Physicochemical and biological evaluation of Bioinspired Zea mays starch-derived self-healing composite hydrogels with dynamic boronate crosslinks for critical bone defects

Introduction and importanceFracture with a critical bone loss is associated with a profound burden of disease impact. Although there are several options exist for its treatment, but still those reconstructive procedures are technically demanding, relatively expensive and sometimes the result is less than what was expected. The objective of this study is to report a rare case of spontaneous healing of a critical radial bone defect in an adolescent. Case presentationWe reported a 15 year old boy with a segmental open fracture of left radius, open fracture of left distal shaft ulna and closed fracture of left intercondylar humerus. The middle fragment of a fractured radius was extruded out, pulled out and then thrown away by his parent. Debridement, open reduction, and internal fixation for ulna were performed as well as reposition and internal fixation for the intercondylar humerus fracture. The plan was to wait until the ulnar fracture and intercondylar fracture to heal without any sign of infection and proceed to overcome the radial critical bone defect. This case report had been reported in line with SCARE criteria. The patient showed up seven months later with solid union of the critical radius bone defect and fully functioning hand with only slight limitation in pronation. Clinical discussionOsteogenesis in fracture requires osteogenic cells, osteoinductive components, osteoconductive scaffold, and stability. Despite the fact that critical bone defect poses great challenge for its management, intact periosteum and sufficient soft tissue perfusion were able to provide those biologic requirements adequately for fracture healing and ensure spontaneous healing of a traumatic critical bone loss in adolescent without any reconstructive procedure. ConclusionSpontaneous healing in critical bone defect is possible, provided all the favorable factors present to support this phenomenon.

Contemporary reconstructive approaches for critical size bone defects carry significant disadvantages. As a result, clinically driven research has focused on the development and translation of alternative therapeutic concepts. Scaffold-guided tissue regeneration (SGTR) is an emerging technique to heal critical size bone defects. However, issues synchronizing scaffold vascularization with bone-specific regenerative processes currently limit bone regeneration for extra large (XL, 19 cm3) critical bone defects. To address this issue, we developed a large animal model that incorporates a corticoperiosteal flap (CPF) for sustained scaffold neovascularization and bone regeneration. In 10 sheep, we demonstrated the efficacy of this approach for healing medium (M, 9 cm3) size critical bone defects as demonstrated on plain radiography, microcomputed tomography, and histology. Furthermore, in two sheep, we demonstrate how this approach can be safely extended to heal XL critical size defects. This article presents an original CPF technique in a well-described preclinical model, which can be used in conjunction with the SGTR concept, to address challenging critical size bone defects in vivo. Impact statement This article describes a novel scaffold-guided tissue engineering approach utilizing a corticoperiosteal flap for bone healing in critical size long bone defects. This approach will be of use for tissue engineers and surgeons exploring vascularized tissue transfer as an option to regenerate large volumes of bone for extensive critical size bone defects both in vivo and in the clinical arena.

We examined whether recombinant human bone morphogenetic protein-2 (rhBMP-2) when applied to collagen membranes, would reinforce them during guided bone regeneration. Four critical cranial bone defects were created and treated in 30 New Zealand white rabbits, including a control group, critical defect only; group 1, collagen membrane only; group 2, biphasic calcium phosphate (BCP) only; group 3, collagen membrane + BCP; group 4, collagen membrane with rhBMP-2 (1.0 mg/mL); group 5, collagen membrane with rhBMP-2 (0.5 mg/mL); group 6, collagen membrane with rhBMP-2 (1.0 mg/mL) + BCP; and group 7, collagen membrane with rhBMP-2 (0.5 mg/mL) + BCP. After a 2-, 4-, or 8-week healing period, the animals were sacrificed. The combination of collagen membranes with rhBMP-2 and BCP yielded significantly higher bone formation rates compared to the other groups (control group and groups 1–5 < groups 6 and 7; p < 0.05). A 2-week healing period yielded significantly lower bone formation than that at 4 and 8 weeks (2 < 4 = 8 weeks; p < 0.05). This study proposes a novel GBR concept in which rhBMP-2 is applied to collagen membranes outside instead of inside the grafted area, thereby inducing quantitatively and qualitatively enhanced bone regeneration in critical bone defects.

