Student Corner: Ottawa Ankle Rules

The Ottawa Ankle Rules are a set of criteria that are designed to help clinicians identify which patients that present with acute ankle injuries require imaging. The 1992 paper which outlined the criteria (PMID:1554175) consisted of a prospective study of 750 patients who came into the Ottawa Civic and Ottawa General hospitals with acute ankle injuries. The study was designed to record each patient’s particular presentation (area of tenderness, amount of swelling, ecchymoses, etc) and see if any aspect of their presentation correlated with a fracture identified on subsequent imaging (i.e. if a patient has pain over the medial malleolus, how likely are images of that ankle to show a fracture?).

MD Calc has a good summary picture of the criteria here. I’ll summarize it below as well:

A series of ankle x-rays is necessary if:

There is tenderness in the malleolar zone (lateral or medial) AND bony tenderness at the posterior edge of the medial malleolus OR bony tenderness at the posterior edge of the lateral malleolus OR an inability to bear weight immediately and in the ED

OR

There is tenderness in the midfoot zone AND bony tenderness at the base of the 5th metatarsal OR bony tenderness at the navicular OR an inability to bear weight immediately and in the ED

The picture on the link above is probably more helpful to visualize the algorithm. They note that 102 patients out of the 750 cohort had “significant” fractures and these criteria would have led to imaging on all of those cases. Also, they report that this criteria would have led to a 32.3% decrease in the number of radiographs ordered. The algorithm’s sensitivity was 100% and specificity was 40% for identifying fractures that were later confirmed by imaging. In other words, it was touted as a great screening tool since it was highly sensitive in picking up an ankle fracture.

(Note: The original criteria included an age stipulation, so that every patient with ankle pain [but not midfoot pain] over the age of 55 was recommended to get imaging. Additional research and subsequent modification of the algorithm proved that age was actually not a predictive variable. [PMID: 8433468])

Now on to a case:

Homeless male, in his 50’s, with ankle and foot pain after falling 10 feet. Walked into the E.D. with some pain, but had the ability to bear weight. Pt had swelling on exam, but no tenderness at the lateral malleolus, medial malleolus, mid foot or lateral foot.

The question is, do you get imaging on this patient?

Oh, look, it turns out we have criteria for that! And, in short, if you follow the Ottawa Ankle Criteria, the answer is no. The patient can bear weight and has no tenderness at any of the 4 areas that the criteria specifies, therefore according to the algorithm, imaging should not be ordered.

But we have a twist! This patient did indeed get ankle x-rays.

Ottawa Ankle 1

Why did this patient end up getting ankle x-rays despite not having met the Ottowa Ankle criteria?

Dr. Jones plays “devil’s advocate” in arguing against the use of the Ottowa Ankle Rules:

“Despite high negative likelihood ratio’s found on creation and validation of the Ottowa Ankle Rules, ED physicians are still ordering x-rays for most traumatic ankle complaints.  Why?  Because they are immediately available, low cost, and low radiation.  Many of our radiology decision rules pertain to expensive tests that are 10-100 times the amount of radiation (CT head, CT c-spine) and/or may not be readily available.  It is less practical to try and decrease a test that has little downside…such as an ankle radiograph.  

There is usually significant comorbidity associated with many different types of ankle fractures including calcaneal and talar fractures (I mention these because in my experience these are the two fracture patterns that are missed by the Ottowa Ankle Rules despite their reported 100% sensitivity…see the case above).  In our medicolegal environment in the United States, it is very difficult to defend missing an ankle fracture when you have a low cost, low radiation, readily available test at your disposal.  One must take into account that it is nearly impossible to recreate an exam with our current medical documentation.  A radiograph is an objective picture of a non-fractured ankle while a nicely worded exam is not so defendable in the eyes of a layman jury.  You open yourself up to legal problems if you miss a high-morbitidy injury because you used a rule that “decreases medical costs and increases efficiency” (these are the main benefits of the Ottowa Ankle Rules).  Courts are more patient-centered, they don’t care about our waiting room times!

We practice medicine taking into account more than just evidence-based medicine.  Until the “standard of care” we are held up to in court is in line with evidence-based medicine, we will always have to take into account the burden of the medicolegal consequences.  Be careful utilizing any clinical decision rules until they are universally accepted as standard of care among all ED physicians.  

I personally use “shared decision making” with most of my decision rule utilization.  My practice pattern using Ottowa Ankle Rules involves (1) A medical record documenting negative Ottowa Ankle Rules AND (2) a patient that understands the decision not to x-ray AND (3) the patient agrees.  This situation is rare but I will sometimes not x-ray if all the above parameters are met.  This is easier to defend if you happen to miss something by not getting an x-ray.  

The above statement is of course my own opinion and practice pattern.  Please utilize the Ottowa Ankle Rules as you feel fit and I appreciate any comments for and against their use in the ED.    

-Russell Jones, MD”

So, there you have it. As is the case with many different areas of medicine, real-life practice varies from guidelines, rules and algorithms (even if they are backed up by multiple research studies) for various different reasons which include, but are not limited to differences in: availability of testing methods, medical setting, hospital policies, patient needs, legal considerations and the physician’s own interpretation of all of the above factors and the medical research/literature.

For students, this means that you’ll have to soon adapt yourself to an environment and way of thinking that takes multiple variables into account when it comes to decision making. Almost every patient is a different shade of grey, not black and white. After all, medicine is both art and science.

