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

Exploring Acute Kidney Injury Incidence in Hip Periprosthetic Joint Infection Treatment With Combined Intravenous and Intra-articular Antibiotic Infusion

Background

Periprosthetic joint infections (PJIs) are a significant complication following total hip arthroplasty, impacting patient health and healthcare costs. This study examines the incidence of acute kidney injury (AKI) in patients undergoing hip PJI treatment with a combination of intravenous and intra-articular antibiotic infusion therapies.

Methods

A retrospective review of 151 patient records from May 1, 2010 to December 30, 2022 was conducted at a single academic hospital. Patients were treated for hip PJIs using debridement, antibiotics, and implant retention or single-stage revision surgeries. AKI was classified according to the Kidney Disease: Improving Global Outcomes criteria.

Results

Among 151 patients, 17 (11.26%) developed AKI, with 13 cases resolving transiently before discharge. The median onset of AKI was on postoperative day 2, with stage I AKI being the most prevalent, accounting for 64.71% of cases. Diabetes and low baseline serum creatinine levels were identified as independent risk factors for AKI, with odds ratios of 9.69 and 1.09, respectively.

Conclusions

The combined regimen of intra-articular and intravenous antibiotic infusion appears to have a manageable risk profile regarding AKI. This approach could serve as a viable alternative for PJI management, emphasizing the importance of careful patient monitoring and tailored antibiotic regimens. Further studies are recommended to optimize treatment protocols and mitigate risks.

Antibiotic-loaded cement in total joint arthroplasty: a comprehensive review

This review evaluates the decision-making framework for using antibiotic-loaded cement (ALC) in the management of prosthetic joint infection (PJI). Drawing on available literature, we offer orthopaedic surgeons a guided discussion on several critical considerations. First, we explore the impact of antibiotic-loading on the mechanical properties of polymethylmethacrylate (PMMA) cement, assessing both strength and durability. We then explore the optimal antibiotic dosage to load into cement, aiming to achieve effective local concentrations for infection control without compromising mechanical stability. Furthermore, we explore how cement and antibiotic properties affect the overall antibiotic elution characteristics of ALC. Finally, we discuss risks of systemic toxicity, particularly acute kidney injury, when using ALC. The principal goal in this review is to provide a balanced approach based on best available evidence that optimises antibiotic elution from ALC whilst minimising potential harms associated with its use.

The immediate ex vivo covering and filling characteristics of antibiotic-loaded resorbable calcium sulfate paste around intramedullary nails

Background: Antibiotic-laden polymethyl methacrylate (PMMA)-coated intramedullary nails (IMNs) are an effective treatment for osteomyelitis, but they pose multiple disadvantages. Antibiotic-loaded resorbable calcium sulfate (ARCS) paste is an alternative option to deliver a local antibiotic depot around IMNs, but such use has been minimally investigated. This study aimed to define the immediate covering and filling characteristics of ARCS around IMNs by using anatomic bone models. Method: Five tibia models (foam with cortical shell) were prepared by reaming a uniform 13 mm cylindrical path. Three 40 cc kits of ARCS (STIMULAN, Biocomposites Ltd, Keele, UK) were mixed with 3 g vancomycin and 1.2 g tobramycin powder and injected into the intramedullary canal while wet, completely filling the canal. A 10 mm × 345 mm tibial IMN was immediately inserted without interlocking screws and allowed to completely cure for 2 h. The models were then longitudinally cut without disrupting the dry ARCS covering on the nail. The ARCS was removed from the nail at five equidistant locations along the nail. The thickness of the ARCS was measured with a caliper. A repeated-measures ANOVA test was used to compare the mean width of each segment for each model. Results: In all five trials, the tibial canal volume surrounding the nail remained completely filled. The ARCS paste was confluent along the length of the IMN. There were no gaps or air pockets between the paste and reamed model bone. There was no statistically significant difference among the five samples at each location ( p = 0.913 ) or among the five locations along the bone ( p = 0.210 ). Conclusion: In a model setting, ARCS fully fills the intramedullary canal of a tibia and covers an IMN uniformly. Study of the in vivo material properties of ARCS may further elucidate the bone penetration as well as the clinical utility of this antibiotic depot technique.

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.

Daptomycin-Impregnated PMMA Cement against Vancomycin-Resistant Germs: Dosage, Handling, Elution, Mechanical Stability, and Effectiveness

BACKGROUND

The number of periprosthetic joint infections caused by vancomycin-resistant pathogens is increasing. Currently, no PMMA cement is commercially available to cover VRE. Daptomycin shows promising results in treating infection, offering a good safety profile and a reduced risk of developing resistance. The purpose of this in vitro study was to investigate the mechanical stability, handling properties, elution behavior, and antimicrobial effectiveness of PMMA cement loaded with three different daptomycin concentrations in comparison to commercially available antibiotic-loaded bone cement (ALBC).

METHODS

Mechanical properties and handling characteristics (ISO 5833, DIN 53435), HPLC elution, antimicrobial effectiveness with proliferation assay (DIN 17025), and inhibition zone testing were investigated.

RESULTS

All tested daptomycin concentrations met the ISO and DIN standards for mechanical strength. Loading of 40 g of PMMA cement with 0.5 g of daptomycin did not show any antimicrobial effectiveness, in contrast to 1.0 g and 1.5 g. PMMA cement with 1.5 g of daptomycin was the best in terms of elution and effectiveness, and it showed good ISO mechanical strength; ISO doughing was sticky for a little longer and setting was faster compared to the vancomycin-containing reference cement.

