Bone and joint infection for children presenting to hospital
DIAGNOSIS
Temperature ≥38.5°C, unable to weight bear, pain on passive joint movement
A raised CRP in a child with corresponding clinical history and examination findings is suspicious for bone and joint infection (but normal CRP/ESR does not exclude infection if early in disease course)1.
Amended Kocher’s criteria for septic arthritis (SA)2:
- Temperature > 38.5°C
- Unable to weight bear
- CRP >20mg/L
- WCC >12 x 109/L
In cellulitis not responding to standard treatment, deeper infection should be considered
DIFFERENTIAL DIAGNOSES3
- Septic arthritis
- Osteomyelitis
- Transient synovitis
- Discitis
- Fracture/soft tissue injury
- Inflammatory joint or muscle disease
- Lyme arthritis
- Development dysplasia of hip
- Perthes disease (4-10 year olds, boys > girls)
- Slipped upper femoral epiphysis (11-14 year olds, boys > girls, more likely if obese)
- Non accidental injury
- Malignancy
- Sickle cell vaso-occlusive crisis
- Chronic recurrent multifocal osteomyelitis (CRMO) / chronic non-bacterial osteomyelitis (CNO) - consider if unusual location e.g. clavicle, multifocal, no antibiotic response
See Table 1 for differentials of limp in children by age
INVESTIGATIONS
- FBC, CRP, ESR, blood cultures (before antibiotics commenced)
- Plain radiographs of affected bone or joint
- Ultrasound is the first line investigation for septic arthritis
- If joint or bone washout + aspiration performed, fluid should be sent for microscopy including gram stain and culture in plain universal culture pot and also in blood culture bottles (follow local guidance). Consider sending sample for molecular testing (targeted PCRs [see list of most likely organisms] +/- 16s PCR) in particular if patient on antibiotics at time of surgery or if culture negative at 48 hours.
- If immunocompromised child or risk factors for atypical infection, discuss with micro/ID about additional investigations.
- MRI is gold standard imaging for osteomyelitis or discitis, however may not always be feasible in all settings*
- In osteomyelitis, bone biopsy should only be performed when diagnostic uncertainty or symptoms not resolving with treatment
- Uncomplicated osteomyelitis# does not require biopsy or surgery
*prioritise if diagnostic uncertainty or persisting fever despite antibiotics indicating possible collection requiring source control. If an osteoarticular infection is diagnosed, may consider repeat plain radiographs after 1-2 weeks (as outpatient) to establish whether bony changes present (would require longer total treatment course than septic arthritis)
Most likely causative organisms
- Staphylococcus aureus
- Kingella kingae (particularly in children <5 years)
- Streptococcus pyogenes (GAS)
- Streptococcus pneumoniae
- Haemophilus influenzae
- Salmonella spp. (in those with sickle cell disease)
- Consider TB
- Consider Group B Streptococcus in neonates
MANAGEMENT PRINCIPLES4
- Admit for inpatient care at local hospital if expertise is sufficient - MDT input (orthopaedics, paediatrics, microbiology) with regional paediatric infectious diseases team input where required
- Early transfer of complex cases# to specialist centres for management by paediatric orthopaedics and paediatric infectious diseases teams, with repatriation when clinically appropriate
- Empirical intravenous antibiotics should be started immediately in children with septic shock (even prior to confirmation diagnosis of bone and joint infection). Choice of antibiotics as per local / national guidelines
- Management of presumed septic arthritis is urgent washout of the joint
- Where possible, sampling should precede antibiotics, but do not withhold antibiotics if sampling delayed
- Early IV to oral switch is safe in the majority of children with osteoarticular infections and reduces length of hospital stay and the need for central intravenous access5,6
- Early consideration of definitive intravenous access in complex cases# ideally to coincide with another procedure (e.g. at time of biopsy or washout)
- In patient with uncomplicated disease, early IV to oral switch (at 48-72 hours) should be considered if good clinical and biochemical response
- Oral switch after 72 hours can also be considered in those with S. aureus bacteraemia if good clinical and biochemical response (improvement in pain, resolution of fever and falling CRP)6
- If child well enough for discharge but not ready for oral switch, consider provision for intravenous antibiotics through a paediatric outpatient parenteral antimicrobial therapy (OPAT) service7 unless Social / caregiver risk factors. Ensure robust clinical governance systems and documentation in place for children being ambulated. Provide verbal and written safety netting information (septic arthritis / osteomyelitis)
- Each child should have discharge plan with dates, location of follow up, duration of treatment and predicted complications / parameters for seeking review
- Follow up with orthopaedic specialist who anticipates bone fragility, monitors growth and can manage consequences of growth disturbance and joint damage. Clinical examination and x-ray imaging required as part of out-patient follow-up to assess long term complications (joint contracture, growth arrest, hyaline cartilage loss, Brodie abscess formation)
- If complex infection# or not improving, discuss with regional infectious diseases team
OSTEOMYELITIS
- Surgical intervention (with every effort to protect growth plates) to be considered if:
- inadequate response to antibiotics
- large collection of pus on imaging
- If adjacent joint effusions, these should be aspirated with joint washout
Total antibiotic duration: 3-4 weeks if simple infection**, may require ≥6 weeks treatment if complex infection# 8
SEPTIC ARTHRITIS
- In septic arthritis urgent irrigation and drainage of joint is required, and repeated if necessary
- Consider possibility of osteomyelitis in the adjacent bones
Total antibiotic duration: 2-3 weeks if simple infection**, may require longer treatment course if complex infection# 8
SIMPLE INFECTION
(i.e. unifocal site / no evidence complex infection)
Consider oral antibiotic switch at 48-72 hours if:5,6
- Improvement in pain
- Resolution of fever
- Falling CRP
Choice of antibiotics as per local / national guidelines
COMPLEX INFECTION#
(i.e. age <3 months, multifocal site, significant bone destruction, significant immunosuppression, sepsis/shock)
- Duration of IV therapy usually up to 14 days with oral switch when clinically appropriate
- Timing of IV to oral switch and total duration of antimicrobial therapy should involve discussion with paediatric infectious diseases team. If under 1 month of age, decide timing of IV to oral switch in consultation with regional peadiatric infectious diseases team.
- For associated prosthesis / metalwork infection, evidence supports IV to oral switch after 7 days9
- Discitis is not an indication for a prolonged course of IV antibiotics. An IV to oral switch should be considered when the CRP is falling and symptoms/pain improving
