Technology Behind Cell Therapy Augmentation of Fracture Healing: Concentrated Bone Marrow Aspirate.

With an aging population, and an anticipated increase in overall fracture incidence, a sound understanding of bone healing and how technology can optimize this process is crucial. Concentrated bone marrow aspirate (cBMA) is a technology that capitalizes on skeletal stem and progenitor cells (SSPCs) to enhance the regenerative capacity of bone. This overview highlights the science behind cBMA, discusses the role of SSPCs in bone homeostasis and fracture repair, and briefly details the clinical evidence supporting the use of cBMA in fracture healing. Despite promising early clinical results, a lack of standardization in harvest and processing techniques, coupled with patient variability, presents challenges in optimizing the use of cBMA. However, cBMA remains an emerging technology that may certainly play a crucial role in the future of fracture healing augmentation.

Mechanosensitive protein polycystin-1 promotes periosteal stem/progenitor cells osteochondral differentiation in fracture healing.

Background: Mechanical forces are indispensable for bone healing, disruption of which is recognized as a contributing cause to nonunion or delayed union. However, the underlying mechanism of mechanical regulation of fracture healing is elusive. Methods: We used the lineage-tracing mouse model, conditional knockout depletion mouse model, hindlimb unloading model and single-cell RNA sequencing to analyze the crucial roles of mechanosensitive protein polycystin-1 (PC1, Pkd1) promotes periosteal stem/progenitor cells (PSPCs) osteochondral differentiation in fracture healing. Results: Our results showed that cathepsin (Ctsk)-positive PSPCs are fracture-responsive and mechanosensitive and can differentiate into osteoblasts and chondrocytes during fracture repair. We found that polycystin-1 declines markedly in PSPCs with mechanical unloading while increasing in response to mechanical stimulus. Mice with conditional depletion of Pkd1 in Ctsk+ PSPCs show impaired osteochondrogenesis, reduced cortical bone formation, delayed fracture healing, and diminished responsiveness to mechanical unloading. Mechanistically, PC1 facilitates nuclear translocation of transcriptional coactivator TAZ via PC1 C-terminal tail cleavage, enhancing osteochondral differentiation potential of PSPCs. Pharmacological intervention of the PC1-TAZ axis and promotion of TAZ nuclear translocation using Zinc01442821 enhances fracture healing and alleviates delayed union or nonunion induced by mechanical unloading. Conclusion: Our study reveals that Ctsk+ PSPCs within the callus can sense mechanical forces through the PC1-TAZ axis, targeting which represents great therapeutic potential for delayed fracture union or nonunion.

SVF Therapy of Delayed Fracture Union in Patients with Multiple Combat Injury. Case Report.

Delayed union of fractures is one of the most frequent complications in orthopedic practice, especially in polytrauma patients. With the development of new methods of regenerative medicine, including the use of adipose derived stromal cells as a component of the stromal-vascular fraction (SVF), new possibilities for conservative treatment of this problem have emerged. This article presents a clinical case of conservative treatment of delayed union of a radial bone fracture using local SVF injections. In the fracture space, SVF with PRP creates a pool of cells that could differentiate towards surrounding tissue, releases various inducers of tissue growth and, via an indirect chemotactic effect on receptors, mobilizes the body's own resources and creates conditions for angiogenesis and trophism in the injured segment. In the patient with delayed consolidation after SFV-therapy, progress in clinical and radiological dynamics was noted with complete healing within 7 months. The positive clinical result provides a basis for further study and implementation in practice.

Human nonunion tissues display differential gene expression in comparison to physiological fracture callus.