CONCLUSION

PMMA cement containing 0.5 g of gentamicin and 1.5 g of daptomycin could be a good alternative to the already established COPAL® (Wehrheim, Germany) G+V for the treatment of PJIs caused by VRE.

Composite Bone Cements with Enhanced Drug Elution

Antibiotic-loaded bone cement (ALBC) has become an indispensable material in orthopedic surgery in recent decades, owing to the possibility of drugs delivery to the surgical site. It is applied for both infection prophylaxis (e.g., in primary joint arthroplasty) and infection treatment (e.g., in periprosthetic infection). However, the introduction of antibiotic to the polymer matrix diminishes the mechanical strength of the latter. Moreover, the majority of the loaded antibiotic remains embedded in polymer and does not participate in drug elution. Incorporation of the various additives to ALBC can help to overcome these issues. In this paper, four different natural micro/nanoscale materials (halloysite, nanocrystalline cellulose, micro- and nanofibrillated cellulose) were tested as additives to commercial Simplex P bone cement preloaded with vancomycin. The influence of all four materials on the polymerization process was comprehensively studied, including the investigation of the maximum temperature of polymerization, setting time, and monomer leaching. The introduction of the natural additives led to a considerable enhancement of drug elution and microhardness in the composite bone cements compared to ALBC. The best combination of the polymerization rate, monomer leaching, antibiotic release, and microhardness was observed for the sample containing nanofibrillated cellulose (NFC).

Nephrotoxicity Related to Antibiotic-Loaded Spacers in a 2-Stage Revision for Periprosthetic Joint Infection

Antibiotic-loaded bone cement (ALBC) spacers are the mainstay in 2-stage revision, but antibiotics (vancomycin plus aminoglycosides) may undergo systemic absorption, resulting in acute kidney injury (AKI). Data on spacer antibiotics are heterogeneous. Our objective was to review risk factors for AKI and dosage of antibiotics. Significant AKI risk factors were antibiotic concentration greater than 3 or 3.6 g per cement batch, comorbidities, chronic kidney disease, and hypovolemia. Despite similar spacer antibiotic dosing, there was remarkable variability in serum concentrations. To err on the side of caution, it appears that antibiotic dose below 3 g per cement batch might be relatively safe until more evidence surfaces. Consideration of risk factors for AKI calls for appropriate antibiotic use in 2-stage revision. [Orthopedics. 20XX;XX(X):xx-xx.].

Total Femur Antibiotic Spacers: Effective Salvage for Complex Periprosthetic Joint Infections

BACKGROUND

A simultaneous periprosthetic joint infection (PJI) of an ipsilateral hip and knee arthroplasty is a challenging complication of lower extremity reconstructive surgery. We evaluated the use of total femur antibiotic-impregnated polymethylmethacrylate (PMMA) bone cement spacers in the staged treatment of such limb-threatening PJIs.

METHODS

Thirteen patients were treated with a total femur antibiotic spacer. The mean age at the time of spacer placement was 65 years. Nine patients had polymicrobial PJIs. All spacers incorporated vancomycin (3.0 g/40 g PMMA) and gentamicin (3.6 g/40 g PMMA), while 8 also included amphotericin (150 mg/40 g PMMA). Eleven spacers were biarticular. Twelve spacers were implanted through one longitudinal incision, while 8 of 12 reimplantations occurred through 2 smaller, separate hip and knee incisions. Mean follow-up after reimplantation was 3 years.

RESULTS

Twelve (92%) patients underwent reimplantation of a total femur prosthesis at a mean of 26 weeks. One patient died of medical complications 41 days after spacer placement. At latest follow-up, 3 patients had experienced PJI recurrence managed with irrigation and debridement. One required acetabular component revision for instability. All 12 reimplanted patients retained the total femur prosthesis with no amputations. Eleven (91%) were ambulatory, and 7 (58%) remained on suppressive antibiotics.

CONCLUSION

Total femur antibiotic spacers are a viable, but technically demanding, limb-salvage option for complex PJIs involving the ipsilateral hip and knee. In the largest series to date, there were no amputations and 75% of reimplanted patients remained infection-free. Radical debridement, antimicrobial diversity, prolonged spacer retention, and limiting recurrent soft tissue violation are potential tenets of success.

LEVEL OF EVIDENCE

IV.

Silver ion-doped calcium phosphate-based bone-graft substitute eliminates chronic osteomyelitis: An experimental study in animals