Bone defects are a challenging clinical situation, and the development of hydroxyapatite-based biomaterials is a prolific research field that, in addition, can be joined by stem cells and growth factors in order to deal with the problem. This study compares the use of synthetic hydroxyapatite and xenograft, used pure or enriched with bone marrow mononuclear fraction for the regeneration of critical size bone defects in rat calvaria through histomorphometric (Masson’s staining) and immunohistochemical (anti-VEGF, anti-osteopontin) analysis. Forty young adult male rats were divided into five groups (n = 8). Animals were submitted to critical size bone defects (Ø = 8 mm) in the temporoparietal region. In the control group, there was no biomaterial placement in the critical bone defects; in group 1, it was filled with synthetic hydroxyapatite; in group 2, it was filled with xenograft; in group 3, it was filled with synthetic hydroxyapatite, enriched with bone marrow mononuclear fraction (BMMF), and in group 4 it was filled with xenograft, enriched with BMMF. After eight weeks, all groups were euthanized, and histological section images were captured and analyzed. Data analysis showed that in groups 1, 2, 3 and 4 (received biomaterials and biomaterials plus BMMF), a significant enhancement in new bone matrix formation was observed in relation to the control group. However, BMMF-enriched groups did not differ from hydroxyapatite-based biomaterials-only groups. Therefore, in this experimental model, BMMF did not enhance hydroxyapatite-based biomaterials’ potential to induce bone matrix and related mediators.

Diaphyseal bone defect represents a significant problem for orthopaedic surgeons and patients. In order to improve and fasten bone regenerating process we implanted HA biodegradable magnetized scaffolds in a large animal model critical bone defect. A critical long bone defect was created in 6 sheep metatarsus diaphysis; then we implanted a novel porous ceramic composite scaffold (20.0 mm in length; 6.00 mm inner diameter and 17.00 mm outer diameter), made of Hydroxyapatite that incorporates magnetite (HA/Mgn 90/10), proximally fixated by two small cylindrical permanent parylene coated NdFeB magnets (one 6.00 mm diameter magnetic rod firmly incorporated into the scaffold and one 8.00 mm diameter magnetic rods fitted into proximal medullary canal, both 10.00 mm long); to give stability to the complex bone-scaffold-bone, screws and plate was used as a bridge. Scaffolds biocompatibility was previously assessed in vitro using human osteoblast-like cells. Magnetic forces through scaffold were calculated by finite element software (COMSOL Multiphysics, AC/DC Model). One week after surgery, magnetic nanoparticles functionalized with vascular endothelial growth factor (VEGF) were injected at the mid portion of the scaffold using a cutaneous marker positioned during surgery as reference point. After sixteen weeks, sheep were sacrificed to analyze metatarsi. Macroscopical, radiological and microCT examinations were performed. Macroscopical examination shows bone tissue formation inside scaffold pores and with complete coverage of scaffolds, in particular at magnetized bone-scaffold interface. X-rays show a good integration of the scaffold with a good healing process of critical bone defect, and without scaffolds mobilization. These datas were confirmed by the microCT that shown new formation of bone inside the scaffolds, in particular at magnetized bone-scaffold interface. These preliminary results lead our research to exploiting magnetic forces to stimulate bone formation, as attested in both in vitro and in vivo models and to improve fixation at bone scaffold interface, as calculated by finite element software, and moreover to guide targeted drug delivery without functionalized magnetic nanoparticles dissemination in all body. Histological analysis will be performed to confirm and quantify bone tissue regeneration at both interfaces.