The healing of bone fractures can become aberrant and lead to nonunions which in turn have a negative impact on patient health. Understanding why a bone fails to normally heal will enable us to make a positive impact in a patient's life. While we have a wealth of molecular data on rodent models of fracture repair, it is not the same with humans. As such, there is still a lack of information regarding the molecular differences between normal physiological repair and nonunions. This study was designed to address this gap in our molecular knowledge of the human repair process by comparing differentially expressed genes (DEGs) between physiological fracture callus and two different nonunion types, hypertrophic (HNU) and oligotrophic (ONU). RNA sequencing data revealed over ∼18,000 genes in each sample. Using the physiological callus as the control and the nonunion samples as the experimental groups, bioinformatic analyses identified 67 and 81 statistically significant DEGs for HNU and ONU, respectively. Out of the 67 DEGs for the HNU, 34 and 33 were up and down-regulated, respectively. Similarly, out of the 81 DEGs for the ONU, 48 and 33 were up and down-regulated, respectively. Additionally, we also identified common genes between the two nonunion samples; 8 (10.8 %) upregulated and 12 (22.2 %) downregulated. We further identified many biological processes, with several statistically significant ones. Some of these were related to muscle and were common between the two nonunion samples. This study represents the first comprehensive attempt to understand the global molecular events occurring in human nonunion biology. With further research, we can perhaps decipher new molecular pathways involved in aberrant healing of human bone fractures that can be therapeutically targeted.

Increased ß2-adrenergic signaling promotes fracture healing through callus neovascularization in mice.

Traumatic brain injury (TBI) leads to skeletal changes, including bone loss in the unfractured skeleton, and paradoxically accelerates healing of bone fractures; however, the mechanisms remain unclear. TBI is associated with a hyperadrenergic state characterized by increased norepinephrine release. Here, we identified the ß2-adrenergic receptor (ADRB2) as a mediator of skeletal changes in response to increased norepinephrine. In a murine model of femoral osteotomy combined with cortical impact brain injury, TBI was associated with ADRB2-dependent enhanced fracture healing compared with osteotomy alone. In the unfractured 12-week-old mouse skeleton, ADRB2 was required for TBI-induced decrease in bone formation and increased bone resorption. Adult 30-week-old mice had higher bone concentrations of norepinephrine, and ADRB2 expression was associated with decreased bone volume in the unfractured skeleton and better fracture healing in the injured skeleton. Norepinephrine stimulated expression of vascular endothelial growth factor A and calcitonin gene-related peptide-α (αCGRP) in periosteal cells through ADRB2, promoting formation of osteogenic type-H vessels in the fracture callus. Both ADRB2 and αCGRP were required for the beneficial effect of TBI on bone repair. Adult mice deficient in ADRB2 without TBI developed fracture nonunion despite high bone formation in uninjured bone. Blocking ADRB2 with propranolol impaired fracture healing in mice, whereas the ADRB2 agonist formoterol promoted fracture healing by regulating callus neovascularization. A retrospective cohort analysis of 72 patients with long bone fractures indicated improved callus formation in 36 patients treated with intravenous norepinephrine. These findings suggest that ADRB2 is a potential therapeutic target for promoting bone healing.

A novel surgical method for treating fractures of the middle third of the clavicle.

BACKGROUND: The clavicle is recognized as the bone most vulnerable to fractures. Moreover, approximately 80% of fractures occur in the middle third of the clavicle. Conservative treatment is associated with a higher rate of nonunion, while surgical treatment of fracture via internal fixation may have a variety of postoperative complications. Therefore, to improve patient satisfaction and reduce the complications related to internal fixation techniques, we modified the surgical approach to external fixation. OBJECTIVE: The purpose of this study was to assess the modified intervention's prospects for clinical application. METHODS: A total of 36 patients with middle clavicle fractures were treated with screw-rod external fixation between April 2015 and October 2019. We observed the operative time, intraoperative blood loss, length of hospital stay, and fracture healing time. The patients were followed up regularly, and the clinical efficacy of the modified intervention was evaluated. Finally, the patients' shoulder function was assessed based on the disabilities of the arm, shoulder, and hand (DASH) score. RESULTS: For the screw-rod external fixation, the mean operative time was found to be 48.6 ± 6.8 min, the intraoperative blood loss was 30.6 ± 17.2 mL, the length of hospital stay was 4.5 ± 1.5 days, and the fracture healing time was 2.8 ± 0.4 months. Eventually, all the patients healed well, with the combined "excellent" and "good" rate of shoulder function being assessed to be as high as 94.44%. Furthermore, the DASH scores were all less than 10, with the average score being 4.65 ± 3.34. CONCLUSIONS: The screw-rod external fixation technique offers the advantages of convenience, reliability, and good aesthetics, suggesting that it could be used as an alternative treatment method for fractures of the middle third of the clavicle.

