Aims

Extracellular matrix (ECM) is a critical determinant of tissue mechanobiology, yet remains poorly characterized in joint tissues beyond cartilage in osteoarthritis (OA). This review aimed to define the composition and architecture of non-cartilage soft joint tissue structural ECM in human OA, and to compare the changes observed in humans with those seen in animal models of the disease.

Aims

Electromagnetic induction heating has demonstrated in vitro antibacterial efficacy over biofilms on metallic biomaterials, although no in vivo studies have been published. Assessment of side effects, including thermal necrosis of adjacent tissue, would determine transferability into clinical practice. Our goal was to assess bone necrosis and antibacterial efficacy of induction heating on biofilm-infected implants in an in vivo setting.

Introduction. The objective of the work is construction of a multi-bioactive scaffold based on that allows a space/time control over the regeneration of damaged bones by Medication-Related Osteonecrosis of the Jaw using a minimal invasive approach based on the injection of the fast-degrading pro neuro and angiogenic ELR (Elastin-Like Recombinamers) based hydrogels. Method. Chemical crosslinking facilitated the creation of multi-bioactive scaffolds using ELRs with reactive groups. Cell-loaded multi-bioactive scaffolds, prepared and incubated, underwent evaluation for adhesion, proliferation, angiogenic, and neurogenic potential. In vitro assessments utilized immunofluorescence staining and ELISA assays, while live-recorded monitoring and live-dead analysis ensured cytocompatibility. In rat and rabbit models, preformed scaffolds were subcutaneously implanted, and the regenerative process was evaluated over time. Rabbit models with MRONJ underwent traditional or percutaneous implantation, with histological evaluation following established bone histological techniques. Result. A 3D scaffold using ELR that combines various peptides with different degradation rates to guide both angiogenesis and neurogenesis has been developed. Notably, scaffolds with different degradation rates promoted distinct patterns of vascularization and innervation, facilitating integration with host tissue. This work demonstrates the potential for tailored tissue engineering, where the scaffold's bioactivities and degradation rates can control angiogenesis and neurogenesis. In an animal model of medication-related osteonecrosis of the jaw (MRONJ), the scaffold showed promising results in promoting bone regeneration in a necrotic environment, as confirmed by histological and imaging analyses. This study opens avenues for novel tissue-engineering strategies where precise control over vascularization and nerve growth is crucial. Conclusion. A groundbreaking dual approach, simultaneously targeting angiogenesis and innervation, addresses the necrotic bone in MRONJ syndrome. Vascularization and nerve formation play pivotal roles in driving reparative elements for bone regeneration. The scaffold achieves effective time/space control over necrotic bone regeneration. The authors are grateful for funding from the Spanish Government (PID2020-118669RA-I00)

Introduction. The healing of rotator cuff injuries poses significant challenges, primarily due to the complexity of recreating the native tendon-to-bone interface, characterized by highly organized structural and compositional gradients. Addressing this, our innovative approach leverages bioprinted living tissue constructs, incorporating layer-specific growth factors (GFs) to facilitate enthesis regeneration. This method aims to guide in situ zonal differentiation of stem cells, closely mirroring the natural enthesis tissue architecture. Method. Our strategy involves the utilization of advanced bioprinting technology to fabricate living tissue constructs. These constructs are meticulously designed with embedded microsphere-based delivery carriers, ensuring the sustained release of tenogenic, chondrogenic, and osteogenic growth factors. This layer-specific release mechanism is tailored to promote the precise differentiation of stem cells across different regions of the construct, aligning with the gradient nature of enthesis tissues. Result. In vitro studies demonstrated that our layer-specific tissue constructs significantly outperformed basal constructs without GFs, achieving region-specific differentiation of stem cells. More critically, in a rabbit model of rotator cuff tear, these bioprinted living tissue constructs expedited enthesis regeneration. Key outcomes included improved biomechanical properties, enhanced collagen deposition and alignment, and the formation of a gradient fibrocartilage interface with aligned collagen fibrils. After 12 weeks, the constructs achieved an ultimate load failure of 154.3 ± 9.5 N resembling that of native enthesis tissues, marking a notable achievement in tissue engineering. Conclusion. Our exploration introduces a viable and innovative strategy for engineering living tissue constructs that exhibit region-specific differentiation capabilities. This approach holds significant promise for the functional repair of gradient enthesis tissues, potentially revolutionizing the treatment of rotator cuff injuries by closely replicating the natural tendon-to-bone interface, thus offering a promising avenue for future clinical applications

Aims

This study aimed to demonstrate the promoting effect of elastic fixation on fracture, and further explore its mechanism at the gene and protein expression levels.

