Review of calcium-sulphate-based ceramics and synthetic bone substitutes used for antibiotic delivery in PJI and osteomyelitis treatment

Induction Heating Triggers Antibiotic Release and Synergistic Bacterial Killing on Polymer-Coated Titanium Surfaces

Infection is a major complication associated with orthopedic implants. It often involves the development of biofilms on metal substrates, which act as barriers to the host's immune system and systemic antibiotic treatment. The current standard of treatment is revision surgery, often involving the delivery of antibiotics through incorporation into bone cements. However, these materials exhibit sub-optimal antibiotic release kinetics and revision surgeries have drawbacks of high cost and recovery time. Herein, a new approach is presented using induction heating of a metal substrate, combined with an antibiotic-loaded poly(ester amide) coating undergoing a glass transition just above physiological temperature to enable thermally triggered antibiotic release. At normal physiological temperature, the coating provides a rifampicin depot for >100 days, while heating of the coating accelerates drug release, with >20% release over a 1-h induction heating cycle. Induction heating or antibiotic-loaded coating alone each reduce Staphylococcus aureus (S. aureus) viability and biofilm formation on Ti, but the combination causes synergistic killing of S. aureus as measured by crystal violet staining, determination of bacterial viability (>99.9% reduction), and fluorescence microscopy of bacteria on surfaces. Overall, these materials provide a promising platform enabling externally triggered antibiotic release to prevent and/or treat bacterial colonization of implants.

Efficacy and Safety of Antibiotic Impregnated Microporous Nanohydroxyapatite Beads for Chronic Osteomyelitis Treatment: A Multicenter, Open-Label, Prospective Cohort Study

Chronic osteomyelitis is still a serious health problem that causes disabling conditions and has an impact on the quality of life. The objective of this study was to determine the clinical efficacy and safety of localized antibiotics delivery via impregnated microporous nanohydroxyapatite (nHA-ATB) beads for chronic osteomyelitis treatment. A total of 62 patients were enrolled in this study. After radical surgical debridement, the bone defect was filled with three types of antibiotics (vancomycin or gentamicin or fosfomycin) impregnated HA beads. The follow-up period was 48 weeks. It was found that the success rate was approximately 98% with a re-infection in only one patient. Quality of life of all patients after treatment improved significantly over time. Systemic exposure to vancomycin and gentamicin after beads implantation was limited and high local antibiotics concentrations were found in wound drainage fluid at 24, 48 and 72 h. Blood biochemistry measurements did not show any nephrotoxic or hepatotoxic effects. 20 adverse events were reported, but 90% of the events were resolved without having to remove the beads and the patients recovered. Satisfactory outcomes were observed in terms of success rate, quality of life and adverse effect. nHA-ATB beads impregnated by vancomycin or gentamicin or fosfomycin could potentially be employed as an alternative product of choice for localized antibiotics delivery in chronic osteomyelitis treatment.

Calcium Phosphate Cements as Carriers of Functional Substances for the Treatment of Bone Tissue

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

In Situ Imaging and Anti-inflammation of 3D Printed Scaffolds Enabled by AIEgen

Three-dimensional (3D) printed bioactive scaffolds have been widely used in the field of bone tissue engineering. However, its in vivo visualization and bacterial inflammation are intractable issues during the surgery and treatment. Herein, we first synthesized an aggregation-induced emission-active luminogen (AIEgen) named 4BC with efficient reactive oxygen species (ROS) generation. Then, a series of 3D bioactive scaffolds loaded with 4BC were fabricated by a precipitation adsorption method, namely 4BC@scaffolds, which showed good in situ imaging performance for the implanted scaffolds by using simple UV light irradiation. Among them, the 4BC@TMP scaffold composed of trimagnesium phosphate (TMP) had excellent bactericidal ability for Escherichia coli and Staphylococcus aureus in vitro and resisted bacterial inflammation in vivo through photodynamic action. H&E and immunofluorescence staining were performed to further evaluate the inhibitory effect of bacterial inflammation in vivo. This work verified that AIEgen-based 3D scaffolds are promising bioactive frameworks for bioimaging and antibacterial applications.