Despite the latest technologies and advances in microbiology and orthopedic surgery, chronic osteomyelitis is still a challenging disorder. Antibiotic resistance and bacterially induced bone destruction can have very serious consequences. We hypothesized that calcium phosphate-based bone graft substitution with silver ion doping would simultaneously treat bone infection and the bony defect in the chronic osteomyelitis. An unicortical 10-mm-diameter bone was harvested in the proximal tibial metaphysis of 24 rabbits. After contaminating the wounds with an infective dose of methicillin-resistant Staphylococcus aureus (MRSA), osteomyelitis was proven radiographically and microbiologically in all rabbits. Animals were than divided into three groups. The first group received vancomycin-impregnated bone cement beads (comparative control group), the second/experimental group received silver ion-doped calcium phosphate beads and the third group received pure calcium phosphate beads (negative controls). Radiographs, intraosseous cultures, and histopathological examinations were performed on postoperative Week 10. The cultures showed no evidence of intramedullary infection in the silver ion-doped calcium phosphate beads group, but they were positive for MRSA in four of the six rabbits in the vancomycin- impregnated bone cement beads group and in all of the eight rabbits in the pure calcium phosphate beads group. Quantitative assessment of histopathological examination showed lowest total damage score in silver ion-doped calcium phosphate beads group (p < .001). Percentage of osteoid tissue + bony tissue was also higher in this group compared with other groups. In the final radiological examinations, it was observed that the changes caused by osteomyelitis in the bone tissue in the silver ion-doped calcium phosphate beads group were much improved compared with the vancomycin-impregnated bone cement beads group. Silver ion doped calcium phosphate-based bone-graft substitute offer the ability to stimulate bone growth, combat infection, and, ultimately, treat experimental chronic osteomyelitis in an animal model.

The Basic Science Behind the Clinical Success of the Induced Membrane Technique for Critical-Sized Bone Defects

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The induced membrane technique (IMT) takes advantage of an osteoinductive environment that is created by the placement of a cement spacer into a bone defect.

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Most commonly, a polymethylmethacrylate (PMMA) spacer has been used, but spacers made from other materials have emerged and achieved good clinical outcomes.

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The IMT has demonstrated good results for long-bone repair; however, more research is required in order to optimize union rates as well as delineate more precise indications and surgical timing.

Elution properties of a resorbable magnesium phosphate cement

OBJECTIVE

This study tests the elution capabilities of a magnesium phosphate cement (MPC). Study objectives were to quantify the passive release of magnesium ions from MPC and to assess the effects of antibiotic-loaded MPC on bacterial growth and osteoblast viability.

METHODS

MPC constructs were created and incubated in fetal bovine serum (FBS). At 2, 4, and 17 weeks, a sample was collected for magnesium ion concentration analysis. Control and vancomycin-loaded (vanc) MPC beads were also created. Zone of inhibition was measured after incubating beads on Staphylococcus aureus agar plates for 24 h. Osteoblasts were seeded onto control and vanc beads and cultured for 9 days. Metabolic activity was measured via a resazurin assay. ANOVA with Tukey HSD post-hoc tests and t-tests were performed.

RESULTS

Magnesium ions were eluted at 2 and 4-week time points without significant difference, but demonstrated a significant spike at the 17-week time point. Zones of inhibition for the bacterial species was observed for Vanc-MPC beads, but not control beads. No cytotoxic effects on osteoblasts were noted.

CONCLUSION

MPC has potential to improve bone regeneration based on its ability to passively elute magnesium. Additionally, antibiotic-loaded MPC inhibits bacterial growth while avoiding osteoblast cytotoxicity.

Evaluation of the Effect of Ciprofloxacin and Vancomycin on Mechanical Properties of PMMA Cement; a Preliminary Study on Molecular Weight

Antibiotic-loaded bone cement (ALBC) is commonly used in joint replacement therapy for prevention and treatment of bone infection and mechanical properties of the cement is still an important issue. The effects of ciprofloxacin and vancomycin was investigated on mechanical characterization of PMMA bone cement. Different properties of cement containing (0, 2.5, 5 and 10% W/W) antibiotics, including compressive and bending properties, microstructural, porosity and density were evaluated. Both antibiotics significantly reduced the density values and mechanical properties (compressive and flexural strength and modulus) in all groups in comparison to control over first two weeks (p < 0.05). This reduction was due to increased porosity upon antibiotic addition (3.05 and 3.67% for ciprofloxacin and vancomycin, respectively) in comparison to control (2.08%) (p < 0.001) and exposure to aqueous medium. Vancomycin as antibiotic with higher molecular weight (MW = 1485) had significant effect on compressive strength reduction of the cement at high amount compared to ciprofloxacin (MW = 367) (P < 0.01), there was no difference between two antibiotics at lower concentrations (P > 0.05). The effect of antibiotic loading is both molecular weight and drug content dependent. The time is also an important parameter and the second week is the probably optimum time to study mechanical behavior of ALBC.

Do Antibiotic-Impregnated Intramedullary Dowels Assist in Eradicating Infection in Total Knee Arthroplasty? Pro

Antibiotic-loaded bone cement (ALBC) spacer constructs for the treatment of periprosthetic joint infections of the knee continue to evolve from the original hockey puck designs. Countless techniques have since been described for augmentation of ALBC spacers with the use of intramedullary (IM) dowels. The use of IM dowels has become a vital addition to any knee spacer construct. ALBC IM dowels are an excellent vessel to provide targeted local antibiotic treatment to high-risk areas like the medullary canal while increasing the overall therapeutic antibiotic elution. In addition, IM dowels provide needed stabilization to the relatively unstable intra-articular spacer component, thereby reducing spacer-related complications like displacement and fracture. Therefore, we recommend regular use of IM dowel augmentation to ALBC spacer constructs.

Does the Effectiveness and Mechanical Strength of Kanamycin-Loaded Bone Cement in Musculoskeletal Tuberculosis Compare to Vancomycin-Loaded Bone Cement

BACKGROUND

Antibiotic-loaded bone cement (ALBC) is used to deliver antimycobacterial agents into the focal lesion of musculoskeletal tuberculosis. Although kanamycin is currently used as an antimycobacterial agent for the treatment of multidrug-resistant tuberculosis, there is no information about its suitability in ALBC.

