Ankle Fracture Workup

Updated: Oct 26, 2016
  • Author: Kara Iskyan, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Laboratory Studies

No laboratory studies are necessary in patients with isolated ankle fracture when caused by a plausible mechanism. However, repeated ankle fracture or a fracture caused by simple, low force trauma can require investigation for osteoporosis, Charcot-Marie-Tooth disease, arthritis, connective tissue disease, or peripheral vascular disease.


Imaging Studies

Routinely obtaining radiographs following an ankle injury is not cost-effective because fewer than 15% of affected patients have fractures. Patients without fractures are identified reliably from the physical examination. Ottawa ankle rules provide practical guidelines to select patients for radiographic studies. [9, 10] Diagnostic guidelines are available from the American College of Radiology Appropriateness Criteria for suspected ankle fractures. [11]

Indications for ankle radiographs in patients with acute ankle pain include pain in the ankle region plus one of the following [12] :

  • Bony tenderness at the distal 6 cm of the posterior edge of the medial malleolus

  • Bony tenderness at the distal 6 cm of the posterior edge of the lateral malleolus

  • Inability to bear weight both immediately and in the ED (defined as 4 steps)

  • Confounding variables to the Ottawa rules are (1) underlying neurologic deficit affecting lower limb(s), (2) altered mental status, and (3) multisystem trauma.

Application of the Ottawa Ankle Rules to patients younger than 18 years is controversial. While some advocate the rules can be applied to children old enough to talk and walk, others use the ages 5 or 6 as a cut-off. [13]

Perform a standard 3-view radiographic examination (anteroposterior [AP], lateral, and mortise views) of the ankle. In the mortise view, the foot is rotated approximately 15° internally, allowing better visualization of the ankle mortise. Check radiograph for headset sign (ie, tibia sits atop the talus resembling a headpiece on a receiver). Normally, the space between the cradle and the handle should be equal. Lack of symmetry suggests injury.

The ankle joint usually adheres to the ring axiom (eg, a fracture in one part of the ring often is associated with a second injury). Always look for an associated medial malleolar fracture when a spiral fracture of the fibula proximal to the ankle mortise is seen. A vertical fracture of the medial malleolus is also associated with either a lateral malleolar fracture or rupture of the lateral ligaments.

Accessory ossicles appear frequently adjacent to the medial and lateral malleoli and may mimic fractures. Clinical correlation is important. Accessory ossicles demonstrate well-corticated margins, whereas fracture fragments exhibit less-defined borders.

Radiographic examination of the foot is not required in patients with an isolated ankle complaint. Although there may be an occult fracture of the base of the fifth metatarsal, those should be found with adequately performed ankle radiographs. [14]

Externally rotated lateral radiographic projection can provide surgeons with additional information regarding the presence, size, and displacement of posterior malleolar ankle fractures, according to one study. In this study, posterior malleolar fractures were accurately identified on 86.67% (26 of 30) of standard lateral radiographs and on 100% (30 of 30) of externally rotated lateral radiographs. In addition, surgeons described the fracture with greater precision and had greater interclass correlation coefficient values regarding sagittal plane displacement (0.977 versus 0.939) and percentage of involvement of the tibial plafond (0.972 versus 0.775) with an externally rotated lateral projection, as compared with a standard lateral projection. [15]

ACR Appropriateness Criteria for acute trauma to the ankle includes the following [16] :

  • The use of 3-view (anteroposterior, lateral, and mortise) radiographic evaluation of patients meeting the criteria of the Ottawa ankle rules.
  • Cross-sectional imaging has a limited secondary role primarily as a tool for preoperative planning and as a problem-solving technique in patients with persistent symptoms and suspected of having occult fractures.

CT and MRI imaging studies may be part of outpatient management where imaging features by the other modalities are equivocal. [17]

Advanced imaging is most useful to diagnose talar dome and triplane fractures, distinguish pilon from trimalleolar fractures, and differentiate an accessory ossicle from an avulsion fracture. Occasionally, these tests are used to assess the complexity of the fracture and any associated ligamentous and intra-articular injuries.

A bone scan rarely is indicated emergently. It may be useful for diagnosing and localizing stress fractures, infections, and neoplastic lesions.

A study of patients who presented to an urban level 1 trauma center with acute ankle injuries found that the sensitivity of bedside ultrasonography in detecting foot and/or ankle fractures was 100%  and that the specificity of Ottawa Foot and Ankle Rules increased from 50% to 100% with the addition of ultrasonography. The negative predictive value was 100%, and the positive predictive value was 100%. [18]


Other Tests

Stress radiographs assess the ankle during stress testing; however, results of this test generally do not affect immediate ED management.