Aims

Bacteriophages infect, replicate inside bacteria, and are released from the host through lysis. Here, we evaluate the effects of repetitive doses of the Staphylococcus aureus phage 191219 and gentamicin against haematogenous and early-stage biofilm implant-related infections in Galleria mellonella.

Aims

To explore the efficacy of extracorporeal shockwave therapy (ESWT) in the treatment of osteochondral defect (OCD), and its effects on the levels of transforming growth factor (TGF)-β, bone morphogenetic protein (BMP)-2, -3, -4, -5, and -7 in terms of cartilage and bone regeneration.

The April 2024 Foot & Ankle Roundup³⁶⁰ looks at: Safety of arthroscopy combined with radial extracorporeal shockwave therapy for osteochondritis of the talus; Bipolar allograft transplantation of the ankle; Identifying risk factors for osteonecrosis after talar fracture; Balancing act: immediate versus delayed weightbearing in ankle fracture recovery; Levelling the field: proximal supination osteotomy’s efficacy in severe and super-severe hallux valgus; Restoring balance: how adjusting the tibiotalar joint line influences movement after ankle surgery.

Aims. Fracture-related infection (FRI) is commonly classified based on the time of onset of symptoms. Early infections (< two weeks) are treated with debridement, antibiotics, and implant retention (DAIR). For late infections (> ten weeks), guidelines recommend implant removal due to tolerant biofilms. For delayed infections (two to ten weeks), recommendations are unclear. In this study we compared infection clearance and bone healing in early and delayed FRI treated with DAIR in a rabbit model. Methods. Staphylococcus aureus was inoculated into a humeral osteotomy in 17 rabbits after plate osteosynthesis. Infection developed for one week (early group, n = 6) or four weeks (delayed group, n = 6) before DAIR (systemic antibiotics: two weeks, nafcillin + rifampin; four weeks, levofloxacin + rifampin). A control group (n = 5) received revision surgery after four weeks without antibiotics. Bacteriology of humerus, soft-tissue, and implants was performed seven weeks after revision surgery. Bone healing was assessed using a modified radiological union scale in tibial fractures (mRUST). Results. Greater bacterial burden in the early group compared to the delayed and control groups at revision surgery indicates a retraction of the infection from one to four weeks. Infection was cleared in all animals in the early and delayed groups at euthanasia, but not in the control group. Osteotomies healed in the early group, but bone healing was significantly compromised in the delayed and control groups. Conclusion. The duration of the infection from one to four weeks does not impact the success of infection clearance in this model. Bone healing, however, is impaired as the duration of the infection increases. Cite this article: Bone Joint Res 2024;13(3):127–135

Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses

Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses

Healing after bone fracture is assessed by frequent radiographs, which expose patients to radiation and lacks behind biological healing. This study aimed to investigate whether the electrical impedance using electrical impedance spectroscopy correlated to quantitative scores of bone healing obtained from micro-CT and mechanical bending test.

Eighteen rabbits were subjected to tibial fracture that was stabilized with external fixator. Two electrodes were positioned, one electrode placed within the medullary cavity and the other on the lateral cortex, both three millimeters from the fracture site. Impedance was measured daily across the fracture site at a frequency range of 5 Hz to 1 MHz. The animals were divided into three groups with different follow-up time: 1, 3 and 6 weeks for micro-CT (Bone volume/tissue volume (BV/TV, %)) and mechanical testing (maximum stress (MPa), failure energy (kJ/cm3), young modulus (Mpa)).