METHODS

An in vitro experiment was conducted with cylindrical shape of 40 g of bone cement with 1, 2, and 3 g of kanamycin. Eluate (1 mL) was extracted from each specimen to measure the level of elution and antimycobacterial activity on days 1, 4, 7, 14, and 30. The quantity of kanamycin in eluates was evaluated by a liquid chromatography-mass spectrometry system, and the antimycobacterial activity of eluates against Mycobacterium tuberculosis H37Rv was calculated by comparing the minimal inhibitory concentration. The ultimate compression strength was conducted using a material testing system machine (Instron 3366; Instron, Norwood, MA) before and after elution.

RESULTS

Eluates from ALBC containing 2 and 3 g of kanamycin had effective antimycobacterial activity for 30 days, whereas eluates from ALBC containing 1 g of kanamycin were partially active until day 30. The pre-eluted compression strength of kanamycin-loaded cement and vancomycin-loaded cement was weaker as they contained a larger amount of antibiotics. There was no statistical difference between the strength of all kanamycin regimens and 1 g of vancomycin in the ultimate compression test. After 30 days of elution, the strength of all kanamycin-loaded cement and vancomycin-loaded cement cylinders was significantly lower than that of initial specimens (P < .05).

CONCLUSION

The antimycobacterial activity of ALBC containing more than 2 g of kanamycin was effective during a 30-day period. The ultimate compression strength of bone cement loaded with 1-3 g of kanamycin was comparable with 1 g of vancomycin while maintaining effective elution until day 30.

CLINICAL EVALUATION OF PATIENTS WITH VANCOMYCIN SPACER RETAINED FOR MORE THAN 12 MONTHS

Objective:

There is no consensus in the literature regarding the time taken to remove antibiotic spacers in the treatment of bone infections. The aim of this study is to evaluate the clinical results of patients with prolonged retention of the same.

Methods:

Patients selected were diagnosed with post-osteosynthesis infection and/or osteomyelitis and were submitted to treatment using an orthopedic cement spacer (polymethylmethacrylate) with vancomycin, retaining it for a period of more than 12 months. They were clinically evaluated to determine the presence of local or systemic infectious signs via hemogram, investigations of inflammatory markers, liver, renal and, with radiographic control.

Results:

Eighteen patients were included in the study. The mean retention time of the spacer was 30.4 months (15 – 61 months). No patient had clinical signs of local or systemic infectious relapse at the time of evaluation. Seven patients (39%) presented non-disabling pain in the operated limb. Seventeen patients (94%) presented a reduction in C-reactive protein values compared to the preoperative period. Radiographically, no migration, no spacer failure, or bone sequestration occurred.

Conclusion:

In this retrospective case series, cement spacer retention with vancomycin for more than 12 months was associated with good clinical results, without relapse of the infectious condition. Nível de Evidência IV. Estudos Terapêuticos - Investigação dos Resultados do Tratamento.

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.

Altering polymerization temperature of antibiotic-laden cement can increase porosity and subsequent antibiotic elution

PURPOSE

To examine the role of polymerization temperature on the cement porosity and antibiotic elution to optimize antibiotic release from antibiotic-laden cement (ABLC).

METHODS

Elution profiles of vancomycin and tobramycin from ABLC discs prepared with low- and high-dose antibiotic dosages, cured at 8, 21, and 37 °C, and placed in phosphate buffered saline (PBS) at 37 °C were examined. Samples were collected at one, four, eight, 24, 72, 168, 336, and 1008 hours to calculate the quantity of antibiotic eluted. Porosity was determined by MicroCT analysis.

RESULTS

ABLC porosity and antibiotic elution were increased up to five times the amount eluted from room temperature discs (p < 0.05). Low-dose ABLC group saw decreased but similar porosity at 8 °C and 21 °C compared to cement cured at 37 °C (p < 0.001). High-dose ABLC group porosities were all significantly different (p < 0.02).

CONCLUSIONS

Altering the polymerization temperature of ABLC led to more porous constructs yielding increased antibiotic elution.

Antibiotic Elution and Mechanical Strength of PMMA Bone Cement Loaded With Borate Bioactive Glass

Introduction: Local delivery of antibiotics using bone cement as the delivery vehicle is an established method of managing implant-associated orthopedic infections. Various fillers have been added to cement to increase antibiotic elution, but they often do so at the expense of strength. This study evaluated the effect of adding a borate bioactive glass, previously shown to promote bone formation, on vancomycin elution from PMMA bone cement.

Methods: Five cement composites were made: three loaded with borate bioactive glass along with 0, 1, and 5 grams of vancomycin and two without any glass but with 1 and 5 grams vancomycin to serve as controls. The specimens were soaked in PBS. Eluate of vancomycin was collected every 24 hours and analyzed by HPLC. Orthopedic-relevant mechanical properties of each composite were tested over time.

Results: The addition of borate bioactive glass provided an increase in vancomycin release at Day 1 and an increase in sustained vancomycin release throughout the treatment period. An 87.6% and 21.1% increase in cumulative vancomycin release was seen for both 1g and 5g loading groups, respectively. Compressive strength of all composites remained above the weight-bearing threshold of 70 MPa throughout the duration of the study with the glass-containing composites showing comparable strength to their respective controls.

Conclusion: The incorporation of borate bioactive glass into commercial PMMA bone cement can significantly increase the elution of vancomycin. The mechanical strength of the cement-glass composites remained above 70 MPa even after soaking for 8 weeks, suggesting their suitability for orthopedic weight-bearing applications.

