What are the Ottawa Ankle Rules (OAR) for determining if an X-ray is necessary for ankle injuries?

Ottawa Ankle Rules for Determining X-ray Necessity in Ankle Injuries

The Ottawa Ankle Rules (OAR) are the gold standard clinical decision tool for determining when radiographs are necessary for ankle injuries, with 92-100% sensitivity for detecting fractures while reducing unnecessary imaging by approximately 30%. 1, 2

Ankle Rules Criteria

An ankle X-ray series is only required when there is:

• Pain in the malleolar region AND either:
  • Bone tenderness along the distal 6 cm of the posterior edge or tip of either malleolus 1, 2
  • Inability to bear weight for four steps both immediately after injury and in the emergency department 1, 2

Foot Rules Criteria

A foot X-ray series is only required when there is:

• Pain in the midfoot region AND either:
  • Bone tenderness at the navicular bone 1, 2
  • Bone tenderness at the base of the fifth metatarsal 1, 2
  • Inability to bear weight for four steps both immediately after injury and in the emergency department 1, 2

Clinical Performance

• Sensitivity: 92-100% for detecting clinically significant fractures 1, 2, 3
• Specificity: 16-51% 1, 3
• Adding swelling as a criterion can increase sensitivity to 100% and specificity to 55% for the malleolar region 1, 4
• Implementation of the OAR can reduce X-ray usage by 5-36% 5, 6, 3

Standard Radiographic Views When Indicated

When X-rays are indicated based on the OAR, the following views should be obtained:

• Three standard views: anteroposterior, lateral, and mortise views 1
• The views should include the base of the fifth metatarsal bone distal to the tuberosity 1
• Weight-bearing radiographs, if possible, provide important information for fractures of uncertain stability 1

Exclusionary Criteria

The OAR should not be used or should be used with caution in:

• Children under 5 years of age 1, 2
• Patients with penetrating trauma 2
• Pregnancy 2
• Skin wounds 2
• Injuries older than 10 days 2
• Return visits for continued traumatic foot pain 2
• Polytrauma patients 2
• Altered mental status 2
• Neurologic abnormalities affecting the foot 2
• Underlying bone disease 2

Special Considerations

• For suspected calcaneal fractures, an axial Harris-Beath view may be needed 1
• For suspected lateral process fracture of the talus (snowboarder's fracture), a Broden view may be helpful 1
• In bicycle spoke injuries in children, if an ankle fracture is present, lower leg imaging may be important 1
• For suspected distal fibular avulsion fractures in children with lateral ankle sprain, an anterior talofibular ligament view may be useful 1

Implementation Tips

• Proper assessment of all criteria is essential before ruling out the need for imaging 2
• Consider age-specific modifications for elderly patients to improve sensitivity 2
• The ability to walk again within 48 hours after trauma is an auspicious sign and indicates a good prognosis 1
• Pain intensity (VAS score ≥5) may be used as an additional criterion to improve specificity 4

By consistently applying these evidence-based rules, clinicians can effectively identify patients who require radiographic imaging while reducing unnecessary radiation exposure, healthcare costs, and emergency department wait times.