The Concept of Scaffold-Guided Bone Regeneration for the Treatment of Long Bone Defects: Current Clinical Application and Future Perspective

Assessing Cardiopulmonary Safety of Intramedullary Bone Graft Harvesting: A Comparative Study of the RIA 2 System and the ARA Concept

The management of large osseous defects requires innovative intramedullary bone graft harvesting techniques to optimize healing while minimizing complications. Intramedullary bone graft harvesting is, however, associated with potential cardiopulmonary adverse events due to embolic phenomena and systemic inflammation. This study compares the newly introduced aspirator + reaming-aspiration (ARA) concept with the established second-generation Reamer-Irrigator-Aspirator (RIA 2) system, focusing on cardiopulmonary safety in a non-fracture sheep femur model. Sixteen female Merino sheep underwent intramedullary bone grafting using either the RIA 2 system or the ARA concept. The primary outcomes measured were blood loss, hemodynamic parameters, pulmonary function via the Horovitz index, and systemic inflammatory responses postprocedure. Findings revealed minimal and comparable blood loss between the two groups (p = 0.55). Additionally, no significant differences were found in hemodynamic stability (all p ≥ 0.05), pulmonary function (p = 0.96), or systemic inflammation (all p ≥ 0.10) between the RIA 2 system and ARA concept groups, demonstrating the comparable safety profile of the ARA concept to the RIA 2 system. In conclusion, the ARA concept emerges as a viable and effective alternative to the RIA 2 system for intramedullary bone graft harvesting, with similar safety profiles. These promising results advocate for further clinical trials to validate the utility of the ARA concept in human patients.

[3D printing in surgery: relevance of technology maturity assessment in bioprinting research studies]

Biological 3D printing (bioprinting) is an extension of what is defined as additive manufacturing in the American Society for Testing and Materials (ASTM) and International Organization for Standardization (ISO) standards and is based on the automated printing of living cells and biomaterials. Researchers and experts in the field of biomaterial science, tissue engineering and regenerative medicine (TE&RM) are constantly pointing to the potential of biological 3D printing and scientific articles regularly announce the imminent clinical application. We argue in this article that these announcements are often premature and counterproductive as they focus heavily on technological progress but regularly ignore the critical stages that need to be completed in order to successfully translate a technology into the healthcare market. The technology readiness level (TRL) scale is a potentially useful tool for measuring the relative maturity of a technology in terms of overcoming a series of critical milestones. We propose an adaptation of the TRL scale and use it to discuss the current state of research on biological 3D printing. Finally, we provide specific recommendations for optimizing future research projects to pave the way for clinical applications of biological 3D printing and thus achieve a direct positive impact on surgical patient care.

Advancements in 3D printing technologies for personalized treatment of osteonecrosis of the femoral head

Three-dimensional (3D) printing technology has shown significant promise in the medical field, particularly in orthopedics, prosthetics, tissue engineering, and pharmaceutical preparations. This review focuses on the innovative application of 3D printing in addressing the challenges of osteonecrosis of the femoral head (ONFH). Unlike traditional hip replacement surgery, which is often suboptimal for younger patients, 3D printing offers precise localization of necrotic areas and the ability to create personalized implants. By integrating advanced biomaterials, this technology offers a promising strategy approach for early hip-preserving treatments. Additionally, 3D-printed bone tissue engineering scaffolds can mimic the natural bone environment, promoting bone regeneration and vascularization. In the future, the potential of 3D printing extends to combining with artificial intelligence for optimizing treatment plans, developing materials with enhanced bioactivity and compatibility, and translating these innovations from the laboratory to clinical practice. This review demonstrates how 3D printing technology uniquely addresses critical challenges in ONFH treatment, including insufficient vascularization, poor mechanical stability, and limited long-term success of conventional therapies. By introducing gradient porous scaffolds, bioactive material coatings, and AI-assisted design, this work outlines novel strategies to improve bone regeneration and personalized hip-preserving interventions. These advancements not only enhance treatment efficacy but also pave the way for translating laboratory findings into clinical applications.

Evaluation of the comparative efficacy and safety of surgical strategies for long bone defects: a network meta-analysis

BACKGROUND

To evaluate the safety and efficacy of various surgical treatments for long bone defects. Despite numerous observational studies, randomized controlled trials (RCTs), and meta-analyses, the optimal surgical treatment for long bone defects remains undetermined.

METHODS

A network meta-analysis (NMA) was conducted. PubMed, Embase, and the Cochrane Library were searched for articles published between 1 January 2000 and 12 January 2023 on surgical treatments for long bone defects. RCTs and observational studies comparing five surgical treatments were selected: the Masquelet technique (MT), bone transport (BT), vascularized bone graft (VBG), non-VBG (NVBG), and bone tissue engineering (BTE). Data were extracted by two independent reviewers. The NMA aggregated direct and indirect evidence. Treatments were ranked using the surface under the cumulative ranking curve (SUCRA) scores. Data are presented as mean differences and 95% confidence intervals. The primary outcomes were the postoperative healing rate, with subgroup analysis based on defect size (4-8 cm and >8 cm). The secondary outcomes included postoperative complications.

RESULTS

This NMA included 23 studies (three RCTs and 20 observational studies) with 930 participants (median age, 35 years). There were no significant differences in clinical outcomes among the treatments. VBG (SUCRA, 75.1%) was rated as optimal for healing, and BTE (SUCRA, 28.5%) was the least effective. BTE had the highest complication rate (SUCRA, 90.9%), whereas NVBG had the lowest complication rate (SUCRA, 27.6%). Subgroup analysis showed reduced heterogeneity: for 4-8 cm defects, VBG (SUCRA, 80.4%) was optimal, and for >8 cm defects, BT (SUCRA, 76.2%) was optimal.

CONCLUSIONS

VBG and BT may offer superior clinical outcomes for long bone defects compared to MT, NVBG, and BTE. However, BTE is associated with a high risk of complications. Further high-quality, large-sample RCTs are required to confirm these findings.

Investigation of the biodegradation kinetics and associated mechanical properties of 3D-printed polycaprolactone during long-term preclinical testing

Polycaprolactone (PCL) is a bioresorbable polymer increasingly utilized for customized tissue reconstruction as it is readily 3D printed. A critical design requirement for PCL devices is determining the in vivo bioresorption rate and the resulting change in device mechanics suited for target tissue repair applications. The primary challenge with meeting this requirement involves accurate prediction of degradation in the target tissues. PCL undergoes bulk hydrolytic degradation following first order kinetics until an 80-90 % drop in the starting number average molecular weight (Mn) after 2-3 years in vivo. However, initial polymer architecture, composite incorporation, manufacturing modality, device architecture, and target tissue can impact degradation. In vitro models do not fully capture device degradation, and the limited long-term (2-3 year) models primarily utilize subcutaneous implants. In this study, we investigate the degradation rate of 3D-printed airway support devices (ASDs) comprised of PCL and 4 % hydroxyapatite (HA) when implanted on Yucatan porcine tracheas for two years. After one year of degradation, we report a mass loss of less than 1 % and Mn reduction of 25 %. After two years, mass and Mn decreased by 10 % and 50 % respectively. These changes are accompanied by an increase in elastic modulus from 146.7 ± 5.2 MPa for freshly printed ASDs to 291.7 ± 16.0 MPa after one year and 362.5 ± 102.4 MPa after two years. Additionally, there was a decrease in yield strain, and increase in yield stress from implantation to 1-year (p < 0.001). Plastic strain completely diminished by two years, resulting in brittle failure at a yield stress of 12.5 MPa. The significantly lower rate of hydrolysis coupled with hydrolytic embrittlement indicates alternate degradation kinetics compared to subcutaneous models. Fitting a new model for degradation and predicting elastic and damage properties of this new degradation paradigm provide significant advancements for 3D-printed device design in clinical repair applications.

Progress of porous tantalum surface-modified biomaterial coatings in bone tissue engineering

Tantalum (Ta) metal has emerged as a prominent material within the realm of bone tissue engineering, owing to its favorable biocompatibility, commendable mechanical attributes, and notable biological properties such as osteoconductivity, osteoinductivity, and angiogenic potential. However, as clinical applications have expanded, Ta implants have unveiled a spectrum of limitations. Consequently, porous tantalum (PTa) has garnered escalating interest, attributable to its unique microstructural attributes, tunable mechanical characteristics, and inherent biocompatibility. Various methodologies have been proposed to modify the surface of PTa, with the aim of accelerating and enhancing osseous integration while fostering more robust osseointegration. Strategic surface modifications have the potential to augment the inherent advantages of PTa, thereby offering diverse avenues for exploration within the realm of surface effects on PTa. This review elucidates the ongoing research endeavors concerning diverse biomaterial coatings applied to PTa surfaces in the context of bone tissue engineering.

