Introduction• Septic arthritis is inflammation of a synovial membrane with purulent effusion into the joint capsule, due to infection. Synovial membrane Membrane surrounding joint cavity Produce synovial fluid Contain rich capillary network for phagocytic and hyaluronate- producing function
• Bacterial, but sometimes viral,mycobacterial, and fungal.• Usually caused by Staphylococcus aureus . Other organisms are : E.coli , Proteus , Streptococcus Predisposing Factor : Rheumatoid arthritis Immunosuppressive drug therapy Chronic disorder AIDS Intravenous drug abuse
Pathogenesis • Bacteria can gain entrance to a joint via 3 routes:Haematogenous Direct spread from adjacent focal infection Direct inoculation
Most common form of spreadUsually affect people with underlying medical problemMay result from penetrating traumaIntroduction of organisms during diagnostic and surgical procedures. For eg arthroscopy and intra-articular injectionMore common in children.Osteomyelitis usually begin in the metaphyseal region,from which it breaks through the periosteum into thejoint.
Synovial membrane is highly vascularised. ↓ Bacteria can easily enter synovial joint via blood stream. ↓There will be inflammatory reaction with seropurulent exudate and increase in synovial fluid. ↓ As pus appear in the joint, the articular cartilage is eroded and destroyed. Partly by the bacterial enzyme, and partly by the enzyme released from synovium, inflammatory cell and pus Infant Adult Children Destroy the epiphysis, Effect confined on Vascular occlusion lead which is still largely articular cartilage to necrosis of cartilaginous. Extensive erosion can epiphyseal bone occur due to synovial proliferation and ingrowth
a) In the early stage, there is an acute synovitis with a purulent joint effusionb) Soon the articular cartilage is attacked by bacterial and cellular enzyme.c) If infection is not arrested , the cartilage may be completely destroyedd) Healing then leads to ankylosis
If left untreated, it will spread to the underlying bone and out of joint to form abscess and sinus.Healing with:1.Complete resolution2.Partial loss of articular cartilage and fibrosis of joint3.Loss of articular cartilage and bony ankylosis4.Bony destruction and permanent deformity
Clinical Features Differ according to age In new born infants In children In adults o acute pain in single More on septicaemia large joint(esp hip) Often in the superficialRather than joint pain joint(knee, wrist or ankle ) o Pseudoparesis Baby is irritable & Joints painful, swollenrefuse to feed o Child is ill,rapid pulse & inflamed. and swingingfever Tachycardia with fever Warmth and marked o Overlying skin looks red local tenderness & Joints are warmth, & superficial joint swelling movement restricted.tenderness, resistance may be obviousto movement look for gonococcal o Local warmth and infection or drug abuse. Umbilical cord and marked tendernessinflamed IV site should be Patient withsuspicious of source of o All movements are rheumatoid arthritis and infection restricted by pain or spasm. especially those on corticosteroid may o Look for source of develop “silent” joint infection from septic toe or infection. discharge ear
Physical examination:• Lower limb antalgic limp / cannot walk• Upper limb affected part is closedly guarded• Marked tenderness, active and passive range of motion are limited• Examine for synovial effusion, erythema, heat and tenderness.• Spasm of muscles around the joint may be marked.• Patient may hold the joint in a position to reduce the intra-articular pressure to minimize pain.
Investigations Investigations ExplainationFull blood count Elevated white blood cell countESR > 40 mm/hrCRP > 20 mg/dLBlood culture May be positive
Synovial fluid analysisAseptic technique is used during aspiration of synovial fluid.Avoid taken from infected site of skin.The fluid is then analyzed by gross and microscopicexamination and culture.Gross examinations include appearance, volume,viscosity, mucin clotting (amount of proteoglycans).Microscopic examinations include leucocyte count,staining of smears, serum glucose ratio, protein.Finally, culture and sensitivity for definitive diagnosisand treatment.
Suspected Appearanc Viscosity White Crystals Biochemistry Bacteriologycondition e cellsNormal Clear High Few - As for plasma - yellowSeptic Purulent Low + - Glucose low +arthritisTuberculous Turbid Low + - Glucose low +arthritisRheumatoid Cloudy Low ++ - - -arthritisGout Cloudy Normal ++ Urate - -Pseudogout Cloudy Normal + Pyropho - - sphateOsteoarthrit Clear High few Often + - -is yellow
ImagingX ray Early Stage – NormalLook for soft tissue swelling, loss of tissue planes,widening of joint space and slight subluxation due to fluid injoint. Gas may be seen with E. coli infection Late stage – Narrowing and irregularity of joint space Plain film findings of superimposed osteomyelitis maydevelop (periosteal reaction, bone destruction, sequestrumformation).
Narrowing of joint space and irregularity of subchondral bone. subchondral erosions and osteonecrosis andJoint space loss sclerosis of the femoral complete collapse of head the femoral head
Ultrasonography• More reliable in revealing a joint effusion in early cases.• Widening of space between capsule and bone of > 2mm indicates effusion.• Echo-free transient synovitis• Positively echogenic septic arthritis
TreatmentGeneral supportive care-Analgesics-IV fluidsSplintage- The joint must be rested either on a splint or in a widely splitplaster-In neonates and infants, with hip infection the joint is heldabducted and 30 degree flexed, on traction to prevent dislocation.AntibioticsTreatment is started once the blood and samples are obtainedwithout waiting for the detail results.Choice of antibiotic depends on the most likely pathogen
Surgical Management Surgical Drainage Arthroscopic debridement and copious irrigation with normalsaline – more frequently in knee joint septic arthritis
Complications• Bone destruction and dislocation of the joint (espHip)•Cartilage destruction-may lead to either fibrosis or bony ankylosis- in adult partial destruction of the joint will result insecondary osteoarthritis•Growth disturbance- presenting as either localised deformity or shorteningof the bone