View source for EBQ:Ottawa Ankle Rule Study

{{JC info
| title= Decision rules for the use of radiography in acute ankle injuries. Refinement and prospective validation.
| abbreviation= Ottawa Ankle Rule Study
| expansion= Ottawa Ankle Rule Study
| published= 1993 
| author= Stiell I. et al. 
| journal= JAMA
| year= 1993 
| volume= 269
| issue= 9
| pages= 1127-32
| pmid= 8433468
| fulltexturl= http://jama.jamanetwork.com/article.aspx?articleid=403941
| pdfurl=http://www.udel.edu/PT/PT%20Clinical%20Services/journalclub/caserounds/05_06/apr06/ottawa2.pdf
| status=Complete
}}
==Clinical Question==
Can a clinical decision rule be used to aid in the efficient use of radiography in acute ankle injuries?

==Conclusion==
The Ottawa Ankle Rule is a highly sensitive decision rule used to determine the need for radiography in patients with acute ankle injuries.

==Major Points==
[[File:anklexray.jpg|thumbnail]]
{{Ottawa Ankle Rules}}

''Rule had 100% sensitivity and 49% specificity for identifying 50 clinically significant malleolar zone fractures in the prospective validation study.''

{{Ottawa Foot Rules}}

''Rule had 100% sensitivity and and 79% specificity for identifying 19 clinically significant midfoot fractures in the prospective validation study.''

==Study Design==
*Conducted in 2 stages in 2 Canadian EDs, both prospective cohort studies
*First stage
**Each patient was evaluated for 15 clinical variables as defined by previously derived clinical decision rules. All patients then underwent radiographs--standard ankle series for patients with pain in malleolar zone vs. standard foot series for patients with pain in the midfoot zone. 
**Original decision rule then refined by univariate and recursive partitioning analyses. 
*Second stage
**Each patient was evaluated for 6 clinical variables, and the decision rule was applied to determine necessity of radiographs. 
*In both studies, a subset of patients were also assessed by second EM physician independently when possible.
*Clinically significant fracture seen in ankle or foot radiographic series was the primary outcome
**Defined as bone fragments greater than 3 mm in breadth. 
*All radiographic series were interpreted by qualified radiologists who were blinded to the data collection sheets.

==Population==
===Patient Demographics===
Similar characteristics in stage 1 (refinement) vs. stage 2 (validation)
*Mean age: 35 vs. 36
*Male sex: 52% vs. 52%
*Pt at Ottawa Clinic: 60% vs. 64%
*Twisting mechanism: 84% vs. 86%
*Clinically significant fractures: 16% vs. 15%
*Clinically insignificant fractures: 6% vs. 7%
*Ankle rediographs performed: 85% vs. 85%
*Foot radiographs performed: 39% vs. 35%

===Inclusion Criteria===
*Patients who presented to the emergency department with pain or tenderness 2/2 to blunt ankle trauma due to any mechanism 
*Ankle defined as area commonly involved in twisting injuries
**Malleolar zone
***Distal 6 cm of tibia, fibula, talus
**Midfoot zone
***Navicular bone, cuboid, cuneiforms, anterior process of calcaneus, base of 5th metatarsal
*1 of 21 designated EM physicians had to be on duty

===Exclusion Criteria===
*Age <18 years old
*Pregnant 
*Isolated injuries of the skin
*Referred from outside hospital with radiographs
*Injury occurred >10 days previously
*Returned for reassessment of the same injury

==Interventions== 
*Refinement stage was a prospective observational study
*In validation phase, the clinical decision rule was applied. If patients were positive for any 1 of the 6 clinical variables (listed in major points), an x-ray series was performed.  
**Standard ankle series completed in patients with positive Ottawa Ankle Rule, standard foot series completed in patients with positive Ottawa Foot Rule

==Outcomes==
First stage (validation and refinement of original rules): n=1032 enrolled and assessed <br/>
Second stage (validation of refined rules): n=453 enrolled and assessed

===Primary Outcome===
First stage (refinement): 121 (12%) clinically significant malleolar zone fractures and 49 (5%) clinically significant midfoot zone fractures identified <br/>

'''Performance of the Ottawa Decision Rule in the second stage (validation) cohort'''
{| class="wikitable"
|-
! Ankle Decision Rule !! Fracture !! No Fracture
|-
| Rule Positive || 50 || 205
|-
| Rule Negative || 0 || 198
|}

Sensitivity 100% (95% CI 93% to 100%)<br/>
Specificity 49% (95% CI 44% to 54%)



{| class="wikitable"
|-
! Foot Decision Rule !! Fracture !! No Fracture
|-
| Rule Positive || 19 || 90
|-
| Rule Negative || 0 || 344
|}

Sensitivity 100% (95% CI 83% to 100%)<br/>
Specificity 79% (95% CI 75% to 83%)

===Secondary Outcomes===
'''Stage 1 (refinement)'''
*Physicians correctly classified patients according to the ankle and foot decision rules in 97% and 98%
*Inter-observer agreement between physicians for ankle and foot decision rules was 56% and 69%

'''Stage 2 (validation)'''
*Physicians correctly classified patients according to the ankle and foot decision rules in 99% and 100%
*Potential reduction in radiography for ankle and foot series estimated to be 34% and 30% 
*Likelihood ratio negative for a fracture estimated to be 0

===Subgroup analysis===

==Further Discussion==
*Rules may not be useful in patients with multiple painful injuries, altered sensorium, intoxication, paraplegia, or bone disease
*During the study, the rule had limited experience with uncommon fractures
**2 fractures of talus
**12 fractures of midfoot other than base of 5th metatarsal
*A subsequent study by Stiell in 1994 confirmed the high sensitivity and demonstrated reduction the number of ankle X-rays by 36% <ref>Stiell IG et al. Implementation of the Ottawa ankle rules. JAMA. 1994 Mar 16;271(11):827-32.</ref>
*The rules have been shown to be easily applied with education in multiple centers <ref>Stiell I. et al. Multicentre trial to introduce the Ottawa ankle rules for use of radiography in acute ankle injuries. Multicentre Ankle Rule Study Group. BMJ. 1995 Sep 2;311(7005):594-7</ref> but due to poor interrater reliability from the general public, self application of the rule to decrease ED visits was not possible <ref>Blackham JE et al. Can patients apply the Ottawa ankle rules to themselves? Emerg Med J. 2008 Nov;25(11):750-1.</ref>
*The rules have been validated in assessing children 2-16 years old, with 100% sensitivity <ref>Plint AC. et al. Validation of the Ottawa Ankle Rules in children with ankle injuries. Acad Emerg Med. 1999 Oct;6(10):1005-9.</ref>
**However in 1 of the 2 centers in this study, the decision rules would have increased the use of x-ray for ankle injuries, suggesting that the benefit of these decision rules may not be as great in a pediatric setting.

==Criticisms==
*High sensitivity but relatively low specificity leads to continued high rates of radiography
*Validated primarily in adults; pediatric applicability is limited (though subsequently validated in children >5 years)
*Does not account for patients who may have injuries that are not initially tender (e.g., stress fractures)
*Implementation studies show variable physician adherence to the rule in clinical practice
*The rule was derived in a predominantly ambulatory ED population and may not apply to polytrauma patients

==Funding==
Grant from Emergency Health Services Branch of Ontario Ministry of Health, Toronto

==See Also==
*[[Ottawa ankle rules]]

==References==
<references/>

[[Category:EBQ]][[Category:Orthopedics]]