Long-Term Follow-Up of Open Gustilo-Anderson IIIB Fractures Treated With an Adjuvant Local Antibiotic Hydroxyapatite Bio-Composite

Background Open fractures associated with significant tissue loss are complex and present challenges in management; they are associated with poor outcomes such as infection, non-union or amputation. This study aimed to evaluate outcomes of using an adjuvant local antibiotic hydroxyapatite bio-composite in the management of open Gustilo-Anderson IIIB fractures with up to eight years of follow-up. Methods This was a retrospective study. A total of 81 patients with Gustilo-Anderson IIIB fractures treated with "fix and flap" limb reconstruction with adjuvant local antibiotic therapy using a bio-composite carrier were reviewed. Results  The mean follow-up time for all the patients, at the time of data collection, was 55.8 months. Union was achieved in 96% with a limb salvage rate of 96.3% and a deep infection rate of 3.7%. Conclusion The use of local antibiotic therapy, together with a combined orthoplastic "fix and flap" approach for Gustilo-Anderson IIIB open fractures, was found to be associated with a very low rate of metalwork infection and high union and limb salvage rates. Future studies should include some functional and quality of life outcome measures to see the efficacy of this method.

Debridement, Antibiotic Pearls, and Retention of the Implant (DAPRI) in the Treatment of Early Periprosthetic Joint Infections: A Consecutive Series

INTRODUCTION

Periprosthetic joint infections (PJI) represent a devastating consequence following total joint arthroplasty (TJA). In this study, the authors describe a modified surgical technique developed to enhance the classical irrigation and debridement procedure (DAIR) to improve the possibilities of retaining an acutely infected TJA.

MATERIALS AND METHODS

This technique, debridement antibiotic pearls and retention of the implant (DAPRI), aims to remove the intra-articular biofilm allowing a higher and prolonged local antibiotic concentration by using calcium sulphate antibiotic-added beads in a setting of acute (<4 weeks from symptoms onset) PJI with pathogen identification. The combination of three different surgical techniques (tumor-like synovectomy, argon beam/acetic acid application and chlorhexidine gluconate brushing) aims to remove the bacterial biofilm from the implant without explanting the original hardware.

RESULTS

In total, 62 patients met the acute infection criteria (<4 weeks of symptoms); there were 57 males and five females. The patients' average age at the time of treatment was 71 years (62-77) and the average BMI was 37 kg/m². The micro-organism, always identified through synovial fluid analysis (culture, multiplex PCR or Next Generation Sequencing), was an aerobic Gram + in 76% (S. Coag-Neg 41%; S. aureus 16%), Gram-in 10% (E. coli 4%) and anaerobic Gram + in 4%. The DAPRI treatment was performed at an average of 3 days from symptoms onset (1-7 days). All patients underwent a 12-week course of post-operative antibiotic therapy (6 weeks I.V. and 6 weeks oral). All patients were available at the 2-year minimum FU (24-84 months). A total of 48 (77.5%) patients were infection-free at the final FU, while 14 patients underwent 2-stage revision for PJI recurrence. In total, four patients (6.4%) had a prolonged drainage from the wound after placement of the calcium sulphate beads.

CONCLUSIONS

This study suggests that the DAPRI technique could represent a valid alternative to the classic DAIR procedure. The current authors do not recommend this procedure outside of the main inclusive criteria (acute scenario micro-organism identification).

Local Antibiotic Delivery Options in Prosthetic Joint Infection

Prosthetic Joint Infection (PJI) causes significant morbidity and mortality for patients globally. Delivery of antibiotics to the site of infection has potential to improve the treatment outcomes and enhance biofilm eradication. These antibiotics can be delivered using an intra-articular catheter or combined with a carrier substance to enhance pharmacokinetic properties. Carrier options include non-resorbable polymethylmethacrylate (PMMA) bone cement and resorbable calcium sulphate, hydroxyapatite, bioactive glass, and hydrogels. PMMA allows for creation of structural spacers used in multi-stage revision procedures, however it requires subsequent removal and antibiotic compatibility and the levels delivered are variable. Calcium sulphate is the most researched resorbable carrier in PJI, but is associated with wound leakage and hypercalcaemia, and clinical evidence for its effectiveness remains at the early stage. Hydrogels provide a versatile combability with antibiotics and adjustable elution profiles, but clinical usage is currently limited. Novel anti-biofilm therapies include bacteriophages which have been used successfully in small case series.

