Hip Pain and Septic Arthritis

Objectives Recognize the clinical presentation of a septic joint and transient synovitis Be able to differentiate septic arthritis and transient synovitis based on evidence based medicine Develop an approach to the assessment of patients with a swollen or painful joint Know the appropriate management of septic arthritis

Definition Septic Arthritis - disorder of joint where joint capsule is infiltrated by bacteria Transient synovitis - nonspecific inflammation and hypertrophy of the synovial membrane

Incidence Transient Synovitis Age 3 – 8 years old Male : Female 2:1 0.4-0.9% of pediatric admissions to ER Child’s risk of developing during lifetime is 3% ?Seasonal Septic Arthritis Unknown number Non-gonococcal  before age 5 male: female 2:1) Gonococcal  adolescent females

Etiology of Transient Synovitis (or so we think) Viral agent Fourfold increase in viral titers in 45% of patients with diagnosis (Tolat et al) Elevated serum interferon levels in 43% patients Trauma 17-30% of patients with diagnosis Local contusion as self-limiting chemical synovitis Allergy – response to antihistamines??

Etiology of Septic Arthritis Metaphysis – tiny blood vessel loops where low flow and O2 content  traumatic rupture may provide area of bacterial growth Synovial membrane receptors may have predilection for bacteria

Anatomy of Region

Sequence of Events Bacteria deposited in subsynovial capillary network Immune response – may abort at this point if bacterial growth halted Inflammatory cascade initiated with release of proteolytic enzymes and toxins Articular cartilage degradation Increased fluid and pus leading to pressure and ischemia from compression

Physical Examination Unilateral joint (90%) No traumatic lesion +/- fever and other signs of infection including: n/v, diarrhea,headache Limp or refusal to bear weight Decreased range of motion Palpation of effusion and tenderness Prefer position of hip to be slightly flexed and externally rotated  maximize joint space to decrease pressure

Current Standards of Care Labs: CBC, ESR (or CRP) Blood Culture – in 1 study only 50% of patients with documented septic arthritis had positive blood culture Radiography of hip: AP and frog leg views of hip  some studies question need for these X-rays Gold standard – aspiration of fluid for cell count, gram stain, culture and sensitivity (97% sensitivity) Another study showed 12/23 (52%) and 19/33 (58%) had pathogens isolated

Other Imaging Modalities Standard US – demonstrates an effusion but cannot differentiate an infectious from noninfectious etiology Doppler Sonography (1998) – look at increase blood flow; preliminary evidence shows poor sensitivity but high specificity MRI – signal intensity changes seen in bone marrow of septic arthritis (no difference in signal of soft tissue or in grade of effusion) MRI was preliminary study involving 9 patients who had septic arthritis with 14 patients with transient synovitis

How can one be sure a painful hip with effusion is not a septic joint???

Evidence Based Medicine Study 1 Retrospective study looked at 509 patients who presented with irritable hip and limp. Presence of any two of these clinical criteria (see next page for graph and criteria) was 95% sensitive and 91% specific for septic arthritis.

Clinical Criteria – Study 1 Retrospective study looked at 509 patient patients who presented with irritable hip and limp. Presence of any two of these clinical criteria was 95% sensitive and 91% specific for septic arthritis.

EBM – Study 2 Four Predictors: Recommendation: Fever Non-weight bearing ESR > 40 WBC > 12 Recommendation: 3-4 predictors good candidates for aspiration in OR b/c high likelihood that arthrotomy and drainage will be needed 2 predictors aspirate with U/S or fluroscopy

Clinical Criteria – Study 2 Fever 2.Non-weight bearing 3.ESR > 40 4.WBC > 12 Recommendation: 3-4 predictors good candidates for aspiration in OR b/c high likelihood that arthrotomy and drainage will be needed 2 predictors aspirate with U/S or fluroscopy

Predicted Probability – Study 2

Treatment & Prognosis Transient synovitis Septic Arthritis Tx  rest and anti-inflammatory agents Lasts 3-10 days Septic Arthritis Treatment: Naficillin and 3rd generation cephalosporin Vanco and aminoglycoside Oxacillin and gentamicin Most important prognostic indicators: 4 to 5 days to begin treatment to avoid long-term consequences Evidence of osteomyelitis  poor prognosis

Complications of Septic Arthritis Osteonecrosis Cartilage destruction Postinfectious degenerative arthritis Joint instability Deformity

Bibliography Do Twee T. Transient synovitis as a cause of painful limps in children. Current Opinion in Pediatrics. 12 (1): 48-51. Klein D, Barbera C, Gray S, Spero C, Perrier G, Teicher, J. Sensitivity of objective parameters in the diagnosis of pediatric septic hips. Clinical Orthopaedics and Related Research. 338: 153-159. Kocher M, Zurakowski D, Kasser J. Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. The Journal of Bond and Joint Surgery. Chen C, Ko J, Li C, Wang C. Acute septic arthritis of the hip in children. Archives of Orthopedic Trauma Surgery. 121: 521-526.