Septic arthritis

Question 1

An 18 month old boy is brought in to ED by his parents. He has a 2 day history of fevers, malaise, and refusing to weight bear on his right leg.

Answer 1

Impression
Given the non-weight bearing in conjunction with the hx of fevers, I am concerned about a possible septic arthritis. This is a medical emergency and requires urgent treatment to prevent joint degeneration and systemic infection.

DDx to consider include;
- Other infective: cellulitis, erysipelas, chest/urinary infection
- MSK: other bony/soft-tissue injury (SUFE, Perthes disease[osteonecrosis of femoral head], DDH), acute myositis, transient hip synovitis (post viral infection)
- Arthritis: reactive arthritis, juvenile idiopathic arthritis, Kawasaki disease
- NAI
- Malignancy

Goals
- conduct thorough assessment including A to E to rule out systemic illness
-institute appropriate

Question 2

Septic arthritis - Assessment

Answer 2

Assessment
- Screen for any HD instability and treat emergently

Question 3

Septic arthritis - History

Answer 3

History
- Sx: sx: fevers, chills, sweats, localising features (chest sx, urinary sx, bowel changes, ), joint pain? - SOCRATES. Hx of non-weight bearing - temporal relationship to fevers? Had this before? Any trauma
- associated: systemic features, rash
- REDS: 7 days of sx, night pain, constitutional sx of malignancy, complete inability to weight bear/walk, urine or bowel changes, severe pain
- RISKS: sick contacts, immunocompromised, recent trauma/surgery, weight loss,
- Medications (corticosteroids)
- Paeds Hx: developmental, blue book, immunisations

Question 4

Septic arthritis - Examination

Answer 4

Examination
- General appearance + vitals: usually appear unwell if septic arthritis (look toxic)
- MSK: palpation, ROM, inspection (erythema, tenderness, swelling), tenderness/irritable hip?, resting limb position
o hip
o knee
- Skin: signs of cellulitis, erysipelas, etc

Question 5

Septic arthritis - Investigations

Answer 5

Investigations
Key/diagnostic
- joint aspirate and MCS (controversial)
o looking for predominance of PMNs.
- septic screen
- X-Ray of Joint

• Bedside: Swabs and MCS if skin rashes/lesions
• Bloods: Cultures, FBC, lactate/VBG, UEC, CRP/ESR, ASOT, ANCA/ASCA
• Imaging: X-Ray, Ultrasound, MRI, Bone scan

Other: utilise Kocher Criteria for septic arthritis

Question 6

Septic arthritis - Management

Answer 6

Management

Definitive
- empirical ABx (IV)
o staph: fluclox and Vanc, cephazolin if under 4
o strep or gram -ve: Ceftriaxone
- Contact paeds ortho for wash out in theatres and surgical debridement of necrotic tissue; can be done via open, arthroscopy or needle aspiration

Supportive
- hospital admission for monitoring and theatres/ABx
- NBM before theatres
- fluids + electrolytes
- analgesia, antipyretics
- regular observations
- physical therapy