Accelerated tibia fracture healing in traumatic brain injury in accordance with increased hematoma formation

Brain-Bone Crosstalk in a Murine Polytrauma Model Promotes Bone Remodeling but Impairs Neuromotor Recovery and Anxiety-Related Behavior

Traumatic brain injury (TBI) and long bone fractures are a common injury pattern in polytrauma patients and modulate each other's healing process. As only a limited number of studies have investigated both traumatic sites, we tested the hypothesis that brain-bone polytrauma mutually impacts neuro- and osteopathological outcomes. Adult female C57BL/6N mice were subjected to controlled cortical impact (CCI), and/or osteosynthetic stabilized femoral fracture (FF), or sham surgery. Neuromotor and behavioral impairments were assessed by neurological severity score, open field test, rotarod test, and elevated plus maze test. Brain and bone tissues were processed 42 days after trauma. CCI+FF polytrauma mice had increased bone formation as compared to FF mice and increased mRNA expression of bone sialoprotein (BSP). Bone fractures did not aggravate neuropathology or neuroinflammation assessed by cerebral lesion size, hippocampal integrity, astrocyte and microglia activation, and gene expression. Behavioral assessments demonstrated an overall impaired recovery of neuromotor function and persistent abnormalities in anxiety-related behavior in polytrauma mice. This study shows enhanced bone healing, impaired neuromotor recovery and anxiety-like behavior in a brain-bone polytrauma model. However, bone fractures did not aggravate TBI-evoked neuropathology, suggesting the existence of outcome-relevant mechanisms independent of the extent of brain structural damage and neuroinflammation.

Relationship between preoperative hemoglobin levels and length of stay in elderly patients with hip fractures: A retrospective cohort study

Globally, hip fractures in elderly individuals are a prevalent and serious issue. Patients typically have a longer length of stay (LOS), which increases the risk of complications and increases hospitalization costs. Hemoglobin (Hb) is a routine blood test that is associated with disease prognosis. This study aimed to investigate the relationship between preoperative Hb and LOS in elderly hip fracture patients and to determine a reliable transfusion threshold. The clinical data of hip fracture patients (aged ≥ 60 years) admitted to the Department of Orthopaedics, Shenzhen Second People's Hospital, between January 2012 and December 2021 were retrospectively analyzed. Multiple linear regression analysis was used to assess the linear relationship between preoperative Hb and LOS. Smooth curve fitting was performed to investigate potential nonlinear relationships. In the case of discovering nonlinear relationships, a weighted two-piecewise linear regression model was built, and the inflection points were determined using a recursive algorithm. Subgroup analyses were conducted based on age and gender. A total of 1444 patients with an average age of (77.54 ± 8.73) years were enrolled. After adjusting for covariates, a nonlinear relationship was found between preoperative Hb and LOS. The two-piecewise linear regression model revealed an inflection point of 10 g/dL. On the left of the inflection point (Hb < 10 g/dL), the LOS was reduced by 0.735 days for every 1 g/dL increase in Hb (β = -0.735, 95% confidence interval: -1.346 to -0.124, P = .019). On the right side of the inflection point (Hb > 10 g/dL), the relationship was not statistically significant (β = 0.001, 95% confidence interval: -0.293 to 0.296, P = .992). In elderly hip fracture patients, there is a nonlinear association between preoperative Hb and LOS. However, when Hb levels were <10 g/dL, there was a negative correlation with the LOS. No correlation was observed when Hb levels were >10 g/dL. These findings underscore the importance of timely intervention to manage Hb levels in elderly patients with hip fractures, potentially reducing hospitalization durations and associated complications.

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.

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.

[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.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Anatomical characterization of the intraosseous arteries of the porcine tibia

Introduction

Tibial fractures have a high rate of post-fracture complications. Blood supply is recognized as a positive factor in tibial fracture healing. However, it's difficult to assess blood supply damage after tibial fracture because of the lack of understanding of the tibial intraosseous arteries. This study aimed to delineate and anatomically characterize porcine tibial intraosseous arteries, as a model for the human system.

Methods

Twenty right calf specimens with popliteal vessels were prepared from ordinary Landrace pigs. Epoxy resin was perfused into the vasculature from the popliteal artery. After 24 h, casts of the intraosseous arteries of the tibia were exposed through acid and alkali corrosion. The distribution and anatomy of the exposed intraosseous arteries were observed and measured under a microscope, and the data were statistically analyzed.

Results

Sixteen complete specimens were obtained. The medullary artery bifurcated into the main ascending and descending branches, which each split into two upward primary branches that further divided into 1-3 secondary branches. Among all specimens, 56 ascending and 42 descending secondary branches, which were all ≥0.3 mm in diameter. Furthermore, the horizontal plane was divided into three zones-safety, buffer, and danger zones-according to the probability of the presence of intraosseous artery.

Discussion

The cast perfusion and corrosion approach was successfully applied for anatomical characterization of the intraosseous arteries of the porcine tibia. These observations provide a theoretical basis for understanding the tibial vasculature in humans and will facilitate the establishment of novel "safe corridor" in the tibia for the protection of the blood supply during surgery.

Altered early immune response after fracture and traumatic brain injury

Introduction

Clinical and preclinical data suggest accelerated bone fracture healing in subjects with an additional traumatic brain injury (TBI). Mechanistically, altered metabolism and neuro-endocrine regulations have been shown to influence bone formation after combined fracture and TBI, thereby increasing the bone content in the fracture callus. However, the early inflammatory response towards fracture and TBI has not been investigated in detail so far. This is of great importance, since the early inflammatory phase of fracture healing is known to be essential for the initiation of downstream regenerative processes for adequate fracture repair.

Methods

Therefore, we analyzed systemic and local inflammatory mediators and immune cells in mice which were exposed to fracture only or fracture + TBI 6h and 24h after injury.

Results

We found a dysregulated systemic immune response and significantly fewer neutrophils and mast cells locally in the fracture hematoma. Further, local CXCL10 expression was significantly decreased in the animals with combined trauma, which correlated significantly with the reduced mast cell numbers.

Discussion

Since mast cells and mast cell-derived CXCL10 have been shown to increase osteoclastogenesis, the reduced mast cell numbers might contribute to higher bone content in the fracture callus of fracture + TBI mice due to decreased callus remodeling.