BACKGROUND: The Ottawa Ankle Rules, Ottawa Knee Rule, and Canadian C-Spine 
Rule-together known as The Ottawa Rules-are a set of internationally validated 
clinical decision rules developed to decrease unnecessary diagnostic imaging in 
the emergency department. In this study, we sought to develop and evaluate the 
use of a mobile app version of The Ottawa Rules.
OBJECTIVE: The primary objective of this study was to determine acceptability of 
The Ottawa Rules app among emergency department clinicians. The secondary 
objective was to evaluate the effect of publicity efforts on uptake of The 
Ottawa Rules app.
METHODS: The Ottawa Rules app was developed and publicly released for free on 
iOS and Android operating systems in April 2016. Local and national news and 
academic media coverage coincided with app release. This study was conducted at 
a large tertiary trauma care center in Ottawa, Canada. The study was advertised 
through posters and electronically by email. Emergency department clinicians 
were approached in person to enroll via in-app consent for a 1-month study 
during which time they were encouraged to use the app when evaluating patients 
with suspected knee, foot, or neck injuries. A 23-question survey was 
administered at the end of the study period via email to determine self-reported 
frequency, perceived ease of use of the app, and participant Technology 
Readiness Index scores.
RESULTS: A total of 108 emergency department clinicians completed the study 
including 42 nurses, 33 residents, 20 attending physicians, and 13 medical 
students completing emergency department rotations. The median Technology 
Readiness Index for this group was 3.56, indicating a moderate degree of 
openness for technological adoption. The majority of survey respondents 
indicated favorable receptivity to the app including finding it helpful to 
applying the rules (73/108, 67.6%), that they would recommend the app to 
colleagues (81/108, 75.0%), and that they would continue using the app (73/108, 
67.6%). Feedback from study participants highlighted a desire for access to more 
clinical decision rules and a higher degree of interactivity of the app. Between 
April 21, 2016, and June 1, 2017, The Ottawa Rules app was downloaded 
approximately 4000 times across 89 countries.
CONCLUSIONS: We have found The Ottawa Rules app to be an effective means to 
disseminate the Ottawa Ankle Rules, Ottawa Knee Rule, and Canadian C-Spine Rule 
among all levels of emergency department clinicians. We have been successful in 
monitoring uptake and access of the rules in the app as a result of our 
publicity efforts. Mobile technology can be leveraged to improve the 
accessibility of clinical decision tools to health professionals.