How Good Are Ankle Rules for Determining If a Patient Needs An X-Ray?

Patient Presentation
A 16-year-old male came to clinic with a 24 hour history of right ankle injury. He had been playing basketball and had an inversion injury. He denied any pops or other sounds at the time. He had not been able to walk right after the injury. He had elevated the leg, used intermittent ice and had some ibuprofen, yet he was still having a reasonable amount of pain and was still limping. The past medical history was negative for other extremity injuries.

The pertinent physical exam showed a well-appearing male with normal vital signs and growth parameters. His left ankle was moderately bruised and swollen over the lateral malleolar area. He had tenderness over the posterior talofibular and fibulocalcaneal ligaments. There was no tenderness along the fibula itself but the swelling made the examination difficult to tell. He also wasn’t sure if there was pain near the 5th metacarpal. The medial malleolus, tibia and navicular had no pain with palpation. There was no other foot pain and he was neurovascularly intact.

The diagnosis of a possible ankle sprain versus fracture was made. The pediatric resident said that he knew that there were criteria for when you should get an ankle x-ray but wasn’t sure what they were nor how good they were for diagnosing fractures. The attending physician reviewed the Ottawa Ankle Rules with him, demonstrating that the patient was not able to walk and had swelling that compromised the examination making it difficult to tell if there was point tenderness in some key areas or not. The radiologic evaluation showed no fracture. The patient was placed into a removeble aircast and crutches. He was referred to physical therapy for rehabilitation as the patient was finishing his basketball season but was starting another sport in 3 weeks.

Ankle sprains result from force around the ankle that exceeds the tensile strength of the supporting ligaments of the ankle but less than that which breaks the ankle bones. The ankle capsule – ligament complex has 5 primary ligaments:

Medial ankle – the deltoid is the strongest ligament in the ankle and has two parts:

  • Superficial deltoid ligament – runs from the medial malleolus to the calcaneus posteriorly
  • Deep deltoid ligament – runs from medial malleolus to the talus

Lateral ankle – these ligaments act like 3 guidewires to the lateral ankle and are generally injuried in the following order:

  • Anterior talofibular ligament – runs anteriorly to the lateral malleolus
  • Fibulocalcaneal ligament – runs laterally to the lateral malleolus
  • Posterior talofibular ligament – runs posterior to the lateral malleolus

Most ankle injuries involve an inversion of the ankle. The ability to walk generally excludes a fracture. People with third-degree ankle sprains often give a history of an audible snap. The physical examination revels intact skin with swelling. Pain upon motion is common as is point tenderness over the ligaments. An anterior drawer sign indicates anterior talofibular ligament rupture.

Clinical decision rules are tools to help clinicians make diagnostic decisions. There are two validated ankle decision rules that can help clinicians determine if an ankle injury requires a radiograph.

The Ottawa Ankle Rules
An ankle radiograph is only recommended if there is any pain in the malleolar areas plus one of the following

    1. Bone tenderness posterior aspect of the distal 6 cm of the tibia
    2. Bone tenderness posterior aspect of the distal 6 cm of the fibula
    3. Inability to bear weight (taking 4 complete steps)

A foot series radiograph is only recommended if there is any pain in the midfoot areas plus one of the following

    1. Bone tenderness of the navicular bone
    2. Bone tenderness at the 5th metatarsal
    3. Inability to bear weight (taking 4 complete steps)

The Ottawa Ankle Rules are used in the adult and pediatric populations.

The Low Risk Ankle Rules
“The Low Risk Ankle Rules states that if a child with an ankle injury has a low-risk examination (i.e., tenderness and swelling isolated to the distal fibula and/or adjacent lateral ligaments distal to the tibial anterior joint line), ankle radiography may not be necessary to further exclude a high-risk ankle injury…”
A high-risk injury includes any fracture of the foot, distal tibia and fibula proximal to the distal physis, tibiofibuar syndemosis injury and ankle dislocations.”
Low risk injuries are managed by supportive splinting and returning to activities as tolerated. Low risk injuries would include avulsion fractures of the distal fibula or lateral talus, and non-displaced Salter-Harris type I and II of the distal fibula and lateral ankle sprains.

Obviously overall clinical judgment must be kept in mind. If there is significant swelling such that the entire area cannot be palpated properly, there is potential neurovascular compromise, the patient’s mental status is compromised, or for some other reason the area cannot be properly evaluated then radiographs should be considered.

Learning Point
A systematic review and meta-analysis of using the Ottawa Ankle rules found the sensitivity to be ~99% and specificity of ~35%. The pediatric age group has a slightly lower sensitivity (97.9%) and lower specificity (21%).
This study supports that if the clinical examination indicates a low risk injury, then radiographs are not indicated. If the examination indicates a potential high risk injury, then the radiographs would be indicated because the clinical examination cannot discern well enough if a fracture is present or not.

Use of the Low Risk Ankle Rule was evaluated in a Canadian study of 3-16 year old children. The study found a decrease in radiographs by 22% using the Low Risk Ankle Rules. Overall the sensitivity was 100% and the specificity was 53.1%.
This study supports that if the examination indicates a low risk injury, then radiographs are not indicated. Fractures that were missed in the low risk group (i.e. false negatives) were low risk fractures that were treated like ankle sprains. If the examination indicated a potential high risk injury, then the radiographs would be indicated because the clinical examination cannot discern well enough if a fracture is present or not.
This group also found cost savings of $37 Canadian dollars per patient.

While most of the studies using these ankle rules are in emergency departments or physician offices some time period after the injury, similar data has been shown for athletic trainers treating acute (<1 hour after injury) ankle injuries.
In this study, which utilized the Ottawa Ankle Rules, it is understandable that the need for radiographs was overestimated (i.e. false positive clinical examination) because of increased pain, guarding and/or unwillingness to bear weight right after the injury. In this study, the sensitivity was 88% but had 0 specificity. The authors point out that negative clinical findings ruled out the need for radiographs and decision making "…based on the totality of the examination findings is the best filter in determining referral for radiographs."

Questions for Further Discussion
1. What are the Ottawa Rules for knees?
2. What other validated clinical decision rules do you use?

Related Cases

    Symptom/Presentation: Pain

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Ankle Injuries and Disorders and Sprains and Strains.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Boutis K, Grootendorst P, Willan A, et. al.. Effect of the Low Risk Ankle Rule on the frequency of radiography in children with ankle injuries. CMAJ. 2013 Oct 15;185(15):E731-8.

Boutis K, von Keyserlingk C, Willan A, Cost Consequence Analysis of Implementing the Low Risk Ankle Rule in Emergency Departments. Ann Emerg Med. 2015 Nov;66(5):455-463.e4.

Browne GJ, Barnett PL. Common sports-related musculoskeletal injuries presenting to the emergency department. J Paediatr Child Health. 2016 Feb;52(2):231-6.

David S, Gray K, Russell JA, Starkey C. Validation of the Ottawa Ankle Rules for Acute Foot and Ankle Injuries. J Sport Rehabil. 2016 Feb;25(1):48-51.

Beckenkamp PR, Lin CC, Macaskill P, Michaleff ZA, Maher CG, Moseley AM. Diagnostic accuracy of the Ottawa Ankle and Midfoot Rules: a systematic review with meta-analysis. Br J Sports Med. 2016 Nov 24. pii: bjsports-2016-096858. doi: 10.1136/bjsports-2016-096858. [Epub ahead of print]

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital