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Concept: Osteology

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Bone fractures are one of the most commonly occurring injuries of the musculoskeletal system. A highly complex physiological process, fracture healing has been studied extensively. Data from in vivo, in vitro and clinical studies, have shown pulsed electromagnetic fields (PEMFs) to be highly influential in the fracture repair process. Whilst the underlying mechanisms acting to either inhibit or advance the physiological processes are yet to be defined conclusively, several non-invasive point of use devices have been developed for the clinical treatment of fractures. With the complexity of the repair process, involving many components acting at different time steps, it has been a challenge to determine which PEMF exposure parameters (i.e., frequency of field, intensity of field and dose) will produce the most optimal repair. In addition, the development of an evidence-backed device comes with challenges of its own, with many elements (including process of exposure, construct materials and tissue densities) being highly influential to the field exposed. The objective of this review is to provide a broad recount of the applications of PEMFs in bone fracture repair and to then demonstrate what is further required for enhanced therapeutic outcomes.

Concepts: Osteoporosis, Bone fracture, Physiology, In vivo, In vitro, Orthopedic surgery, Bone healing, Osteology

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One of the fundamental questions in forensic medicine and anthropology is whether or not a bone or bone fragment is human. Surprisingly at times for the extreme degradation of the bone (charred, old), DNA cannot be successfully performed and one must turn to other methods. Histological analysis at times can be proposed. However, the variability of a single human skeleton has never been tested. Forty-nine thin sections of long, flat, irregular and short bones were obtained from a well-preserved medieval adult human skeleton. A qualitative histomorphological analysis was performed in order to assess the presence of primary and secondary bone and the presence, absence and orientation of vascular canals. No histological sections exhibited woven or fibro-lamellar bone. Long bones showed a higher variability with an alternation within the same section of areas characterized by tightly packed secondary osteons and areas with scattered secondary osteons immersed in a lamellar matrix. Flat and irregular bones appeared to be characterized by a greater uniformity with scattered osteons in abundant interstitial lamellae. Some cases of “osteon banding” and “drifting osteons” were observed. Although Haversian bone represent the most frequent pattern, a histomorphological variability between different bones of the same individual, in different portions of the same bone, and in different parts of the same section has been observed. Therefore, the present study has highlighted the importance of extending research to whole skeletons without focusing only on single bones, in order to have a better understanding of the histological variability of both human and non-human bone.

Concepts: Bone, Skeletal system, Osseous tissue, Human anatomy, Endocrine system, Human skeleton, Skeleton, Osteology

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Most models of osteoporotic bone fractures are performed unilaterally (UL). We investigated healing of tibia osteotomy performed either UL or bilaterally (BL) in ovariectomized rats. Behavior of animals and muscle structure were assessed. Three-month-old female Sprague-Dawley rats were ovariectomized (n = 32). After 10 weeks, half the rats underwent UL osteotomy of tibia metaphysis (right limb) with plate osteosynthesis. The other rats were osteotomized BL. Half of the rats in each group received either standard pain treatment with carprofen (5 mg/kg body weight (BW), 1x/day for 2 days) or carprofen and buprenorphine (5 mg/kg BW, 1x/day and 0.03 mg/kg BW, 2x/day for 5 days) after osteotomy. The UL rats started to load the injured limb from day 27 ± 9; BL rats did this from day 4 ± 4 onward. The UL rats more frequently loaded only one hind limb; BL rats more often loaded both hind limbs. Osteotomy was not bridged in 20% of UL rats and in 4% of BL rats. Callus volume and bone volume fraction were lower in UL group. Weight and fiber size of UL-intact limb muscles were enhanced, compared to the osteotomized limb and those in BL group. Most of the other parameters which assess physiology, activity, body posture, head, or coat were not different. The effect of two pain therapies was not significant on any variable studied. Welfare of the animals was acceptable in all rats. In UL rats, bone healing was delayed. The more advanced healing in BL rats suggested a positive effect of earlier loading. In studies on bone healing, it is advisable to perform BL osteotomy.

Concepts: Osteoporosis, Bone fracture, Collagen, Healing, Orthopedic surgery, Osteology, Bilateralism, Unilateralism

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Bone fracture healing is sensitive to the fixation stability. However, it is unclear which phases of healing are mechano-sensitive and if mechanical stimulation is required throughout repair. In this study, a novel bone defect model, which isolates an experimental fracture from functional loading, was applied in sheep to investigate if stimulation limited to the early proliferative phase is sufficient for bone healing. An active fixator controlled motion in the fracture. Animals of the control group were unstimulated. In the physiological-like group, 1 mm axial compressive movements were applied between day 5 and 21, thereafter the movements were decreased in weekly increments and stopped after 6 weeks. In the early stimulatory group, the movements were stopped after 3 weeks. The experimental fractures were evaluated with mechanical and micro-computed tomography methods after 9 weeks healing. The callus strength of the stimulated fractures (physiological-like and early stimulatory) was greater than the unstimulated control group. The control group was characterized by minimal external callus formation and a lack of bone bridging at 9 weeks. In contrast, the stimulated groups exhibited advanced healing with solid bone formation across the defect. This was confirmed quantitatively by a lower bone volume in the control group compared to the stimulated groups. The novel experimental model permits the application of a well-defined load history to an experimental bone fracture. The poor healing observed in the control group is consistent with under-stimulation. This study has shown early mechanical stimulation only is sufficient for a timely healing outcome. This article is protected by copyright. All rights reserved.

