Paediatrics: Osteomyelitis

Osteomyelitis

• Inflammation of bone usually results from bacterial infection.
• Early recognition and diagnosis are crucial.
• 50% of cases occur in children less than 5 years old.
• No racial differences, but males are twice as likely to be affected as females.
• Long bones of the lower extremities are more likely affected.

Aetiology of Osteomyelitis

• Hematogenous dissemination of bacteria to bones, especially in growing bones with rich vascular supply.
• Organisms deposited in metaphyseal capillaries replicate and spread to cortical bone.
• Osteomyelitis may also occur from contiguous spread of infection after trauma or bite wounds.

Pathophysiology

• Bacterial focus establishment leads to phagocyte migration, inflammatory exudate (metaphyseal abscess), and tissue destruction.
• Pressure increases, spreading through the porous metaphyseal space to the subperiosteal space.
• Purulence beneath the periosteum may lift the periosteal membrane, impairing blood supply to the cortex and metaphysis.

Clinical Features

• Long bones (femur, tibia, humerus) are most commonly affected.
• Symptoms include fever, malaise, bone pain, swelling, redness, and pseudoparalysis.
• Children may refuse to bear weight, walk, or move the affected extremity.
• Asymmetric movement of extremities and past medical history of underlying conditions (e.g., sickle cell disease or immunodeficiency) are relevant.

Examination Findings

• Patients may look ill and febrile.
• Edema, erythema, and warmth are evident over the affected portion of bone.
• Palpation of the bone reveals a focal site of maximum tenderness.
• Normal range of movement of the affected limb is usually preserved.

Diagnosis

• Radiologic:
  • Radiography: initial films may be normal, with or without soft tissue swelling; bone destruction occurs in 10-15 days.
  • MRI: gold standard in early infections, shows increased marrow intensity with surrounding inflammation.
  • Technetium radionuclide bone scan: reveals increased osteoblastic activity of the infected bone.
• Laboratory investigations:
  • Blood culture
  • Bone aspirate for m/c/s
  • FBC
  • C-reactive protein
  • ESR

Treatment

• Medical:
  • Therapy considerations: age, local resistance pattern, suspected pathogens
  • Empiric treatment: anti-staph agents (e.g., vancomycin), 3rd generation cephalosporin; duration: 3-6 weeks
• Surgical: debridement may be needed

Complications

• Chronic osteomyelitis
• Venous thrombosis
• Bone necrosis
• Pathologic fractures
• Disturbance in bone growth
• Abnormal gait
• Limb shortening
• Arthritis

Differential Diagnosis

• Cellulitis
• Pyomyositis
• ALL
• Subcutaneous abscess
• Fractures
• Septic arthritis
• Bone tumour (osteosarcoma, Ewing sarcoma)
• Poliomyelitis
• Child abuse
• Trauma

Prognosis

• Re-occurrence in 5-10% of cases

Chronic Osteomyelitis

• Typical radiologic findings: Sequestrum and involucrum
• Treatment: surgical removal of sinus tracts and sequestrum, if present