How Framing Bias Impacts Preferences for Innovation in Bone Tissue Engineering

It is currently unknown if surgeons and biomaterial scientists &or tissue engineers (BS&orTE) process and evaluate information in similar or different (un)biased ways. For the gold standard of surgery to move "from bench to bedside," there must naturally be synergies between these key stakeholders' perspectives. Because only a small number of biomaterials and tissue engineering innovations have been translated into the clinic today, we hypothesized that this lack of translation is rooted in the psychology of surgeons and BS&orTE. Presently, both clinicians and researchers doubt the compatibility of surgery and research in their daily routines. This has led to the use of a metaphorical expression "squaring of the circle," which implies an unsolvable challenge. As bone tissue engineering belongs to the top five research areas in tissue engineering, we choose the field of bone defect treatment options for our bias study. Our study uses an online survey instrument for data capture such as incorporating a behavioral economics cognitive framing experiment methodology. Our study sample consisted of surgeons (n = 208) and BS&orTE (n = 59). And we used a convenience sampling method, with participants (conference attendants) being approached both in person and through email between October 22, 2022, and March 13, 2023. We find no distinct positive-negative cognitive framing differences by occupation. That is, any framing bias present in this surgical decision-making setting does not appear to differ significantly between surgeon and BS&orTE specialization. When we explored within-group differences by frames, we see statistically significant (p < 0.05) results for surgeons in the positive frame ranking autologous bone graft transplantation lower than surgeons in the negative frame. Furthermore, surgeons in the positive frame rank Ilizarov bone transport method higher than surgeons in the negative frame (p < 0.05).

TRUMATCHTM Graft Cage-Long Bone as a solution for tibial bone defect in traumatic aseptic non-union: a case report

BACKGROUND

Tibial fractures, with an annual incidence of 51.7 per 100.000 adults, often result in complications like non-union and infection, particularly in open fractures. Non-union rates after intramedullary nailing are 9.7%. Hypertrophic non-union stems from unstable fracture sites, while atrophic non-union arises from inadequate biological environments. Treatment involves rigid bone fixation for hypertrophic non-union and combining biological tissue supply with mechanical stability for atrophic non-unions. This case report outlines a complex tibial non-union post-high-impact injury, detailing the surgical technique and TRUMATCHTM Graft Cage-Long Bone usage. In addition, we outlined the current literature on this topic.

CASE REPORT

A male patient suffered a traumatic Gustilo II comminuted tibia and fibula fracture, Lisfranc injury and a Schatzker I tibial plateau fracture of the right leg. During follow-up the patient developed an aseptic non-union with eight-centimeter anterolateral bone defect after primary surgery. Surgical intervention was performed using the three-dimensional printed TRUMATCHTM Graft Cage-Long Bone. At one year follow-up, clinical and radiological consolidation of the right tibia was seen.

CONCLUSION

This case report describes a challenging case of aseptic traumatic non-union of the tibia with a critical-sized defect treated with a novel patient-specific implant in a one-stage procedure. The application of the TRUMATCHTM Graft Cage-Long Bone is promising and warrants further investigation in larger, more controlled studies to substantiate our findings.

Advances in growth factor-containing 3D printed scaffolds in orthopedics

Currently, bone tissue engineering is a research hotspot in the treatment of orthopedic diseases, and many problems in orthopedics can be solved through bone tissue engineering, which can be used to treat fractures, bone defects, arthritis, etc. More importantly, it can provide an alternative to traditional bone grafting and solve the problems of insufficient autologous bone grafting, poor histocompatibility of grafts, and insufficient induced bone regeneration. Growth factors are key factors in bone tissue engineering by promoting osteoblast proliferation and differentiation, which in turn increases the efficiency of osteogenesis and bone regeneration. 3D printing technology can provide carriers with better pore structure for growth factors to improve the stability of growth factors and precisely control their release. Studies have shown that 3D-printed scaffolds containing growth factors provide a better choice for personalized treatment, bone defect repair, and bone regeneration in orthopedics, which are important for the treatment of orthopedic diseases and have potential research value in orthopedic applications. This paper aims to summarize the research progress of 3D printed scaffolds containing growth factors in orthopedics in recent years and summarize the use of different growth factors in 3D scaffolds, including bone morphogenetic proteins, platelet-derived growth factors, transforming growth factors, vascular endothelial growth factors, etc. Optimization of material selection and the way of combining growth factors with scaffolds are also discussed.

Functionalized GelMA/CMCS Composite Hydrogel Incorporating Magnesium Phosphate Cement for Bone Regeneration

Background: Bone regeneration remains a challenging issue in tissue engineering. The use of hydrogels as scaffolds for bone tissue repair has gained attention due to their biocompatibility and ability to mimic the extracellular matrix. This study aims to develop a functionalized GelMA/CMCS composite hydrogel incorporating magnesium phosphate cement (MPC) for enhanced bone regeneration. Methods: These composites were developed by incorporating potassium magnesium phosphate hexahydrate (KMgPO4·6H2O, MPC) powders into methacrylated gelatin/carboxymethyl chitosan (GelMA-C) hydrogels. The material's mechanical properties, antibacterial performance, and cytocompatibility were evaluated. In vitro experiments involved cell viability and osteogenic differentiation assays using rBMSCs as well as angiogenic potential assays using HUVECs. The hydrogel was also assessed for its potential in promoting bone repair in a rat (Sprague-Dawley) model of bone defect. Results: The developed GelMA-CM composite demonstrated improved mechanical properties, biocompatibility, and osteogenic potential compared to individual GelMA or CMCS hydrogels. Incorporation of MPC facilitated the sustained release of ions which promoted osteogenic differentiation of pre-osteoblasts. In vivo results indicated accelerated bone healing in the rat bone defect model. Conclusions: The functionalized GelMA-CM composite could be a viable candidate for clinical applications in bone regeneration therapies.

Osteoclastogenesis markers in craniofacial bone defects after demineralized dentin material membrane implantation as guided bone regeneration

Guided bone regeneration (GBR) is an alternative treatment for craniofacial bone defects reconstruction through membrane barrier adaptation, such as demineralized dentin material membrane (DDMM). DDMM is used as a substitute for GBR material, which aligns with Green Economy principles, it has a good biological osteoinductive and osteoconductive effects, and its structure resembles bones. The balance of bone remodeling when experiencing craniofacial defects will be altered and allow changes to resorption activity, so the mechanisms of osteoclastogenesis and bone resorption are vital.

OBJECTIVE

this article aims to analyze the expression of TNF-α, RANKL, and osteoclast cells count after application of DDMM as GBR in mandibular bone defects.

METHODOLOGY

this is an experimental study with a post-test only control group design, which began with the randomization of 120 rats into five groups: K(-), without membrane implantation; K(+), PPCM; P1, DDMM; P2, DDMM + bone graft; P3, PPCM + bone graft. The expression of TNF-α, RANKL, and osteoclast cells count were observed, followed by analysis using a one-way ANOVA and post hoc Tukey HSD comparison test.

RESULTS

there were significant differences in the expression of TNF-α, RANKL, and osteoclast cells count in all study groups (p=0.000). TNF-α showed a decreasing difference with the highest expression in the K(-) group on day 3 of 12.00±2.16. RANKL expression increased on day 14 and decreased on day 21 in all groups. The osteoclast cells count generally showed a critical period with the highest increase in the K(-) group on day 14 of 73.00±0.00.

CONCLUSION

DDMM has the potential to be a superior membrane substitute compared to PPCM as GBR in alternative treatment for craniofacial bone defects reconstruction.

Efficacy of a gelatin-based hemostatic sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) on regeneration of radial bone defects in rabbits

Background

Bone-graft substitutes are a frequently employed method for the clinical reconstruction of osseous bone defects, and research on synthetic biomaterials is currently ongoing. Absorbable hemostatic gelatin sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) have gained popularity in recent years because of their inherent characteristics: osteogenesis, osteoconductivity, osteoinductivity, biodegradability, and biocompatibility.

Aim

The aim of the study was to evaluate the effectiveness of 1) a gelatin-based hemostatic sponge (Surgispon) and 2) a combination of a weight ratio of 75/25 nHAp/CS composite with a Surgispon for osteogenic potential in the treatment of full-thickness segmental osseous defects in the radius of rabbits.

