Orthopaedic infections in children
Acute Haematogenous Osteomyelitis
Pathology
1. Inflammation
- Acute inflammatory reaction with vascular congestion
- Rise in intra-osseous pressure causing intense pain
2. Suppuration
- At 2-3 days pus forms within the bone and forces its way down the haversian canals to the surface where it forms a sub-periosteal abscess
- The pus can spread from here back into the bone, into an adjacent joint or into the soft tissues (Where there is an intra-articular physis)
- Vertebral infection can spread through the end plate, disc and into the next vertebral body
3. Necrosis
- At 7 days, rising pressure, vascular stasis, infective thrombosis and periosteal stripping compromise the blood supply to the bone resulting in bone death resulting in a sequestrum
4. New bone formation
- At 10-14 days this forms from the deep surface of the stripped periosteum forming the involucrum
5. Resolution
- With release of the pressure and appropriate antibiotics healing can occur
- There may be permanent deformity
- Unpublished work (quoted in Dee) shows that experimentally bacteria injected intravenously will settle in the metaphyses of bone preferentially
NB - in 10% of cases there is more than one site of infection.

Clinical Features
Children (invariably)
- Pain, malaise, fever
- Limp or not weight bearing
Infants
- Failure to thrive, drowsiness, irritable
Adults
- The commonest site is the thoracolumbar spine (Batson's venous complex from the pelvis)
- Other bones involved especially in DM, IVDA, immunosuppressed
Examination
- Local erythema, swelling and tenderness indicates that the pus has broken through the periosteum
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