There was a statistically significant correlation between last measured impedance at 5 Hz frequency immediately prior to euthanasia and BV/TV of callus (−0.68, 95%CI: (−0.87; −0.31)). Considering the mechanical testing with three-point bending, no significant correlation was found between last measured impedance at 5 Hz frequency immediately prior to euthanasia and maximum stress (−0.35, 95%CI: (−0.70; 0.14)), failure energy (−0.23, 95%CI: (−0.63; 0.26)), or young modulus (−0.28, 95%CI: (−0.66; 0.22)).

The significant negative correlation between impedance and BV/TV might indicate that impedances correlate with the relative bone volume in the callus site. The lack of correlation between impedance and mechanical parameters when at the same time observing a correlation between impedance and days since operation (0-42 days), might indicate that the impedance can measure biological changes at an earlier time point than rough mechanical testing.

Aims

Several artificial bone grafts have been developed but fail to achieve anticipated osteogenesis due to their insufficient neovascularization capacity and periosteum support. This study aimed to develop a vascularized bone-periosteum construct (VBPC) to provide better angiogenesis and osteogenesis for bone regeneration.

Aim. The time to onset of symptoms after fracture fixation is still commonly used to classify fracture-related infections (FRI). Early infections (<2 weeks) can often be treated with debridement, systemic antibiotics, irrigation, and implant preservation (DAIR). Late infections (>10 weeks) typically require implant removal as mature, antibiotic-tolerant biofilms have formed. However, the recommendations for delayed infections (2–10 weeks) are not clearly defined. Here, infection healing and bone healing in early and delayed FRI is investigated in a rabbit model with a standardized DAIR procedure. Method. Staphylococcus aureus was inoculated into 17 rabbits after plate osteosynthesis in a humerus osteotomy. The infection developed either one week (early group, n=6) or four weeks (delayed group, n=6) before a standardized DAIR procedure and microbiological analysis were performed. Systemic antibiotics were administered for six weeks (two weeks: Nafcillin+Rifampin, four weeks: Levofloxacin+Rifampin). A control group (n=5) also underwent a revision operation (debridement and irrigation) after four weeks, but received no antibiotic treatment. Rabbits were euthanized seven weeks after the revision operation. Bone healing was assessed using a modified radiographic union score for tibial fractures (mRUST). After euthanasia, a quantitative microbiological examination of the entire humerus, adjacent soft tissues, and implants was performed. Results. All animals were infected at the time of revision surgery, with the bacterial load in the early group (especially in soft tissues) being greater than in the delayed group and control group. This indicates infiltration of bacteria into areas that are more difficult to reach after four weeks of debridement. The infection was eradicated in all animals in both the early and delayed groups at euthanasia, but not in the control group (CFU median (IQR): 2.1×10. 7. (1.3×10. 7. -2.6×10. 7. ). The osteotomy healed in the early group, while bone healing was significantly impaired in both the delayed group and control group (mRUST median (IQR): early group: 16 (14–16), delayed group: 7.5 (6–10), control: 7 (5.5–9); early vs. delayed: p=0.0411, early vs. control p=0.0065). Conclusion. The maturation of the infection between the first and fourth week does not affect the success of infection eradication in this rabbit FRI model. However, bone healing appears to be impaired with increasing duration of infection

Aims

Arthroscopic microfracture is a conventional form of treatment for patients with osteochondritis of the talus, involving an area of < 1.5 cm². However, some patients have persistent pain and limitation of movement in the early postoperative period. No studies have investigated the combined treatment of microfracture and shortwave treatment in these patients. The aim of this prospective single-centre, randomized, double-blind, placebo-controlled trial was to compare the outcome in patients treated with arthroscopic microfracture combined with radial extracorporeal shockwave therapy (rESWT) and arthroscopic microfracture alone, in patients with ostechondritis of the talus.

Treatment of bone infection often includes a burdensome two-stage revision. After debridement, contaminated implants are removed and replaced with a non-absorbable cement spacer loaded with antibiotics. Weeks later, the spacer is exchanged with a bone graft aiding bone healing. However, even with this two-stage approach infection persists. In this study, we investigated whether a novel 3D-printed, antibiotic-loaded, osteoinductive calcium phosphate scaffold (CPS) is effective in single-stage revision of an infected non-union with segmental bone loss in rabbits.

