OBJECTIVES:
To correlate interosseous membrane (IOM) tears of the ankle to the height of fibular fractures in operative ankle fractures.

DESIGN:
Prospective clinical trial.

SETTING:
University Level 1 trauma center.

PATIENTS:
All patients admitted with a closed operative ankle fracture were included. Of 93 patients originally evaluated, 73 patients had adequate MRI for evaluation.

INTERVENTION:
Open reduction and internal fixation of each ankle fracture was performed after preoperative MRI evaluation of the IOM. Transsyndesmotic screw fixation was performed when evidence of syndesmotic instability was shown by intraoperative stress testing.

MAIN OUTCOME MEASUREMENTS:
Radiographs were analyzed for fracture classification and prediction of ligamentous injuries about the ankle. MRI evaluated the IOM integrity, correlating it to the height of the fibular fracture.

RESULTS:
Of the 73 ankle fractures with adequate MRI evaluation, 30 had identifiable complete IOM tears on MRI. Ten of the 30 IOM tears did not correlate with the level of the fractured fibula. Seven cases had IOM tears proximal to the fibular fracture as detected by MRI. Five of these cases were Weber B type fractures, and two were Weber C type fracture patterns. Conversely, three cases of Weber C type fractures had IOM tears that remained distal to the level of the fibular fracture.

CONCLUSIONS:
The level of the fibular fracture does not correlate reliably with the integrity or extent of the interosseous membrane tears identified on MRI in operative ankle fractures. One cannot consistently estimate the integrity of the IOM and subsequent need for transsyndesmotic fixation based solely on the level of the fibular fracture. An intraoperative syndesmotic stress test is recommended to establish the presence or absence of syndesmotic instability.





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