Suspected Bone or Joint Infection

Bone or joint infection are serious, can lead to severe complications and can be life threatening if not treated.

Principles of management of suspected septic arthritis and osteomyelitis:

• With a single red and hot swollen joint, infection must be considered. Prompt diagnosis, urgent washout and drainage of joint and rapid treatment with antibiotics.
• There is likely involvement of several clinical teams (paediatrics, orthopaedics, microbiology) to determine the management plan, whether to opt for bone aspiration / biopsy as well as joint aspiration, take the appropriate cultures and choice of antibiotics (given by intravenous route initially).
• Travel history is important - infections that can cause bone and joint infection or reactive arthritis vary across the world and with variable risk factors: e.g., Brucellosis from exposure to animals and unpasteurised milks (more common in the Middle East and Southern Europe), Lyme disease and exposure to ticks (more common in North Europe and North America), Arboviruses (e.g., Chikungunya, Zika and Dengue) are endemic in Asia, Latin America and Sub-Saharan Africa, Blastomycosis in Latin America. The immunocompromised (from disease or treatment or co-existent infection with Human Immunodeficiency Virus [HIV]) are at greater risk. More Information about infections and their musculoskeletal features is available from the Centre for Disease Control and Prevention. 
• Blood tests, cultures and imaging (radiographs, ultrasound and sometimes CT or MRI) are needed. Gram stain cultures are required and tests for mycobacterial infection may also be needed. Acute Rheumatic Fever (ARF) may present with a single swollen joint and needs to be considered with at risk populations in endemic areas. 
• Tuberculosis (TB) needs to be suspected in endemic areas or children who have had contact with family from an endemic area. Children with TB might appear well or have systemic symptoms (night sweats, poor growth or weight loss).  It should also be considered in a child who is unwell with a swollen joint, and especially if they are immunosuppressed due to disease (co-existent HIV is common) or treatment. Inflammatory markers may be elevated and there can be anaemia or chronic disease. The joint may not be hot or red but joint damage can be indolent with chronic abscess and sinus formation. Diagnosis rests on clinical suspicion, Mantoux or positive TB testing using quantiFERON® gold, followed by synovial biopsy.
• Children with sickle cell disease are at risk of osteoarticular complications - these include septic arthritis, osteomyelitis and gout as a consequence of hyperuricaemia.
• There are usually high inflammatory markers (ESR, CRP, procalcitonin), high white cell count (neutrophils) and these guide clinical progress and response to treatment. CRP is a better predictor than ESR for acute infection.
• Radiographs may be normal or show fluid or soft tissue swelling or increased joint space. Bony changes may not be apparent for 2-3 weeks. Ultrasound may show joint effusion and is useful to aid aspiration (particularly the hip joint). MRI is very sensitive to early changes and identify bone involvement. Isotope bone scan (increased uptake or hot spots) can be useful if MRI is not available.
• Antibiotics are usually given empirically whilst awaiting cultures. Antibiotics are usually continued for several weeks (IV) and then oral, pending clinical progress and blood tests (acute phase reactants - ESR, CRP - and white cell count).
• Analgesia and resting the joint / limb (splinting) are important.