Ankle XRay

Aka: Ankle XRay, Ottawa Ankle Rule, Low Risk Ankle Rule

1. Technique: Views
   1. Lateral ankle
   2. Anteroposterior ankle
   3. Ankle Mortis view
      1. Anteroposterior view
      2. Leg internally rotated 15 to 20 degrees
2. Indications: Ottawa Ankle Rules in Acute Ankle Sprain (Over age 5 years old)
   1. Ankle XRay not needed if both are true:
      1. Able to ambulate at injury or in ER for 4 steps
      2. No pain over distal posterior 6 cm (2.4 inches) of tibia, fibula
   2. Foot Xray not needed for mid-Foot Pain if both true:
      1. Able to ambulate at injury or in ER for 4 steps
      2. No pain at fifth Metatarsal base and Tarsal Navicular
   3. Efficacy
      1. Test Sensitivity for Malleolar Fracture: 95%
      2. Requires alert adult or child age 5 or older
      3. Injury within prior 10 days
3. Indications: Low Risk Ankle Rule (children over age 3 years old)
   1. Ankle XRay is not needed if:
      1. No marked swelling, deformity or malalignment AND
      2. No pathologic Fracture risk AND
      3. Tenderness is limited to distal fibula (distal to anterior tibial joint line) and lateral ligaments
   2. Efficacy
      1. Children must be over age 3 years old
      2. Finds high risk injury (e.g. distal tibia, proximal fibula, Ankle Dislocation) in 98-100% of those age >3 years old
      3. Misses nondisplaced distal fibula avulsion Fractures and Salter-Harris I and II Fractures
   3. References
      1. Boutis (2013) CMAJ 185(15):E731-8 +PMID:23939215 [PubMed]
      2. Ramasubbu (2015) Pediatr Emerg Care 31(10):685-7 +PMID:26196362 [PubMed]
4. Imaging: Pitfalls
   1. Growth Plate Fracture in adolescent
      1. May be missed on Ankle XRay
      2. Consider if pain over lateral malleolus (fibula)
   2. Ankle Syndesmotic Sprain (High Ankle Sprain)
      1. Tibiofibular clear space widening >6 mm
   3. Ankle mortise
      1. Space around the talus should be consistent (symmetric) at its margin between the tibia and fibula
   4. Os Trigonum is a normal variant (lateral xray)
      1. Os Trigonum is an Ossification Center posterior to the talus
      2. Normal variant seen on lateral Ankle XRay in up to 14% of patients
5. References
   1. Labovitz (1998) Foot Ankle Int 19:661-7 [PubMed]
   2. Stiel (1994) JAMA 271:827-32 [PubMed]