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Acute Osteomyelitis

 

 

  • Age
    • Usually affects children
      • Septic arthritis more common in adults; osteomyelitis in children

 

  • Hallmark characteristics
    • Destruction of bone
    • Periosteal new bone formation
  • Organisms
    • Newborns
      • S. aureus
      • Group B streptococcus
      • E. coli
    • Children
      • S. aureus
    • Adults
      • S. aureus (most common)
      • Enteric species
      • Streptococcus
    • Drug addicts
      • Pseudomonas (most common)
      • Klebsiella
    • Sickle cell disease
      • Salmonella
  • Pathogenesis
    • Hematogenous spread
    • Direct implantation from a traumatic / iatrogenic source
    • Extension from adjacent soft-tissue infection
  • Location
    • Lower extremity (most common)
      • Over pressure points in diabetic foot
    • Vertebrae
      • Lumbar  > thoracic > cervical
    • Radial styloid
    • Sacroiliac joint

 

ACUTE NEONATAL OSTEOMYELITIS

  • Age
    • Onset <30 days of age
  • Little or no systemic disturbance
  • Multicentric involvement more common
    • Often joint involvement
  • Bone scan falsely negative / equivocal in 70%

ACUTE OSTEOMYELITIS IN INFANCY

 

  • Age
    • <18 months of age
  • Pathomechanism
    • Spread to epiphysis through blood vessels
  • Marked soft-tissue component
  • Subperiosteal abscess with extensive periosteal new bone formation
  • Complications
    • Frequent joint involvement
  • Prognosis
    • Rapid healing
       

ACUTE OSTEOMYELITIS IN CHILDHOOD
 

  • Age
    • 2-16 years of age
  • Pathomechanism
    • Trans-physeal vessels closed
    • Primary focus of infection is in metaphysis
  • Findings
    • Sequestration frequent
    • Periosteal elevation
    • Small single / multiple osteolytic areas in metaphysis
    • Extensive periosteal reaction parallel to shaft (after 3-6 weeks)
    • Shortening of bone with destruction of epiphyseal cartilage
    • Growth stimulation by hyperemia and premature maturation of adjacent epiphysis

ACUTE OSTEOMYELITIS IN ADULTHOOD

  • Delicate periosteal new bone
  • Joint involvement common
    • Septic arthritis
  • X-ray findings
    • Initial radiographs often normal for as long as 7-10 days
    • Localized soft-tissue swelling adjacent to metaphysis with obliteration of usual fat planes (after 3-10 days)
    • Area of bone destruction (lags 7-14 days behind pathologic changes)

 

Bone destruction of head of 2nd metatarsal
with periosteal new bone formation

characteristic of osteomyelitis

 

  • Involucrum = cloak of laminated /spiculated periosteal reaction (develops after 20 days)
  • Sequestrum = detached necrotic cortical bone (develops after 30 days)
  • Cloaca formation = space in which dead bone resides

  • MR findings
    • Bone marrow hypointense on T1WI + hyperintense on T2WI (= water-rich inflammatory tissue)
  • DDx
    • Neuropathic osteoarthropathy
    • Aseptic arthritis
    • Acute fracture
    • Recent surgery
    • Ewing’s sarcoma
  • Findings
    • Focal / linear cortical involvement hyperintense on T2WI
    • Hyperintense halo surrounding cortex on T2WI = subperiosteal infection
    • Hyperintense line on T2WI extending from bone to skin surface and enhancement of borders (= sinus tract)
  • Nuclear Medicine (accuracy approx. 90%):
    • Ga-67 scans
      • 100% sensitivity
      • Increased uptake 1 day earlier than for Tc-99m MDP
    • Gallium helpful for chronic osteomyelitis
  • Static Tc-99m diphosphonate
    • 83% sensitivity
    • 5-60% false-negative rate in neonates and children
  • Complications of osteomyelitis
    • Abscess in soft-tissue
    • Fistula or sinus formation
    • Pathologic fracture
    • Extension into joint producing septic arthritis
    • Growth disturbance due to epiphyseal involvement
    • Severe deformity with delayed treatment

 

 

Dahnert 4th Edition

 

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