Fibrous periosteum repairs bone fracture and maintains the healed bone throughout mouse adulthood.

Bone is regarded as one of few tissues that heals without fibrous scar. The outer layer of the periosteum is covered with fibrous tissue, whose function in bone formation is unknown. We herein developed a system to distinguish the fate of fibrous-layer periosteal cells (FL-PCs) from the skeletal stem/progenitor cells (SSPCs) in the cambium-layer periosteum and bone marrow in mice. We showed that FL-PCs did not participate in steady-state osteogenesis, but formed the main body of fibrocartilaginous callus during fracture healing. Moreover, FL-PCs invaded the cambium-layer periosteum and bone marrow after fracture, forming neo-SSPCs that continued to maintain the healed bones throughout adulthood. The FL-PC-derived neo-SSPCs expressed lower levels of osteogenic signature genes and displayed lower osteogenic differentiation activity than the preexisting SSPCs. Consistent with this, healed bones were thinner and formed more slowly than normal bones. Thus, the fibrous periosteum becomes the cellular origin of bones after fracture and alters bone properties permanently.

Proteomic analysis of exosomal proteins associated with bone healing speed in a rat tibial fracture model.

This study investigates the impact of exosomes on bone fracture healing in a rat tibial model, distinguishing between fast and slow healing processes. Bone healing and protein expression were assessed through X-ray examinations, hematoxylin and eosin staining, and immunohistochemical staining. Exosomes were isolated, characterized and subjected to liquid chromatography-mass spectrometry for protein analysis. Molecular differences were explored using differentially expressed protein analysis, Kyoto Encyclopedia of Genes and Genomes pathway enrichment and protein-protein interaction networks. Differential bone healing patterns and protein expressions were observed between the control and model groups. Exosomes were successfully isolated and characterized, revealing 2004 identified proteins, including distinct expression profiles. Notably, ribosomal proteins, ferritin and beta-actin emerged as pivotal players in bone fracture healing. This study unveils dynamic changes in bone healing and underscores the role of exosomes in the process. Identified proteins and pathways offer valuable insights for developing innovative therapeutic strategies for bone healing.

Dnmt3b ablation affects fracture repair process by regulating apoptosis.

PURPOSE: Previous studies have shown that DNA methyltransferase 3b (Dnmt3b) is the only Dnmt responsive to fracture repair and Dnmt3b ablation in Prx1-positive stem cells and chondrocyte cells both delayed fracture repair. Our study aims to explore the influence of Dnmt3b ablation in Gli1-positive stem cells in fracture healing mice and the underlying mechanism. METHODS: We generated Gli1-CreERT2; Dnmt3bflox/flox (Dnmt3bGli1ER) mice to operated tibia fracture. Fracture callus tissues of Dnmt3bGli1ER mice and control mice were collected and analyzed by X-ray, micro-CT, biomechanical testing, histopathology and TUNEL assay. RESULTS: The cartilaginous callus significantly decrease in ablation of Dnmt3b in Gli1-positive stem cells during fracture repair. The chondrogenic and osteogenic indicators (Sox9 and Runx2) in the fracture healing tissues in Dnmt3bGli1ER mice much less than control mice. Dnmt3bGli1ER mice led to delayed bone callus remodeling and decreased biomechanical properties of the newly formed bone during fracture repair. Both the expressions of Caspase-3 and Caspase-8 were upregulated in Dnmt3bGli1ER mice as well as the expressions of BCL-2. CONCLUSIONS: Our study provides an evidence that Dnmt3b ablation Gli1-positive stem cells can affect fracture healing and lead to poor fracture healing by regulating apoptosis to decrease chondrocyte hypertrophic maturation.

The impact and mechanism of nerve injury on bone metabolism.

