Bone Histology & Fracture Healing

1. “Seeing much, suffering much and studying much are the three pillars of learning.”–Benjamin Disraeli

2. Bone Histology & Fracture Healing

3. 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).

4. Bone Anatomy • Diaphysis • Metaphysis • Epiphysis – Prox/Dist • Epiphyseal line • Periosteum • Compact cortical bone • Spongy bone • Articular Cartilage • Medullary cavity • Marrow • Nutrient artery

5. 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.

6. 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

7. Blood Supply to Bone:

8. Types of Bone tissue: • Woven bone – Irregular – immature – fetus/# • Lamellar bone – regular – mature. • Circumferential • Concentric • Interstitial • Trabecular • Compact & Spongy - lamellar bone • Enchondral / intramembranous formation.

9. Compact Bone:

10. 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.

11. Osteogenic cells:

12. Vitamin D Nutrition Physical activity Age, hormones PTH, PHRP IL1, TNF,TGF-β 5-10% bone / year. Bone Remodeling

13. Osteoclast in lacuna;

14. The Histologic Types: • Compact bone • Spongy bone • Lamellar bone • Woven bone • Osteoid • Callus

15. 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.

16. Compact Bone&Spongy Bone:

17. Spongy (cancellous) Bone • Does not contain osteons. • trabeculae surrounding red marrow spaces

18. Cancellous bone: (Polarization.M)

19. Endochondral Ossification: • Within cartilage. Interstitial growth. Cells swell, burst, replace by osteocytes with Ca+

20. Endochondral Ossification: • Secondary ossification - epiphysis • Articular cartilage and epiphysial plate -

21. Membranous Ossification: • Skull, mandible, clavicle. • Fibrous membrane, Os. center, trabeculae

22. Osteoblasts:

23. Growth plate:

24. Fractures: • Break in the bone. • Simple / Compound – infection. • Single - Horizontal, oblique, spiral, • Comminuted – multiple. • Greenstick – partial children. • Torus – compression of cortex – children.

25. Types of Fracture:

26. 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.

27. 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

28. 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

29. Healing in Bone:

30. Healing in Bone:

31. Compound Fracture

32. Fracture Head of Humerus

33. Immobilization – Plaster cast

34. Bone healing: Callus

35. Callus – Woven bone

36. Callus – Woven bone

37. Factors affecting Healing: • Systemic & Local factors • Immobilization * • Improper reduction – abnormal position • Infection. Debris, dead tissue in wound • Joint involvement

38. Complications: • Delayed healing. • Non healing. • Joint involvement - ankylosis • Abnormal position – arthritis. • Bone necrosis – nutrient artery • Involucrum formation. • Pseudoarthrosis

40. Involucrum

42. 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

43. If You Fail to Plan, Then you plan to Fail!