Methods

The 18 New Zealand rabbits had 10-mm-induced segmental diaphyseal defects of the left limb radius and were randomly allocated into three groups: group I left the defects untreated (control group), group II used a Surgispon, and group III had a weight ratio of 75/25 nHAp/CS composite wrapped with a Surgispon. Quantitative evaluation of the bone repair at the defect site in each group (n = 6), radiographic, gross, computed tomography (CT), and histopathological examinations were performed at 6 weeks (n = 3) and 12 weeks (n = 3) postoperatively.

Results

The quantitative statistical analysis of various evaluation methods at 6 weeks post-implantation demonstrated that there was no statistically significant difference between the groups (p > 0.05). The statistically significant differences (p < 0.05) between groups I and II, while groups I and III, were evident 12 weeks postoperatively.

Conclusion

The findings of the radiographic, macroscopic, CT, and histopathological analyses firmly demonstrate that the combination of a 75/25 weight ratio composite of nHAp/CS with Surgispon is more effective than Surgispon alone in its ability to significantly increase bone formation. This could provide a prospective option for treating segmental bone defects.

Preparation and osteogenesis of a multiple crosslinking silk fibroin/carboxymethyl chitosan/sodium alginate composite scaffold loading with mesoporous silica/poly (lactic acid-glycolic acid) microspheres

Large bone defect repair is a striking challenge in orthopedics. Currently, inorganic-organic composite scaffolds are considered as a promising approach to these bone regeneration. Silicon ions (Si4+) are bioactive and beneficial to bone regeneration and Si4+-containing inorganic mesoporous silica (MS) can effectively load drugs for bone repair. To better control the release of drug, we prepared biodegradable MS/PLGA (MP) microspheres. MP loaded organic silk fibroin/carboxymethyl chitosan/sodium alginate (MP/SF/CMCS/SA) composite scaffolds were further constructed by genipin and Ca2+ crosslinking. All MP/SF/CMCS/SA scaffolds had good swelling ability, degradation rate and high porosity. The incorporation of 1% MP significantly enhanced the compressive strength of composite scaffolds. Besides, MP loaded scaffold showed a sustained release of Si4+ and Ca2+. Moreover, the release rate of rhodamine (a model drug) of MP/SF/CMCS/SA scaffolds was obviously lower than that of MP. When culturing with rat bone marrow mesenchymal stem cells, scaffolds with 1% MP displayed good proliferation, adhesion and enhanced osteogenic differentiation ability. Based on the results above, the addition of 1% MP in SF/CMCS/SA scaffolds is a prospective way for drug release in bone regeneration and is promising for further in vivo bone repair applications.

Efficacy of a gelatin-based hemostatic sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) on regeneration of radial bone defects in rabbits

Background

Bone-graft substitutes are a frequently employed method for the clinical reconstruction of osseous bone defects, and research on synthetic biomaterials is currently ongoing. Absorbable hemostatic gelatin sponge and hydroxyapatite-chitosan nanocomposites (nHAp/CS) have gained popularity in recent years because of their inherent characteristics: osteogenesis, osteoconductivity, osteoinductivity, biodegradability, and biocompatibility.

Aim

The aim of the study was to evaluate the effectiveness of 1) a gelatin-based hemostatic sponge (Surgispon) and 2) a combination of a weight ratio of 75/25 nHAp/CS composite with a Surgispon for osteogenic potential in the treatment of full-thickness segmental osseous defects in the radius of rabbits.

Methods

The 18 New Zealand rabbits had 10-mm-induced segmental diaphyseal defects of the left limb radius and were randomly allocated into three groups: group I left the defects untreated (control group), group II used a Surgispon, and group III had a weight ratio of 75/25 nHAp/CS composite wrapped with a Surgispon. Quantitative evaluation of the bone repair at the defect site in each group (n = 6), radiographic, gross, computed tomography (CT), and histopathological examinations were performed at 6 weeks (n = 3) and 12 weeks (n = 3) postoperatively.

Results

The quantitative statistical analysis of various evaluation methods at 6 weeks post-implantation demonstrated that there was no statistically significant difference between the groups (p > 0.05). The statistically significant differences (p < 0.05) between groups I and II, while groups I and III, were evident 12 weeks postoperatively.

Conclusion

The findings of the radiographic, macroscopic, CT, and histopathological analyses firmly demonstrate that the combination of a 75/25 weight ratio composite of nHAp/CS with Surgispon is more effective than Surgispon alone in its ability to significantly increase bone formation. This could provide a prospective option for treating segmental bone defects.

A Comprehensive Literature Review on Advancements and Challenges in 3D Bioprinting of Human Organs: Ear, Skin, and Bone

The field of 3D bioprinting is rapidly emerging within the realm of regenerative medicine, offering significant potential in dealing with the issue of organ shortages. Despite being in its early stages, it has the potential to replicate tissue structures accurately, providing new potential solutions for reconstructive surgery. This review explores the diverse applications of 3D bioprinting in regenerative medicine, pharmaceuticals, and the food industry, specifically focusing on ear, skin, and bone tissues due to their unique challenges and implications in the field. Significant progress has been made in cartilage and bone scaffold fabrication in ear reconstruction, yet challenges in functional maturation persist. Recent advancements highlight the potential for patient-specific ear substitutes, emphasizing the need for extensive clinical trials. In skin regeneration, 3D bioprinting addresses limitations in existing models, offering opportunities for improved wound healing and realistic skin models. While challenges exist, progress in biomaterials and in-situ bioprinting holds promise. In bone regeneration, 3D bioprinting presents personalized solutions for defects, but scaffold design refinement and addressing regulatory and ethical considerations are crucial. The transformative potential of 3D bioprinting in the field of medicine holds the promise of redefining therapeutic approaches and delivering personalized treatments and functional tissues. Interdisciplinary collaboration is essential for fully realizing the capabilities of 3D bioprinting. This review provides a detailed analysis of current methodologies, challenges, and prospects in 3D bioprinting for ear, skin, and bone tissue regeneration.

Challenges and Innovations in Alveolar Bone Regeneration: A Narrative Review on Materials, Techniques, Clinical Outcomes, and Future Directions

This review explores the recent advancements and ongoing challenges in regenerating alveolar bone, which is essential for dental implants and periodontal health. It examines traditional techniques like guided bone regeneration and bone grafting, alongside newer methods such as stem cell therapy, gene therapy, and 3D bioprinting. Each approach is considered for its strengths in supporting bone growth and integration, especially in cases where complex bone defects make regeneration difficult. This review also looks at different biomaterials, from bioactive scaffolds to nanomaterials, assessing how well they encourage cell growth and healing. Personalized treatments, like customized 3D-printed scaffolds, show promise in enhancing bone formation and tissue compatibility. Additionally, signaling molecules, like bone morphogenetic proteins, play a crucial role in guiding the process of bone formation and remodeling. Despite these advances, challenges remain-particularly with severe bone loss and with refining biomaterials for more reliable, long-term outcomes. This review proposes combining advanced materials, regenerative technologies, and personalized approaches to achieve more effective and consistent outcomes in oral and maxillofacial surgery.

A review of the current status and future prospects of the bone remodeling process: Biological and mathematical perspectives

This review dives into the complex dynamics of bone remodeling, combining biological insights with mathematical perspectives to better understand this fundamental aspect of skeletal health. Bone, being a crucial part of our body, constantly renews itself, and with the growing number of individuals facing bone-related issues, research in this field is vital. In this review, we categorized and classified most common mathematical models used to simulate the mechanical behavior of bone under different loading and health conditions, shedding light on the evolving landscape of bone biology. While current models have effectively captured the essence of healthy bone remodeling, the ever-expanding knowledge in bone biology suggests an update in mathematical methods. Knowing the role of the skeleton in whole-body physiology, and looking at the recent discoveries about activities of bone cells emphasize the urgency of refining our mathematical descriptions of the bone remodeling process. The underexplored impact of bone diseases like osteoporosis, Paget's disease, or breast cancer on bone remodeling also points to the need for intensified research into diverse disease types and their unique effects on bone health. By reviewing a range of bone remodeling models, we show the necessity for tailor-made mathematical models to decipher their roots and enhance patient treatment strategies. Collaboration among scientists from various domains is pivotal to surmount these challenges, ensuring improved accuracy and applicability of mathematical models. Ultimately, this effort aims to deepen our understanding of bone remodeling processes and their broader implications for diverse health conditions.