With an increasing understanding of the mechanisms of fracture healing, it has been found that nerve injury plays a crucial role in the process, but the specific mechanism is yet to be completely revealed. To address this issue and provide novel insights for fracture treatment, we compiled this review. This review aims to study the impact of nerve injury on fracture healing, exploring the role of neurotrophic factors in the healing process. We first revisited the effects of the central nervous system (CNS) and the peripheral nervous system (PNS) on the skeletal system, and further explained the phenomenon of significantly accelerated fracture healing under nerve injury conditions. Then, from the perspective of neurotrophic factors, we delved into the physiological functions and mechanisms of neurotrophic factors, such as nerve growth factor (NGF), Neuropeptides (NPs), and Brain-derived neurotrophic factor (BDNF), in bone metabolism. These effects include direct actions on bone cells, improvement of local blood supply, regulation of bone growth factors, control of cellular signaling pathways, promotion of callus formation and bone regeneration, and synergistic or antagonistic effects with other endocrine factors, such as Sema3A and Transforming Growth Factor ß (TGF-ß). Finally, we discussed the treatments of fractures with nerve injuries and the future research directions in this review, suggesting that the relationship between nerve injury and fracture healing, as well as the role of nerve injury in other skeletal diseases.

Conservative treatment of fragility fracture of the pelvis: A retrospective study.

BACKGROUND: Although an increasing number of studies have reported the usefulness of early minimally invasive surgery (MIS) or fragility fracture of the pelvis (FFP), MIS is difficult to perform in every hospital, partly because of equipment problems. Moreover, different opinions exist on FFP treatment methods and the indication for surgery is usually determined by the fracture type. Since our hospital follows a conservative approach as the basic treatment, this study examined the outcomes of such an FFP approach. HYPOTHESIS: FFP outcomes are influenced by the fracture type and walking ability before the injury. PATIENTS AND METHODS: We investigated the bone fusion rate, bone fusion duration, unloading duration, walking ability trends, and outcomes in 76 patients with FFP treated conservatively at our hospital. RESULTS: The union rate, mean period until union, and follow-up period were 93.4%, 3.3 months, and 14.3 months, respectively. Walking ability significantly decreased from 5.1 points before the injury to 4.4 points during the last follow-up (p<0.01). The average unloading period was 12.8 days, and FFPs showed a high bone fusion rate, even with conservative treatment. DISCUSSION: Most patients eventually returned to their pre-injury status despite slightly decreased walking ability. Given the invasive nature of surgery, the indications for surgery should be carefully assessed after considering the risk-benefit ratio. LEVEL OF EVIDENCE: III; retrospective study.

External Mechanical Stability Regulates Hematoma Vascularization in Bone Healing Rather than Endothelial YAP/TAZ Mechanotransduction.

Bone fracture healing is regulated by mechanobiological cues. Both, extracellular matrix (ECM) deposition and microvascular assembly determine the dynamics of the regenerative processes. Mechanical instability as by inter-fragmentary shear or compression is known to influence early ECM formation and wound healing. However, it remains unclear how these external cues shape subsequent ECM and microvascular network assembly. As transcriptional coactivators, the mechanotransducers yes-associated protein 1 (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) translate physical cues into downstream signaling events, yet their role in sprouting angiogenesis into the hematoma after injury is unknown. Using bone healing as model system for scar-free regeneration, the role of endothelial YAP/TAZ in combination with tuning the extrinsic mechanical stability via fracture fixation is investigated. Extrinsically imposed shear across the gap delayed hematoma remodeling and shaped the morphology of early collagen fiber orientations and microvascular networks, suggesting that enhanced shear increased the nutrient exchange in the hematoma. In contrast, endothelial YAP/TAZ deletion has little impact on the overall vascularization of the fracture gap, yet slightly increases the collagen fiber deposition under semi-rigid fixation. Together, these data provide novel insights into the respective roles of endothelial YAP/TAZ and extrinsic mechanical cues in orchestrating the process of bone regeneration.

Latest Progress of LIPUS in Fracture Healing: A Mini-Review.

