Nonunion of a medial malleolar stress fracture in an adolescent athlete secondary to lateral ankle instability: A case report

INTRODUCTION: Medial malleolar stress fractures are relatively uncommon. This report describes the successful treatment of nonunion of a medial malleolar stress fracture due to chronic lateral ankle instability. PRESENTATION OF CASE: A 13-year-old middle school student who belonged to a football club presented to our clinic with chronic medial left ankle pain lasting over a year. He had sprained his left ankle several times 6 years earlier. A plain anteroposterior ankle radiograph showed a vertical fracture line in the medial malleolus involving the epiphyseal plate, and computed tomography demonstrated the vertical fracture seen on the plain radiographs and bone sclerosis at the fracture site. We performed internal fixation for nonunion of the medial malleolar stress fracture with arthroscopic modified Broström for lateral ankle instability. Two years after surgery, the Self-Administered Foot Evaluation Questionnaire improved in all parameters, and both the anterior drawer and varus stress tests were negative. DISCUSSION: Early diagnosis of medial malleolar stress fracture is important for a rapid return to sports. Magnetic resonance imaging is helpful for early diagnosis. Because lateral ankle instability can cause medial malleolar stress fracture, arthroscopic modified Broström procedure is meaningful for medial malleolar stress fracture with lateral ankle instability. CONCLUSION: Internal fixation and the arthroscopic modified Broström procedure could achieve good clinical outcomes for medial malleolar stress fractures with lateral ankle instability.