetic calcium sulfate beads loaded with tobramycin, vancomycin, or vancomycin-tobramycin dual treatment (in a 1:0.24 [wt/wt] ratio) were assessed for their abilities to eradicate planktonic methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis relative to that of PMMA beads. The ability of the calcium sulfate beads to prevent biofilm formation over multiple days and to eradicate preformed biofilms was studied using a combination of viable cell counts, confocal microscopy, and scanning electron microscopy of the bead surface. Biofilm bacteria displayed a greater tolerance to the antibiotics than their planktonic counterparts. Antibiotic-loaded beads were able to kill planktonic cultures of 10(6) CFU/ml, prevent bacterial colonization, and significantly reduce biofilm formation over multiple days. However, established biofilms were harder to eradicate. These data further demonstrate the difficulty in clearing established biofilms; therefore, early preventive measures are key to reducing the risk of PI. Synthetic calcium sulfate loaded with antibiotics has the potential to reduce or eliminate biofilm formation on adjacent periprosthetic tissue and prosthesis material and, thus, to reduce the rates of periprosthetic infection.