Concepts: Scientific method, Bone fracture, Fracture, Healing, Endochondral ossification, Bone healing, Copyright, Osteology

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The relevance of blood supply for bone fracture healing has been discussed throughout the literature, using scaphoids as the most referred to. But, there is virtually nothing known about the relevance of blood supply for the vertebral fracture healing and even the guidelines of AO do not deal with this issue.

Concepts: Osteoporosis, Bone fracture, Heart, Orthopedic surgery, Bone healing, Osteology

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Fracture haematoma formation is the first and foremost important stage of fracture healing. It orchestrates the inflammatory and cellular processes leading to the formation of callus and the restoration of the continuity of the bone. Evidence suggests that blocking this initial stage could lead to an impairment of the overall bone healing process. This review aims to analyse the existing evidence of molecular contributions to bone healing within fracture haematoma, and to determine the potential to modify the molecular response to fracture in the haematoma with the aim of improving union times.

Concepts: Bone fracture, Wound healing, Healing, Typography, Stage, Bone healing, Periosteum, Osteology

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In the process of fracture healing, there are many cellular and molecular events that are regulated by mechanical stimuli and biochemical signals. To explore the unknown mechanisms underlying bone fracture healing, optimal fixation configurations, and the design of new treatment strategies, computational healing models provide a good solution. With the simulation of mechanoregulatory healing models, bioregulatory healing models and coupled mechanobioregulatory healing models, healing outcomes can be predicted. In this review, first, we provide an overview of current computational healing models. Their clinical applications are also presented. Then, the limitations of current models and their corresponding solutions are discussed in this review. Finally, future potentials are presented in this review. Multiscale modeling from the intracellular level to the tissue level is essential, and more clinical applications of computational healing models are required in future research.

Concepts: Osteoporosis, Molecular biology, Bone fracture, Chemistry, Orthopedic surgery, Model, Bone healing, Osteology

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Loss of hydrostatic pressures in microgravity may alter skin and bone microvascular flows in the lower extremities and may potentially reduce wound healing and bone fracture repair. The purpose of this study was to determine the rate at which skin and bone microvascular flows respond to head down tilt (HDT). We hypothesized that microvascular flows in tibial bone and overlying skin would increase at different rates during HDT. Tibial bone and skin microvascular flows were measured simultaneously using photoplethysmography (PPG) in a total of 17 subjects during sitting (control posture), supine, 6° HDT, 15° HDT, and 30° HDT postures in random order. With greater angles of HDT bone microvascular flow increased significantly, but skin microvascular flow did not change. Tibial bone microvascular flow increased from the sitting control posture (0.77 ± 0.41 V) to supine (1.95 ± 1.01 V, p=0.001), and from supine posture to 15° HDT (3.74 ± 2.43 V, p=0.004) and 30° HDT (3.91 ± 2.68 V, p=0.006). Skin microvascular flow increased from sitting (0.703 ± 0.75 V) to supine (2.19 ± 1.72 V, p=0.02), but did not change from supine posture to HDT (p=1.0). We show for the first time that microcirculatory flows in skin and bone of the leg respond to simulated microgravity at different rates. These altered levels of blood perfusion may affect rates of wound and bone fracture healing in spaceflight.

Concepts: Osteoporosis, Bone fracture, Wound healing, Healing, Orthopedic surgery, Bone healing, Osteology, Posture

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In the process of bone fracture healing, inflammation is thought to be an essential process that precedes bone formation and remodeling. We review recent studies on bone fracture healing from an osteoimmunological point of view.

Concepts: Osteoporosis, Bone fracture, Orthopedic surgery, Endochondral ossification, Bone healing, Osteology, Animal physiology

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During the investigation of fresh bone fractures, it might be difficult to visualize all the fracture lines that could contribute to the interpretation of the biomechanics behind a fracture. To optimize the examination of the fracture, the bones should first be defleshed to expose the osseous surface. To reveal small fracture lines more clearly, we developed two easy, fast, cheap and non-destructive methods to enhance fracture lines and bone defects by coloring the fracture lines with ink. One method consists of cooking the bone in ink, and the second method uses capillary action for ink penetration. We strongly recommend the use of the latter method with Talens® Black Indian Ink for the clearest results.

Concepts: Osteoporosis, Bone, Bone fracture, Fracture, Cartilage, Orthopedic surgery, Biomechanics, Osteology