What is the Ottawa ankle rule (OAR) for determining when an X-ray is needed for ankle injuries?

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

The Ottawa Ankle Rules (OAR) are the most accurate clinical decision tool for determining when X-rays are needed for ankle injuries, with 92-100% sensitivity for detecting fractures while reducing unnecessary imaging by approximately 30%. 1

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, OR
  • Inability to bear weight for four steps both immediately after injury and in the emergency department 2, 1

• Adding swelling as a criterion can increase sensitivity to 100% and specificity to 55% for the malleolar region 2, 1

Foot Rules Criteria

• A foot X-ray series is required only when there is pain in the midfoot AND any one of:
  • Point bone tenderness of the navicular
  • Point bone tenderness of the base of the fifth metatarsal
  • Inability to bear weight or walk 4 steps immediately after injury or in the emergency department 2, 1

Clinical Performance

• The OAR have been extensively validated with sensitivity of 92-100% and specificity of 16-51% 2, 3
• Implementation of the OAR can reduce radiography use by approximately 35% without missing clinically significant fractures 4, 5
• Multiple meta-analyses have confirmed the OAR as the most accurate tool for excluding fractures in acute ankle settings 2

Exclusionary Criteria - When NOT to Use OAR

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

• Penetrating trauma
• Pregnancy
• Skin wounds
• Patients transferred with radiographs already taken
• Injuries >10 days old
• Return visits for continued traumatic foot pain
• Polytrauma
• Altered sensorium
• Neurologic abnormality affecting the foot
• Underlying bone disease 2, 1

Clinical Scenarios Not Addressed by OAR

• Trauma to metatarsal heads and toes
• Penetrating trauma with concern for foreign body in soft tissues 2, 1

Implementation Considerations

• The OAR are validated for adults and children >5 years of age 2, 1
• When X-rays are indicated based on the OAR, standard views should include anteroposterior, lateral, and mortise views 1
• Nurse triage programs using the OAR protocol have shown a reduction in emergency room patient stay by up to 20 minutes 2
• Alternative rules like the Bernese Ankle Rules have been evaluated but show lower sensitivity (69-86%) compared to the OAR 2, 3

Clinical Impact

• Implementation of the OAR can lead to significant cost savings without compromising quality of care 4, 6
• In a quality improvement project, improving compliance with the OAR significantly reduced unnecessary X-ray requests 5
• Recent studies continue to confirm the high sensitivity (100%) and moderate specificity (43-45%) of the OAR in clinical practice 6

The OAR remain the gold standard for clinical decision-making regarding the need for radiography in ankle and foot injuries, with consistent validation across multiple studies showing excellent sensitivity for fracture detection while reducing unnecessary imaging.