According to statistical data from the National Military Medical Clinical Center for the period from February to May 2022, bone defects in gunshot fractures accounted for 76 % of cases, with defects exceeding 6 cm — classified as critical — found in 28 % of cases. Currently, the "gold standard" for reconstructing critical bone defects is the induced membrane technique, also known as the two-stage Masquelet technique. The most promising substitute for autologous bone is considered to be biphasic bioactive ceramics. In this study, we aimed to evaluate the feasibility of reconstructing critical bone defects resulting from combat trauma using a modified bioactive ceramic-autograft mixture during the second stage of the Masquelet technique, combined with additive manufacturing technologies. The study included a sample of 36 patients with critical bone defects who underwent reconstruction using the Masquelet technique. During the second stage, the defect was filled with a mixture of calcium phosphate ceramics (CPC) and autologous cancellous bone. We analyzed the treatment outcomes of patients with critical bone defects caused by combat-related injuries over the past 2.5 years who received treatment at the Dobrobut Medical Center. The evaluation criteria included pain levels, range of motion, axial load capacity, functional recovery (work capacity), and radiological signs of callus formation, deformities, graft migration, or remodeling. After 12 months of follow-up: Complete functional recovery (clinically and in range of motion) was achieved in 28 (78 %) patients. Partial functional recovery was observed in 7 (17 %) patients. Significant functional impairment requiring additional surgical interventions occurred in 1 (5 %) patient. Conclusions. Based on our experience, the use of a CPC-autograft mixture in the two-stage reconstruction of critical diaphyseal bone defects provides positive treatment outcomes in most clinical cases. The integration of 3D modeling and biodegradable materials enhances the range of possibilities for performing bone grafting procedures and simplifies technical challenges in reconstructive surgery.

The objective of this study was to investigate whether porous beads with a leaf-stacked scaffold loaded with bone morphogenetic protein-2, with sustained release for up to four weeks, were beneficial to a dog model of critical long bone defects and capable of promoting bone regeneration without side effects. Critical long bone defects were created in the femoral diaphyses of 21 dogs. Each critical defect was fixed with an intramedullary pin and an universal locking plate. Leaf-stacked scaffold beads were implanted into the defect, which was covered with a membrane. Nineteen samples were evaluated 4, 8, and 12 weeks after surgery using simple radiographs, serum chemistry measurements, histological staining, and gene expression analysis. Sustained bone morphogenetic protein-2 release from the leaf-stacked scaffold continued for four weeks and consistently affected the expression of early and late osteogenesis factors. The results suggest that sustained bone morphogenetic protein-2 release is effective for bone regeneration, with minimal side effects.

IntroductionManaging post-traumatic critical bone defects in the tibia remains challenging. Vascularised free fibula grafts (VFFG) are an attractive option due to their versatility and ability to integrate with host bone. However, they are challenging, and their role compared to alternative techniques, such as bone transport and Masquelet, remains unclear. This study aims to assess the safety and effectiveness of free fibula flaps in reconstructing critical tibia defects following trauma.Materials and methodsFive databases were searched for English-language studies from inception until August 2024. Inclusion criteria involved adult patients undergoing VFFG to the tibia for trauma-induced bone defects. Case reports and studies involving non-traumatic and/or critical bone injury and/or those not undergoing fibula transfer were excluded. Bias was assessed using the ROBINS-I tool.ResultsFifteen studies involving 83 patients with a mean age of 35.07 ± 12.16 (range: 18–65) were included. Ipsilateral fibula transfer was preferred (n = 13, 80%), of and 89.7% fibulas (n = 35) were transferred using a single-barrel approach. The average union rate was 93.08% (95% CI: 86.56, 99.61) across the 74 patients where union outcomes were reported. Flap survival was 100% in seven studies, whilst two studies reported lower survival rates, the lowest being 50%. The overall complication rate was 39.98% (95% CI: 28.25, 51.71), with stress fractures occurring in 35.5% (n = 16) of cases. Revision rates varied from 10 to 40%. The risk of bias was high in 12 studies, and only three studies had a moderate risk. Four studies compared VFFG to alternative management strategies.ConclusionVascularised free fibula grafts are effective for reconstructing large segmental tibia defects post-trauma, achieving high union and flap survival rates. However, complication rates are high, and study heterogeneity limits definitive conclusions on the technique's superiority. Further prospective comparative studies are required to characterise the role of VFFG.How to cite this articleHow to cite this article: Glynou SP, Georgiannakis A, Ardolino D, et al. Vascularised Fibula Transfer for Post-traumatic Critical Tibial Bone Defects: A Systematic Review. Strategies Trauma Limb Reconstr 2025;20(1):37–46.

