Septic arthritis


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  • CMAJ • May 22, 2007; 176 (11). doi:10.1503/cmaj.050258. © 2007 Canadian Medical Association or its licensors Case-based review Septic arthritis in patients with pre-existing inflammatory arthritis Raheem B. Kherani and Kam Shojani
  • Leads to damage to the joint cartilage and increase in pressure within the joint, impairing bloody supply and leading to avascular necrosis of the femoral head, dislocation or osteomyelitis.
  • 32-50% of pts have had a recent URI
    About 50% have had elevated titers to M. pneumoniae or a range of viruses (sometimes more than one), including parvovirus B19
    UTD and emedicine
  • Narrowed down to 5 that specifically discussed the clinical prediction rule developed by Kocher. Two of the studies were prospective studies while the other two had small patient populations. The one chosen was a prospective study that was a validation study by Kocher, the original author of the CPR.
  • ROC= receiver operating characteristic curve.
  • Mean duration of follow up was 11.8 months (5.9 to 23.7 months).
  • The predicted probability of septic arthritis of the hip from the prediction rule was similar to the actual distributions in the new patient population. The area under the ROC curve for the new population was 0.86 compared with 0.96 in the original population. Both close to 1 and indicating still very good diagnostic performance.
  • These are the data values for the original population and the new population to form the ROC curve.
  • Some patients had it, others did not.
  • Septic arthritis

    2. 2. Case Presentation • A previously healthy 4 year old male presents to the ED with a limp. He has been reluctant to bear weight on his left leg during the last 24h and has a temperature of 38.0°C. • Hip exam: shows decreased ROM due to pain. • ROS: 2 day hx of rhinorrhea and cough, resolved 10 days ago.
    3. 3. Review of Septic Arthritis • Septic arthritis (SA) • The synovium is extremely vascular and contains no basement membrane, allowing easy access for bacteria to the synovial space. • Either by hematogenous spread or direct invasion by local soft tissue infection, and or penetrating trauma.
    4. 4. Review of Septic Arthritis • Within 24-48 hrs of bacterial invasion: • Infiltration by neutrophils • Vascular congestion • Synovial proliferation • Within 1 week following bacterial invasion: • Continual purulent effusion • Continual synovial proliferation • Infiltration by mononuclear cells • Granulation tissue • Abscess development • Within 10 days after abscess formation: • Cytokine induced protelytic enzymes are released • End result is joint destruction and or systemic sepsis
    5. 5. Review of Transient Synovitis • Transient Synovitis (TS) • Arthritis secondary to a transient inflammation and hypertrophy of the synovial membrane. • Leads to slight effusion that causes bulging of the anterior joint capsule. • No definitive cause of TS is known • Posttraumatic or allergic mechanisms • Infectious etiology • Antibody titers
    6. 6. Clinical Question • In children presenting with acute hip pain, is there a clinical tool or diagnostic test that will distinguish between septic arthritis and transient synovitis?
    7. 7. PICO • Patient Population: • Children with acute hip pain. • Intervention: • Clinical feature(s) and or diagnostic test(s) that can confirm the diagnosis of SA vs TS. • Comparison: • The gold standard of joint aspiration. • Outcome: • Preventing an invasive procedure with a percentage of certainty without missing an emergent diagnosis.
    8. 8. Search Terms • PubMed Clinical Queries • Search Term: “transient synovitis and septic arthritis.” • With clinical study category as: Clinical prediction guides • Scope: Broad • Results: 15 articles
    9. 9. Article Chosen
    10. 10. Validation Study • The original study published by Kocher, et al. 1999, described a clinical prediction rule based on four independent multivariate predictors of SA of the hip: • A hx of fever • Non weight bearing • ESR of 40mm/hr • WBC >12,000 • The CPR was derived from the data of 82 pts with SA and 86 pts with TS evaluated between 1979-1996. Results showed statistical significance with a p value of <0.0001 with an ROC curve of 0.96.
    11. 11. Validation Study • Objective: To evaluate the diagnostic performance of the previously described CPR for the differentiation between SA and TS of the hip in children in a new pt population.
    12. 12. Material and Methods • Prospective study • Patient Population • All patients who presented to a major tertiary care children’s hospital between 1997-2002 with an acutely irritable hip and a differential diagnosis of TS or SA. • 213 eligible consecutive patients • 24: SA • 27: Presumed SA • 103: TS • 59: Excluded- such as those with immunocompromise, renal failure, neonatal sepsis, postoperative infection of the hip, later development of rheumatologic disease, Calve-Perthes disease and or due to osteomyelitis.
