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Terminology:Terminology:
Bone is a dynamic biological tissue composed of metabolically active cells that are integrated into a rigid framework.
• Graft• Vascularized bone graft• Autograft• Isograft• Homograft (allograft)• Heterograft (xenograft)• Composite graft• Implants• Bone conduction, induction, integration
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Types of bone:Types of bone:
– Histological:• Immature (Woven, Bundle) • Mature (compact, cancellous)
– Anatomical:• Flat (skull, scapula, )• Long (femur, tibia, )• Sesamoid (patella)
– Healing:• Membranous (enchondral) cranial vault, facial bone,• Endochondral skull base, long bones, ribs
• Dual mechanism mandible, sphenoid, occipital bones
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Endochondral Ossification:Endochondral Ossification:
• Within cartilage. Interstitial growth. Cells swell, burst, replace by osteocytes with Ca+
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Endochondral Ossification:Endochondral Ossification:
• Secondary ossification - epiphysis• Articular cartilage and epiphysial plate -
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Membranous Ossification:Membranous Ossification:
• Skull, mandible, clavicle.• Fibrous membrane, Os. center, trabeculae
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Bone StructureBone Structure
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•65% inorganic (Ca)•35% organic (34% collagen, ..)
(1% cells)
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Bone cellsBone cells
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OsteocytesOsteocytes
• Derived from:– Mesenchymal precursor cells – stem cells in bone marrow – osteoprogenitor cells of periosteum
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OsteoclastsOsteoclasts
• Derived from:– Hematopoetic stem cells in bone marrow (GM-CFU) that
undergo endoreduplication – old theory = fusion of monocytes
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RemodelingRemodeling
• Wolff’s law
-“bone formed in response to mechanical load”
dynamization/staged destabilization-increased load can lead to increased bone formation
-lamellar bone and marrow cavity form
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Type of Fracture HealingType of Fracture Healing
• Direct Healing– Primary Osteonal Reconstruction• Contact healing• Gap healing
– Secondary Osteonal Reconstruction
• Indirect Healing
• Distraction Osteogenesis
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Indirect Bone Healing
Stages:
1) the inflammatory stage (hematoma);
2) the repair stage (soft hard callus);
3) the late remodeling stage.
Types:- Rigid- Semi-rigid- Non-fusion
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Indirect Bone Healing(continue)
Factors affecting healing: I) General… II) Local…
Complications:• Malunion – arthritis.• Delayed union.• Non union.• Joint involvement - ankylosis• Bone necrosis – nutrient artery• Pseudoarthrosis
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Indications of bone graftIndications of bone graft
• Nonunion fractures• Highly comminuted fractures• Fractures with bone loss• When expecting a delayed union• Augmentation and normalization of facial
contour• Creation of congenitally missing parts of
skeleton
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Why we do bone graft?Why we do bone graft?
• Osteognesis– viable cells contribute to new bone formation
• Osteoinduction– proteins, factors, hormones are transferred that
modulate host cells
• Osteoconduction– matrix upon which new bone can be formed– implants can be osteoconductive
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Types of autogenous graftTypes of autogenous graft
• Cancellous bone– metaphyseal regions, increase surface area, 80%
porosity• Cortical bone– Increase mechanical strength, 10% porosity– frequently corticocancellous
• Osteochondral– cartilage attached to parent bone
• Composite– fresh graft added to preserved allograft
• Vascularized grafts– Vascularized corticocancellous grafts
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Sources of autogenous graftsSources of autogenous grafts
• Iliac creast• Rib• Calverial bone• Scapula• Radius• Vascularized fibula• Vascularized rib• medial aspect of tibial diaphysis
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Healing of autograft:Healing of autograft:
• Inflammation• Revascularization– 2x time for Cancellous grafts due to porosity
• Osteoinduction– decreased with cortical grafts
• Osteoconduction– decreased with cortical grafts
• Remodeling – initiated with osteoclasts (vs. osteoblasts) with
cortical grafts
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Healing of allograft:Healing of allograft:
• “Creeping substitution”
• Basic bone remodeling at graft-host interface– bone resorption is followed by bone
production
• May take years
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Bone Graft Substitute (BMP)Bone Graft Substitute (BMP)
Bone
Morphogenetic Protein
Only known extracellular protein known to be able to initiate new bone formation
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BONE and CARTILAGEBONE and CARTILAGE• Bone (osteo)
• vascular• mesodermal origin• cells and matrix• osteoblasts• osteocytes• osteoclasts• periosteum• collagen type 1• appositional growth• -----• compact, cancellous, woven
• Cartilage (chondro)• avascular - requires diffusion• mesodermal origin• cells and matrix• chondroblasts• chondrocytes• -----• *perichondrium• collagen types 1,2• appositional growth• interstitial growth• hyaline, elastic, fibrocartilage
*except articular cartilage
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THANK YOUTHANK YOU