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Chapter: Paediatrics: Bones and joints

Paediatrics: Infections: osteomyelitis

Infection of bone. The frequency of osteomyelitis is greatest in infants, with 33% of all cases in the first 2yrs, and 50% occurring by 5yrs. Male > female (2:1).

Infections: osteomyelitis

 

Infection of bone. The frequency of osteomyelitis is greatest in infants, with 33% of all cases in the first 2yrs, and 50% occurring by 5yrs. Male > female (2:1).

 

Pathogenesis

 

Infection usually seen in the metaphyseal region of bones. Most infections are spread via the haematogenous route from a p site of entry (e.g. res-piratory, GI, ENT, or skin sites). Infection may also occur by direct in-oculation (open fractures, penetrating wounds) or local extension from adjacent sites. In the infant, transphyseal vessels are patent and infection may spread to the adjacent joint causing a septic arthritis. In adolescents infection tends to spread through the medullary canal.

 

Types of osteomyelitis

 

   Acute.

   Subacute (2–3wks duration).

   Chronic: may develop ‘sequestrum’ (dead bone) and ‘involucrum’ (new bone).

   Bone abscesses may become surrounded by thick, fibrous tissue and sclerotic bone (Brodie’s abscess).

 

Aetiology

 

The yield for bacterial growth from synovial fluid and bone aspirate is small; therefore organisms are not always isolated. Staphylococcus aure-us is most common in children in all age groups. Other organisms seen include the following:

   Neonates: group B streptococcus and Gram –ve enteric bacilli.

 

   <2yrs: Haemophilus influenzae (rare).

 

   >2yrs: Gram +ve cocci, Pseudomonas aeruginosa.

 

   Adolescents: Neisseria gonorrhoeae.

 

Consider salmonella in SCD. Tuberculosis is rare.

 

Symptoms and signs

 

   Neonates characteristically do not appear ill and may not have fever.

 

   Older children have pain, limping, refusal to walk/weight bear, fever, malaise, flu-like symptoms. Overlying bone may be tender (+ warm), with/without swelling. Long bones principally affected: Tibia > femur > humerus.

 

Differential diagnosis

 

This includes:

   JIA

 

   Lyme/post-streptococcal arthritis

 

   Acute leukaemia

 

   Neuroblastoma

 

   Neoplasm (e.g. osteoid osteoma, osteosarcoma, Ewing’s sarcoma).

 

   CRMO.

 

   LCH.

Investigations

 

Blood: FBC, ESR, CRP, blood cultures (positive in 50%).

 

X-ray of bone: early stages may be normal; soft tissue oedema may be visible. Late stages reveal metaphyseal rarefaction. Destructive changes in bone appear after 10 days.

 

US-guided aspiration: for microscopy and culture.

MRI: soft tissue assessment—bone marrow involvement; abscess formation, joint effusion, subperiosteal extension.

Bone scans: good for acute osteomyelitis; can identify up to 90% of joint involvement (seen as hot spots) and differentiate joint from bone involvement; good for infections of pelvis, proximal femur, and spine.

Open biopsy may be necessary.

Consider immunological evaluation if atypical organism.

 

Treatment

 

Medical: IV antibiotics for a minimum of 2wks, followed by oral antibiotics for 4wks. Early liaison with microbiologist required.

 

Surgical: drainage and debridement if there is frank pus on aspiration or a sequestered abscess or collection (not accessible to antibiotics).

 

Prognosis 

Usually excellent if treated early. Disease recurrence/pro-gression to chronic infection is seen in <10%.

 

Complications

 

Systemic: may include septicaemia.

 

Local: pathological fracture, sequestration, growth disturbance.

 

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Paediatrics: Bones and joints


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