The use of low-intensity pulsed ultrasound (LIPUS) for promoting fracture healing has been Food and Drug Administration (FDA)-approved since 1994 due to largely its non-thermal effects of sound flow sound radiation force and so on. Numerous clinical and animal studies have shown that LIPUS can accelerate the healing of fresh fractures, nonunions, and delayed unions in pulse mode regardless of LIPUS devices or circumstantial factors. Rare clinical studies show limitations of LIPUS for treating fractures with intramedullary nail fixation or low patient compliance. The biological effect is achieved by regulating various cellular behaviors involving mesenchymal stem/stromal cells (MSCs), osteoblasts, chondrocytes, and osteoclasts and with dose dependency on LIPUS intensity and time. Specifically, LIPUS promotes the osteogenic differentiation of MSCs through the ROCK-Cot/Tpl2-MEK-ERK signaling. Osteoblasts, in turn, respond to the mechanical signal of LIPUS through integrin, angiotensin type 1 (AT1), and PIEZO1 mechano-receptors, leading to the production of inflammatory factors such as COX-2, MCP-1, and MIP-1ß fracture repair. LIPUS also induces CCN2 expression in chondrocytes thereby coordinating bone regeneration. Finally, LIPUS suppresses osteoclast differentiation and gene expression by interfering with the ERK/c-Fos/NFATc1 cascade. This mini-review revisits the known effects and mechanisms of LIPUS on bone fracture healing and strengthens the need for further investigation into the underlying mechanisms.

Role of the Neurologic System in Fracture Healing: An Extensive Review.

PURPOSE OF REVIEW: Despite advances in orthopedics, there remains a need for therapeutics to hasten fracture healing. However, little focus is given to the role the nervous system plays in regulating fracture healing. This paucity of information has led to an incomplete understanding of fracture healing and has limited the development of fracture therapies that integrate the importance of the nervous system. This review seeks to illuminate the integral roles that the nervous system plays in fracture healing. RECENT FINDINGS: Preclinical studies explored several methodologies for ablating peripheral nerves to demonstrate ablation-induced deficits in fracture healing. Conversely, activation of peripheral nerves via the use of dorsal root ganglion electrical stimulation enhanced fracture healing via calcitonin gene related peptide (CGRP). Investigations into TLR-4, TrkB agonists, and nerve growth factor (NGF) expression provide valuable insights into molecular pathways influencing bone mesenchymal stem cells and fracture repair. Finally, there is continued research into the connections between pain and fracture healing with findings suggesting that anti-NGF may be able to block pain without affecting healing. This review underscores the critical roles of the central nervous system (CNS), peripheral nervous system (PNS), and autonomic nervous system (ANS) in fracture healing, emphasizing their influence on bone cells, neuropeptide release, and endochondral ossification. The use of TBI models contributes to understanding neural regulation, though the complex influence of TBI on fracture healing requires further exploration. The review concludes by addressing the neural connection to fracture pain. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Cracking the Code: The Role of Peripheral Nervous System Signaling in Fracture Repair.

PURPOSE OF REVIEW: The traditionally understated role of neural regulation in fracture healing is gaining prominence, as recent findings underscore the peripheral nervous system's critical contribution to bone repair. Indeed, it is becoming more evident that the nervous system modulates every stage of fracture healing, from the onset of inflammation to repair and eventual remodeling. RECENT FINDINGS: Essential to this process are neurotrophins and neuropeptides, such as substance P, calcitonin gene-related peptide, and neuropeptide Y. These molecules fulfill key roles in promoting osteogenesis, influencing inflammation, and mediating pain. The sympathetic nervous system also plays an important role in the healing process: while local sympathectomies may improve fracture healing, systemic sympathetic denervation impairs fracture healing. Furthermore, chronic activation of the sympathetic nervous system, often triggered by stress, is a potential impediment to effective fracture healing, marking an important area for further investigation. The potential to manipulate aspects of the nervous system offers promising therapeutic possibilities for improving outcomes in fracture healing. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Do Not Lose Your Nerve, Be Callus: Insights Into Neural Regulation of Fracture Healing.