A 3D in vitro model of biphasic calcium phosphate (BCP) scaffold combined with human osteoblasts, osteoclasts, and endothelial cells as a platform to mimic the oral microenvironment for tissue regeneration

OBJECTIVES

This study aimed to develop an innovative 3D in vitro model based on the biphasic calcium phosphate (BCP) scaffold combined with human osteoblasts (hOBs), osteoclasts (hOCs), and endothelial cells to evaluate its effects on bone and vascular cells behavior.

METHODS

To this end, an optimized mixture of hydroxyapatite (HA) and β-tricalcium phosphate (TCP) with a weight ratio of 30/70 was employed to develop a BCP scaffold using the computer-aided design (CAD) approach. The BCP scaffold was combined with primary cultures of hOBs, hOCs and human umbilical vein endothelial cells (HUVECs).

RESULTS

Morphometric analyses using scanning electron microscopy (SEM) and X-ray micro-computed tomography, along with biomechanical testing, revealed that BCP scaffold exhibited a regular 3D structure with large interconnected internal pores (700 µm) and high mechanical strength. In terms of biological behavior, after 14 days of tri-culture with hOBs, hMCs and HUVECs, SEM, immunofluorescence, and histological analyses showed that all cell types were viable and adhered well to the entire surface of the scaffold. Interestingly, SEM and energy-dispersive X-ray spectroscopy analyses also revealed on the BCP scaffold the presence of mineralized matrix crystals of Ca, P, O and C within a tissue-like cell layer produced by the interaction of the three cell types.

CONCLUSIONS

Data confirmed the high performance of the BCP scaffold through biomechanical studies. Notably, for the first time, this study demonstrated the feasibility of combining BCP scaffold with hOBs, hOCs, and HUVEC, which remained viable and maintained their native phenotypes, creating also tissue-like cell layer.

CLINICAL SIGNIFICANCE

Although further investigation is needed, these results underscore the potential to develop a 3D in vitro model that mimics the oral microenvironment, which could be valuable for BTE approaches in vivo studies.

A review of computational optimization of bone scaffold architecture: methods, challenges, and perspectives

The design and optimization of bone scaffolds are critical for the success of bone tissue engineering (BTE) applications. This review paper provides a comprehensive analysis of computational optimization methods for bone scaffold architecture, focusing on the balance between mechanical stability, biological compatibility, and manufacturability. Finite element method (FEM), computational fluid dynamics (CFD), and various optimization algorithms are discussed for their roles in simulating and refining scaffold designs. The integration of multiobjective optimization and topology optimization has been highlighted for developing scaffolds that meet the multifaceted requirements of BTE. Challenges such as the need for consideration of manufacturing constraints and the incorporation of degradation and bone regeneration models into the optimization process have been identified. The review underscores the potential of advanced computational tools and additive manufacturing techniques in evolving the field of BTE, aiming to improve patient outcomes in bone tissue regeneration. The reliability of current optimization methods is examined, with suggestions for incorporating non-deterministic approaches andin vivovalidations to enhance the practical application of optimized scaffolds. The review concludes with a call for further research into artificial intelligence-based methods to advance scaffold design and optimization.

Modular design workflow for 3D printable bioresorbable patient-specific bone scaffolds: extended features and clinical validation

A previously in-house developed patient-specific scaffold design workflow was extended with new features to overcome several limitations and to broaden its adaptability to diverse bone defects, thereby enhancing its fit for routine clinical use. It was applied to three clinical cases for further validation. A virtual surgical resection tool was developed to remove regions of the bone defect models. The minor cavity fill module enabled the generation of scaffold designs with smooth external surfaces and the segmental defect fill module allowed a versatile method to fill a segmental defect cavity. The boundary representation method based surgical approach module in the original workflow was redeveloped to use functional representation, eliminating previously seen resolution dependant artefacts. Lastly, a method to overlay the scaffold designs on computed tomography images of the defect for design verification by the surgeon was introduced. The extended workflow was applied to two ongoing clinical case studies of a complex bilateral femoral defect and a humerus defect, and also to a case of a large volume craniomaxillofacial defect. It was able to successfully generate scaffolds without any obstructions to their surgical insertion which was verified by digital examination as well as using physical 3D printed models. All produced surface meshes were free from 3D printing mesh errors. The scaffolds designed for the ongoing cases were 3D printed and successfully surgically implanted, providing confidence in the extended modular workflow's ability to be applied to a broad range of diverse clinical cases.

Lost in translation: the lack of agreement between surgeons and scientists regarding biomaterials research and innovation for treating bone defects

BACKGROUND

With over 2 million grafts performed annually, bone ranks second only to blood in the frequency of transplants. This high demand is primarily driven by the persistent challenges posed by bone defects, particularly following trauma or surgical interventions such as tumour excision. The demand for effective and efficient treatments has increased exponentially in the twenty-first century. Limitations associated with autologous bone grafts drive exploration into replacements, including allografts, synthetic substitutes, and 3D-printed scaffolds. This research aimed to unravel disparities in the knowledge and evaluation of current and future bone defect treatments between surgeons and biomaterial scientists.

METHODS

A prospective cross-sectional survey, pre-registered with the OSF ( https://osf.io/y837m/?view_only=fab29e24df4f4adf897353ac70aa3361 ) and conducted online from October 2022 to March 2023, collected data on surgeons' views (n = 337) and scientists (n = 99) on bone defect treatments.

RESULTS

Scientists were significantly more optimistic than surgeons regarding the future replacement of autologous bone grafts with synthetic or tissue-engineered substitutes (p < 0.001). Accordingly, scientists foresee a paradigm shift from autologous bone grafts to biomaterial and tissue-engineered solutions, reflecting their confidence in the ongoing advancements within this field. Furthermore, regulatory trepidations for 3D-printed bone scaffolds were acknowledged, with scientists emphasizing the need for a more significant focus on clinical relevance in preclinical studies and regulatory clarity. In a ranked categorical assessment, witnessing the technology in action was deemed most influential in adopting new bone regeneration methods by both scientists and surgeons.

CONCLUSIONS

To conclude, this study was conducted through a web-based survey, highlighting a substantial translational gap. It underscores the immediate need ("call to action") for meaningful interdisciplinary collaboration between surgeons and scientists, often referred to as the need to "walk the talk". The findings underscore the critical importance of aligning clinical needs, research outcomes, and regulatory frameworks to improve the development and implementation of biomaterial-based bone graft substitutes that demonstrate efficacy and efficiency in bone defect treatment.

Magnesium oxide nanoparticle reinforced pumpkin-derived nanostructured cellulose scaffold for enhanced bone regeneration

Considering global surge in bone fracture prevalence, limitation in use of traditional healing approaches like bone grafts highlights the need for innovative regenerative strategies. Here, a novel green fabrication approach has reported for reinforcement of physicochemical performances of sustainable bioinspired extracellular matrix (ECM) based on decellularized pumpkin tissue coated with Magnesium oxide nanoparticles (hereafter called DM-Pumpkin) for enhanced bone regeneration. Compared to uncoated scaffold, DM-Pumpkin exhibited significantly improved surface roughness, mechanical stiffness, porosity, hydrophilicity, swelling, and biodegradation rate. Obtained nanoporous structure provides an ideal three-dimensional microenvironment for the attachment, migration and osteo-induction in human adipose-derived mesenchymal stem cells (h- AdMSCs). Calcium deposition and mineralization, alkaline phosphatase activity, and SEM imaging of the cells as well as increased expression of bone-related genes after 21 days incubation confirmed capability of DM-Pumpkin in mimicking the biological properties of bone tissue. The presence of MgONPs had a silencing effect on inflammatory factors and improved wound closure, verified by in vivo studies. Increased expression of collagen type I and osteocalcin in the h- AdMSCs cultured on DM-Pumpkin compared to control further corroborated gained results. Altogether, boosting physicochemical and biological properties of DM-Pumpkin due to surface modification is a promising approach for guided bone regeneration.

Bioactive polymers: A comprehensive review on bone grafting biomaterials

The application of bone grafting materials in bone tissue engineering is paramount for treating severe bone defects. In this comprehensive review, we explore the significance and novelty of utilizing bioactive polymers as grafts for successful bone repair. Unlike metals and ceramics, polymers offer inherent biodegradability and biocompatibility, mimicking the native extracellular matrix of bone. While these polymeric micro-nano materials may face challenges such as mechanical strength, various fabrication techniques are available to overcome these shortcomings. Our study not only investigates diverse biopolymeric materials but also illuminates innovative fabrication methods, highlighting their importance in advancing bone tissue engineering.

