Septic arthritis is defined as inflammation of joints caused by a bacterial infection in the joint. It can be acute or chronic, monoarticular, or polyarticular.
The incidence of septic arthritis in children less than 5years is 5/1,00,000/year.
The hip joint is the most commonly affected in children followed by knee joint.
Specific causes are rare like primary immunodeficiency, however, many risk factors are present.
Risk factors are pre-term baby, intrauterine growth retardation, delivery of baby in unhygienic condition, NICU admission, umbilical cord sepsis, and ear or throat infection.
The most common mode of spread infection to joints is by hematogenous route, contiguous spread, and followed by direct inoculation.
Staphylococcus aureus is the most common bacteria followed by Group B streptococci, Streptococci pneumonia, gram-negative bacilli like Pseudomonas, and E.Coli, anaerobic bacteria like peptostreptococcus, bacteroids.
The most common joints affected are hip and knee joints.
Varies with the age of the child –
Newborn – Emphasis is on septicemia rather than joint pain
Baby will be irritable, not feeding well, not moving the extremity, sometimes associated with fever
Children – Pain around the joint, reluctance to move the affected limb, not able weight bear or walk, fever
Clinical examination will reveal localized warmth, painfully restricted movement of affected joints, and febrile.
Complete blood count, erythrocyte sedimentation rate (ESR) and C – reactive protein (CRP) are the blood investigation routinely performed.
Radiographs of the affected part and ultrasound of joints are imaging aid helps in making the diagnosis.
Synovial fluid and blood culture sensitivity are performed to find out specific organism responsible for the infection.
Very rarely higher imaging modalities like magnetic resonance imaging (MRI) and bone scan are required in complicated cases.
Treatment for septic arthritis is joint lavage by arthrotomy (Open or arthroscopic) complemented with appropriate antibiotics.
Long term consequences of improper, inadequate and insufficiently treated cases include joint instability, adjacent physeal damage leading the bony deformity and limb length discrepancy.