Osteoid osteoma of the talar neck is an unusual clinical condition that is often overlooked on initial assessment of patients with ankle pain. Here, we present a case report of an adolescent male with talar neck osteoid osteoma who reported persistent pain after an injury. We discuss the differential diagnosis of persistent anterior ankle pain and assess the treatment options for osteoid osteoma of the talar neck. The patient’s guardian provided written informed consent for print and electronic publication of this case report.
Case Report
A 13-year-old boy presented to our clinic 3 months after a right ankle sprain. He had visited the emergency department at the time of injury; radiographs of the ankle were reported negative for fractures, dislocations, or bone pathologies. He was treated conservatively with elastic support, icing, rest, elevation, and weight-bearing as tolerated. Upon presentation to our office, his pain involved the entire ankle joint. He had not put weight on it since the injury. On examination, he had a significant limp, anteromedial swelling, and tenderness over the ankle joint anteromedially. His neurologic and vascular examinations were normal.
His plain radiographs showed a cystic mass, located at the dorsal aspect of the talar neck (Figures 1A, 1B). Computed tomography (CT) showed a round lucent lesion involving the superior aspect of the talar neck, measuring 9 mm by 6 mm. A sclerotic radiodense focus was evident in the center (Figures 2A, 2B). Noncontrast multiplanar, multisequence magnetic resonance imaging (MRI) showed abnormal edema throughout the talus and a 9-mm rounded ossicle overlying the superior margin of the neck of the talus (Figures 3A, 3B).
Differential Diagnosis
The differential diagnosis for anterior ankle pain includes ankle sprain, monoarticular arthritis, anterior ankle impingement, and talar neck fractures. Other related findings include the presence of a talar ridge and a talar beak.
Ankle sprains are very common injuries. The mainstay treatment consists of ice, resting, elevation, and elastic or semirigid support, and patients usually recover over the course of a few weeks. These sprains are typically injuries of the lateral or medial ligaments of the ankle. Extension of a ligament tear across the anterior capsule can explain persistent anterior ankle pain. The presence of a bony lesion on plain radiographs, however, makes the diagnosis of an ankle sprain, with or without extension into the anterior capsule, less likely.
Monoarticular arthritis, which may present in the ankle and has a wide differential diagnosis, usually involves the whole joint.
Anterior ankle impingement typically occurs in athletes who participate in sports that involve kicking. It can be a bony or soft-tissue impingent. Clinically, patients present with pain and loss of motion, specifically dorsiflexion.
Talar neck fractures are usually the result of high-energy trauma. Stress fractures of the neck of the talus are uncommon and are associated with a recent sudden increase in physical activity, such as running, dancing, or military training. Radiographs, CT scans, and MRI help define the fracture line.
The talar ridge is the site of capsular and ligamentous attachment on the superior aspect of the talar neck and may become hypertrophic in athletes. A hypertrophic talar ridge is asymptomatic and is not considered a pathologic finding on radiographs.
The talar beak, a flaring of the anterosuperior aspect of the talar head, is an indirect sign of tarsal coalition. When symptomatic, patients complain of subtalar symptoms, typically pain and limitation of motion. It usually does not present acutely.
Treatment
We offered the patient surgical excision, and his guardian consented to left ankle arthroscopy. We performed synovectomy using a combination of 3.5-mm shaver and radiofrequency probe. We identified the mass: round, soft, and located at the superior-medial aspect of the talar neck. We removed it in piecemeal fashion using manual arthroscopic instruments, and cauterized its base using the radiofrequency probe. We allowed the patient weight-bearing as tolerated starting the day after surgery.
We submitted the specimen for pathologic evaluation (Figure 4). It consisted of multiple pieces of tan/brown tissue. Histologic examination showed benign osteoblastic proliferation composed of anastomosing bony trabeculae with variable mineralization, lined by plump osteoblasts, within vascularized connective tissue; benign giant cells were present, consistent with a nidus of an osteoid osteoma.
On the first postoperative visit, the patient was pain-free and bearing weight with crutches. He was gradually weaned from his crutches and returned to full weight-bearing over the next 4 weeks. At 12-month follow-up, he was symptom-free with good range of motion and full return to previous level of activity.