Comparison of manual and gravity stress radiographs for the evaluation of supination-external rotation fibular fractures.

BACKGROUND:
Isolated distal fibular fractures most commonly result from a supination-external rotation injury of the ankle. Deltoid ligament ruptures can also be associated with these injuries, resulting in an unstable ankle fracture due to incompetent lateral and medial restraints. We hypothesized that a gravity stress radiograph is equivalent to a manual stress radiograph for the detection of deltoid ligament injury in association with an isolated fibular fracture.

METHODS:
All patients presenting to a level-1 trauma hospital emergency department with an isolated fibular fracture were screened. Ankle stability was determined on the basis of radiographic measurements of the medial clear space and talar shift. A manual stress radiograph and a gravity stress radiograph of the injured ankle were made for each patient. The manual stress radiograph was used to determine whether the ankle was stable or unstable.

RESULTS:
A total of twenty-five patients (thirteen with a supination-external rotation type-II fracture and twelve with a supination-external rotation type-IV-equivalent injury) were enrolled in the study. In the type-II group, the average medial clear space was 4.15 and 4.26 mm on the manual and gravity stress radiographs, respectively (p = 0.50). In the type-IV group, the average medial clear space was 5.21 and 5.00 mm on the manual and gravity stress radiographs, respectively (p = 0.69).

CONCLUSIONS:
The gravity stress radiograph is equivalent to the manual stress radiograph for determining deltoid ligament injury in association with an isolated distal fibular fracture, and thus it can be used to determine ankle stability in patients who present with an isolated distal fibular fracture.