Suspected Bone or Joint Infection
- Bone or joint infection are serious, can lead to severe complications and can be life threatening if not treated.
- 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.
- Acute Rheumatic Fever (ARF) may present with a single swollen joint and needs to be considered with at risk populations in endemic areas.
- 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, synovial fluid cell count, gram stain and take the appropriate cultures from the synovial fluid.
- 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.
- In the absence of positive cultures, or response to antibiotics, then Chronic Recurrent Multifocal Osteomyelitis needs to be considered.
- Blood cultures should be done regardless of fever and should be repeated with repeated febrile episodes. This is especially important in a child who is immunocompromised - it is important to consider Tuberculosis (TB), anaerobic organisms and fastidious / unusual organisms, the choice of antibiotics first empirically and then tailored to the organism grown and susceptibilities (given by intravenous route initially).
- 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 can identify bone involvement. CT or Isotope bone scan (increased uptake or hot spots) can be useful if MRI is not available, but radiation risk must always be considered.
- 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.
- 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.
- 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).
- TB 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 Human Immunodeficiency Virus [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 and if necessary, 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.
- Children who are immunocompromised due to immunodeficiencies, or co-existent infection with Human Immunodeficiency Virus [HIV] or due to immunosuppressive treatments are at risk of bone and joint infections. They are at high risk of growing unusual organisms and may present with an atypical clinical presentation. The C- reactive protein (CRP) is reliable marker of burden of disease and response to treatment and can be raised for a prolonged time. Treatment may be prolonged in an immunocompromised host.
More Information about infections and their musculoskeletal features is available from the Centre for Disease Control and Prevention.