One-stage surgery for adult chronic osteomyelitis: concomitant use of antibiotic-loaded calcium sulphate and bone marrow aspirate

PURPOSE

To report our experience with one-stage treatment of chronic osteomyelitis using a prospective protocol involving the concomitant use of the antibiotic-loaded calcium sulphate pellets with addition of bone marrow aspirate after bony debridement.

PATIENTS AND METHODS

A total of 30 patients with the mean age of 26.2 years were treated according to a protocol that included (1) surgical debridement of bone and infected tissues, (2) local antibiotic therapy including vancomycin and garamycin loaded on calcium sulphate space filling biodegradable pellets, (3) bone marrow aspirate added to the biocomposite, (4) primary closure with external fixation (when needed) and (5) intravenous antibiotics according to culture and sensitivity results.

RESULTS

After a minimum of one year follow-up, infection was eradicated in 23 (76.7%) patients, the average rate of filling of the bony defect was 70.47%, complete filling of defect in 15 patients (50%) and pathological fracture in one patient.

CONCLUSION

The technique proved safety and efficacy in eradicating the infection and bony healing of the defects after debridement. Simple bone marrow aspiration is cheap, reproducible, safe and not exhausting the scanty autograft resources.

In-Hospital Acute Kidney Injury After TKA Revision With Placement of an Antibiotic Cement Spacer

BACKGROUND

There is mounting evidence that treatment of periprosthetic joint infection of the knee with an antibiotic cement spacer (ACS) may increase risk for acute kidney injury (AKI). We sought to determine the incidence, as well as potential risk factors, of in-hospital AKI in this cohort.

METHODS

We retrospectively identified 75 patients that received either a static or articulating ACS at a single institution. In-hospital AKI was defined by a more than 50% rise in serum creatinine from preoperative baseline to at least 1.4 mg/dL. Our secondary outcome was percent change in creatinine from preoperative to peak postoperative value. Variables were analyzed for the outcome of AKI with univariate logistic regression. A final multivariate model for percent change in creatinine was formed while controlling for age, gender, body mass index, and baseline creatinine.

RESULTS

The incidence of AKI was 14.6%, occurring at a mean of 6.3 days (2-8 days). A lower preoperative hemoglobin (odds ratio = 1.82, P = .015) significantly increased risk for AKI on univariate analysis. Diagnosis of either hypertension or diabetes also showed a strong statistical trend (P = .056). On multivariate regression, lower preoperative hemoglobin significantly correlated with a greater percent rise in creatinine postoperatively (β = 0.30, P = .015).

CONCLUSION

The incidence of AKI in patients who receive ACS is relatively high, raising clinical concern in the care of periprosthetic joint infection patients. Our results suggest that a lower baseline hemoglobin may be involved in the etiology of AKI in this population. Therefore, it may be clinically appropriate to monitor anemic patients for AKI when implanting an ACS.

How Long Does Antimycobacterial Antibiotic-loaded Bone Cement Have In Vitro Activity for Musculoskeletal Tuberculosis?

BACKGROUND

Antibiotic-loaded bone cement is accepted as an effective treatment modality for musculoskeletal tuberculosis. However, comparative information regarding combinations and concentrations of second-line antimycobacterial drugs, such as streptomycin and amoxicillin and clavulanic acid, are lacking.

QUESTIONS/PURPOSES

(1) In antibiotic-loaded cement, is there effective elution of streptomycin and Augmentin^® (amoxicillin and clavulanic acid) individually and in combination? (2) What is the antibacterial activity duration for streptomycin- and amoxicillin and clavulanic acid -loaded cement?

METHODS

Six different types of bone cement discs were created by mixing 40 g bone cement with 1 or 2 g streptomycin only, 0.6 g or 1.2 g Augmentin^® (amoxicillin and clavulanic acid) only, and a combination of 1 g streptomycin plus 0.6 g amoxicillin and clavulanic acid and 2 g streptomycin plus 1.2 g amoxicillin and clavulanic acid. Five bone discs of each type were incubated in phosphate buffered saline for 30 days with renewal of the phosphate buffered saline every day. The quantity of streptomycin and/or amoxicillin and clavulanic acid in eluates were measured by a liquid chromatography-mass spectrometry system, and the antimycobacterial activity of eluates against Mycobacterium tuberculosis H37Rv, were calculated by comparing the minimal inhibitory concentration of each eluate with that of tested drugs using broth dilution assay on microplate.

RESULTS

Streptomycin was detected in eluates for 30 days (in 1 g and 2 g discs), whereas 1.2 g amoxicillin and clavulanate eluted until Day 7 and 0.6 g amoxicillin and clavulanate until Day 3. All eluates in streptomycin-containing discs (streptomycin only, and in combination with amoxicillin and clavulanic acid) had effective antimycobacterial activity for 30 days, while amoxicillin and clavulanate-only preparations were only active until Day 14. The antimycobacterial activity of eluates of 2 g streptomycin plus 1.2 g amoxicillin and clavulanate were higher than those of discs containing 1 g streptomycin plus 0.6 g amoxicillin and clavulanate until Day 3, without differences (Day 3, 1 g streptomycin plus 0.6 g amoxicillin and clavulanate: 17.5 ± 6.85 ug/mL; 2 g streptomycin plus 1.2 g amoxicillin and clavulanate: 32.5 ± 16.77 ug/mL; p = 0.109). After Day 7, however, values of the two combinations remained no different than that of Day 30 (Day 30, 1 g streptomycin plus 0.6 g amoxicillin and clavulanate: 0.88 ± 0.34 ug/mL; 2 g streptomycin plus 1.2 g amoxicillin and clavulanate: 0.59 ± 0.94 ug/mL; p = 0.107).