Bioglass obtained via one-pot synthesis as osseointegrative drug delivery system

Osseointegration is a fundamental process during which implantable biomaterial integrates with host bone tissue. The surgical procedure of biomaterial implantation is highly associated with the risk of bacterial infection. Thus, the research continues for biodegradable bone void fillers which are able to stimulate the bone tissue regeneration and locally deliver the antibacterial agent. Herein, we obtained bifunctional bioglass (BG) using novel, preoptimized, rapid one-pot synthesis. Following the ISO Standards, the influence of the obtained BG on osteoblast-mediated phenomena, such as osteoconduction and osteoinduction was assessed and compared to two commercial materials: bioactive glass powder 45S and bioactive glass powder 85S. Direct-contact tests revealed osteoblast adhesion to BG particles; whereas, tests on extracts confirmed high viability of cells incubated with BG extract. Analyses of gene expression, alkaline phosphatase activity, and calcium phosphates deposition confirmed the stimulation of early and late stages of osteoblast differentiation and mineralization. Additionally, an extended evaluation of intracellular calcium fluctuations revealed a possible correlation between osteoblast calcium uptake and extracellular matrix mineralization. Moreover, proposed bioglass exhibited satisfactory doxycycline adsorption capacity and release profile. The obtained results confirmed the bifunctionality of the proposed BG and indicated its potential as osseointegrative bone drug delivery system.

Intramedullary application of local antibiotic bullets for the treatment of long bone fracture related infection

PURPOSE

The optimal means of local antibiotic delivery for fracture related infection is unknown. Until now, intramedullary application of calcium sulphate based local antibiotics has been challenging. We report on the use of a newly available mode of preparation and delivery: the Stimulan Bullet Mat and Introducer (Biocomposites Ltd, Staffordshire, England).

METHODS

A retrospective analysis of prospectively collected data for infection cases at two separate tertiary referral institutions was performed. We included cases of long bone FRI with a retained intramedullary nail, treated with a single stage protocol of metalwork removal, debridement, local antibiotic application using the novel mould and applicator, with additional bony stabilisation and soft tissue reconstruction where required.

RESULTS

All 13 patients achieved infection remission rate with an average follow-up of 19.7 months (range 12-28). All 6 patients with infection around an unhealed fracture achieved union at an average 8 months (range 4-12) from debridement. No patients developed aseptic wound leak.

CONCLUSIONS

Antibiotic impregnated calcium sulphate can be used safely as part of a single stage treatment protocol for the treatment of long bone fracture related infection following intramedullary nailing. We have demonstrated high rates of infection remission and union, using a newly available intramedullary applicator.

Is long time to reimplantation a risk factor for reinfection in two-stage revision for periprosthetic infection? A systematic review of the literature

The two-stage revision arthroplasty is a common treatment option for chronic periprosthetic infection (PJI). The time to reimplantation (TTR) reported in the literature varies substantially from a few days to several hundred days. It is hypothesized that longer TTR could be associated with worse infection control after second stage. A systematic literature search was performed according to Preferred Reporting items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, in Pubmed, Cochrane Library and Web of Science Core Collection in clinical studies published until January 2023. Eleven studies investigating TTR as a potential risk factor for reinfection met the inclusion criteria (ten retrospective and one prospective study, published 2012-2022). Study design and outcome measures differed notably. The cutoff points above which TTR was regarded as "long" ranged from 4 to 18 weeks. No study observed a benefit for long TTR. In all studies, similar or even better infection control was observed for short TTR. The optimal TTR, however, is not yet defined. Larger clinical studies with homogeneous patient populations and adjustment for confounding factors are needed.

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.

Tailored therapeutic release from polycaprolactone-silica hybrids for the treatment of osteomyelitis: antibiotic rifampicin and osteogenic silicates

The treatment of osteomyelitis, a destructive inflammatory process caused by bacterial infections to bone tissue, is one of the most critical challenges of orthopedics and bone regenerative medicine. The standard treatment consists of intense antibiotic therapies combined with tissue surgical debridement and the application of a bone defect filler material. Unfortunately, commercially available candidates, such as gentamicin-impregnated polymethylmethacrylate cements, possess very poor pharmacokinetics (i.e., 24 hours burst release) and little to no regenerative potential. Fostered by the intrinsic limitations associated with conventional treatments, alternative osteostimulative biomaterials with local drug delivery have recently started to emerge. In this study, we propose the use of a polycaprolactone-silica sol-gel hybrid material as carrier for the delivery of rifampicin, an RNA-polymerase blocker often used to treat bone infections, and of osteostimulative silicate ions. The release of therapeutic agents from the material is dual, offering two separate and simultaneous effects, and decoupled, meaning that the kinetics of rifampicin and silicate releases are independent from each other. A series of hybrid formulations with increasing amounts of rifampicin was prepared. The antibiotic loading efficacy, as well as the release profiles of rifampicin and silicates were measured. The characterization of cell viability and differentiation of rat primary osteoblasts and antibacterial performance were also performed. Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli were selected due to their high occurrence in bone infections. Results confirmed that rifampicin can be successfully loaded within the hybrids without significant degradation and that it is possible to tailor the antibiotic release according to need. Once in a physiological environment, the rapid release of silicates was associated with optimal cell proliferation and the overexpression of osteoblastic differentiation. Simultaneously, rifampicin is delivered over the course of several weeks with significant inhibition of all tested strains. In particular, the materials caused a growth reduction of 7-10 orders of magnitude in Staphylococcus aureus, the major strain responsible for osteomyelitis worldwide. Our data strongly suggest that PCL/silica hybrids are a very promising candidate to develop bone fillers with superior biological performance compared to currently available options. Thanks to their unique synthesis route and their dual tailored release they can promote bone regeneration while reducing the risk of infection for several weeks upon implantation.

