Medial malleolar stress fracture resulting from repetitive stress caused by lateral ankle instability: A case report

RATIONALE: Stress fractures are most commonly sustained in the lower extremities owing to the repetitive weight-bearing forces. They are overuse injuries that are seen often in athletes, but rare in the general population, so early diagnosis and proper treatment are important to enable athletes to return to activity. This is a rare example of successful treatment of a medial malleolar stress fracture with lateral ankle instability. PATIENT CONCERNS: A 16-year-old athlete presented with acute-onset left ankle pain. He was a baseball pitcher who had previously sprained left ankle while training. Subsequently, the ankle pain worsened, and he had tenderness on the medial aspect of his left ankle. The symptoms were mild at rest, but increased upon walking and training. Three years previously, he had sprained his ankle several times during baseball training. DIAGNOSIS: Plain standing radiographs of the left ankle showed a vertical fracture line in the medial malleolus. Computed tomography also showed the vertical fracture in the medial malleolus. Magnetic resonance imaging revealed mild bone marrow edema in the medial malleolar area and total rupture of the anterior talofibular ligament. INTERVENTIONS: Surgery was performed under general anesthesia, and we checked the instability of his ankle using a C-arm image intensifier, and the varus talar tilt angle was increased (10.3°). The medial malleolus stress fracture was fixed using tension bend wiring, and an arthroscopic modified Broström procedure was done. OUTCOMES: Two months postoperatively, the patient started walking, and raised-heel squatting. The medial malleolar fracture was completely united at the 3 months postoperatively on plain radiography, and return to full activity was achieved by 3 months postoperatively. Then the hardware was removed 1-year after operation and both the anterior drawer and external rotation stress tests were negative. LESSONS: Medial malleolar stress fractures are rare, so they can be overlooked. With these fractures, plain radiographs are frequently normal initially because the medial malleolus consists mainly of cancellous bone. Physicians require a high level of suspicion when taking the patient's history and doing the physical examination. Because most occur in athletes, early diagnosis and proper treatment are important for patients’ subsequent athletic performance.