Foot & Ankle International - July 2018 - 869

869

Kwon et al
treatment if anatomic alignment persists in the setting of
being exposed to that amount of stress generated by weightbearing in a cast or boot. In the authors' opinion, it may be
that protected weight bearing will in some cases actually
lead to improved alignment given the congruent nature of
the tibiotalar joint.
Are stress views or a trial of weight bearing even necessary to predict instability in the patient who presents with an
apparent isolated fibula fracture? Recently, Nortunen et al47
investigated whether radiographic clues could be elicited
from initial, non-weight-bearing radiographs to predict stability in a cohort of 286 patients who all underwent subsequent stress testing. The authors demonstrated that lateral
malleolar fracture gapping of greater than 2 mm on initial
lateral radiographs as well as other associated findings such
as fracture comminution could predict instability and potentially obviate the need for additional stress imaging. While
their findings are promising, the ability to accurately and
precisely measure fibular fracture gapping is still unknown,
and the threshold to determine stability used in their investigation may fall within a yet undefined measurement error.
Further validation of their findings is required.
How about a patient's ability to weight bear immediately
after sustaining an ankle fracture? Chien et al6 recently
investigated whether a patient's self-reported ability to
weight bear at time of ankle fracture was predictive of
radiographic stability. Examining a cohort of 121 patients,
the authors demonstrated that a patient who was able to bear
weight immediately after injury was more than 8 times
more likely to have a stable ankle fracture. When examining
a subset of 43 patients who presented with an isolated fibula
fracture and anatomic mortise on initial radiographs, an
odds ratio of 3.6 was found in predicting ankle stability

Magnetic Resonance Imaging and
Instability
Given that ankle fractures consist of both osseous and ligamentous injury, the use of magnetic resonance imaging
(MRI) to detect injury and predict instability has been
investigated by several authors. In 2006, Gardner et al15
used MRI to assess the accuracy of the predicted ligamentous injuries as hypothesized by Lauge-Hansen. Of the 49
ankle fractures classifiable per the Lauge-Hansen classification, 53% displayed patterns of ligamentous injury and
fracture patterns inconsistent with the predicted injury as
based on their designated classification on plain radiographs. Interestingly, the senior authors on this previous
study published another report in 2015 examining a larger
cohort of 283 ankle fractures classifiable per the LaugeHansen classification. In this series, the authors reported
that 94% displayed ligamentous injury patterns, consistent
with Lauge-Hansen's predictions with a high correlation
with intraoperative findings.

In 2009, Cheung et al5 performed a retrospective study
of 19 patients with isolated distal fibular fractures and positive external rotation stress radiographs who underwent
additional MRI imaging. They found partial or complete
tears in all cases in at least 2 of the major ligament groups
(typically the deltoid and syndesmosis). While 100% of
specimens demonstrated an AITFL injury, the posterior tibiotalar component of the deltoid ligament was generally
injured (18/19 patients) but was only partially torn most of
the time (15/18 patients),5 suggesting a high false-positive
rate of stress radiographs for determining complete deep
deltoid injury. Koval et al28 also used MRI and found that of
21 patients who had stress-positive Weber B ankle injuries,
19 revealed partial tearing of the deep deltoid, with 2 revealing complete rupture.
More recently, Nortunen et al46 in a larger prospective
study of 61 patients revealed a lack of additional prognostic
value of MRI where patients with both positive and negative stress radiographs demonstrated varying MRI evidence
of deltoid ligament injury. While MRI was able to detect
ligament injury, there was no correlation with stress views
indicating an inability of MRI to predict instability. In addition, the interobserver agreement between radiologists
when grading the severity of ligamentous injury was only
fair to moderate.
In summary, it appears that while diagnosis of ligament
injury is possible with MRI, its clinical usefulness in
determining instability (and therefore treatment) is questionable. While MRI may have a role in detecting associated injuries not well visualized on plain radiographs for
patients sustaining ankle fractures, further investigation is
required.

Clinical and Prognostic Relevance of
the Stress-Positive Ankle Fracture
What is the significance of radiographic widening of the
MCS? While multiple authors have demonstrated excellent
results with operative treatment, of more interest are reports
that have demonstrated successful nonoperative treatment
of the unstable ankle fracture, challenging the prognostic
ability of stress views (ie, does it matter if they widen or
not?). In light of recently published studies, it remains
unknown whether these additional radiographic views (and
a resultant positive finding) should indicate patients for
operative treatment. However, the findings of recently published level I investigations must be interpreted with an
understanding of study limitations.
In 2004, Egol et al13 called into question whether a
stress-positive radiograph was a clear indication for surgery
in the SER IV equivalent fracture pattern. Among 30 fractures that had stress-positive radiographs in the setting of
minimal physical findings, 20 received nonoperative management and were found to have good/excellent results on

Table of Contents for the Digital Edition of Foot & Ankle International - July 2018