Functional Scaffolds for Bone Tissue Regeneration: A Comprehensive Review of Materials, Methods, and Future Directions

Bone tissue regeneration is a rapidly evolving field aimed at the development of biocompatible materials and devices, such as scaffolds, to treat diseased and damaged osseous tissue. Functional scaffolds maintain structural integrity and provide mechanical support at the defect site during the healing process, while simultaneously enabling or improving regeneration through amplified cellular cues between the scaffold and native tissues. Ample research on functionalization has been conducted to improve scaffold-host tissue interaction, including fabrication techniques, biomaterial selection, scaffold surface modifications, integration of bioactive molecular additives, and post-processing modifications. Each of these methods plays a crucial role in enabling scaffolds to not only support but actively participate in the healing and regeneration process in bone and joint surgery. This review provides a state-of-the-art, comprehensive overview of the functionalization of scaffold-based strategies used in tissue engineering, specifically for bone regeneration. Critical issues and obstacles are highlighted, applications and advances are described, and future directions are identified.

Bone-derived extracellular matrix hydrogel from thrombospondin-2 knock-out mice for bone repair

Bone extracellular matrix (ECM) has been shown to mimic aspects of the tissue's complex microenvironment, suggesting its potential role in promoting bone repair. However, current ECM-based therapies suffer from limitations such as inefficient scale-up, lack of mechanical integrity, and sub-optimal efficacy. Here, we fabricated hydrogels from decellularized ECM (dECM) from wild type (WT) and thrombospondin-2 knock-out (TSP2KO) mouse bones. TSP2KO bone ECM hydrogel was found to have distinct mechanical properties and collagen fibril assembly from WT. Furthermore, TSP2KO hydrogel promoted mesenchymal stem cell (MSC) attachment, spreading, and invasion in vitro. Similarly, it promoted formation of tube-like structures by human umbilical vein endothelial cells (HUVECs). When applied to a murine calvarial defect model, TSP2KO hydrogel enhanced repair, in part, due to increased angiogenesis. Our study suggests the pro-angiogenic therapeutic potential of TSP2KO bone ECM hydrogel in bone repair. STATEMENT OF SIGNIFICANCE: The study describes the first successful preparation of a novel hydrogel made from decellularized bones from wild-type mice and mice lacking thrombospondin-2 (TSP2). Hydrogels from TSP2 knock-out (TSP2KO) bones have unique characteristics in structure and biomechanics. These gels interacted well with cells in vitro and helped repair damaged bone in a mouse model. Therefore, TSP2KO bone-derived hydrogel has translational potential for accelerating repair of bone defects that are otherwise difficult to heal. This study not only creates a new material with promise for accelerated healing, but also validates tunability of native biomaterials by genetic engineering.

Investigating the Promising P28 Peptide-Loaded Chitosan/Ceramic Bone Scaffolds for Bone Regeneration

Bone has the ability to heal itself; however, bone defects fail to heal once the damage exceeds a critical size. Bone regeneration remains a significant clinical challenge, with autograft considered the ideal bone graft material due to its sufficient porosity, osteogenic cells, and biological growth factors. However, limitations to bone grafting, such as limited bone stock and high resorption rates, have led to a great deal of research into developing bone graft substitutes. The P28 peptide is a small molecule bioactive biomimetic alternative to mimic the bone morphogenetic protein 2 (BMP-2). In this study, we investigated the potential of P28-loaded hybrid scaffolds to mimic the natural bone structure for enhancing the bone regeneration process. We hypothesized that the peptide-loaded scaffolds and nude scaffolds both have the potential to promote bone healing, and the bone healing process is accelerated by the release of the peptide. To verify our hypothesis, C2C12 cells were evaluated for the presence of calcium deposits by histological stain at 7 and 14 days in cultures with hybrid scaffolds. Total RNA was isolated from C2C12 cells cultured with hybrid scaffolds for 7 and 14 days to assess osteoblast differentiation. The project findings demonstrated that the hybrid scaffold could enhance osteoblast differentiation and significantly improve the therapeutic effects of the scaffold in bone regeneration.

Collagen-hydroxyapatite based scaffolds for bone trauma and regeneration: recent trends and future perspectives

Regenerative therapy, a key area of tissue engineering, holds promise for restoring damaged organs, especially in bone regeneration. Bone healing is natural to the body but becomes complex under stress and disease. Large bone deformities pose significant challenges in tissue engineering. Among various methods, scaffolds are attractive as they provide structural support and essential nutrients for cell adhesion and growth. Collagen and hydroxyapatite (HA) are widely used due to their biocompatibility and biodegradability. Collagen and nano-scale HA enhance cell adhesion and development. Thus, nano HA/collagen scaffolds offer potential solutions for bone regeneration. This review focuses on the use and production of nano-sized HA/collagen composites in bone regeneration.

[Reconstruction options for infection-related defects : Plastic surgery armamentarium]

BACKGROUND

The occurrence of infections has always been feared in all surgical disciplines. Plastic reconstructive surgery faces the challenge of treating infection-related defects on a patient-specific basis, which requires a multidisciplinary treatment concept. Satisfactory treatment success can only be achieved through radical debridement for infection cleansing, optimization of the perfusion situation paired with targeted anti-infective treatment and, if necessary, with soft tissue reconstruction by plastic surgery.

OBJECTIVE

This article presents the current possibilities of plastic and reconstructive surgery with respect to the reconstruction of infection-related defects.

MATERIAL AND METHODS

Proven and reliable strategies are presented and supplemented by promising experimental approaches.

RESULTS

Due to the often multilayered defect situation caused by infections, from the epidermis to cancellous bone, the entire armamentarium of plastic and reconstructive surgery is used for reconstruction.

CONCLUSION

The early involvement of plastic surgery in the treatment of infections and the interdisciplinary and multimodal treatment approach have proven their worth in the treatment of complex infection situations.

Chitosan composite with mesenchymal stem cells: Properties, mechanism, and its application in bone regeneration

Bone defects resulting from trauma, illness or congenital abnormalities represent a significant challenge to global health. Conventional treatments such as autographs and allografts have limitations, leading to the exploration of bone tissue engineering (BTE) as an alternative approach. This review aims to provide a comprehensive analysis of bone regeneration mechanisms with a focus on the role of chitosan-based biomaterials and mesenchymal stem cells (MSCs) in BTE. In addition, the physiochemical and biological properties of chitosan, its potential for bone regeneration when combined with other materials and the mechanisms through which MSCs facilitate bone regeneration were investigated. In addition, different methods of scaffold development and the incorporation of MSCs into chitosan-based scaffolds were examined. Chitosan has remarkable biocompatibility, biodegradability and osteoconductivity, making it an attractive choice for BTE. Interactions between transcription factors such as Runx2 and Osterix and signaling pathways such as the BMP and Wnt pathways regulate the differentiation of MSCs and bone regeneration. Various forms of scaffolding, including porous and fibrous injections, have shown promise in BTE. The synergistic combination of chitosan and MSCs in BTE has significant potential for addressing bone defects and promoting bone regeneration, highlighting the promising future of clinical challenges posed by bone defects.

Silver phosphate-modified carbonate apatite honeycomb scaffolds for anti-infective and pigmentation-free bone tissue engineering

Bone regeneration using synthetic materials has a high rate of surgical site infection, resulting in severe pain for patients and often requiring revision surgery. We propose Ag3PO4-based surface modification and structural control of scaffolds for preventing infections in bone regeneration. We demonstrated the differences in toxicity and antibacterial activity between in vitro and in vivo studies and determined the optimal silver content in terms of overall anti-infection effects, bone regeneration, toxicity, and pigmentation. A honeycomb structure comprising osteoconductive and resorbable carbonate apatite (CAp) was used as the base scaffold. CAp in the scaffold surface was partially replaced with different concentrations of Ag3PO4 via controlled dissolution-precipitation reactions in an AgNO3 solution. Both bone regeneration and infection prevention were achieved at 860-2300 ppm of silver. Despite the absence of Ag3PO4, honeycomb scaffolds were less susceptible to infection, even under conditions where infection occurs in clinically used three-dimensional porous scaffolds. Regardless of in vitro cytotoxicity at >5200 ppm of silver, increasing the silver content to 21,000 ppm did not adversely affect in vivo bone formation and scaffold resorption or cause acute systemic toxicity. Rather, bone formation was enhanced with 5200 ppm of silver. However, pigmentation was observed at that concentration. Hence, we concluded that the optimal silver concentration range is 860-2300 ppm for anti-infective and pigmentation-free bone regeneration. Bone regeneration was achieved via surface modification, resulting in the rapid release of silver ions immediately after implantation, followed by gradual release over several months. The scaffold structure may also aid in preventing bacterial growth within the scaffolds.