PURPOSE OF REVIEW: Fractures are a prominent form of traumatic injury and shall continue to be for the foreseeable future. While the inflammatory response and the cells of the bone marrow microenvironment play significant roles in fracture healing, the nervous system is also an important player in regulating bone healing. RECENT FINDINGS: Considerable evidence demonstrates a role for nervous system regulation of fracture healing in a setting of traumatic injury to the brain. Although many of the impacts of the nervous system on fracture healing are positive, pain mediated by the nervous system can have detrimental effects on mobilization and quality of life. Understanding the role the nervous system plays in fracture healing is vital to understanding fracture healing as a whole and improving quality of life post-injury. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Treatment of Severely Shortened or Comminuted Clavicular Fractures in Older Adolescent Athletes.

BACKGROUND: Recent evidence suggests that for completely displaced midshaft clavicular fractures, surgery offers no clear benefit over nonoperative treatment in a general adolescent population from 10 to 18 years of age. However, the comparative outcomes of comminuted and/or severely shortened clavicular fractures specifically in older adolescent athletes have not been explored in a focused, methodologically rigorous fashion. HYPOTHESIS: The study hypothesis was that outcomes would be superior in older adolescent athletes who underwent operative treatment compared with nonoperative treatment for comminuted and/or severely shortened clavicular fractures. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A level 2, multicenter, prospective cohort study investigating the outcomes of midshaft fractures in adolescents between 2013 and 2017 was filtered to analyze the subcohorts of athletes 14 to 18 years of age with either fracture comminution or fracture shortening of ≥25 mm or both. Patient characteristics, injury mechanisms, fracture characteristics, and treatments were compared. Complications, rates, timing of return to sports (RTS), and patient-reported outcomes (PROs) were analyzed. RESULTS: The 2 treatment groups, which included 136 older adolescent athletes (69 nonoperative, 67 operative), showed similar distributions of primary sport type, competition level, comminution, shortening, and 2-year PRO response rate (n = 99; 73%). The operative group demonstrated 3 mm-greater mean superior displacement, which was therefore statistically controlled for as a confounder in the comparative PRO analysis. No 2-year differences in nonunion, delayed union, symptomatic malunion, refracture, clinically significant complications, or rates of RTS were detected between treatment groups. The difference in timing of RTS (operative, 10.3 weeks; nonoperative, 13.5 weeks) was statistically significant. After controlling for the minor difference in superior displacement, regression analysis and matched comparison cohorts demonstrated no differences between the nonoperative and operative groups in mean or dichotomized PRO scores. CONCLUSION: In this prospective, multicenter cohort study investigating older adolescent athletes with comminuted and/or severely shortened clavicular fractures, contrary to the study hypothesis, there were no differences in complications, RTS, or PROs between nonoperatively and operatively treated patients at 2 years. Comparably excellent outcomes of severe clavicular fractures in adolescent athletes can be achieved with nonoperative treatment.

Clinical effect of nice knot-assisted minimally invasive titanium elastic nail fixation to treat Robinson 2B midshaft clavicular fracture.

BACKGROUND: The treatment of completely displaced midshaft clavicle fractures is still controversial, especially Robinson 2B fractures. Titanium elastic nail (TEN) fixation is a good option for simple fractures, but no reports exist on its use in complex fractures. This study aimed to present a surgical method using the Nice knot-assisted TEN fixation to treat Robinson 2B midshaft clavicular fractures. METHODS: A retrospective analysis of 29 patients who underwent fixation with TEN and had a 1-year postoperative follow-up between 2016 and 2020 was performed. The fractures were classified as Robinson type 2B1 in 17 cases and type 2B2 in 12 cases. Length of the incision, postoperative shoulder function Disability of Arm Shoulder and Hand (DASH) score and Constant score, complications rate, and second surgical incision length were recorded. RESULTS: The length of the incision was 2-6 cm (average 3.7 cm). All incisions healed by first intention, and no infection or nerve injury occurred. The Constant score was 92-100 (average 96) and the DASH score was 0-6.2 (mean, 2.64). TEN bending and hypertrophic nonunion occurred in one case (3.4%) and implant irritation occurred in four cases (13.8%) Fixation implants were removed at 12-26 months (mean, 14.6 months) after surgery, and the length of the second incision was 1-2.5 cm (average 1.3 cm). CONCLUSIONS: Intramedullary fixation by TEN is approved as a suitable surgical technique in clavicular fracture treatment. Nice knot-assisted fixation provides multifragmentary fracture stabilization, contributing to good fracture healing. Surgeons should consider this technique in treating Robinson 2B midshaft clavicular fractures. TRIAL REGISTRATION: Retrospectively registered. This study was approved by the Ethics Committee of Wuxi Ninth People's Hospital (LW20220021).