CONCLUSIONS

Streptomycin, in the form of antibiotic-loaded bone cement, had effective elution characteristics and antimycobacterial effects during a 30-day period, whereas amoxicillin and clavulanate only had effective elution and antimycobacterial characteristics during the early period of this study. The two drugs did not interfere with each other during the elution test.

CLINICAL RELEVANCE

This research revealed that combinations of streptomycin and amoxicillin and clavulanate mixed with bone cement are effective for 30 days. Further trials to determine various different combinations of drugs are necessary to improve the effectiveness of treatments for musculoskeletal tuberculosis.

Acute Kidney Injury After First-Stage Joint Revision for Infection: Risk Factors and the Impact of Antibiotic Dosing

BACKGROUND

Scarce literature exists regarding risk factors associated with postoperative acute kidney injury (AKI) after first-stage revision procedures. The purpose of this study was to determine risk factors for AKI and the efficacy of intra-articular antibiotics in infection eradication.

METHODS

We retrospectively identified 247 patients who underwent a 2-stage revision procedure for the treatment of hip or knee periprosthetic joint infection. We applied previously published diagnostic criteria for AKI to determine its incidence and risk factors for its development.

RESULTS

A 26% incidence of AKI was found after first-stage joint revision for infection. Higher body mass index (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.01-1.13; P = .02), lower baseline hemoglobin level (OR, 0.70; 95% CI, 0.51-0.96; P = .03), and existence of a comorbid condition (OR, 2.67; 95% CI, 1.26-5.64; P = .01) were significant risk factors for AKI. Neither a higher dose of vancomycin (OR, 0.99; 95% CI, 0.88-1.11; P = .83) nor tobramycin (OR, 0.89; 95% CI, 0.77-1.04; P = .15) used in the cement spacer increased the risk of AKI. Each unit increase in vancomycin dose in the cement spacer decreased the odds of failing to clear the infection at 1 and 2 years by a factor of 0.82 (95% CI, 0.70-0.95; P = .01).

CONCLUSION

AKI after first-stage revision procedures for periprosthetic joint infection occurs more commonly than previously reported. Patients with identified risk factors should be managed carefully with attention paid to hemoglobin levels, to avoid AKI after this procedure. Further research is needed to determine the optimal local antibiotic type and dosing to maximize infection clearance and minimize potential side effects.

A Fully Functional Drug-Eluting Joint Implant

Despite advances in orthopedic materials, the development of drug-eluting bone and joint implants that can sustain the delivery of the drug and maintain the necessary mechanical strength in order to withstand loading has remained elusive. Here, we demonstrate that modifying the eccentricity of drug clusters and the percolation threshold in ultrahigh molecular weight polyethylene (UHMWPE) results in maximized drug elution and in the retention of mechanical strength. The optimized UHMWPE eluted antibiotic at a higher concentration for longer than the clinical gold standard antibiotic-eluting bone cement while retaining the mechanical and wear properties of clinically used UHMWPE joint prostheses. Treatment of lapine knees infected with Staphylococcus aureus with the antibiotic-eluting UHMWPE led to complete bacterial eradication and to the absence of detectable systemic effects. We argue that the antibiotic-eluting UHMWPE joint implant is a promising candidate for clinical trials.

Enhancing Drug Release From Antibiotic-loaded Bone Cement Using Porogens

OBJECTIVE

To evaluate whether the addition of porogens to polymethyl methacrylate (PMMA) enhances the antibiotic elution rate from antibiotic-loaded bone cement.

METHODS

Two porogens, gelatin sponge (Spongostan, Ferrosan Medical Devices) and ceramic granules (Bicera, Wiltrom), were added to liquid gentamicin-loaded PMMA at increasing concentrations. Porosity was analyzed using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. Young's modulus and drug elution were also measured. The gentamicin content of the eluents was evaluated by o-phthaldialdehyde (OPA) assay on days 1, 2, 5, 7, 10, and 14.

RESULTS

After day 5, the drug-releasing rate of Spongostan was significantly higher than that of Bicera in the order G3 > G2 > T3 > G1 > T2 > T1 > bone cement, where G represents the concentration of Spongostan and T represents the concentration of Bicera. The addition of Bicera and Spongostan increased the drug-releasing efficiency of PMMA by 3.75-fold and 5.65-fold, respectively. Spongostan also resulted in larger pores (ie, 70 to approximately 200 μm) compared with Bicera (5 to 10 μm) but reduced biomechanical strength.

CONCLUSION

Both gelatin sponge and ceramic granules improved the local antibiotic elution rate, although the drug-releasing rate of Spongostan was significantly higher than that of Bicera.