The effect of local delivery of strontium ranelate (SR) on bone regeneration of critical size bone defects filled with collagen sponge was evaluated. Bone defects of 5 mm diameter created in rat calvaria were filled with collagen sponge (C); collagen sponge with 5 mM Sr2+ SR (C5SR) or collagen sponge with 50 mM Sr2+ SR (C50SR). After 2, 4, and 6 weeks, bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were evaluated by computed microtomography. At 6 weeks, histological analysis was performed. Intragroup comparisons were made by the Friedman test, while comparisons between groups were made by Kruskal-Wallis test (α = 5%). All groups showed increased BV, BS, Tb.Th, and Tb.N over time, but only C50SR promoted the reduction of Tb.Sp (p < 0.05). No significant differences between groups were detected at weeks 2 and 4. However, C50SR showed the highest values of BV, BS, and Tb.Th at 6 weeks (p < 0.05). Histological analysis revealed connective tissue in C and C5SR and immature bone tissue in C50SR. Local delivery of SR 50 mM Sr2+ associated with collagen sponge increased and accelerated bone regeneration in critical bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 333-341, 2018.

Optimize the pore size-pore distribution-pore geometry-porosity of 3D-printed porous tantalum to obtain optimal critical bone defect repair capability

Bone defects are repaired using either natural or synthetic bone grafts. Poly(ϵ-caprolactone) (PCL), β-tricalcium phosphate (TCP), and poly(lactic-co-glycolic acid) (PLGA) are widely used as synthetic materials for tissue engineering. This study aimed to investigate the bone-healing capacity of PCL/PLGA/duck beak scaffold in critical bone defects and the oxidative stress status of the graft site in a rabbit model. The in vivo performance of 48 healthy New Zealand White rabbits, weighing between 2.5 and 3.5 kg, was evaluated. The rabbits were assigned to the following groups: group 1 (control), group 2 (PCL/PLGA hybrid scaffolds), group 3 (PCL/PLGA/TCP hybrid scaffolds), and group 4 (PCL/PLGA/DB hybrid scaffolds). A 5 mm critical defect was induced in the diaphysis of the left radius. X-ray, micro-CT, and histological analyses were conducted at (time 0) 4, 8, and 12 weeks after implantation. Furthermore, bone formation markers (bone-specific alkaline phosphatase, carboxyterminal propeptide of type I procollagen, and osteocalcin) were measured and oxidative stress status was determined. X-ray, micro-CT, biochemistry, and histological analyses revealed that the PCL/PLGA/duck beak scaffold promotes new bone formation in rabbit radius by inducing repair, suggesting that it could be a good option for the treatment of fracture.

The optimum fixation device for the critical size bone defect is not established yet. A reliable, feasible and low-cost fixation device for the long-term maintenance of a critical bone defect. A custom-made plate made of poly-methyl-methacrylate was used for the fixation of a critical defect of rats' femurs. The screws were securely fixing both on the plate and the bone. A three point bending test, aimed to resemble the in vivo loading pattern, a Finite Element Analysis and a 24-week in vivo monitoring of the integrity of the plate fixation were utilized. The plate has linear and reproducible behavior. It presents no discontinuities in the stress field of the fixation. Its properties are attributed to the material and the locking principle. It fails beyond the level of magnitude of the normal ambulatory loads. In vivo, 100% of the plates maintained the bone defect intact up to 12 weeks and 85% of them at 24 weeks. This novel locking plate shows optimal biomechanical performance and reliability with high long-term in vivo survival rate. It is fully implantable, inexpensive and easily manufactured. It can be qualified for long term critical defect fixation in bone regeneration studies.

