Gravity stress test in Weber B ankle fractures: an added value?

Ankle fractures are regulary seen at the emergency department. They represent
about 10% of all fractures and according to expectations this number will
increases over the years. The fracture can occure in the fibula (lateral
malleolus) and/or the tibia (medial and/or posterior malleolus). Next to this
there can be damage to de ligaments. The damage to the bones/ligaments
distinguishes between a stable or an instable fracture. Instable fractures are
generaly treated by operative fixation, stable fractures are generaly treated
conservative.

Ankle fractures can be classified in different ways. The most commonly used
classification is the Weber classification. We differentiate between Weber A, B
and C fractures. Weber A fractures are distal of the syndesmosis, Weber-B
fractures at the level of the syndesmosis and Weber C fractures are above the
syndesmosis. Weber A fractures are stable and generaly treated as ligament
damage. Weber C fractures are generaly instable and treated bij operative
fixation. In Weber B fractures it is relevant to know if there is next to the
fibula fracture damage to the bones and/or ligaments at the medial site of the
ankle (deltoid ligament). The deltoid ligament is build up out of a deep and a
superficial part. The deep deltoid ligament is the primary stabilizer of the
ankle and prevents lateral talar shift and external rotation of the talus. In
patients with a Weber B fracture it is important to differentiate between a
fracture with or without damage of the deltoid ligament for the consideration
of conservative or surgical treatment.

To determine the integrity of the deep deltoid ligament we make use of an
x-anterior posterior, x-lateral and x-Mortise view of the ankle. The amount of
medial clear space widening has been somewhat variable in the literature but
more than 5 mm is generally regarded as most reliable to predict rupture of the
deltoid ligament. Adequate treatment for these patients is surgical treatment
instead of conservative treatment. However in some cases it stays unclear if
the deltoid ligament is ruptured or not.

Other diagnostic methods for determine the integrity of the deltoid ligament is
the external rotation stress test and the gravity stress test. The external
rotation stress test turn out to be a more painful, no correlation was found
between a positive ankle stress test and the outcomes of the MRI and patients
with a positive ankle stress test without clinical symptomes of deltoid
ligament damage who were treated conservative kept all a good function of the
ankle.

Not much research has been done to test the sensitivity and specifity of the
gravity stress testt and there is no literature which compares positive ankle
stress test with MRI results.

What is the sensitivity and specificity of the gravity stress test compared
with MRI?
Is it possible to differentiate between stable and instable fractures with the
gravity stress test?
Is it possible to differentiate between partial and total rupture of the
deltoid ligament with the gravity stress test?

All patients presenting at the emergency department of the MC Haaglanden with
an acute Weber-B fracture are diagnosed and treated as said in the guidelines.
Patients who meet the inclusion criteria will be informed about the trial in
the emergency department and they will get an information package. In case the
patient decides to participate in the trial, within one week an MRI and an
gravity stress test wil be made. the conclusion of the MRI will be taken into
account in the treatment plan of the fracture. All patients will be seen in
follow-up at the regular times.

After all patients are included the gravity ankle stress test and de X-mortise
will be coded anonymous and presented to a panel of 4 doctors. Two trauma
surgeons and two radiologists will individual assess the X-mortise and the
gravity stress test. They will assess the dislocation of the fracture, medial
widening, the aspect of the syndesmose and indication to operate yes or no.

These results will be compared to the conclusion of the MRI, which will be
assessed by an independent radiology assistent and an independent radiologist.
The outcomes will be collected and analyzed by an independent researcher.

Analysis will show if the gravity ankle stress test has any value to
distinguish between stable and instable fractures.

Next to this inter-observer study an intra-observer study will take place. All
X-ray will be assess a second time by the same panel to determine the
intra-observer variability

The patients have to visit the hospital one time extra in the first week after
trauma to go into the MRI-scan. The treatment will not differ from the regular
treatment, but in the future hopefully less patients need to be operated.