Principles of paediatric trauma
Sebastian Dawson-Bowling, Pramod Achan, Timothy Briggs, Manoj Ramachandran, Stephen Key, Daud Chou in Orthopaedic Trauma, 2014
Embryonic bone development is either intramembranous or enchondral. Intramembranous ossification occurs in flat bones whereby undifferentiated mesenchymal cells aggregate into layers and differentiate directly into osteoblasts. In long bones, however, enchondral ossification proceeds by initial formation of a cartilage Anlage that is subsequently invaded by vascular buds, thus bringing osteoprogenitor cells that differentiate into osteoblasts. Early bone is highly vascular and consequently much less dense than mature bone, and, in addition, deposition is initially disorganized woven bone. Immature bone therefore has a lower Young’s modulus and is softer, more flexible and more ductile when compared with mature bone. It displays plastic behaviour not seen in adult bone.
Craniofacial Regeneration—Bone
Vincenzo Guarino, Marco Antonio Alvarez-Pérez in Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Blood vessels of the bone develop through the process of angiogenesis, which involves the proliferation of local endothelial cells to produce new blood vessels from pre-existing vessels in a remodeling process. The vasculogenesis is the formation of a vascular network, from a progenitor cell, angioblast or hemangioblast. The blood vessels supply the bone system with nutrients and oxygen, excrete waste biological materials, remove metabolites from the bone, provide the bone with specific hormones, growth factors and neurotransmitters secreted by other tissues, maintaining the bone cells survival and stimulating their activity. The craniofacial bones develop by two processes: intramembranous ossification and endochondral ossification. Intramembranous ossification is the main mechanism leading to a development of flats bones (e.g., maxillae, palatal bones, nasal bones, zygomatic bones) this process is related to a direct differentiation of mesenchymal stem cells into osteoblasts, initially with a fibrous membrane and finally replaced by a spongy bone, whereas the endochondral ossification is typical of long bones and the cranial base, this process has an intermediate stage with cartilage (Chu et al. 2014; Fishero et al. 2014; Filipowska et al. 2017). The development and maintenance of the endochondral and intramembranous bone formation are dependent on the bone vascular network (Filipowska et al. 2017; Prisby 2017).
Prenatal Development of the Facial Skeleton
D. Dixon Andrew, A.N. Hoyte David, Ronning Olli in Fundamentals of Craniofacial Growth, 2017
Intramembranous ossification is preceded by a fibrocellular proliferation derived from ectomesenchyme, in a matrix or ground-substance rich in mucopolysaccharides (Gardner, 1971), forming a membranous skeleton of the future skeletal elements (Johnson, 1986; Hall, 1987). Condensation of mesenchyme initiates the differentiation of bone-forming cells and is thus another critical step in the normal skeletal development sequence. When a given condensation fails to achieve its optimal, designated size there is potential for the resulting bone to be either smaller, of abnormal shape, or entirely absent. Condensations arise either by migration of cells from the immediate vicinity to form the focus or nucleus of the condensation, inhibition of cell death at the site compared to the rate in the surrounding cellular environment, or an increased cell packing density due to intensified mitotic activity (Bowen and Lockshin, 1981; Johnson, 1986; Thompson et al., 1989).
Comparison of the Bone Regenerative Capacity of Three-Dimensional Uncalcined and Unsintered Hydroxyapatite/Poly-d /l -Lactide and Beta-Tricalcium Phosphate Used as Bone Graft Substitutes
Published in Journal of Investigative Surgery, 2021
Yunpeng Bai, Jingjing Sha, Takahiro Kanno, Kenichi Miyamoto, Katsumi Hideshima, Yumi Matsuzaki
The human OCN gene encodes bone γ-carboxyglutamic acid protein, a secreted protein produced primarily by osteoblasts [39]. Consequently, OCN is routinely used as a serum marker of well-differentiated osteoblastic bone formation and is thought to regulate mineralization within the bone matrix. During the bone-defect healing period, calcium granules first expand into the fracture containing callus chondrocytes and are then transported into the extracellular matrix (ECM), where they form the initial mineral deposits with phosphate [40]. During this process, soft callus is transformed into hard callus; generally, the peak of hard callus formation is reached by 14 days in animal models. This change can be defined not only by the histomorphometry of mineralized tissue but also by the detection of ECM markers such as OCN, type I procollagen, alkaline phosphatase, and osteonectin [30]. OCN is also considered an osteoblast-specific gene that is expressed during ossification, along with master transcriptional factors such as Runx2 and Osterix [41, 42]. During embryonic and postnatal bone development and fracture healing, intramembranous ossification consists mainly of osteogenic mesenchymal condensation and direct differentiation into osteoblasts, eventually producing bone [43, 44]. By contrast, the process of endochondral ossification is characterized not only by the differentiation of chondrocytes by mesenchymal condensation to form a cartilaginous template that is eventually replaced with bone but also by osteoblast cells that sometimes participate to form the bone collar, which subsequently becomes cortical bone [43].
The Efficacy of Recombinant Platelet-Derived Growth Factor on Beta-Tricalcium Phosphate to Regenerate Femoral Critical Sized Segmental Defects: Longitudinal In Vivo Micro-CT Study in a Rat Model
Published in Journal of Investigative Surgery, 2020
Mohammed Badwelan, Mohammed Alkindi, Sundar Ramalingam, Nasser Nooh, Khalid Al Hezaimi
Platelet derived growth factor (PDGF) is a potent mitogen and chemoattractant for mesenchymal and osteogenic cells and stimulates angiogenic molecules which play an essential role in bone regeneration [11]. Although several isoforms of recombinant PDGF (AA, AB, BB, CC, and DD) have been reported to be released from platelets following tissue injury, PDGF-BB is considered capable of binding with all known receptor isotypes and possesses profound physiological functions [12, 13]. Preclinical studies in animals have reported the ability of PDGF, when used alone, to increase the rate of fracture repair [14] and induce new bone formation when injected subperiosteally [15]. Similarly, PDGF used in combination with mineralized bone allografts and xenografts, within calvarial and dental alveolar ridge bone defects, has been reported to form significant volumes of new bone both in animal and clinical studies [16, 17]. Based on a clinical study, Nevins and Reynolds [18] reported better bone augmentation around dental implant sites when using a combination of PDGF with beta-TCP. Nevertheless, new bone formation around dental implant sites at best mimics intramembranous ossification and is not comparable to bone regeneration within segmental defects, which occurs through endochondral ossification [19, 20].
Modelling the fracture-healing process as a moving-interface problem using an interface-capturing approach
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
M. Pietsch, F. Niemeyer, U. Simon, A. Ignatius, K. Urban
Nevertheless, woven-bone production exhibits similar characteristics in the compared models: first, intramembranous ossification starts on the cortical periosteal surface at some distance from the fracture site. In stiff fixation (case A), bone starts growing in an axial direction after a few weeks from both the periosteal and endosteal surfaces. However, with more flexible fixation, woven bone first forms a more pronounced callus by growing perpendicularly to the cortex, increasing the cross-sectional area and thus stabilising the fracture. Only then, can bone also grow towards the fracture gap, eventually closing it. Bridging first occurs peripherally to the initial gap, which reduces the strain within the gap, such that ossification can now occur directly between the cortical ends. The predicted time-to-bridging of both models differs by less than a week.
Related Knowledge Centers
- Bone
- Bone Healing
- Cartilage
- Fetus
- Medullary Cavity
- Mesenchyme
- Skeleton
- Skull
- Mesenchymal Stem Cell
- Endochondral Ossification