Osteomyelitis

Question 1

Osteomyelitis - background

Answer 1

1. Def = bone infection
2. Frequency greatest in infants, with 1/3 of cases in first 2y and 1/2 by 5y; M:F = 2:1
3. Infection usually seen in metaphyseal region of bones
4. Most infections spread via haematogenous route from primary site of entry (e.g. respiratory, GI, ENT or skin sites).
5. May also occur by direct inoculation (open fractures, penetrating wounds) or by local extension from adjacent sites

Question 2

Osteomyelitis - types (3)

Answer 2

1. Acute
2. Subacute (2-3 weeks’ duration)
3. Chronic - may develop sequestrum (dead bone) and involucrum (new bone)

Question 3

Osteomyelitis - etiology

Answer 3

1. Staphylococcus aureus is the most common pathogen in all age groups

Other organisms seen include:

2. Neonates = GBS and gram negative enteric bacilli
3. 2y = gram positive cocci, Pseudomonas aeruginosa
4. Adolescents = Neisseria gonorrhoeae

Question 4

Osteomyelitis - sx

Answer 4

Neonates
1. Typically do not appear ill and may not have fever

Older children

2. Pain, limping, refusal to weight bear
3. Overlying bone may be tender (+ warm), with or without swelling
4. +/- fever, malaise, flu-like symptoms
5. Long bones typically affected (tibia > femur > humerus)

Question 5

Osteomyelitis - ix

Answer 5

1. Bloods = FBE, ESR, CRP, blood cultures (positive in 50%)
2. X-ray of bone. Early stages may be normal. Destructive changes after 10d
3. Ultrasound (may show periosteal elevation); may perform U/S guided aspiration for MCS
4. MRI for soft tissue ax (bone marrow involvement, abscess formation, joint involvement…)
5. Radionuclide bone scan if site of infection is unclear

Question 6

Osteomyelitis - mx

Answer 6

1. Refer to orthopaedics
2. Empirical therapy = flucloxacillin 50mg/kg up to 2g IV QID. Modify tx based on results of MCS

Duration of therapy:
Acute osteomyelitis
3. Neonate: IV 4 weeks, total duration 4 weeks (i.e. all IV)
4. Child: IV 3d, total duration minimum 3 weeks (can be completed with oral therapy)

Chronic osteomyelitis
5. Child: IV may not be necessary, total duration minimum 6 weeks oral therapy

Question 7

Osteomyelitis - complications (4)

Answer 7

Systemic
1. Septicaemia

Local

2. Pathological fracture
3. Sequestration (dead bone becomes separated during process of necrosis)
4. Growth disturbance