IntroductionThis study aimed to assess the efficacy of adipose-derived mesenchymal stem cell exosomes (ASCs exosome) and platelet-rich fibrin (PRF) in treating critical long bone defects in Sprague-Dawley rats. Critical long bone defects, defined as exceeding 2 cm or 50% of the bone diameter, often pose a healing challenge. While autologous bone grafts have been considered, they have shown unreliable results and donor-site complications, necessitating alternative treatments.MethodsThe research followed a quasi-experimental post-test only control group design involving 30 male Sprague-Dawley rats. The rats were divided into five groups and subjected to femur bone defect creation, internally fixed with a 1.4 mm K-wire, and treated with various combinations of hydroxyapatite (HA), bone graft (BG), ASCs exosome, and PRF. Histomorphometry and BMP-2 gene expression analysis were performed to evaluate bone healing.Results and DiscussionThe results indicated that the group treated with HA + BG + ASCs exosome (group IV) exhibited the highest BMP-2 gene expression, while group III (HA + BG + ASCs exosome + PRF) had the highest chordin level. Overall, groups receiving ASCs exosome or PRF intervention showed elevated BMP-2 expression compared to the control group. The use of ASCs exosome and PRF showed comparable outcomes compared to bone graft administration in terms of histomorphometry analysis.ConclusionThe administration of adipose tissue derived mesenchymal stem cells and PRF has a comparable outcome with the use of bone graft in terms of osseus area and expression of BMP-2 in critical bone defect.

Reconstruction osseuse métacarpienne par membrane induite sans ciment

This thesis describes the experimental development of new dynamic hydrogels based on reversible thiol conjugate additions. Redox-controlled hydrogels and self-healing injectable hydrogels have been achieved by introducing reversible thiol conjugate additions to crosslink polymers, leading to hydrogel formation. The overall objective in this thesis was to develop a new fuel-driven transient polymeric hydrogel formation system. Although this final aim was not entirely met, we developed several important concepts along the way, which are described in Chapters 2-5. Chapter 2 describes a new chemical reaction network for fuel-driven transient formation of covalent S-C bonds, based on redox-controlled conjugate addition and elimination. We found that the formation and breaking of covalent bonds in the reaction cycle can be realized in separate reactions, but side reactions hindered the operation in full cycle. If such problems would be solved, this CRN could have potential to be used to form fuel-driven polymer materials. Chapter 3 investigates the formation of a self-healing injectable hydrogel by introducing dynamic thiol-alkynone double addition crosslinks in a polymer network. Such dynamic hydrogels show self-healing and shear thinning properties, confirmed by rheological measurements, macroscopic self-healing, and injection tests. Good cytocompatibility of these hydrogels opens an opportunity for future biomedical applications such as tissue engineering and drug delivery. Chapter 4 describes a redox-controlled reversible thiol-alkynone double addition. First, we created a redox-responsive hydrogel by using such reversible addition for the formation of crosslinks in hydrogels. Second, based on this thiol-alkynone double addition, we developed a fuel-driven transient formation of thiol-alkynone double adduct on small molecules. Chapter 5 explores coupling and decoupling reactions of thiols to an azanorbornadiene bromo sulfone. A self-healing hydrogel can be formed by using azanorbornadiene bromo sulfone to couple two thiol groups together. Such hydrogels are also degradable, trigged by glutathione. Glutathione-triggered dye release experiments suggest this self-healing hydrogel is a potential carrier of drugs, cells or vaccines for biomedical applications.