Knee Trauma
Ottawa Knee Rules
The Ottawa Knee Rules state that X-rays are only indicated if patients present with the following:
- Age older than 55 years;
- Isolated tenderness of the patella or fibular head;
- Inability to flex the knee to 90°; or
- Inability to bear weight (limping is allowed) for four steps both immediately following injury and at the ED.
In a prospective validation cohort of 1,096 adult patients, the rule was found to be 100% sensitive for detecting clinically important fractures—defined as any bone fragment at least 5 mm or avulsion if associated with complete disruption as tendons or ligaments—with a potential reduction in radiography use by 28%.25 Though the rule was designed for adult patients, it was validated in 750 children aged 2 to 16 years and found to be 100% sensitive with a 31% potential reduction in radiographs.26
Pittsburgh Knee Rules
The Pittsburgh Knee Rules only apply to patients with blunt trauma or fall to the knee—not twisting injury—and state X-rays are indicated if patients are younger than age 12 years or older than age 50 years, and are unable to bear weight fully on toe pads and heels for four steps (limping is not allowed).
An initial validation of 133 patients demonstrating 100% sensitivity was followed by a larger external validation study.27 That study prospectively applied the Pittsburgh and the Ottawa rules in over 700 patients and found the sensitivity and specificity of the rules to be 99% and 60% for Pittsburgh and 97% and 27% for Ottawa.28
Comment: The ability to apply a rule to “all-comers” is important to EPs. The Ottawa instrument is more broadly applicable and has even been assessed in pediatric populations.
Foot and Ankle Trauma
Ottawa Foot and Ankle Rule
The most well-studied clinical decision rule in this category is the Ottawa Foot and Ankle Rule.29 This rule states that an ankle X-ray is only required if there is pain in the malleolar zone and bony tenderness to palpation at the posterior edge or tip of either the lateral or medial malleolus, or the inability to bear weight both immediately after injury and in the ED. The anatomic landmarks are shown in Figure 3.
Figure 3.
- Pain in the midfoot zone and either tenderness at the base of the fifth metatarsal;
- Tenderness over the navicular; or
- Inability to bear weight both immediately after the injury and at the ED.
The prospective validation study included over 1,400 adult patients with blunt trauma or twisting injury within 10 days of presentation. Clinically significant fractures were defined as malleolar or midfoot fractures with bone fragments greater than 3 mm. The rule was found to be 100% sensitive for detecting both ankle and midfoot fractures, and would lead to a reduction of radiographs by 34% for the ankle and 30% for the foot.29 These results have borne out in multiple studies including a recent meta-analysis comparing six different decision instruments where the Ottawa rule was found to be superior.30
Though the initial validation cohort of the Ottawa rule did not include pediatric patients, it has subsequently been applied to this population. The initial validation study in the pediatric population included 670 patients aged 2 to 16 years. In addition to the criteria for clinically significant injuries in the original validation study, Salter Harris type I fractures, though treated with immobilization, were not deemed to be clinically significant injuries in this cohort.
Although the Ottawa rules were determined to be 100% sensitive for detecting significant ankle and midfoot fractures in the pediatric cohort, one of the study sites experienced an increase rather than a decrease in X-rays when this rule was applied.31