The cement spacer with multiple indentations: increasing antibiotic elution using a cement spacer 'teabag'

We investigated whether the indentation of bone cement spacers used in revision of infected joint arthroplasty with a MacDonald dissector increased the elution of antibiotic in vitro. A total of 24 cement discs containing either 0.17 g (0.88% w/w), 0.25 g (1.41% w/w), or 0.33 g (1.75% w/w) gentamicin of constant size were made. Of these, 12 were indented with the dissector. Each disc was immersed in ammonium acetate buffer in a sealed container, and fluid from each container was sampled at zero, one, three, six, 24, 48 and 72 hours and at one, and two weeks. The concentration of gentamicin in the fluid was analysed using high performance liquid chromatography mass spectrometry. The fluid sampled at 72 hours from the indented discs containing 0.17 g gentamicin (0.88% w/w) contained a mean of 113 mcg/ml (90.12 to 143.5) compared with 44.5 mcg/ml (44.02 to 44.90) in the fluid sampled from the plain discs (p = 0.012). In discs containing 0.33 g gentamicin (1.75% w/w), the concentration eluted from the indented discs at 72 hours was a mean of 316 mcg/ml (223 to 421) compared with a mean of 118 mcg/ml (100 to 140) from the plain discs (p < 0.001). At two weeks, these significant differences persisted. At nine weeks the indented discs eluted a greater concentration for all gentamicin doses, but the difference was only significant for the discs containing 0.17 g (0.88% w/w, p = 0.006). However if the area under the curve is taken as a measure of the total antibiotic eluted, the indented discs eluted more gentamicin than the plain discs for the 0.17 g (0.88% w/w, p = 0.031), the 0.25 g (1.41% w/w, p < 0.001) and the 0.33 g (1.75% w/w, p < 0.001) discs. When preparing antibiotic spacers for use in staged revision arthroplasty surgery we recommend indenting the spacer with a MacDonald dissector to increase the elution of antibiotic.

Combination of modified mixing technique and low frequency ultrasound to control the elution profile of vancomycin-loaded acrylic bone cement

OBJECTIVES

The objective of this study was to determine if combining variations in mixing technique of antibiotic-impregnated polymethylmethacrylate (PMMA) cement with low frequency ultrasound (LFUS) improves antibiotic elution during the initial high phase (Phase I) and subsequent low phase (Phase II) while not diminishing mechanical strength.

METHODS

Three batches of vancomycin-loaded PMMA were prepared with different mixing techniques: a standard technique; a delayed technique; and a control without antibiotic. Daily elution samples were analysed using flow injection analysis (FIA). Beginning in Phase II, samples from each mix group were selected randomly to undergo either five, 15, 45, or 0 minutes of LFUS treatment. Elution amounts between LFUS treatments were analysed. Following Phase II, compression testing was done to quantify strength. A-priori t-tests and univariate ANOVAs were used to compare elution and mechanical test results between the two mix groups and the control group.

RESULTS

The delayed technique showed a significant increase in elution on day one compared with the standard mix technique (p < 0.001). The transition point from Phase I to Phase II occurred on day ten. LFUS treatments significantly increased elution amounts for all groups above control. Delayed technique resulted in significantly higher elution amounts for the five-minute- (p = 0.004) and 45-minute- (p < 0.001) duration groups compared with standard technique. Additionally, the correlations between LFUS duration and total elution amount for both mix techniques were significant (p = 0.03). Both antibiotic-impregnated groups exhibited a significant decrease in offset yield stress compared with the control group (p < 0.001), however, their lower 95% confidence intervals were all above the 70 MPa limit defined by International Standards Organization (ISO) 5833-2 reference standard for acrylic bone cement.

CONCLUSION

The combination of a delayed mix technique with LFUS treatments provides a reasonable means for increasing both short- and long-term antibiotic elution without affecting mechanical strength.Cite this article: Dr. T. McIff. Combination of modified mixing technique and low frequency ultrasound to control the elution profile of vancomycin-loaded acrylic bone cement. Bone Joint Res 2016;5:26-32. doi: 10.1302/2046-3758.52.2000412.

Biomaterials approaches to treating implant-associated osteomyelitis

Orthopaedic devices are the most common surgical devices associated with implant-related infections and Staphylococcus aureus (S. aureus) is the most common causative pathogen in chronic bone infections (osteomyelitis). Treatment of these chronic bone infections often involves combinations of antibiotics given systemically and locally to the affected site via a biomaterial spacer. The gold standard biomaterial for local antibiotic delivery against osteomyelitis, poly(methyl methacrylate) (PMMA) bone cement, bears many limitations. Such shortcomings include limited antibiotic release, incompatibility with many antimicrobial agents, and the need for follow-up surgeries to remove the non-biodegradable cement before surgical reconstruction of the lost bone. Therefore, extensive research pursuits are targeting alternative, biodegradable materials to replace PMMA in osteomyelitis applications. Herein, we provide an overview of the primary clinical treatment strategies and emerging biodegradable materials that may be employed for management of implant-related osteomyelitis. We performed a systematic review of experimental biomaterials systems that have been evaluated for treating established S. aureus osteomyelitis in an animal model. Many experimental biomaterials were not decisively more efficacious for infection management than PMMA when delivering the same antibiotic. However, alternative biomaterials have reduced the number of follow-up surgeries, enhanced the antimicrobial efficacy by delivering agents that are incompatible with PMMA, and regenerated bone in an infected defect. Understanding the advantages, limitations, and potential for clinical translation of each biomaterial, along with the conditions under which it was evaluated (e.g. animal model), is critical for surgeons and researchers to navigate the plethora of options for local antibiotic delivery.

