In this feature, AAOS Now publishes a series of images, challenging readers to diagnose the condition depicted.
This month’s challenge was submitted by Jill Larson, MD, a resident member of Northwestern University Feinberg School of Medicine, department of orthopaedic surgery.
The patient is a 27-year-old healthy woman who complained of left dorsal midfoot pain after running a half marathon. The patient reported inverting her left foot approximately 6 miles into the race, but she was able to finish despite the pain. She was evaluated a few days after the race and placed in a CAM boot after a radiograph and MRI (Figs. 1 and 2) were obtained. What’s your diagnosis?
Find the answer below
“A coalition represents an abnormal fusion between two or more tarsal bones and is a frequent cause of foot and ankle pain,” explained Dr. Larson. “It’s often overlooked in young patients who are first seen with hindfoot or tarsal pain/stiffness. Most patients are in the second decade of life and the condition is often diagnosed after antecedent trauma, weight gain, or an increase in athletic activity.
“Calcaneonavicular coalitions are best depicted on 45° internal oblique radiographs,” continued Dr. Larson. “The MRI will show nonosseous lesions. Normally, the calcaneus and navicular do not articulate. With a nonosseous coalition, the bones are in close proximity, have irregular surfaces, and the anteromedial calcaneus is abnormally widened or flattened. On lateral imaging, elongation of the anterior dorsal calcaneus may simulate an ‘anteater’s nose’ deformity. Initial treatment is usually conservative, but if this is unsuccessful, surgical resection of the calcaneonavicular coalition may be performed.”