Background: The accessory bones are common bone variations around the feet and ankles, which usually originate from nonunion of the secondary ossification center adjacent to the main bone mass, and most of them remain asymptomatic. Os subcalcis is an accessory bone at the plantar aspect of the calcaneus, which is located just posterior to the insertion of the plantar fascia. Focal bone formation at the calcaneal plantar pole with heel pain has rarely been reported.
Case summary: A 55-year-old man presented to our clinic with left plantar heel pain and a progressive swelling for 8 years. X-ray, computer tomography and magnetic resonance imaging showed a large os subcalcison the plantar side of the calcaneus, located at the insertion of the plantar fascia. He underwent surgical excision of the lesion. Microscopically the bony trabeculae were intermingled with fat and covered with cartilage.
Conclusion: This is a rare case with accessory os subcalcis leading to heel pain. It highlights the awareness of os subcalcis and helps avoid future misdiagnosis of heel pain.
Keywords: Accessory ossicle; Calcaneus; Case report; Heel pain; Os subcalcis.
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