Osteomyelitis

Question 1

Define

Answer 1

Infection of the bone marrow, which may spread to the bone

cortex and periosteum via the Haversian canals

→Results in inflammation destruction of the bone±Necrosis if the periosteum becomes involved

Subsequent bone remodelling and often, associated deformity

*Sequestrum –when dead bone becomes detached from healthy bone
Sequestrum remains in situ and acts as a focus for ingoing infection

Most common site of infection is the distal femur and the

proximal tibia in children and cancellous bone in adults

Infection resulting from haematological bacterial seeding

from a remote source

More commonly associated with children

Occurs with rapidly growing and vascular metaphysis of

growing bones

Also in pts with distant foci of infection (e.g. infected

catheters)

Direct (continuous)

Infection due to direct contact of infected tissue with bone –

e.g. during surgical procedure or direct trauma

Clinical signs will be more localised and often multiple

organisms involved

Question 2

Causes

Answer 2

90% staph aureus

Bacterial infection from indirect inoculation from skin (e.g. trauma, operative, chronic skin ulcers, haematogenous spread)

Question 3

Risk factors

Answer 3

trauma, prosthetic device, DM (freq in diabetic foot ulcers); peripheral artery disease; chronic joint disease; alcoholism/IVDU; chronic steroids use/immunosuppression; TB, HIV/AIDS, sickle cell, catheter related bloodstream infection

Question 4

Epidemiology

Answer 4

prevalence increasing due to ↑prevalence ofpredisposing conditions such as DM and PVD

Bimodal age distribution with acute haematogenous more likely in children; and contiguous more likely in adults

Question 5

Symptoms

Answer 5

Pain in the affected area

Fever

Malaise

Rigors

History of preceding skin lesion, sore throat, trauma or operation

NOTE: infants may not show localising signs

Question 6

Signs

Answer 6

Localised erythema

Tenderness

Swelling

Warmth

Painful/limited movement of affected limb

Seropurulent discharge from an associated wound or ulcer

Question 7

Investigations

Answer 7

Bloods

• FBC
• Blood culture
• ESR
• CRP

Swabs of wound or discharge

Radiographs

Radioisotope bone scan - shows areas of increased activity