Pittsburgh knee rules

Clinical decision rule for knee radiographs.

Seaberg DC1, Jackson R.

Author information

Abstract

The objective of this study was to develop a decision rule for ordering x-rays in knee injuries. Phase I was a retrospective chart review of 201 consecutive patients receiving knee radiographs in the emergency department in a 10-month period. Logistic regression was performed on 11 clinical indicators to develop a clinical decision rule. Phase II was a prospective validation study on 133 consecutive patients with knee injuries. All patients received radiographs to validate the decision rule. Sensitivity, specificity, and misclassification rate were calculated. Logistic regression analysis found that a fall or blunt trauma mechanism yielded a logistic regression sensitivity of 92%, specificity of 57%, with a false-negative rate of 0.9%. The addition of inability to ambulate and age (younger than 12 or older than 50 years of age) yielded a sensitivity of 92% with a specificity of 63%. The prospective study found the combination of fall or blunt trauma with either inability to ambulate or age (younger than 12 to older than 50 years of age) was 100% sensitive, with a specificity of 79%. The misclassification rate was 20%. Using this decision rule, the number of x-rays taken could have been reduced by 78%. A larger multicenter validation study of this knee radiograph decision rule is needed before widespread clinical usage.

The Pittsburgh knee rules are medical rules created to ascertain whether a knee injury requires the use of X-ray to assess a fracture.

Contents

  [hide] 

• 1 Criteria
• 2 Accuracy
• 3 See also
• 4 References

Criteria[edit]

• Blunt trauma or a fall as mechanism of injury AND either of the following
  • Age younger than 12 years or older than 50 years
  • Inability to walk four weight-bearing steps in the emergency department.

If the patient satisfies the above criteria, they should receive an X-ray to assess for a possible fracture.

Accuracy[edit]

The sensitivity of using the Pittsburgh knee rules is 99% with a specificity of 60%. That means the use of the above rules has a false negative result of 1% and a false positive result of 40%.^[1]

The false positive result is less important as if the patient is positive, they should receive an X-ray to assess for a possible fracture, which has a much higher specificity. However, the Pittsburgh knee rules offer less false positives than do the Ottawa knee rules, though the Ottawa knee rules are more commonly used. ^[2]

The use of the Pittsburgh knee rules reduces the use of knee radiographs by 52%.^[3]

1. Seaberg DC, Jackson R (1994). "Clinical decision rule for knee radiographs.". Am J Emerg Med 12 (5): 541–3. PMID 8060409
2. MDCalc. "Pittsburgh Knee Rules". MDCalc. Retrieved 2014-10-15.
3. Tandeter HB, Shvartzman P (December 1999). "Acute knee injuries: use of decision rules for selective radiograph ordering". Am Fam Physician 60 (9): 2599–608.PMID 10605994

http://www.ncbi.nlm.nih.gov/pubmed/8060409