Role of Implantable Drug Delivery Devices with Dual Platform Capabilities in the Prevention and Treatment of Bacterial Osteomyelitis

As medicine advances and physicians are able to provide patients with innovative solutions, including placement of temporary or permanent medical devices that drastically improve quality of life of the patient, there is the persistent, recurring problem of chronic bacterial infection, including osteomyelitis. Osteomyelitis can manifest as a result of traumatic or contaminated wounds or implant-associated infections. This bacterial infection can persist as a result of inadequate treatment regimens or the presence of biofilm on implanted medical devices. One strategy to mitigate these concerns is the use of implantable medical devices that simultaneously act as local drug delivery devices (DDDs). This classification of device has the potential to prevent or aid in clearing chronic bacterial infection by delivering effective doses of antibiotics to the area of interest and can be engineered to simultaneously aid in tissue regeneration. This review will provide a background on bacterial infection and current therapies as well as current and prospective implantable DDDs, with a particular emphasis on local DDDs to combat bacterial osteomyelitis.

Antibacterial Honeycomb Scaffolds for Achieving Infection Prevention and Bone Regeneration

Surgical site infection (SSI) is a severe complication associated with orthopedic bone reconstruction. For both infection prevention and bone regeneration, the framework surface of osteoconductive and bioresorbable scaffolds must be locally modified by minimum antibacterial substances, without sacrificing the osteoconductivity of the scaffold framework. In this study, we fabricated antibacterial honeycomb scaffolds by replacing carbonate apatite, which is the main component of the scaffold, with silver phosphate locally on the scaffold surface via dissolution-precipitation reactions. When the silver content was 9.9 × 10^-4 wt %, the honeycomb scaffolds showed antibacterial activity without cytotoxicity and allowed cell proliferation, differentiation, and mineralization. Furthermore, the antibacterial honeycomb scaffolds perfectly prevented bacterial infection in vivo in the presence of methicillin-resistant Staphylococcus aureus, formed new bone at 2 weeks after surgery, and were gradually replaced with a new bone. Thus, the antibacterial honeycomb scaffolds achieved both infection prevention and bone regeneration. In contrast, severe infection symptoms, including abscess formation, osteolytic lesions, and inflammation, occurred 2 weeks after surgery when honeycomb scaffolds without silver phosphate modification were implanted. Nevertheless, the unmodified honeycomb scaffolds eliminated bacteria and necrotic bone through their scaffold channels, resulting in symptom improvement and bone formation. These results suggest that the honeycomb structure is inherently effective in hindering bacterial growth. This novel insight may contribute to the development of antibacterial scaffolds. Moreover, our modification method is useful for providing antibacterial activity to various biomaterials.

Potential New Treatments for Knee OA: A Prospective Review of Registered Trials

We aimed to evaluate potential new treatments for knee osteoarthritis (OA). The National Institute of Health ClinicalTrials.gov database was searched for “Osteoarthritis, Knee”. We found 565 ongoing interventional studies with a total planned enrollment of 111,276 subjects. Ongoing studies for knee OA represent a very small fraction of the registered clinical trials, but they are over a quarter of all knee trials and over two thirds of all OA studies. The most researched topic was arthroplasty, with aspects such as implant design changes, cementless fixation, robotic guidance, pain management, and fast track recovery. Intraarticular injections focused on cell therapies with mesenchymal stem cells sourced from adipose tissue, bone marrow, or umbilical cord. We could see the introduction of the first disease modifying drugs with an impact on knee OA, as well as new procedures such as geniculate artery embolization and geniculate nerve ablation.