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Kocher’s criteria differentiate between pediatric septic arthritis and transient synovitis of the hip [Classics Series] | Medicine in 2 Minutes

This study summary is an excerpt from the book 2 Minute Medicine’s The Classics in Medicine: Summaries of the Landmark Trials

1. Children with septic arthritis of the hip could be accurately differentiated from transient synovitis of the hip based on the presence or absence of four major clinical predictors: fever, lack of weight bearing, speed erythrocyte sedimentation (ESR) > 40 mm/h and leukocytosis greater than 12,000 cells/cm3.

2. Several other variables increased the risk of septic arthritis, including radiographic evidence of joint effusion, fever with chills, female gender, and recent antibiotic use.

Original publication date: December 1999

Summary of the study: When evaluating a child with acute hip pain, only a few diagnoses can be made primarily by the radiographic appearance, including Legg-Calve-Perthes disease, slipped capital femoral epiphysis, and fracture. The differentiation between septic arthritis and transient synovitis of the hip remains a diagnostic dilemma. Appropriate management of septic arthritis requires prompt initiation of intravenous antibiotics and surgical drainage of the infected joint, thus making prompt and accurate diagnosis vital to avoid both the sequelae of treatment failure and treatment-associated morbidity in those without a septic joint. .

In the reviewed article, Kocher et al. aims to simplify the diagnostic process of differentiating between a septic hip and transient synovitis by developing and validating a set of clinical criteria by which an individual’s risk of septic arthritis can be stratified. In a retrospective review of all cases of extremely irritable hip in children between 1979 and 1996 at a large tertiary care pediatric hospital, several variables were found to be significantly different between those with true septic arthritis and those with transient synovitis of hip. The four variables most predictive of true septic arthritis were a history of fever, inability to bear weight on the affected hip, ESR greater than 40 mm/h, and leukocytosis greater than 12,000 cells/cm3. Patients meeting all four criteria were 99.6% likely to have septic arthritis, while those with zero of the four criteria had septic arthritis effectively ruled out with less than 0.2% chance of an infected joint. Patients with true septic arthritis were also significantly more likely to be female, to experience chills, to have recently used antibiotics, and to demonstrate radiographic evidence of joint effusion at the affected site, although these features were not included in the final clinical decision algorithm due to reduced specificity. Following publication, Caird et al. prospectively assessed these criteria in a distinct pediatric population, finding that the algorithm remained effective, but the inclusion of C-reactive protein >2.0 mg/dL was additionally predictive of septic arthritis as a fifth criterion and was independently more valuable than a SV. However, with additional prospective use of the Kocher criteria in alternative pediatric populations, such as that published in Luhmann et al. and refuted by Kocher et al. in 2004, clinical prediction rules demonstrated reduced but still reasonable diagnostic performance, possibly due to suboptimal modeling of selected variables within a new population. This algorithm was the first and remains a durable and effective evidence-based guideline for the clinical differentiation of septic arthritis from transient synovitis of the hip in multiple pediatric populations.

Click to read the study in The Journal of Bone & Joint Surgery

In depth [retrospective cohort]: A total of 282 children with acute hip irritability between 1979 and 1996 at a major pediatric hospital in the Northeast were included in this retrospective review. Patients were excluded if they had complicating factors including immunocompromised state, renal failure, neonatal sepsis, postoperative hip infection, juvenile rheumatoid arthritis, later development of Legg-Calve disease -Perthes or associated proximal femoral osteomyelitis. Patients were stratified into one of three disease categories: True septic arthritis (38 patients), evidenced by positive bacterial growth from synovial fluid aspiration with a white blood cell (WBC) count in the fluid associated > 50,000 cells/cm3; suspected septic arthritis (44 patients) based on synovial fluid aspiration with > 50,000 leukocytes/cm3 but no bacterial growth in culture; or transient synovitis of the hip (86 patients), with < 50,000 leukocytes/cm3 on synovial aspiration, no bacterial growth on culture and spontaneous resolution of symptoms without antibiotics or surgery. Several clinical variables were monitored to determine which differed most between the groups by univariate analysis and multiple logistic regression analysis.

Overall, children with true septic arthritis were significantly more likely to be female and had a positive history of fever >38.5 degrees Celsius, chills, recent antibiotic use, x-ray evidence joint effusion, non-supporting state on the affected side, elevated ESR, reduced hematocrit and leukocytosis (p < 0.05 for all). On further analysis, the four variables that were most predictive of septic arthritis formed the final Kocher Criteria and included fever > 38.5 C, unloaded state, ESR > 40 mm/h and leukocytosis > 12,000 leukocytes/cm3. Meeting zero of the four criteria effectively excluded septic arthritis (<0.2% probability), while meeting all four criteria effectively excluded it (99.6% probability). With three of the four criteria met, the probability of disease was 93.1%, which reduced to 40.0% for two criteria and 3% for one criterion.

Kocher MS, Zurakowski D, Kasser JR. Differentiate between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. The Journal of Bone and Joint Surgery. 1999 Dec 1;81-A(12):1662–70.

Additional examination:

Kocher MS, Mandiga R, Murphy JM, Goldmann D, Harper M, Sundel R, et al. Clinical practice guideline for the treatment of septic arthritis in children: efficacy in improving the process of care and effect on outcomes in septic arthritis of the hip. The Journal of Bone and Joint Surgery. 2003 Jun 1;85-A(6):994–99.

Caird MS, Flynn JM, Leung YL, Millman JE, D’Italia JG, Dormans JP. Factors distinguishing septic arthritis transient synovitis of the hip in children: a prospective study. The Journal of Bone and Joint Surgery. 2006 Jun 1;88-A(6):1251–57.

Luhmann SJ, Jones A, Schootman M, Gordon JE, Schoenecker PL, Luhmann JD. Differentiation Between Septic Arthritis and transient synovitis of the hip in children with clinical prediction algorithms. The Journal of Bone and Joint Surgery. 2004 May 1;86-A(5):956–62.

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