An innovative intramedullary bone graft harvesting concept as a fundamental component of scaffold-guided bone regeneration: A preclinical in vivo validation

Background

The deployment of bone grafts (BGs) is critical to the success of scaffold-guided bone regeneration (SGBR) of large bone defects. It is thus critical to provide harvesting devices that maximize osteogenic capacity of the autograft while also minimizing graft damage during collection. As an alternative to the Reamer-Irrigator-Aspirator 2 (RIA 2) system - the gold standard for large-volume graft harvesting used in orthopaedic clinics today - a novel intramedullary BG harvesting concept has been preclinically introduced and referred to as the ARA (aspirator + reaming-aspiration) concept. The ARA concept uses aspiration of the intramedullary content, followed by medullary reaming-aspiration of the endosteal bone. This concept allows greater customization of BG harvesting conditions vis-à-vis the RIA 2 system. Following its successful in vitro validation, we hypothesized that an ARA concept-collected BG would have comparable in vivo osteogenic capacity compared to the RIA 2 system-collected BG.

Methods

We used 3D-printed, medical-grade polycaprolactone-hydroxyapatite (mPCL-HA, wt 96 %:4 %) scaffolds with a Voronoi design, loaded with or without different sheep-harvested BGs and tested them in an ectopic bone formation rat model for up to 8 weeks.

Results

Active bone regeneration was observed throughout the scaffold-BG constructs, particularly on the surface of the bone chips with endochondral bone formation, and highly vascularized tissue formed within the fully interconnected pore architecture. There were no differences between the BGs derived from the RIA 2 system and the ARA concept in new bone volume formation and in compression tests (Young's modulus, p = 0.74; yield strength, p = 0.50). These results highlight that the osteogenic capacities of the mPCL-HA Voronoi scaffold loaded with BGs from the ARA concept and the RIA 2 system are equivalent.

Conclusion

In conclusion, the ARA concept offers a promising alternative to the RIA 2 system for harvesting BGs to be clinically integrated into SGBR strategies.

The translational potential of this article

Our results show that biodegradable composite scaffolds loaded with BGs from the novel intramedullary harvesting concept and the RIA 2 system have equivalent osteogenic capacity. Thus, the innovative, highly intuitive intramedullary harvesting concept offers a promising alternative to the RIA 2 system for harvesting bone grafts, which are an important component for the routine translation of SGBR concepts into clinical practice.

T. gondii excretory proteins promote the osteogenic differentiation of human bone mesenchymal stem cells via the BMP/Smad signaling pathway

BACKGROUND

Bone defects, resulting from substantial bone loss that exceeds the natural self-healing capacity, pose significant challenges to current therapeutic approaches due to various limitations. In the quest for alternative therapeutic strategies, bone tissue engineering has emerged as a promising avenue. Notably, excretory proteins from Toxoplasma gondii (TgEP), recognized for their immunogenicity and broad spectrum of biological activities secreted or excreted during the parasite's lifecycle, have been identified as potential facilitators of osteogenic differentiation in human bone marrow mesenchymal stem cells (hBMSCs). Building on our previous findings that TgEP can enhance osteogenic differentiation, this study investigated the molecular mechanisms underlying this effect and assessed its therapeutic potential in vivo.

METHODS

We determined the optimum concentration of TgEP through cell cytotoxicity and cell proliferation assays. Subsequently, hBMSCs were treated with the appropriate concentration of TgEP. We assessed osteogenic protein markers, including alkaline phosphatase (ALP), Runx2, and Osx, as well as components of the BMP/Smad signaling pathway using quantitative real-time PCR (qRT-PCR), siRNA interference of hBMSCs, Western blot analysis, and other methods. Furthermore, we created a bone defect model in Sprague-Dawley (SD) male rats and filled the defect areas with the GelMa hydrogel, with or without TgEP. Microcomputed tomography (micro-CT) was employed to analyze the bone parameters of defect sites. H&E, Masson and immunohistochemical staining were used to assess the repair conditions of the defect area.

RESULTS

Our results indicate that TgEP promotes the expression of key osteogenic markers, including ALP, Runx2, and Osx, as well as the activation of Smad1, BMP2, and phosphorylated Smad1/5-crucial elements of the BMP/Smad signaling pathway. Furthermore, in vivo experiments using a bone defect model in rats demonstrated that TgEP markedly promoted bone defect repair.

CONCLUSION

Our results provide compelling evidence that TgEP facilitates hBMSC osteogenic differentiation through the BMP/Smad signaling pathway, highlighting its potential as a therapeutic approach for bone tissue engineering for bone defect healing.

Design of chemobrionic and biochemobrionic scaffolds for bone tissue engineering

Chemobrionic systems have attracted great attention in material science for development of novel biomimetic materials. This study aims to design a new bioactive material by integrating biosilica into chemobrionic structure, which will be called biochemobrionic, and to comparatively investigate the use of both chemobrionic and biochemobrionic materials as bone scaffolds. Biosilica, isolated from Amphora sp. diatom, was integrated into chemobrionic structure, and a comprehensive set of analysis was conducted to evaluate their morphological, chemical, mechanical, thermal, and biodegradation properties. Then, the effects of both scaffolds on cell biocompatibility and osteogenic differentiation capacity were assessed. Cells attached to the scaffolds, spread out, and covered the entire surface, indicating the absence of cytotoxicity. Biochemobrionic scaffold exhibited a higher level of mineralization and bone formation than the chemobrionic structure due to the osteogenic activity of biosilica. These results present a comprehensive and pioneering understanding of the potential of (bio)chemobrionics for bone regeneration.

3D-printed porous zinc scaffold combined with bioactive serum exosomes promotes bone defect repair in rabbit radius

Currently, the repair of large bone defects still faces numerous challenges, with the most crucial being the lack of large bone grafts with good osteogenic properties. In this study, a novel bone repair implant (degradable porous zinc scaffold/BF Exo composite implant) was developed by utilizing laser melting rapid prototyping 3D printing technology to fabricate a porous zinc scaffold, combining it under vacuum conditions with highly bioactive serum exosomes (BF EXO) and Poloxamer 407 thermosensitive hydrogel. The electron microscope revealed the presence of tea saucer-shaped exosomes with a double-layered membrane structure, ranging in diameter from 30-150 nm, with an average size of 86.3 nm and a concentration of 3.28E+09 particles/mL. In vitro experiments demonstrated that the zinc scaffold displayed no significant cytotoxicity, and loading exosomes enhanced the zinc scaffold's ability to promote osteogenic cell activity while inhibiting osteoclast activity. In vivo experiments on rabbits indicated that the hepatic and renal toxicity of the zinc scaffold decreased over time, and the loading of exosomes alleviated the hepatic and renal toxic effects of the zinc scaffold. Throughout various stages of repairing radial bone defects in rabbits, loading exosomes reinforced the zinc scaffold's capacity to enhance osteogenic cell activity, suppress osteoclast activity, and promote angiogenesis. This effect may be attributed to BF Exo's regulation of p38/STAT1 signaling. This study signifies that the combined treatment of degradable porous zinc scaffolds and BF Exo is an effective and biocompatible strategy for bone defect repair therapy.

Towards Stem Cell Therapy for Critical-Sized Segmental Bone Defects: Current Trends and Challenges on the Path to Clinical Translation

The management and reconstruction of critical-sized segmental bone defects remain a major clinical challenge for orthopaedic clinicians and surgeons. In particular, regenerative medicine approaches that involve incorporating stem cells within tissue engineering scaffolds have great promise for fracture management. This narrative review focuses on the primary components of bone tissue engineering-stem cells, scaffolds, the microenvironment, and vascularisation-addressing current advances and translational and regulatory challenges in the current landscape of stem cell therapy for critical-sized bone defects. To comprehensively explore this research area and offer insights for future treatment options in orthopaedic surgery, we have examined the latest developments and advancements in bone tissue engineering, focusing on those of clinical relevance in recent years. Finally, we present a forward-looking perspective on using stem cells in bone tissue engineering for critical-sized segmental bone defects.