But, I digress from the patient. Can you spot the fracture in the above image? Answer below:

Calcaneal fracture with arrow

 

There is indeed a fracture of the calcaneus right around the inferior edge of the bone. Good thing this patient got imaging, right?

Author: Jaymin Patel

References:

Stiell IG, Greenberg GH, McKnight RD, Nair RC, McDowell I, Worthington JR. A study to develop clinical decision rules for the use of radiography in acute ankle injuries. Ann Emerg Med. 1992 Apr;21(4):384-90. PubMed PMID: 1554175

Stiell IG, Greenberg GH, McKnight RD, Nair RC, McDowell I, Reardon M, Stewart JP, Maloney J. Decision rules for the use of radiography in acute ankle injuries. Refinement and prospective validation. JAMA. 1993 Mar 3;269(9):1127-32. PubMed PMID: 8433468.


Filed under: Ankle XR, Articles, Radiology Rules, Student Corner, XR Tagged: Ankle Criteria, ankle XR, Ottawa, Ottawa ankle criteria, ottawa ankle rules, student corner

Back pain…

Back pain is one of the most frequent complaints in the ED.  The vast majority of patients do not have a life threatening or highly morbid pathology.  Unfortunately, this patient did:

 

CT LSpine 1 LS spine 2

This is a CT scan under bone windows.  It shows erosive changes based around the L4-L5 disc, eroding into the inferior endplate of L4 and the superior endplate of L5. These findings are concerning for discitis-osteomyelitis. It is favored to have both acute
and chronic components.

Finding this pathology is somewhat like finding a needle in a haystack.  However, pay attention to signs such as fever, repeat ED visits without a firm diagnosis, focal weakness, and predisposing factors such as IV drug abuse, history of endocarditis, or immunosuppression.  Sedimentation rate and C-reactive protein are often elevated in this disorder (among others).

CT is a readily available, quick way to diagnose this pathology but it isn’t as sensitive as MRI.  Plain films are not reliable but may show changes similar to the CT above.  Nuclear medicine bone scans as well as PET scans can be used but are not commonplace in the ED.

Author:  Russell Jones, MD

Image Contributor:  Zachary Skaggs


Filed under: CT, Non-Trauma, Orthopedics Tagged: Discitis, Osteomyelitis

Lunate dislocation…

This patient presented with wrist pain after a fall:

 

Lunate 1Lunate edits

This is an example of a lunate dislocation.  The lunate can be seen on the lateral view (blue arrow).  It is dislocated quite a far distance.  Also note that the lunate is not in its usual location on the AP view.

The above radiographs are not subtle.  Keep in mind that lunate dislocation is sometimes not so obvious.  We visited lunate and perilunate dislocation on a prior post (lunate).  Stay tuned in the future for tips on reading wrist radiographs to avoid missing any subtle injuries.

Author:  Russell Jones, MD


Filed under: Orthopedics, Trauma, Wrist XR, XR Tagged: Lunate dislocation, Wrist

How to identify a cardiac rhythm device with CXR…

How many times have you had trouble with figuring out what type of cardiac device (e.g. pacemaker/defibrillator) a patient has implanted?  A patient presented to our ED with chest pain, palpitations.  He did not have his device card with them, no prior visits to our ED, and did not know the manufacturer of the device.  How do you decide which company to call for interrogation?

Here is an article I found with radiologic characteristics of devices that can help identify which company produced the device.  It has a great identification algorithm they coined the CaRDIA-X algorithm:

http://www.ianchristoph.com/physician-resources-2/device_id.pdf

There are 5 major manufacturers currently:  Medtronic, Boston Scientific, St. Jude, Biotronik, and Sorin Group.  Each device manufactured by these companies have certain differentiating characteristics of can shape, battery shape, alphanumeric codes, capacitor shadows, coil types, etc.  Turns out you can identify the manufacturer using the device characteristics on chest X-ray relatively easily.

In the case I was describing above the patient had an easily identifiable Medtronic device and we were able to get it interrogated.  Our ED now has the algorithm posted at our doctor’s station so we can utilize it for device identification.

Author:  Russell Jones, MD

References

Jacob S et al.  Cardiac Rhythm Device Identification Algorithm Using X-Rays: CaRDIA-X.  Heart Rhythm 2011; 8(6): 915-922.


Filed under: Articles, Cardiac, Chest XR, Devices, Non-Trauma, XR

Acromioclavicular separation…

This person fell from bike and won’t move their shoulder:

AC separation 1 AC separation 2

On initial evaluation we actually thought this person had a shoulder dislocation (glenohumeral dislocation) because of the significant deformity visible externally.  They had the classic anterior “divot” on the shoulder and wouldn’t perform shoulder range of motion.  We were somewhat surprised when we found an acromioclavicular (AC) separation instead.

This case is a good argument as to why often it is appropriate to obtain pre-reduction X-rays for possible shoulder (glenohumeral) dislocations.  Unless the patient will allow a good exam, sometimes it is very hard to differentiate AC separation from glenohumeral dislocation without imaging.   In this case, if we went directly to attempted “reduction”  it would have been very difficult to “reduce” the shoulder!  Hence the need for an X-ray.

There are six different types/degrees of AC separation that are summed up well on the following LearningRadiology.com webpage:

AC Separation Types

 

Author:  Russell Jones, MD

References

1.  Acromio-clavicular separation.  www.LearningRadiology.com

 

 


Filed under: Orthopedics, Shoulder XR, Trauma, XR