[Research progress on mechanism of traumatic brain injury promoting fracture healing].

Objective: To summarize the research progress on the mechanism related to traumatic brain injury (TBI) to promote fracture healing, and to provide theoretical basis for clinical treatment of fracture non-union. Methods: The research literature on TBI to promote fracture healing at home and abroad was reviewed, the role of TBI in fracture healing was summarized from three aspects of nerves, body fluids, and immunity, to explore new ideas for the treatment of fracture non-union. Results: Numerous studies have shown that fracture healing is faster in patients with fracture combined with TBI than in patients with simple fracture. It is found that the expression of various cytokines and hormones in the body fluids of patients with fracture and TBI is significantly higher than that of patients with simple fracture, and the neurofactors released by the nervous system reaches the fracture site through the damaged blood-brain barrier, and the chemotaxis and aggregation of inflammatory cells and inflammatory factors at the fracture end of patients with combined TBI also differs significantly from those of patients with simple fracture. A complex network of humoral, neural, and immunomodulatory networks together promote regeneration of blood vessels at the fracture site, osteoblasts differentiation, and inhibition of osteoclasts activity. Conclusion: TBI promotes fracture healing through a complex network of neural, humoral, and immunomodulatory, and can treat fracture non-union by intervening in the perifracture microenvironment.

Intramedullary implant stability affects patterns of fracture healing in mice with morphologically different bone phenotypes.

Almost all prior mouse fracture healing models have used needles or K-wires for fixation, unwittingly providing inadequate mechanical stability during the healing process. Our contention is that the reported outcomes have predominantly reflected this instability, rather than the impact of diverse biological conditions, pharmacologic interventions, exogenous growth factors, or genetic considerations. This important issue becomes obvious upon a critical review of the literature. Therefore, the primary aim of this study was to demonstrate the significance of mouse-specific implants designed to provide both axial and torsional stability (Screw and IM Nail) compared to conventional pins (Needle and K-wires), even when used in mice with differently sized marrow canals and diverse genetic backgrounds. B6 (large medullary canal), DBA, and C3H (smaller medullary canals) mice were employed, all of which have different bone morphologies. Closed femoral fractures were created and stabilized with intramedullary implants that provide different mechanical conditions during the healing process. The most important finding of this study was that appropriately designed mouse-specific implants, providing both axial and torsional stability, had the greatest influence on bone healing outcomes regardless of the different bone morphologies encountered. For instance, unstable implants in the B6 strain (largest medullary canal) resulted in significantly greater callus, with a fracture region mainly comprising trabecular bone along with the presence of cartilage 28 days after surgery. The DBA and C3H strains (with smaller medullary canals) instead formed significantly less callus, and only had a small amount of intracortical trabeculation remaining. Moreover, with more stable fracture fixation a higher BV/TV was observed and cortices were largely restored to their original dimensions and structure, indicating an accelerated healing and remodeling process. These observations reveal that the diaphyseal cortical thickness, influenced by the genetic background of each strain, played a pivotal role in determining the amount of bone formation in response to the fracture. These findings are highly important, indicating the rate and type of tissue formed is a direct result of mechanical instability, and this most likely would mask the true contribution of the tested genes, genetic backgrounds, or various therapeutic agents administered during the bone healing process.