    13. 13. Materials and Methods • True septic arthritis defined: • Positive culture of joint fluid or • WBC ≥50,000 in the joint fluid with a positive blood culture. • Presumed septic arthritis defined: • WBC ≥50,000 in the joint fluid with negative cultures of the joint aspirate and blood. • Transient synovitis defined: • WBC <50,000 in the joint fluid. • Negative culture and resolution of symptoms without antimicrobial therapy and no further development of a disease process as documented in the medical record.
    14. 14. Material and Methods • Data obtained from all patients: • Age, gender, date of presentation, duration of sx, hx of fever, hx of recent infx, hx of recent abx, temp, ESR, WBC, evidence of hip joint effusion on X-ray, results of gram stain, cell count, differential, and cx of joint fluid. • Fever: • PO temp 38.5°C during wk before presentation. • Weight bearing status: • Based on clinical hx and was considered the inability or refusal to bear weight even with support. • Effusion: • As side to side distance of > 2mm from the medial part of the femoral head to the medial part of acetabulum on anteroposterior pelvic radiograph.
    15. 15. Material and Methods • Analysis of data • Univariate analysis by Student T- test. • Predictors with p<0.20 in univariate analysis were entered into multivariate logistic regression using backward selection to identify independent clinical predictors of SA and TS groups. • Receiver operating characteristic curve was than constructed to assess the diagnostic performance of the group of multivariate predictors in identifying SA.
    16. 16. Results of Multivariate Analysis • Showed the same four independent multivariate predictors of SA in the current population as they had in the original population.
    17. 17. Results of Algorithm for Probability of SA PREDICTORS ORIGINAL STUDY NEW STUDY Zero < 0.2% 2.0% One 3.0% 9.5% Two 40.0% 35.0% Three 93.1% 72.8% Four 99.6% 93.0%
    18. 18. Results of Receiver Operating Characteristic Curves
    19. 19. Results
    20. 20. Study Limitations • CRP not included in new study. • Authors admitted CRP shows greater benefit than ESR for detecting SA in children. However, at the beginning of the study CRP testing was limited at the hospital as the study progressed it became routine testing. Therefore, to avoid biases associated with incomplete data analysis CRP was not incorporated into the CPR. • Not an external validation.
    21. 21. Study Limitations • Diagnostic cut off <50,000 WBC in joint fluid was considered TS and >50,000 considered SA or presumed SA. Other sources state 60,000 or greater. • When comparing SA to TS in multivariate analysis, the study does not specify if its true SA and presumed SA or just true SA. • Variables might be different in a community based population vs this tertiary care hospital’s population.
    22. 22. Are the results of this diagnostic study valid? 1. Was there an independent, blind comparison with a reference (“gold”) standard of diagnosis? • yes 1. Was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom it would be used in practice)? • yes 1. Was the reference standard applied regardless of the diagnostic test result? • maybe 1. Was the test (or cluster of tests) validated in a second, independent group of patients? • yes
    23. 23. Are the valid results of this diagnostic study important? • Yes
    24. 24. Can we apply this valid, important evidence about a diagnostic test in caring for our patient? 1. Is the diagnostic test available, affordable, accurate, and precise in our setting? • yes 1. Can we generate a clinically sensible estimate of our patients pre-test probability (from personal experience, prevalence statistics, practice databases or primary studies? • yes A. Are the study patients similar to our own? • yes A. Is it unlikely that the disease possibilities or probabilities have changed since this evidence was gathered? • yes
    25. 25. Caring for our patient cont. 3. Will the resulting post test probabilities affect our management and help our patient? • yes A.Could it move us across a test-treatment threshold? • yes A.Would our patient be a willing partner in carrying it out? • yes
    26. 26. Conclusions • In my patient’s case: • My patient had 3 of the predictors (fever, elevated WBC count, and inability to bear weight, CRP was not elevated. I chose not to aspirate and dx him with TS. • How would I make a better study? • CRP • External validation • Strictly SA versus TS
    27. 27. Resources Kocher MS., Zurakowski D., Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence based clinical prediction algorithm. J Bone Joint Surg Am. 1999; 81: 1662-70. Raheem B., Shojani, et al. Case-based review : Septic arthritis in patients with pre-existing inflammatory arthritis. Canadian Medical Association Journal. May 22, 2007; 176 (11). Electronic based medical databases. E-medicine and UpToDate. And…. Harriet :)