SEPTIC ARTHRITIS DR O E NWANKWO FMCS (Ortho) FWACS, FICS

Introduction This is an infection of the joint caused by pyogenic micro-organisms. It is commonly acute & suppurative. It is a disease that affects all the age groups. Predisposing conditions are chronic debilitating disorders like diabetes mellitus, rheumatoid arthritis; others include intravenous drug abuse, immunosuppressive drug therapy and acquired immunodeficiency syndrome (AIDS), etc. In infants, the adjacent articular bones are invariably involved because anastomosis still exists between epiphyseal & metaphyseal vessels, so septic arthritis commonly co-exists with acute osteomyelitis.

Pathology Microorganisms may reach the joint through various routes: i) Through the blood stream from distant sites. ii) By direct invasion through a penetrating wound, intra-articular injection or arthroscopy iii) By direct spread from an adjacent bone abscess.

Pathology contd The causal organism is commonly Staphylococcus aureus. However, in infants Haemophilus influenzae is frequent. Occasionally other organisms like Streptococcus, E. coli and Proteus are encountered.

Pathology contd The infection usually starts in the synovium. An acute inflammatory reaction is provoked with exudation of seropurulent fluid and cells. There is also increase in the synovial fluid. As pus appears in the joint, articular cartilage is eroded and being destroyed by enzymes released by the bacteria, the synovium, the inflammatory cells and pus. In infants the epiphysis which largely cartilaginous may be destroyed; in older children, vascular occlusion may lead to necrosis of the epiphysis while in adults, the effects are largely confined to the articular cartilage.

Pathology contd If the infection continues untreated, it may spread to the underlying bone or burst out of the joint to form abscesses in surrounding tissues or sinuses. With healing there may be complete resolution and return to normal if treated early or there may be partial loss of articular cartilage and fibrosis if intervention is late or inadequate. Neglect or poor treatment may lead to complete loss of articular cartilage, fibrous or bony ankylosis, bony destruction and permanent joint deformity.

Clinical features Clinical features differ according to the age group: Infants will present with irritability and refusal to feed. There is usually associated fever. A high index of suspicion is necessary because the infection could be anywhere. Joints should be carefully examined for local signs of infection such as differential warmth, tenderness and resistance to movement.

Clinical features contd In children the features are usually acute pain in a large joint with swinging fever. The child looks ill with raised body temperature, rapid pulse and reluctance to move the limb or allow it to be touched. There is swelling especially in a superficial joint with marked tenderness and local warmth. All movements are restricted and often completely abolished by pain and muscle spasm.

Clinical features contd In adults there is equally pain in a large joint with or without fever. The joint is swollen, tender and inflamed with local warmth. All movements of the joint are markedly restricted. The patient should be questioned and examined for predisposing co-morbid illness.

Investigations Diagnostic imaging: 1. X-rays in the first few wks (1&2 nd ) will not reveal much except evidence of soft tissue swelling. In children joint space may seem widened (because of effusion). Later, there is irregularity of the articular margins and narrowing of the joint space. 2. Ultrasound will show evidence of effusion early in the disease. 3. MRI will show effusion & erosion of the cartilage.

Investigation contd Blood tests: Blood culture may be positive WBC & ESR will be raised Joint aspirate: May show frank pus or seropurulent fluid but early cases may be clear Gram stain may show Gram +ve or –ve organisms C/S of the aspirate will reveal the offending organism and it sensitivity.

Differential diagnosis Acute osteomyelitis: There is point tenderness and nearby joints can be moved. However both commonly co-exist in infants and children Traumatic synovitis or haemarthrosis may be confused but history of injury to the joint and colour of the joint aspirate may help in resolving the confusion.

Differential diagnosis contd Rheumatoid fever: The pain flits from one joint to another Gout: Microscopic examination of the aspirate in polarized light will show the characteristic gouty crystals Haemophilic joint bleed: History is helpful

Treatment This should be started after taken blood sample for blood culture and joint aspirate for C/S Treatment includes: 1.General supportive measures:-.analgesics for pain.intravenous fluid for dehydration and for administration of antibiotics.correction of anaemia if present.

Treatment contd 2. Antibiotics: The initial choice of antibiotics should be based on empirical judgment of the most likely pathogen(s). However, this should be substituted if necessary immediately after the result of C/S is available. Antibiotic is given intravenously initially for the first few days (2-7), thereafter, it can be continued orally for another 3wks.

Treatment contd 3. Splintage: This is necessary to rest the joint & avoid deformity. Cast backslab or traction can be used depending on the joint involved. Traction is ideal for the hip joint and the limb should be in abduction & slight flexion (30 0 ) to avoid dislocation. 4. Drainage: This is a safety policy to preserve the joint especially in very young infants or when the hip is involved and if the aspirate is thick. Under anaesthesia and using aseptic measures, the joint is opened through a small incision, drained & washed out with N/Saline. In the knee arthroscopic debridement and copious irrigation is equally effective.

Treatment contd Aftercare: Once the patient’s general condition improves and the joint is no longer painful; gentle and gradually increasing active movement is encouraged. However, if there is serious damage to the articular cartilage, the joint should be immobilized in the optimum position for function until ankylosis to takes place fully.

Complications In the hip especially in children, cartilage and bone destruction may lead to dislocation of the joint. Septicaemia may result Can spread to the adjacent bone leading to osteomyelitis as well. Cartilage destruction can lead to partial damage of the joint and therefore secondary osteoarthritis or to complete damage of the joint leading to either fibrous or bony ankylosis. Growth disturbance may occur in children from affectation the growth plate which may result in localized deformity or limb shortening.