“Seeing much, suffering much and studying much are the three pillars of learning.” –Benjamin Disraeli. Bone Histology & Fracture Healing. Introduction:. Bone is a dynamic tissue Osteoblasts - osteoid (type 1 collagen) Calcium and phosphate (calcium hydroxyapatite)
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“Seeing much, suffering much and studying much are the three pillars of learning.”–Benjamin Disraeli
Introduction: • Bone is a dynamic tissue • Osteoblasts - osteoid (type 1 collagen) • Calcium and phosphate (calcium hydroxyapatite) • Osteoclasts are multi-nucleated cells which resorb bone (PTH).
Bone Anatomy • Diaphysis • Metaphysis • Epiphysis – Prox/Dist • Epiphyseal line • Periosteum • Compact cortical bone • Spongy bone • Articular Cartilage • Medullary cavity • Marrow • Nutrient artery
Bone Formation: Key Words: Mineralization Calcification Ossification Hardness Tensile strength Volkmann’s canal Haversian canal Lacunae Osteon Trabeculae • Intramembranous • Endochondral Bone Growth: • Interstitial • Oppositional Bone Function: • Mineral homeostasis. • Hemopoiesis.
An individual at prolonged bed rest quickly begins to lose bone mineral density (BMD). Conversely, an athlete who engages in sports requiring repetitive jumping and landing is likely to have a higher BMD
Types of Bone tissue: • Woven bone – Irregular – immature – fetus/# • Lamellar bone – regular – mature. • Circumferential • Concentric • Interstitial • Trabecular • Compact & Spongy - lamellar bone • Enchondral / intramembranous formation.
The matrix of bone : • Contains inorganic salt Calcium Hydroxyapatite in collagen framework. • Osteoblasts - Calcification - Mineralization • Minerals hardness • Collagen fibres Tensile strength. • Collagen is necessary for Calcification.
Vitamin D Nutrition Physical activity Age, hormones PTH, PHRP IL1, TNF,TGF-β 5-10% bone / year. Bone Remodeling
The Histologic Types: • Compact bone • Spongy bone • Lamellar bone • Woven bone • Osteoid • Callus
Compact Bone: • Osteons or Haversian systems. • Osteons contain blood vessels, lymphatic vessels, nerves, and osteocytes along with the calcified matrix. • Osteons are aligned in the same direction along lines of stress - Lamellar bone. • No osteons or BV in trabecular bone.
Spongy (cancellous) Bone • Does not contain osteons. • trabeculae surrounding red marrow spaces
Endochondral Ossification: • Within cartilage. Interstitial growth. Cells swell, burst, replace by osteocytes with Ca+
Endochondral Ossification: • Secondary ossification - epiphysis • Articular cartilage and epiphysial plate -
Membranous Ossification: • Skull, mandible, clavicle. • Fibrous membrane, Os. center, trabeculae
Fractures: • Break in the bone. • Simple / Compound – infection. • Single - Horizontal, oblique, spiral, • Comminuted – multiple. • Greenstick – partial children. • Torus – compression of cortex – children.
Healing in Bone: 1D - Hematoma formation (fibrin mesh) 3D - Inflammation – PDGF, IL, TGF 1W - Softcallus – granulation, matrix. 3-6W - Callus – ossification, woven bone 8+W -Re-modeling – absorb/deposit, strength, lamellate.
Stages of wound healing Resolution/ Remodeling Vessel regression, Collagen remodeling Proliferation Reepithelialization, Angiogenesis, Fibrogenesis, Inflammation PMNs, Macrophages, Lymphocytes Hemostasis Fibrin clot, platelet deposition Time after injury
Stages of wound healing Resolution/ Remodeling Vessel regression, Collagen remodeling Proliferation Reepithelialization, Angiogenesis, Fibrogenesis, Inflammation PMNs, Macrophages, Lymphocytes Hemostasis Fibrin clot, platelet deposition 1D 3D 1wk 6wk 8wk Time after injury
Factors affecting Healing: • Systemic & Local factors • Immobilization * • Improper reduction – abnormal position • Infection. Debris, dead tissue in wound • Joint involvement
Complications: • Delayed healing. • Non healing. • Joint involvement - ankylosis • Abnormal position – arthritis. • Bone necrosis – nutrient artery • Involucrum formation. • Pseudoarthrosis
Summary & Further Reading: • Bone types, histology, formation, • Osteons, HS, lacunae, lamellae • Calcium, PO4 ,Vit D, PTH & Calcitonin, • Healing - stages, factors, complications • Pseudoarthrosis, involucrum, • Diseases: • Osteoporosis, Osteomalacia & Rickets
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