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Performance of a decision rule for radiographs of pediatric knee injuries
Brian R Moore1, Louis C Hampers, Kathryn D Clark
1Section of Pediatric Emergency Medicine, The Children's Hospital, Denver, Colorado.
Insights
Assessing a child's ability to bear weight after a knee injury can safely reduce knee X-ray use by 53%. This prospective study found no fractures were missed when this rule was applied to pediatric patients.
Area of Science:
- Pediatric Emergency Medicine
- Radiology
- Orthopedic Surgery
Background:
- Decision rules for pediatric knee radiographs are often based on limited retrospective data.
- Prospective evaluation of these rules is crucial for clinical validation.
Purpose of the Study:
- To prospectively assess the performance of a clinical decision rule for pediatric knee injuries.
- To determine if the ability to bear weight, flex the knee, or presence of bony tenderness can safely reduce radiography use.
Main Methods:
- Prospective study in pediatric emergency departments and urgent care centers.
- Children aged 3-18 with acute knee injuries were assessed for weight-bearing ability, knee flexion, and tenderness.
- Radiographs were interpreted by a blinded radiologist.
Main Results:
- 10.3% of 146 patients had fractures; 53% could bear weight and had no fractures (Negative Predictive Value 1.0).
- Assessing weight-bearing ability alone could have reduced radiography by 53% without missing fractures.
- Adding knee flexion or tenderness assessment did not improve the rule's diagnostic value.
Conclusions:
- The ability to bear weight is a reliable criterion for ruling out fractures in pediatric knee injuries.
- Clinical decision rules focusing on weight-bearing capacity can significantly decrease unnecessary radiography in children.
- Further refinement of decision rules can optimize imaging utilization in pediatric emergency care.
Abstract:
Although decision rules for radiographs of pediatric knee injuries have been suggested from retrospective studies, prospective evaluations of such rules have been limited. We sought to prospectively assess the performance of a rule in children presenting with acute knee injuries. Eligible participants were children aged 3-18 years with an acute knee injury. The settings for the study were a tertiary pediatric emergency department (ED), a community hospital ED, and a pediatric urgent care center. All of the participants received standard knee radiographs. Before radiography, each patient was assessed by a pediatrician or pediatric emergency physician for presence of the following: 1) inability to bear weight, 2) inability to flex the knee to 90( degrees ), 3) presence of bony tenderness. The radiographs were interpreted by a radiologist blinded to the study; those with findings reported as consistent with acute fracture were considered positive. A total of 146 patients were enrolled (65% male, mean age 11.6 years). Of these, 15 (10.3%) had a fracture on their radiograph, 6 of which were related to trampoline use. Seventy-seven (53%) were negative for criterion 1 (i.e., able to bear weight immediately after the accident and in the ED), none (0%) of whom had fractures. The negative predictive value of this criterion was 1.0 (95% CI 0.94-1.0). The positive predictive value was 0.22 (95% CI 0.13-0.34). The sensitivity was 1.0 (95% CI 0.82-1.0). The specificity was 0.59 (95% CI 0.50-0.67). Three patients negative for criterion 3 were found to have fractures. The proximal tibia was the most common fracture site (47%). In conclusion, assessment of the ability to bear weight would have decreased the use of radiography by 53% without missing any fractures in our study population. No additional value to the rule was found by adding assessment of the ability to flex the knee or bony tenderness.
