Osteomyelitis

Question 1

What is osteomyelitis? Causative organisms?

Answer 1

(1. ) Osteo = bone, myelo = marrow, it is = inflammation
(2. ) Inflammation of the bone or bone marrow that typically results from an infection.
(3. ) Most common causative organism is Stap. Aureus.

(4. ) Other pathogens:
- Coagulase -ve staph
- Aerobic gram -ve bacilli
- Strep, Ent, Anaerobes, Fungi, Myobacterium

(5. ) Specific ones to consider:
- Salmonella in sickle cell anaemia
- P.Aeruginosa in IV drug users

Question 2

RF of osteomyelitis (4).

Answer 2

1. Weak immune system or poor circulation due to uncontrolled co-morbidities e.g. DM, peripheral vascular disease
2. IVDU
3. Arthroplasties (joint replacements)
4. More common in children

Question 3

Pathophysiology of osteomyelitis

Answer 3

Microorganisms reach the bone and causes infection. This can be done by the following routes (and aetiologies):

1. Direct infection into the bone via trauma or surgery
2. Contagious spread
   - From soft tissues and joints e.g. cellulitis
   - DM, chronic ulcers, vascular disease, arthroplasties/prosthetic material
3. Haematogenous seeding (originating from bacteraemia)
   - Affects long bone’s metaphysis (children) or vertebrae (adults)
   - IV drug users: often pelvis or clavicle area
   - individuals undergoing hemodialysis, dental extraction

Question 4

Signs and Sx of osteomyelitis (6.)

Answer 4

(1. ) Look for: IVDU?, TB? Diabetic foot? bone/joint problems? inc risk for bacteraemia e.g. UTI, dialysis, catheter?
(2. ) Onset: several days

(3. ) Dull non-specific pain
- May be aggravated by movement –> reduced ROM

(4. ) Can be localised, acute = tenderness, warmth, erythema, swelling
(5. ) Systemic sx = Fever, rigors, sweats, malaise

(6. ) Location
- lumbar> thoracic> cervical
- hip, pelvis too
- OM in joint can also present as septic arthritis

Question 5

Ix of osteomyelitis

Answer 5

(1. ) Bloods: FBC, hi WCC. ESR, CRP
(2. )Bone biopsy and blood cultures: identify causative organism and sensitivities

(3. ) Plain X-ray
- Acute OM = osteopenia (dec bone density) after onset of infection
- Chronic OM = intramedullary scalloping, cavities, ‘fallen leaf’ sign.
- Other features: Cortical erosion, Periosteal reaction, Mixed lucency (darker on image), Sclerosis, Sequestra (necrotic bone), Soft tissue swelling

(4. ) Additional tests
- MRI = Marrow oedema from 3-5d, inflammation
- US = May show effusion, collections, abscesses

Question 6

Tx and Mx of osteomyelitis

Answer 6

Acute osteomyelitis:

• Affected limb should be immobilised
• Analgesia
• High dose Abx: 2w IV then 4w oral (organism must be identified)

Chronic Osteomyelitis:

• Surgical debridement if there is dead bone, biofilm development, tx failed
• IV antibiotics
• Long term functional rehabilitation.