A 5 mm defect was created in the radius of female New Zealand White rabbits. The bone fragment was replaced, stabilized with cerclage wire and inoculated with Staphylococcus aureus (MSSA). After 4 weeks, the infected bone fragment was removed, the site debrided and a spacer implanted. Depending on group allocation, rabbits received: 1) PMMA spacer with gentamycin; 2) CPS loaded with rifampin and vancomycin and 3) Non-loaded CPS. These groups received systemic cefazolin for 4 weeks after revision. Group 4 received a loaded CPS without any adjunctive systemic therapy (n=12 group1-3, n=11 group 4). All animals were euthanized 8 weeks after revision and assessed by quantitative bacteriology or histology. Covariance analysis (ANCOVA) and multiple regression were performed.

All animals were culture positive at revision surgery. Half of the animals in all groups had eliminated the infection by end of study. In a historical control group with empty defect and no systemic antibiotic treatment, all animals were infected at euthanasia. There was no significant difference in CFU counts between groups at euthanasia.

Our results show that treating an osteomyelitis with segmental bone loss either with CPS or PMMA has a similar cure rate of infection. However, by not requiring a second surgery, the use of CPS may offer advantages over non-resorbable equivalents such as PMMA.

In chronically infected fracture non-unions, treatment requires extensive debridement to remove necrotic and infected bone, often resulting in large defects requiring elaborate and prolonged bone reconstruction. One approach includes the induced membrane technique (IMT), although the differences in outcome between infected and non-infectious aetiologies remain unclear. Here we present a new rabbit humerus model for IMT secondary to infection, and, furthermore, we compare bone healing in rabbits with a chronically infected non-union compared to non-infected equivalents.

A 5 mm defect was created in the humerus and filled with a polymethylmethacrylate (PMMA) spacer or left empty (n=6 per group). After 3 weeks, the PMMA spacer was replaced with a beta-tricalcium phosphate (chronOs, Synthes) scaffold, which was placed within the induced membrane and observed for a further 10 weeks. The same protocol was followed for the infected group, except that four week prior to treatment, the wound was inoculated with Staphylococcus aureus (4×10⁶ CFU/animal) and the PMMA spacer was loaded with gentamicin, and systemic therapy was applied for 4 weeks prior to chronOs application.

All the animals from the infected group were culture positive during the first revision surgery (mean 3×10⁵ CFU/animal, n= 12), while at the second revision, after antibiotic therapy, all the animals were culture negative. The differences in bone healing between the non-infected and infected groups were evaluated by radiography and histology. The initially infected animals showed impaired bone healing at euthanasia, and some remnants of bacteria in histology. The non-infected animals reached bone bridging in both empty and chronOs conditions.

We developed a preclinical in vivo model to investigate how bacterial infection influence bone healing in large defects with the future aim to explore new treatment concepts of infected non-union.

There is no optimal therapy to stop or cure chondral degeneration in osteoarthritis (OA). Beside cartilage, subchondral bone is involved. The often sclerotic bone is mechanically less solid which in turn influences negatively chondral quality. Microfracturing as therapeutic technique aims to enhance bone quality but is applied only in smaller cartilage lesions. The osteoproliferative properties of Magnesium (Mg) have been shown repeatedly^1-3. The present study examined the influence of micro-scaled Mg cylinders compared to sole drilling in an OA model.

Ten New Zealand White rabbits underwent anterior crucial ligament transection. During 12 weeks after surgery, the animals developed OA as previously described⁴. In a second surgery, half of the animals received 20 drill holes (ø 0.5mm) and the other half received 20 drill holes, which were additionally filled with one Mg cylinder each. Extracapsular plication was performed in all animals. During the follow-up of 8 weeks three µ-computed tomographic (µCT) scans were performed: immediately after surgery and after four and eight weeks. Changes of bone volume, trabecular thickness and bone density were calculated and compared.

