Bones Degenerative - Pathology

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Bones and Cartilage - Metabolic diseases

Bones and Cartilage - Fractures

Osteoporosis (Atrophy)

  • Lesion, not a disease
  • Reduction in bone mass due to reduced osteoid (bone atrophy)
  • Bone resorption exceeds formation -> pathological loss of bone
  • Resorbed from:
    • Trabeculae, preserving the weight bearing ones until last
    • Endosteal surface of cortical bone
    • Along vascular channels
  • Longitudinal section
    • Fewer thin trabeculae
    • Enlarged medulla
    • Thin, porous cortex
  • Bone which remains is normally mineralised
  • Can be localised or generalised*Caused by:
    • Starvation - in farm animals due to protein and energy deficiency
    • Nutritional deficiency (calcium) and hypocalcaemia -> bone resorption
    • Senility
    • Physical inactivity (disuse) - muscular inactivity and reduced weight bearing, e.g. during limb casting
    • Glucocorticoids
    • Intestinal parasitism - in ruminants, malabsorption due to severe infestation
    • Copper deficiency - in lambs, calves, foals, pigs and dogs -> brittle bones
  • May be reversed in young growing animals


Osteosis

  • Also called Aseptic necrosis or Ischaemic necrosis
  • Degeneration and necrosis of osseous tissue
  • Due to bone marrow pressure and ischaemia resulting from
  • Grossly:
    • Necrotic bone difficult to recognise
    • Sometimes, periosteum becomes dry, dull and detaches easily
    • On longitudinal section
      • Yellow-white necrotic bone
      • Scattered cancellous and endosteal bone
  • Histologically:
  • Necrotic bone is slowly resorbed, sequstered or covered by new woven bone
  • Persists
  • May not be detected radiographically
  • Associated with Calve-Legg Perthe's disease


Bone cysts

Bone cysts (Image sourced from Bristol Biomed Image Archive with permission)
  • May be seen radiographically
  • Must be distinguished from neoplasia
  • Expansile lytic masses
  • Do not appear aggressive
  • Subchondral cysts
  • Simple cysts
  • Aneurysmal bone cysts
    • Expansie lesions
    • Arise from disturbance of vascular tissue of bone marrow
    • Grossly:
      • Appear as blood filled sponge
      • Spaces separated by fibrous trabeculae
    • Histologically:
      • Proliferation of undifferentiated mesenchymal cell with multinucleated osteoclast-like cells
      • Haemorrhage and haemosiderosis
  • Radiography is essential to help differentiate with cavity of a neoplasm


Calcium hydroxylapatite deposition disease


Physeal dysplasia with slipped capital femoral epiphysis

  • Slipped capital femoral epiphysis seen in dogs, foals and calves
  • Associated with severe trauma
  • Pigs – manifestation of osteochondrosis with only minimal trauma required
  • Most common type of physeal fracture in small animals and the proximal femur is the most common site
  • In horses, physeal dysplasia is synonymus with physitis
  • More about Physeal dysplasia