Recent Research Progress on Polyamidoamine-Engineered Hydrogels for Biomedical Applications

Hydrogels are three-dimensional crosslinked functional materials with water-absorbing and swelling properties. Many hydrogels can store a variety of small functional molecules to structurally and functionally mimic the natural extracellular matrix; hence, they have been extensively studied for biomedical applications. Polyamidoamine (PAMAM) dendrimers have an ethylenediamine core and a large number of peripheral amino groups, which can be used to engineer various polymer hydrogels. In this review, an update on the progress of using PAMAM dendrimers for multifunctional hydrogel design was given. The synthesis of these hydrogels, which includes click chemistry reactions, aza-Michael addition, Schiff base reactions, amidation reactions, enzymatic reactions, and radical polymerization, together with research progress in terms of their application in the fields of drug delivery, tissue engineering, drug-free tumor therapy, and other related fields, was discussed in detail. Furthermore, the biomedical applications of PAMAM-engineered nano-hydrogels, which combine the advantages of dendrimers, hydrogels, and nanoparticles, were also summarized. This review will help researchers to design and develop more functional hydrogel materials based on PAMAM dendrimers.

A case series utilizing bone marrow aspirate concentrate, cancellous bone autograft, platelet-rich plasma and autologous fibrin for the treatment of femur nonunions

Aim: To assess the efficacy of a bioregenerative scaffold derived from bone marrow aspirate, cancellous bone autograft, platelet-rich plasma and autologous fibrin in treating supracondylar femur nonunions. Methods & materials: Three patients with nonunions following multiple surgical failures underwent bone stabilization and the application of a novel bioregenerative scaffold. x-rays and subjective scales were collected before surgery and at 6, 12 and 24 months post-surgery. Results: All nonunions exhibited healing with sufficient callus formation, as confirmed radiologically. After 6 months, all patients resumed full weight-bearing walking without pain. Statistical analysis showed improvements in all scales compared with pre-surgical values. Conclusion: This method presents itself as an option for treating supracondylar femur nonunions following multiple surgical failures.

In vivo study to assess fat embolism resulting from the Reamer-Irrigator-Aspirator 2 system compared to a novel aspirator-based concept for intramedullary bone graft harvesting

INTRODUCTION

Fat embolism (FE) following intramedullary (IM) reaming can cause severe pulmonary complications and sudden death. Recently, a new harvesting concept was introduced in which a novel aspirator is used first for bone marrow (BM) aspiration and then for subsequent aspiration of morselized endosteal bone during sequential reaming (A + R + A). In contrast to the established Reamer-Irrigator-Aspirator (RIA) 2 system, the new A + R + A concept allows for the evacuation of fatty BM prior to reaming. In this study, we hypothesized that the risk of FE, associated coagulopathic reactions and pulmonary FE would be comparable between the RIA 2 system and the A + R + A concept.

MATERIALS AND METHODS

Intramedullary bone graft was harvested from intact femora of 16 Merino sheep (age: 1-2 years) with either the RIA 2 system (n = 8) or the A + R + A concept (n = 8). Fat intravasation was monitored with the Gurd test, coagulopathic response with D-dimer blood level concentration and pulmonary FE with histological evaluation of the lungs.

RESULTS

The total number and average size of intravasated fat particles was similar between groups (p = 0.13 and p = 0.98, respectively). D-dimer concentration did not significantly increase within 4 h after completion of surgery (RIA 2: p = 0.82; A + R + A: p = 0.23), with an interaction effect similar between groups (p = 0.65). The average lung area covered with fat globules was similar between groups (p = 0.17).

CONCLUSIONS

The use of the RIA 2 system and the novel A + R + A harvesting concept which consists of BM evacuation followed by sequential IM reaming and aspiration of endosteal bone, resulted in only minor fat intravasation, coagulopathic reactions and pulmonary FE, with no significant differences between the groups. Our results, therefore, suggest that both the RIA 2 system and the new A + R + A concept are comparable technologies in terms of FE-related complications.

3D Printing Materials and Technologies for Orthopaedic Applications

SUMMARY

3D printing technologies have evolved tremendously over the last decade for uses in orthopaedic surgical applications, including being used to manufacture implants for spine, upper extremity, foot and ankle, oncologic, and traumatic reconstructions. Materials used for 3D-printed orthopaedic devices include metals, degradable and nondegradable polymers, and ceramic composites. There are 2 primary advantages for use of 3D printing technologies for orthopaedics: first, the ability to create complex porous lattices that allow for osseointegration and improved implant stability and second, the enablement of complex geometric designs allowing for patient-specific devices based on preoperative imaging. Given continually evolving technology, and the relatively early stage of the materials and 3D printers themselves, the possibilities for continued innovation in orthopaedics are great.

[Individualized surgical treatment of sarcomas of the extremities]

Sarcomas of the extremities are rare entities, the treatment of which requires special expertise. Even if the treatment of patients is always interdisciplinary, the surgical R0 resection is the key point of each curatively intended treatment. In addition to resection in sano, the aim is to preserve the extremities and function, so that defect reconstruction after resection plays a decisive role. Due to the heterogeneity of tumors as well as their localization and extent, reconstruction is always an individually adapted treatment. Modular tumor endoprostheses are often used in this context, which can be constructed according to the size of the defect. The transplantation of autologous or allogeneic bone is also frequently used alone or as an additive procedure. Patient-specific (mega)prostheses are used particularly for pelvic tumors. Defect reconstruction using scaffold-based procedures from the field of tissue engineering is being tested as a promising procedure for the future. This article provides an overview of the treatment principles for sarcomas of the extremities and their individual reconstruction options.

Regeneration of Rabbit Calvarial Defects with Combination of Stem Cells and Enamel Matrix Derivative: A Microcomputed Tomography and Histological Evaluation Comparing Two- and Three-Dimensional Cell Constructs

Background and Objectives: This study addresses the challenge of bone regeneration in calvarial defects, exploring the efficacy of stem cell-based therapies and enamel matrix derivative (EMD) in tissue engineering. It assesses the regenerative potential of two- and three-dimensional cell constructs combined with mesenchymal stem cells (MSCs) and EMD in rabbit calvarial defects. Materials and Methods: This research involved the use of bone-marrow-derived MSCs cultured in silicon elastomer-based concave microwells to form spheroids. White rabbits were grouped for different treatments, with Group 1 as control, Group 2 receiving only EMD, Group 3 getting EMD plus stem cells, and Group 4 being treated with EMD plus stem cell spheroids. Computed tomography (CT) and microcomputed tomography (micro-CT) imaging were used for structural assessment, while histological evaluations were conducted using hematoxylin and eosin, Masson's trichrome, and Picro-sirius red staining. Results: CT and micro-CT analyses revealed varying degrees of bone regeneration among the groups. Group 4, treated with three-dimensional MSC spheroids and EMD, showed the most significant improvement in bone regeneration. Histological analyses corroborated these findings, with Group 4 displaying enhanced bone formation and better collagen fiber organization. Conclusions: The study supported the biocompatibility and potential efficacy of three-dimensional MSC constructs combined with EMD in bone regeneration. Further investigations are needed to confirm these findings and optimize treatment protocols.

Reconstruction of an Extensive Segmental Radial Shaft Bone Defect by Vascularized 3D-Printed Graft Cage

We report here a 46-year-old male patient with a 14 cm segmental bone defect of the radial shaft after third degree open infected fracture caused by a shrapnel injury. The patient underwent fixed-angle plate osteosynthesis and bone reconstruction of the radial shaft by a vascularized 3D-printed graft cage, including plastic coverage with a latissimus dorsi flap and an additional central vascular pedicle. Bony reconstruction of segmental defects still represents a major challenge in musculo-skeletal surgery. Thereby, 3D-printed scaffolds or graft cages display a new treatment option for bone restoration. As missing vascularization sets the limits for the treatment of large-volume bone defects by 3D-printed scaffolds, in the present case, we firstly describe the reconstruction of an extensive radial shaft bone defect by using a graft cage with additional vascularization.

A Bioactive Gelatin-Methacrylate Incorporating Magnesium Phosphate Cement for Bone Regeneration

Maintaining proper mechanical strength and tissue volume is important for bone growth at the site of a bone defect. In this study, potassium magnesium phosphate hexahydrate (KMgPO4·6H2O, MPC) was applied to gelma-methacrylate hydrogel (GelMA) to prepare GelMA/MPC composites (GMPCs). Among these, 5 GMPC showed the best performance in vivo and in vitro. These combinations significantly enhanced the mechanical strength of GelMA and regulated the degradation and absorption rate of MPC. Considerably better mechanical properties were noted in 5 GMPC compared with other concentrations. Better bioactivity and osteogenic ability were also found in 5 GMPC. Magnesium ions (Mg2+) are bioactive and proven to promote bone tissue regeneration, in which the enhancement efficiency is closely related to Mg2+ concentrations. These findings indicated that GMPCs that can release Mg2+ are effective in the treatment of bone defects and hold promise for future in vivo applications.