µCT evaluation showed an increase in bone volume and trabecular thickness in both groups. This increase was significantly higher in rabbits which received Mg cylinders showing thrice as high values for both parameters (bone volume: Mg group +44.5%, drilling group +15.1%, p≤0.025; trabecular thickness: Mg group +53.2%, drilling group +16.9%, p≤0.025). Also bone density increased in both groups, but on a distinctly lower level and with no significant difference.

Although profound higher bone volume was found after implantation of Mg cylinders, µCT showed similar levels of bone density indicating adequate bone quality in this OA model. Macroscopic and histological evaluation of cartilage condition have to reveal possible impact on OA progression. Additionally, current examination implement different alloys and influence on lameness.

Osteoarthritis (OA), the most prevalent chronic joint disease, represents a relevant social and economic burden worldwide. Human umbilical cord mesenchymal stem cells (HUCMSCs) have been used for injection into the joint cavity to treat OA. The aim of this article is to clarify whether Huc-MSCs derived exosomes could inhibit the progression of OA and the mechanism in this process. A rabbit OA model was established by the transection of the anterior cruciate ligament. The effects of HUCMSCs or exosomes derived from HUCMSCs on repairing articular cartilage of knee osteoarthritis was examined by micro-CT. Immunohistochemical experiments were used to confirm the expression of relevant inflammatory molecules in OA. In vitro experiments, Transwell assay was used to assess the migration of macrophages induced by TNF-a. Results showed that a large number of macrophages migrated in arthcular cavity in OA model in vivo, while local injection of HUCMSCs and exosomes did repair the articular cartilage. Immunohistochemical results suggested that the expression of CCL2 and CD68 in the OA rabbit model increased significantly, but was significantly reduced by HUCMSCs or exosomes. Transwell assay showed that both HUCMSCs and exosomes can effectively inhibit the migration of macrophage. In conclusion, the exosomes derived by HUCMSCs might might rescue cartilage defects in rabbit through its anti-inflammatory effects through inhibiting CCL2

In this study, we developed biocompatible adhesive which enables implanted chondrogenic-enhanced hASCs being strongly fixed to the lesion site of defected cartilage. The bioengineered mussel adhesive protein (MAP) was produced and purified using a bacterial expression system as previously reported. The cell encapsulated coacervate was formulated with two polyelectrolyte, the MAP and 723kDa hyaluronic acid (HA). MAP formed liquid microdroplets with HA and subsequently gelated into microparticles, which is highly viscous and strongly adhesive. The MAP with chondro-induced hASCs were implanted on the osteochondral defect created in the patellar groove/condyle of OA-induced rabbits. Rabbits were allocated to three different groups as follows: Group1 – Fibrin only; Group2 – Fibrin with hASCs (1.5×10. 6. chondro-induced hASCs); Group3; MAP with hASCs. The implanted cells were labeled with a fluorescent dye for in vivo visualization. After 35 days, fluorescent signals were more potently detected for MAP with hASCs group than Fibrin with hASCs group in osteochondral defect model. Moreover, histological assessment showed that MAP with hASCs group had the best healing and covered with hyaline cartilage-like tissue. The staining image shows that MAP with hASCs group were filled with perfectly differentiated chondrocytes. Although Fibrin with hASCs group had better healing than fibrin only group, it was filled with fibrous cartilage which owes its flexibility and toughness. As MAP with hASCs group has higher possibility of differentiating to complete cartilage, Fibrin only group and Fibrin with hASCs group have failed to treat OA by rehabilitating cartilage. In order to clarify the evidence of remaining human cell proving efficacy of newly developed bioadhesive, human nuclear staining was proceeded with sectioned rabbit cartilage tissue. The results explicitly showed MAP with hASCs group have retained more human cells than Fibrin only and Fibrin with hASCs groups. We investigated the waterproof bioadhesive supporting transplanted cells to attach to defect lengthily in harsh environment, which prevents cells from leaked to other region of cartilage. Collectively, the newly developed bio-adhesive, MAP, could be successfully applied in OA treatment as a waterproof bioadhesive with the capability of the strong adhesion to target defect sites