Bone Histology

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Seeing much, suffering much and studying much
are the three pillars of learning. Benjamin
Disraeli
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Bone Histology Fracture Healing

• Dr. Venkatesh M. Shashidhar
• Associate Professor of Pathology
• Fiji School of Medicine

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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).

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Bone Anatomy

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

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Bone Formation
Key Words Mineralization Calcification Ossificati
on Hardness Tensile strength Volkmanns
canal Haversian canal Lacunae Osteon Trabeculae

• Intramembranous
• Endochondral

Bone Growth

• Interstitial
• Oppositional

Bone Function

• Mineral homeostasis.
• Hemopoiesis.

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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
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Blood Supply to Bone
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Types of Bone tissue

• Woven bone Irregular immature fetus/
• Lamellar bone regular mature.
• Circumferential
• Concentric
• Interstitial
• Trabecular
• Compact Spongy - lamellar bone
• Enchondral / intramembranous formation.

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Compact Bone
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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.

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Osteogenic cells
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Bone Remodeling

• 5-10 bone / year.

• Vitamin D
• Nutrition
• Physical activity
• Age, hormones
• PTH, PHRP
• IL1, TNF,TGF-ß

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Osteoclast in lacuna
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The Histologic Types

• Compact bone
• Spongy bone
• Lamellar bone
• Woven bone
• Osteoid
• Callus

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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.

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Compact BoneSpongy Bone
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Spongy (cancellous) Bone

• Does not contain osteons.
• trabeculae surrounding red marrow spaces

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Cancellous bone (Polarization.M)
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Endochondral Ossification

• Within cartilage. Interstitial growth. Cells
  swell, burst, replace by osteocytes with Ca

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Endochondral Ossification

• Secondary ossification - epiphysis
• Articular cartilage and epiphysial plate -

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Membranous Ossification

• Skull, mandible, clavicle.
• Fibrous membrane, Os. center, trabeculae

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Osteoblasts
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Growth plate
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Fractures

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

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Types of Fracture
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Healing in Bone

• 1D - Hematoma formation (fibrin mesh)
• 3D - Inflammation PDGF, IL, TGF
• 1W - Soft callus granulation, matrix.
• 3-6W - Callus ossification, woven bone
• 8W - Re-modeling absorb/deposit, strength,
  lamellate.

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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
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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
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Healing in Bone
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Healing in Bone
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Compound Fracture
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Fracture Head of Humerus
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Immobilization Plaster cast
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Bone healing Callus
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Callus Woven bone
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Callus Woven bone
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Factors affecting Healing

• Systemic Local factors
• Immobilization
• Improper reduction abnormal position
• Infection. Debris, dead tissue in wound
• Joint involvement

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Complications

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

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Involucrum
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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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If You Fail to Plan, Then you plan to Fail!