Investigation and optimization of In-Vitro behaviour of Perovskite barium titanate as a scaffold and protective coatings

The piezoelectric effect is widely known to have a significant physiological function in bone development, remodeling, and fracture repair. As a well-known piezoelectric material, barium titanate is particularly appealing as a scaffold layer to improve bone tissue engineering applications. Currently, the chemical bath deposition method is used to prepare green synthesized barium titanate coatings to improve mechanical and biological characteristics. Molarity of the solutions, an essential parameter in chemical synthesis, is changed at room temperature (0.1-1.2 Molar) to prepare coatings. The XRD spectra for as deposited coatings indicate amorphous behavior, while polycrystalline nature of coatings is observed after annealing (300 °C). Coatings prepared with solutions of relatively low molarities, i.e. from 0.1 to 0.8 M, exhibit mixed tetragonal - cubic phases. However, the tetragonal phase of Perovskite barium titanate is observed using solution molarities of 1.0 M and 1.2 M. Relatively high value of transmission, i.e. ∼80%, is observed for the coatings prepared with high molarities. Band gap of annealed coatings varies between 3.47 and 3.70 eV. For 1.2 M sample, the maximum spontaneous polarization (Ps) is 0.327x10-3 (μC/cm2) and the residual polarization (Pr) is 0.072x10-3 (μC/cm2). For 1.2M solution, a high hardness value (1510 HV) is recorded, with a fracture toughness of 28.80 MPam-1/2. Low values of weight loss, after dipping the coatings in simulated body fluid, is observed. The antibacterial activity of BaTiO3 is tested against E. coli and Bacillus subtilis. Drug encapsulation capability is also tested for different time intervals. As a result, CBD-based coatings are a promising nominee for use as scaffold and protective coatings.

Histological and Immunohistochemical Characterization of Osteoimmunological Processes in Scaffold-Guided Bone Regeneration in an Ovine Large Segmental Defect Model

Large-volume bone defect regeneration is complex and demands time to complete. Several regeneration phases with unique characteristics, including immune responses, follow, overlap, and interdepend on each other and, if successful, lead to the regeneration of the organ bone's form and function. However, during traumatic, infectious, or neoplastic clinical cases, the intrinsic bone regeneration capacity may exceed, and surgical intervention is indicated. Scaffold-guided bone regeneration (SGBR) has recently shown efficacy in preclinical and clinical studies. To investigate different SGBR strategies over periods of up to three years, we have established a well-characterized ovine large segmental tibial bone defect model, for which we have developed and optimized immunohistochemistry (IHC) protocols. We present an overview of the immunohistochemical characterization of different experimental groups, in which all ovine segmental defects were treated with a bone grafting technique combined with an additively manufactured medical-grade polycaprolactone/tricalcium phosphate (mPCL-TCP) scaffold. The qualitative dataset was based on osteoimmunological findings gained from IHC analyses of over 350 sheep surgeries over the past two decades. Our systematic and standardized IHC protocols enabled us to gain further insight into the complex and long-drawn-out bone regeneration processes, which ultimately proved to be a critical element for successful translational research.

In vivo characterization of 3D-printed polycaprolactone-hydroxyapatite scaffolds with Voronoi design to advance the concept of scaffold-guided bone regeneration

Three-dimensional (3D)-printed medical-grade polycaprolactone (mPCL) composite scaffolds have been the first to enable the concept of scaffold-guided bone regeneration (SGBR) from bench to bedside. However, advances in 3D printing technologies now promise next-generation scaffolds such as those with Voronoi tessellation. We hypothesized that the combination of a Voronoi design, applied for the first time to 3D-printed mPCL and ceramic fillers (here hydroxyapatite, HA), would allow slow degradation and high osteogenicity needed to regenerate bone tissue and enhance regenerative properties when mixed with xenograft material. We tested this hypothesis in vitro and in vivo using 3D-printed composite mPCL-HA scaffolds (wt 96%:4%) with the Voronoi design using an ISO 13485 certified additive manufacturing platform. The resulting scaffold porosity was 73% and minimal in vitro degradation (mass loss <1%) was observed over the period of 6 months. After loading the scaffolds with different types of fresh sheep xenograft and ectopic implantation in rats for 8 weeks, highly vascularized tissue without extensive fibrous encapsulation was found in all mPCL-HA Voronoi scaffolds and endochondral bone formation was observed, with no adverse host-tissue reactions. This study supports the use of mPCL-HA Voronoi scaffolds for further testing in future large preclinical animal studies prior to clinical trials to ultimately successfully advance the SGBR concept.

The Use of Free Fibula Flap in Different Extremities and Our Clinical Results

Background and objectives Plastic, orthopedic, otolaryngology, and oromaxillofacial surgery specialists rely on fibula grafts to solve reconstructive problems. The aim of this study is to discuss the use and results of vascular fibula flaps in the treatment of bone and soft tissue defects in various regions with different etiologies. Materials and methods In our clinic, we treated 32 patients with osteocutaneous fibular flaps due to bone and soft tissue defects of different etiologies and varying anatomical regions. In our study, age, gender, side, cause of injury, surgical technique, treatment results, and complications were evaluated for each patient. Results Of the 32 patients, 25 were male, and 7 were female. The average age is 37.2 (27-56). The mean bone defect size was 10.45 cm. Bone defect occurred in eight patients due to osteomyelitis, eleven patients due to gunshot wounds, nine patients due to pseudoarthrosis, and four patients due to a giant cell tumor. We applied osteocutaneous fibula flap in 27 patients and vascularized fibular flap in five patients. Bone union could not be achieved in four patients, and bone grafting was performed as a secondary surgery. Local infection occurred in five patients, and their treatment was completed with debridement and antibiotic administration. Wound complications occurred in three patients at the donor site, which were treated with debridement and skin grafting. The mean duration of radiological union was three months, and complete union was achieved in the seventh month. Conclusions We have shown in our case series that free vascularized fibula transfer has gained an important place in the field of skeletal reconstruction and is a reliable method for various bone reconstructions.

An in vivo study to investigate an original intramedullary bone graft harvesting technology

BACKGROUND

Harvesting bone graft (BG) from the intramedullary canal to treat bone defects is largely conducted using the Reamer-Irrigator-Aspirator (RIA) system. The RIA system uses irrigation fluid during harvesting, which may result in washout of osteoinductive factors. Here, we propose a new harvesting technology dedicated to improving BG collection without the potential washout effect of osteoinductive factors associated with irrigation fluid. This novel technology involves the conceptual approach of first aspirating the bone marrow (BM) with a novel aspirator prototype, followed by reaming with standard reamers and collecting the bone chips with the aspirator (reaming-aspiration method, R-A method). The aim of this study was to assess the harvesting efficacy and osteoinductive profile of the BG harvested with RIA 2 system (RIA 2 group) compared to the novel harvesting concept (aspirator + R-A method, ARA group).

METHODS

Pre-planning computed tomography (CT) imaging was conducted on 16 sheep to determine the femoral isthmus canal diameter. In this non-recovery study, sheep were divided into two groups: RIA 2 group (n = 8) and ARA group (n = 8). We measured BG weight collected from left femur and determined femoral cortical bone volume reduction in postoperative CT imaging. Growth factor and inflammatory cytokine amounts of the BGs were quantified using enzyme-linked immunosorbent assay (ELISA) methods.

RESULTS

The use of the stand-alone novel aspirator in BM collection, and in harvesting BG when the aspirator is used in conjunction with sequential reaming (R-A method) was proven feasible. ELISA results showed that the collected BG contained relevant amounts of growth factors and inflammatory cytokines in both the RIA 2 and the ARA group.

CONCLUSIONS

Here, we present the first results of an innovative concept for harvesting intramedullary BG. It is a prototype of a novel aspirator technology that enables the stepwise harvesting of first BM and subsequent bone chips from the intramedullary canal of long bones. Both the BG collected with the RIA 2 system and the aspirator prototype had the capacity to preserve the BG's osteoinductive microenvironment. Future in vivo studies are required to confirm the bone regenerative capacity of BG harvested with the innovative harvesting technology.