Does a positive ankle stress test indicate the need for operative treatment after lateral malleolus fracture? A preliminary report.

OBJECTIVES: At our institution, a standardized protocol using magnetic resonance imaging (MRI) to evaluate ankle stability and need for surgery following a positive manual stress test for isolated lateral malleolus fractures has been used. The purpose of this study was to evaluate the results using this standardized protocol.
DESIGN: Retrospective review.
SETTING: University teaching hospital. PATIENTS: : Twenty-one patients who had a positive ankle stress test (>or=5 mm clear space widening) after isolated Weber B lateral malleolus fracture were further evaluated by MRI to determine the status of the deep deltoid ligament. INTERVENTION: If the MRI showed the deltoid ligament was completely disrupted, the patient was advised to have operative ankle repair. However, if the MRI demonstrated that the deep deltoid was intact or only partially disrupted, the patient was treated nonoperatively in a walking boot with weightbearing as tolerated ambulation. MAIN OUTCOME MEASUREMENT: Patients were followed until fracture union and contacted at 12-month minimum follow-up to determine outcomes by radiographic evaluation, health related quality of life (HRQOL) based on Short Form (SF)-36 results and functional outcomes based on the American Orthopaedic Foot and Ankle (AOFAS) and patient report of treatment satisfaction.
RESULTS: Twenty-one patients had an MRI after a positive ankle stress test and comprised the study group. There were 12 men and 9 women with an average age of 27 years (range, 16-62 years). Absolute medial clear space measurement on stress testing ranged from 5 to 8 mm. In all, 19 of 21 patients (90%) had evidence of partially torn deep deltoid ligament on MRI and were treated nonoperatively, whereas two patients had MRI findings of a complete deep deltoid injury and underwent surgical treatment. There were no statistically significant correlations between the medial clear space measurements and MRI documentation of complete deltoid ligament rupture. All fractures united without evidence of residual medial clear space widening or posttraumatic joint space narrowing. Of the 15 patients who were available for 1 year minimum follow-up and agreed to come back for clinical and radiographic evaluation, 14 had an AOFAS score of 100, with the remaining patient having a score of 85. HRQOL based on SF-36 results indicated all patients were above or at normal levels, and all patients reported that they were satisfied with their treatment; 93% (14/15) indicated that they would make the same treatment decision again.
CONCLUSIONS: Using our protocol, we were able to identify and provide effective nonoperative care to 19 patients who otherwise might have underwent operative treatment after an isolated lateral malleolus fracture. Further work is needed to identify the subset of patients who could be treated nonoperatively without a need for MRI scanning.