Single-Stage Hip and Knee Exchange for Periprosthetic Joint Infection

Periprosthetic joint infections following hip and knee arthroplasty are challenging complications for Orthopaedic surgeons to manage. The single-stage exchange procedure is becoming increasingly popular with promising results. At our Institute we have demonstrated favourable or similar outcomes compared to the 'gold-standard' two-stage exchange, and other published single-stage results. The aim of this study is to describe the patient selection criteria and perioperative steps in a single-stage exchange for hip and knee arthroplasty undertaken at our Institute. The outlined protocol can be performed using standard debridement, attention to detail and well-recognised reconstructive techniques.

Evaluation of Elution and Mechanical Properties of High-Dose Antibiotic-Loaded Bone Cement: Comparative "In Vitro" Study of the Influence of Vancomycin and Cefazolin

Use of antibiotic-loaded bone cements is one of the most effective methods for the prevention and treatment of prosthetic joint infection. However, there is still controversy about the optimal combination and doses of antibiotics that provide the maximum antimicrobial effect without compromising cement properties. In this study, vancomycin and cefazolin were added to a bone cement (Palacos R+G). Antibiotic release, fluid absorption, and mechanical properties were evaluated under physiological conditions. The results show that the type of antibiotic selected has an important impact on cement properties. In this study, groups with cefazolin showed much higher elution than those containing the same concentration of vancomycin. In contrast, groups with cefazolin showed a lower strength than vancomycin groups.

Local antibiotic therapy strategies in orthopaedic trauma: Practical tips and tricks and review of the literature

The use of local antibiotics for the prevention of infection in the setting of open fractures and as part of the treatment of osteomyelitis is well established. Antibiotics are most commonly incorporated into polymethylmethacrylate (PMMA) cement, which can then be formed into beads, moulded to fit a bone defect or used to coat a guide wire or IM nail. Newer delivery vehicles and techniques are being evaluated to improve upon these methods. Many factors influence how local antibiotics are applied. Treatment strategies are challenging to standardise due to the variability of clinical presentations. The presence of hardware, upper versus lower extremity, healed versus non-healed fracture and quality of soft tissues overlying the affected bone, as well as patients' comorbidities all need to be considered. Despite the accepted use of local antibiotic therapy in orthopaedic trauma, high-quality evidence regarding the use of local antibiotics is lacking. Indications, techniques, dosages, types of antibiotics, elution properties and pharmacokinetics are poorly defined in the clinical setting. The purpose of our manuscript is to review current strategies and provide practical tips for local application of antibiotics in orthopaedic trauma. We focus on delivery vehicles, types of antibiotics, dosage recommendations when mixed with PMMA and indications.

The effects of different mixing speeds on the elution and strength of high-dose antibiotic-loaded bone cement created with the hand-mixed technique

We evaluated the effects of the mixing speed of hand-mixed bone cement and the different phases of antibiotic mixing on the elution, mechanical properties, and porosity of antibiotic-loaded bone cement. Vancomycin-loaded Palacos LV bone cement was prepared at two hand-mixing speeds, normal and high-speed, and with antibiotic addition during three phases (directly mixing with the PMMA powder, in the liquid phase, and in the dough phase). The cumulative antibiotic elution over 15 days in the high-speed group was increased by 24% compared with the normal-speed group (P < 0.001). The delayed antibiotic addition produced higher vancomycin elution (P < 0.05), but no difference was observed between the liquid and dough phases (P > 0.05). Our study demonstrated that bone cement prepared with high-speed hand mixing and delayed antibiotic addition can exhibit increased vancomycin release.

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.

Establishing a role for vancomycin powder application for prosthetic joint infection prevention-results of a wear simulation study

Topical vancomycin powder (VP) has shown efficacy and safety in decreasing post-operative spine infections. VP use in arthroplasty has not been established. Concerns remain for third-body wear with the addition of crystalline substrate at the implant interface. The study's purpose was to compare wear behavior of CoCr on UHMWPE to identical wear couples with VP. A six-station wear simulator was utilized and cyclic articulations were run for 10 million cycles (Mc). UHMWPE wear was measured using photography, stereomicroscopy, and gravimetric measurement. There were no differences in wear mark length (P = 0.43), width (P = 0.49), or gravimetric wear at 10 Mc (P = 0.98). VP and control groups lost 0.32 and 0.33 mg, respectively. VP may have a role in PJI prevention. A well-designed clinical study is needed.

The two-stage standard in revision total hip replacement

Two-stage exchange remains the gold standard for treatment of peri-prosthetic joint infection after total hip replacement (THR). In the first stage, all components and associated cement if present are removed, an aggressive debridement is undertaken including a complete synovectomy, and an antibiotic-loaded cement spacer is put in place. Patients are then treated with six weeks of parenteral antibiotics, followed by an ‘antibiotic free period’ to help ensure the infection has been eradicated. If the clinical evaluation and serum inflammatory markers suggest the infection has resolved, then the second stage can be completed, which involves removal of the cement spacer, repeat debridement, and placement of a new THR.

Cite this article: Bone Joint J 2013;95-B, Supple A:84–7.

Periprosthetic joint infections: clinical and bench research

Prosthetic joint infection is a devastating complication with high morbidity and substantial cost. The incidence is low but probably underestimated. Despite a significant basic and clinical research in this field, many questions concerning the definition of prosthetic infection as well the diagnosis and the management of these infections remained unanswered. We review the current literature about the new diagnostic methods, the management and the prevention of prosthetic joint infections.