Bone Injury and Inflammatory Bone Diseases

• Bone Necrosis

  Friable texture
• Scratching bone with sharp object

  Reveals crumbly bone
• Osteocytes of normal bone appear as dark cells
• If bone is necrotic, osteocytes are not visible and lacunae are empty
• Resorption

  Fractured Bone Spicule
• Woven Bone

  Scar (callus)
• Inflammation

  • Proliferation
  • Suppurative (pyogenic)
• Compared to other tissues, bone infections are difficult to treat
• Bone infections

  • Actinocycosis
  • Spinal Abscess
  • Chronic Osteomyelitis
• Chronic Osteomyelitis in horses (foals)

  • Rhodococcus equi
  • Omphaleblitis
  • Can cause meningitis
• Chronic Osteomyelitis in canines

  • Blastomycosis
  • Pulmonary hypertrophic Osteoarthropathy
  • Craniomandibular Osteopathy
• Bone Sequestrum


  Formed when a large piece of necrotic bone becomes isolated from circulation and cannot be reached by osteoclasts
• Involucrum


  A band of connective tissue that generally surrounds the sequestered dead bone
• Chronic, proliferative osteomyelitis

  Inflammation and necrosis of bone that induces abnormal remodeling characterized by the growth of bone nodules known as Osteophytes
• Osteophytes


  • Cover large portions of the periosteal bone or joint
  • Obliterate the entire diaphysis of the femur in this pig
• Suppurative (pyogenic) osteomyelitis

  Inflammation of bone resulting from bacteremia in a young animal
• Suppurative osteomyelitis

  • Characterized by neutrophilic inflammation and osteolysis
  • Exudate in the diaphysis and metaphysis of the bone
  • Metaphyseal blood vessels are commonly the site of septic osteomyelitis in farm animals and foals
• In osteomyelitis, the suffix myelitis means inflammation of bone marrow. It should not be confused with myelitis as in inflammation of the spinal cord (i.e., encephalomyelitis)
• Suppurative osteomyelitis

  • Neutrophils induce extensive lysis of the bone which often results in pathological fractures
  • Aspirate would reveal large numbers of neutrophils, some of which may contain bacteria
• Histopathology of osteomyelitis


  • Large cluster of leukocytes in the bone
  • Bone trabecula reabsorbed by osteoclastic activity and replaced by fibrotic tissue as a first step for repair
  • New woven bone will replace this localized area of fibrosis if infection is controlled
• Osteophytes


  • Cover large portions of the periosteal bone or joint
  • Obliterate the entire diaphysis of the femur in this pig
• Suppurative (pyogenic) osteomyelitis

  Inflammation of bone resulting from bacteremia in a young animal
• Suppurative (neutrophilic) inflammation and osteolysis

  • Appear as a large pale area of discolored bone
  • Exudate in the diaphysis and metaphysis of the bone
• Myelitis

  Inflammation of the spinal cord
• Osteomyelitis


  Inflammation of bone marrow
• Metaphyseal blood vessels

  • Common site of septic osteomyelitis in farm animals and foals
• Suppurative (pyogenic) osteomyelitis

  • Neutrophils induce extensive lysis of the bone often resulting in pathological fractures
• Osteomyelitis histopathology

  • Large cluster of leukocytes in the bone
  • Bone trabecula reabsorbed by osteoclastic activity and replaced by fibrotic tissue as a first step for repair
  • New woven bone will replace this localized area of fibrosis if infection is controlled
• Bone infections

  • Commonly occur as a sequel of bacteremia
  • Difficult to treat compared to other tissues
• Actinomycosis - Lumpy Jaw

  • Localized osteomyelitis with exudate in the ulcerated skin (fistula)
  • Pyogranulomatous inflammation of the mandible generally unilateral
  • Bone deformation and severe exostosis occur following episodes of bone necrosis and repair
• Spinal abscess

  Abscess in the vertebrae, common in pigs and cattle
• Tail bite skin infections

  Often result in bacterial emboli lodging in the vertebral bodies (spondylitis)
• Several animals affected in a herd

  Indicates poor health management
• Vertebral inflammation

  Often extends to the meninges and causes meningitis
• Compression of the spinal cord could lead to pathological fractures in the vertebrae
• Causes of spinal abscess


  • Tail biting in the herd
  • Poor health management
• Spondylitis

  Inflammation of the vertebrae
• Meningitis


  Inflammation of the meninges
• Chronic osteomyelitis


  Chronic bone inflammation
• Rhodococcus equi


  Bacteria that can cause osteomyelitis in foals