Osteomyelitis

Key Features

Essentials of Diagnosis

• Movement of the extremity causes pain, resulting in pseudoparalysis.

• Soft tissue swelling.

• Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).

• Surgical drainage of abscess plus antibiotics.

• Antibiotic therapy for early osteomyelitis without abscess.

General Considerations

• An infectious process that usually starts in the spongy or medullary bone and extends into compact or cortical bone

• Commonly preceded by trauma, the lower extremities are more likely to be affected

• Most commonly caused by hematogenous spread of bacteria from other infected or colonized areas (eg, pyoderma or upper respiratory tract) but it may occur as a result of direct invasion from the outside (exogenous), through a penetrating wound (nail) or open fracture

• Staphylococcus aureus is the most common infecting organism and has a tendency to infect the metaphyses of growing bones

• Streptococci (group B Streptococcus in neonates and young infants, Streptococcus pyogenes in older children) are a less common cause of osteomyelitis

• Pseudomonas aeruginosa is common in cases of nail puncture wounds

• Children with sickle cell anemia are especially prone to osteomyelitis caused by Salmonella species

Clinical Findings

• In infants

  • Irritability

  • Diarrhea

  • Failure to feed properly

  • Temperature may be normal or slightly low

  • White blood cell count may be normal or only slightly elevated

  • Pseudoparalysis of the involved limb may be present

• In older children

  • Severe local tenderness and pain

  • High fever, rapid pulse

  • Knee joints may be affected in age 7–10 years

  • Tenderness is most marked over the metaphysis of the bone where the process has its origin

Diagnosis

Laboratory Findings

• Elevated ESR and CRP

• Blood cultures are often positive early

• Important test is the aspiration of pus or biopsy of involved bone

• It is useful to insert a needle into the bone in the area of suspected infection and aspirate any fluid present

• Fluid should be stained for organisms and cultured

Imaging

• Radiography

  • Findings progress from nonspecific local swelling, to elevation of the periosteum, with formation of new bone from the cambium layer of the periosteum occurring after 3–6 days

  • As infection becomes chronic, areas of cortical bone are isolated by pus spreading down the medullary canal, causing rarefaction and demineralization of the bone

  • Isolated pieces of cortex become ischemic and form sequestra (dead bone fragments)

• Bone scan is sensitive (before plain radiographic findings are apparent) but nonspecific and should be interpreted in the clinical context

• MRI

  • Can demonstrate early edema and subperiosteal abscess

  • Can help confirm and localize disease prior to plain film changes

Treatment

Nonpharmacologic

• Splinting minimizes pain and decreases spread of the infection through lymphatic channels in the soft tissue

Pharmacologic

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