Makindo Medical Notes

In patients with Sickle cell disease - Staph aureus and salmonella are the most commonly involved organisms.

About

• Infection of bone which can lead to pain, deformity and chronic disease if untreated
• A surgical, sometimes paediatric, microbiological emergency

Aetiology

As with septic arthritis, bone infection is usually caused by haematogenous spread. Infection often occurs in the metaphyses of long bones where the slow flow through the looped vessels combined with microtrauma is believed to encourage seeding of infection during a bacteraemia

• Differing picture in adults and children
• Association with sickle cell disease commonly asked about
• Microbial source from the skin, or another infective source

Microbiology

• Staphylococcus aureus 85%
• E.coli (IVDU/Urosepsis)
• Pseudomonas (IVDU/Urosepsis)
• Klebsiella (IVDU/Urosepsis)
• Salmonella (sickle cell)
• Haemophilus influenza (neonates)
• Group B Streptococcus (neonates)
• Fungal immunocompromised

Types

• Direct from open fracture, skin wound, post op
• Indirect: blood spread from infection elsewhere

Adult disease

• In those over the age of 45 the vertebral bodies are more likely infected
• This is due to changes in blood flow with spinal osteomyelitis
• Tuberculosis still remains prevalent in certain groups

Childhood disease

• Haematogenous spread usually to seed long bone metaphysis
• Infants - Staph aureus, Streptococcus agalactiae, Escherichia coli
• After 1st year - S. aureus, Streptococcus pyogenes, Haemophilus influenzae
• Haemophilus influenzae falling due to new vaccination policies

Risks

• Open fractures, prostheses, Diabetes, Alcoholism, Chronic steroids
• AIDS, Immunosuppression, Sickle cell
• IV drug abuse - haematogenous spread to vertebrae

Clinical

• Toxic, Febrile and rigors, Localised Bone pain, tenderness, warmth, swelling
• Children can have just vague symptoms for weeks however many hold the joint
• Can be simply also a PUO and suspicious organism

Investigations

• Plain X-Ray unreliable (will take 2-4 weeks for demineralization of bone)
  • Tissue swelling, demineralization
  • Sequestra (necrotic bone with granulation tissue)
  • Involucrum (periosteal new bone around the sequestra)
  • Brodie's abscess a small oval cavity in metaphysis of long bone
• CT: useful to depict margins. See findings on X Ray
• MRI (Gold standard) most sensitive and specific and is able to identify soft-tissue/joint complications. Shows bone marrow oedema.
• USS (may show periosteal lifting)
• Three phase bone scan
• Blood cultures are positive in 50 per cent of cases of acute osteomyelitis
• CRP and ESR and WCC are typically raised
• Need to obtain pus by open surgery and biopsy or needle aspiration before starting antibiotics ideally

Differential

• Synovitis
• Trauma and fracture
• Bone cancer

Management (Take microbiological advice on all cases)

General principles for the management of infection should be followed. Pus needs to be drained but otherwise the treatment is medical. Debate continues over the duration of treatment and indeed whether antibiotics should be parenteral or oral: management varies from region to region and relates to the local bacteriological prevalences. In addition to antibiotics, treatment consists of: Rest/splintage of affected limb and Analgesia. Treatment of the underlying condition, e.g. nutritional deficiency, sickle cell disease.

• Based on results of culture and local sensitivities
• Flucloxacillin and Fusidic acid for 4–6 weeks with IV initially.
• Patients may need a central line or long line
• Specific Organisms and antibiotics
  • Staph aureus - IV Penicillin or Vancomycin + Rifampicin
  • Streptococci - Penicillin
  • Anaerobes - Clindamycin or Metronidazole
  • Pseudomonas - Ciprofloxacin
• Surgical Management
  • Debridement and removal of necrotic tissue and drainage
  • Replacement of dead space with tissue flaps or bone grafts
  • Internal/external fixation. Amputation may be needed