Histologic features of bone

• Types (Fig. 1.1; Table 1.1)

  •  bone: lamellar or mature

  • Immature and pathologic bone: woven, more random, more osteocytes, increased turnover, weaker

    • Lamellar bone is stress oriented; woven bone is not.

  • Cortical (compact) bone

    • Constitutes 80% of the skeleton

    • Consists of tightly packed osteons or haversian systems

      • Connected by haversian (or Volkmann) canals

      • Contains arterioles, venules, capillaries, nerves, possibly lymphatic channels

    • Interstitial lamellae: between osteons

      • Fibrils connect lamellae but do not cross cement lines.

      • Cement lines define the outer border of an osteon.

    • Nutrition provided by intraosseous circulation through canals and canaliculi (cell processes of osteocytes)

    • Characterized by slow turnover rate, higher Young’s modulus of elasticity, more stiffness

  • Cancellous bone (spongy or trabecular bone)

    • Less dense, more remodeling according to lines of stress (Wolff ’s law)

    • Characterized by high turnover rate, smaller Young’s modulus, more elasticity

       

      FIG. 1.1 Types of bone. Cortical bone consists of tightly packed osteons. Cancellous bone consists of a meshwork of trabeculae. In immature bone, unmineralized osteoid lines the immature trabeculae. Pathologic bone is characterized by atypical osteoblasts and architectural disorganization.

      Colorized from Brinker MR, Miller MD: Fundamentals of

      orthopaedics, Philadelphia, 1999, Saunders, p 2.

       

       

      Microscopic Subtypes Characteristics Examples Appearance
      Lamellar	Cortical	Structure is oriented along lines of stress Strong	Femoral shaft
      	Cancellous	More elastic than cortical bone	Distal femoral metaphysis
      Woven	Immature	Not stress oriented	Embryonic skeleton Fracture callus
      	Pathologic	Random organization Increased turnover Weak Flexible	Osteogenic sarcoma Fibrous dysplasia

       

      Table 1.1 Types of Bone

       

       

       

      Modified from Brinker MR, Miller MD: Fundamentals of orthopaedics,

      Philadelphia, 1999, Saunders, p 1.