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Basic science in Orthopaedic
- 1. ORTHOrocks Keiko Gwendoline A.Victoria RN, MD Department of Orthopaedic Region II Trauma and Medical Center Bayombong, Nueva Vizcaya
- 2. Bony skeleton • remarkableorgan that serves both a • Structural function • Reservoir function
- 4. Modeling • allows forthe formation of new bone at one site and the removal of old bone from another site within the same bone.
- 5. Remodeling • Much ofthe cellular activity in a bone consists of removal and replacement at the same site
- 6. Cells • Osteoblasts, osteocytes,osteoclasts
- 8. BONE CELL TYPES •Osteoblasts •Function: produce bone matrix (“osteoid”). Make type 1 collagen and other matrix proteins • Line new bone surfaces and follow osteoclasts in cutting cones • Receptors: PTH (parathyroid hormone), vitamin D, glucosteroids, estrogen, PGs, ILs
- 9. Osteocytes • Osteoblast surroundedby bone matrix. • Represent 90% of all bone cells • Function: maintain & preserve bone. Long cell processes communicate via canaliculi. • Receptors: PTH (release calcium), calcitonin (do not release calcium)
- 10. Osteoclasts • Large, multinucleatedcells derived from the same line of cells as monocytes & macrophages • Function: when active, use a “ruffled border” to resorb bone; found in Howship’s lacunae • Receptors: calcitonin, estrogen, IL-1, RANK L. Inhibited by bisphosphonates
- 11. BONE FORMATION • Boneformation (ossification) occurs in 3 different ways: 1. Enchondral 2. Intramembranous 3. Appositional
- 12. Enchondral • Bone replacesa cartilage anlage (template). • Osteoclasts remove the cartilage, and osteoblasts make the new bone matrix, which is then mineralized. • • Typical in long bones (except clavicle).
- 14. Intramembranous • • Bonedevelops directly from mesenchymal cells without a cartilage anlage. • Mesenchymal cells differentiate into osteoblasts, which produce bone. • • Examples: flat bones (e.g., the cranium) and clavicle
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- 18. Lamellar • Mature bone •highly organized with stress orientation
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- 20. • Proteoglycans • Macromoleculesmade up of a hyaluronic backbone w/ multiple glycosaminoglycans • Glycosaminoglycans (GAG): made of core protein w/ chondroitin & keratin branches Gives bone compressive strength
- 21. CORTICAL (COMPACT BONE)CANCELLOUS BONE
- 22. Cortical (compact) • Strong,dense bone, makes up 80% of the skeleton • Composed of multiple osteons (haversian systems) with intervening interstitial lamellae
- 24. Cancellous (spongy/trabecular) • Crossedlattice structure, makes up 20% of the skeleton • High bone turnover rate.
- 25. BONE FORMS • Longbones •Form by enchondral ossification (except clavicle): primary (in shaft) and secondary growth centers
- 26. • 3 partsof long bone: • Diaphysis: shaft, made of thick cortical bone, filled with bone marrow • Metaphysis: widening of bone near the end, typically made of cancellous bone • Epiphysis: end (usually articular) of bone, forms from secondary ossification centers
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- 30. • Bone iscomposed of multiple components: • 1. Organic phase (“matrix:” proteins, macromolecules, cells) • 2. Inorganic phase (minerals, e.g., Ca) • 3. Water
- 31. Inorganic phase • Approximately60% of bone weight • Calcium hydroxyapatite Ca10(PO4)6(OH) Primary mineral in bone. Adds compressive strength. • Osteocalcium phosphate “Brushite” is a secondary/minor mineral in bone.
- 32. Organic phase • 90%of organic phase • Type 1 collagen gives tensile strength • Mineralization occurs at ends (hole zones) and along sides (pores) of the collagen fibers.
- 33. Collagen types andlocations
- 34. Noncollagen proteins • e.gosteocalcin • #1 indicator of increased bone turnover • Osteonectin and osteopontin
- 35. Water • Approximately 5%of bone weight (varies with age and location) • Periosteum surrounds the bone, is thicker in children, and responsible for the growing diameter (width) of long bones.
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- 40. BONE METABOLISM Calcium Calcium(Ca) plays a critical role in cardiac, skeletal muscle, and nerve function. • Normal dietary requirement 500-1300mg. • 99% of body’s stored calcium is in the bone. • Calcium levels directly regulated by PTH and Vitamin D 1,25. Phosphate • Important component of bone mineral (hydroxyapatite) and body metabolic functions • 85% of body’s stored phosphate is in the bone.
- 46. Regulation of Calciumand Phosphate Metabolism Hormone Parathyroid hormone (PTH) 1,25-D3 (steroid) Calcitonin (peptide) Factors stimulating production Decreased serum Ca++ Elevated PTH Decreased serum Ca++ Decreased serum Pi Elevated serum Ca++ Factors inhibiting production Elevated serum Ca++ Elevated 1,25(OH)2D Decreased PTH Elevated serum Ca++ Elevated serum Pi Decreased serum Ca++ Net effect on calcium and phosphate concentrations in extracellular fluid and serum Increased serum calcium Decreased serum phosphate Increased serum calcium Decreased serum calcium (transient)
- 47. • STAGES OFENCHONDRAL F RACTURE REPAIR
- 48. •Hematoma Formation •Soft callus •Hardcallus •Remodeling
- 49. Hematoma Formation • Firstconsequence of fracture is a local structural disruption of the bone and the associated marrow, periosteum, surrounding muscle, and blood vessels. • Lasts for 7 days • Periosteum and local soft tissues are stripped off
- 52. Repair of softcallus formation • Soft callus forms, initially composed of collagen; • this is followed by progressive cartilage and osteoid formation.
- 53. Repair of hardcallus formation • Osteoid and cartilage of external, periosteal, and medullary soft callus become mineralized as they are converted to woven bone (hard callus)
- 54. Remodeling • Osteoclastic and osteoblasticactivity converts woven bone to lamellar bone with true haversian systems. • Normal bone contours are restored; even angulation may be partially or completely corrected.