Fracture Biomechanics / Classification Flashcards
Bone Macroarchitecture
Rigid endoskeleton (epiphysis, metaphysis, diaphysis)
Mineralized osseous tissue (marrow, endosteum, periosteum, nerves, vessels, cartilage)
Cortical bone
Shaft of long bones
Highly dense / relatively acellular
Develops in direct proportion to stress
Blood surrounds bone
Trabecular bone
Ends of long bones
Porous network
Large surface area
Bathed in blood
Microscopic bone anatomy
Cellular components + ECM (organic + inorganic)
Osteoblasts
Cover bone surfaces
Form organic matrix osteoid
Osteocytes
Osteoblasts incorporated into osteoid
(Bone cell)
Contain cytoplasmic projections
Osteoclast characteristics
Large, multinucleated cells
Function: bone resorption (control by local acid environment)
Form from blood monocytes
Organic components of ECM
95% Type I collagen
5% ground substance (Proteoglycans + glycosaminoglycans)
Inorganic ECM components
Hydroxyapatite (Ca-phosphate)
Laid down by osteoblasts as unmineralized osteoid —> mineralized by alkaline phosphates
Weak spot of bone during longitudinal growth
Zone of hypertrophy (where cells are stacked in rows)
Function of bone
Protection
Shape
Blood cell production
Mineral/fat storage
Movement
Acid-base balance
Bone formation
“Condensations” - aggregates of bone elements in fetal tissues - undifferentiated mesenchymal stem cells - osteoprogenitor cells
Intramembranous ossification (direct development from condensations)
Endochondral ossification (via cartilage intermediate)
Intramembranous ossification
Flat bones of skull
Osteoprogenitor cells in cell condensation —> osteoblasts —> produce bone matrix
Bony spicules form + fuse —> trabeculae —> unit to form spongy bone
OP cells in spongy area produce marrow + periosteum —> osteoblasts of periosteum produce compact bone
Endochondral ossification
OP cells —> chondrocytes —> growth of cartilaginous bone-to-be —> primary/secondary centers of ossification —> formation of articular cartilage and epiphyseal plate (growth/phsyeal plate)
Primary center of ossification forms …
Before or after birth
Forms diaphysis