Osteomyelitis

Question 1

Explain Osteomyelitis

Answer 1

Infection the bone.

Usually bacterial in origin, especially if acute.

Some chronic can be fungal.

Question 2

What type of bone is most commonly affected

Answer 2

Vertebrae

In children long bones more common

Question 3

How does infection reach the bone?

Answer 3

Haematogenous spread

Direct inoculation (from open fracture e.g.)

Direct spread from nearby infection

Question 4

Common causative organisms

Answer 4

S. aureus (msot common)

Streptococci spp.

Enterobacter spp.

H. influenzae

P. aeruginosa (especially in IVDU)

Salmonella spp. (especially in patients with sickle cell disease)

Question 5

Pathophysiology

Answer 5

Once bacteria enter the bone tissue they express adhesins to bind to the tissue and produce a ECM.

Through this the pathogen is able to propagate, spread and seed.

In chronic cases it can lead to devascularisation of the affected bone and necrosis.

This leads to a floating piece of dead bone called sequestrum acting like a reservoir for infection.

An involucrum can also form following sequestrum formation where the region becomes encased in a thick sheath of periosteal new bone.

Question 6

Risk factors

Answer 6

DM

Immunosuppression

Alcohol excess

IVDU

Question 7

What does any suspicion of OM in DM warrant?

Answer 7

MRI scan for diagnosis

Question 8

Clinical features

Answer 8

Severe pain (unless diabetic)

Low grade pyrexia

Constant pain that can be worse at night.

Question 9

Examination findings

Answer 9

Site will be tender

Overlying swelling and erythema

If lower limb is affected the patient may be unable to weight bear.

Question 10

What else to examine?

Answer 10

Potential soruces of infection like pock marks or sinuses from IVDU.

Cellulitic areas

Penetrating wounds

Stigmata of concurrent infection

Question 11

Dx

Answer 11

SA

Traumatic injuries

Primary or secondary bone tumours

Question 12

Ix

Answer 12

Routine blood tests including FBC, CRP and ESR

Blood cultures

Plain X-ray

Definitive diagnosis is through MRI imaging

Gold standard diagnosis is from culture from bone biopsy at debridement

Question 13

X-ray findings

Answer 13

Tend to only be visible from 7-10 days post-initial infection

Osteopaenia

Periosteal thickening

Endosteal scalloping

Focal cortical bone loss

Question 14

Management

Answer 14

If clinically well -> Long term IV abx (>4 wks) tailed to any cultures avaiable.
Usually no surgical intervention is needed.

If patient deteriorates, limb shows evidence of deterioration or imaging shows progressive bone destruction -> Surgical management involving curettage of the area.

Question 15

Complications

Answer 15

Overwhelming sepsis and mortality

Growth disturbance and premature physeal closure in children.

Recurrence of infection

Question 16

Clinical features of chronic OM

Answer 16

Localised ongoing bone pain and non-specific infection symptoms.

Draining sinus tract and they may have difficulties in mobility

Question 17

Ix.

Answer 17

Often show normal inflammatory markes and negative blood cultures.

X-ray

MRI

Biopsy

Question 18

Management

Answer 18

Surgical management with local bone and soft tissue debridement + extensive long-term abx therapy.

Question 19

Post-op management

Answer 19

Complex staged reconstruction with prolonged rehabilitation.