Osteoporosis

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
    • Physiological loss of skeletal mass with age
    • May be excessive in some individuals
    • Histologically - dead osteocytes and empty lacunea
  • 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