A Rare Pediatric Cause of Lateral Foot Pain: Symptomatic Os Vesalianum Pedis Requiring Excision and Peroneus Brevis Repair

Introduction: Os vesalianum pedis (OV) is a rare accessory ossicle located posterior to the proximal base of the fifth metatarsal, with an estimated prevalence of 0.6%. It results from the failure of fusion between the secondary ossification site and the primary ossification center. Most cases are asymptomatic and identified incidentally, but symptomatic presentations can occur following acute trauma or repetitive stress. Reported adolescent cases are limited, with prior literature documenting ages 13-19. We present the youngest reported case of a skeletally immature symptomatic OV in our findings of the English literature - a 12-year-old female - managed successfully with surgical excision and peroneus brevis tendon repair. Case Report: A healthy 12-year-old female developed acute lateral left foot pain after striking her foot against a table. Urgent care radiographs suggested a non-displaced pseudo-Jones fracture. She was initially managed conservatively, being placed in a controlled ankle motion boot. At 4 weeks, persistent pain and absent callus formation prompted contralateral foot radiographs, revealing a similar ossicle. Magnetic resonance imaging (MRI) confirmed bilateral OV with peroneus brevis attachment, with the left side symptomatic. After 6 weeks of activity restriction failed to improve symptoms, surgical excision of the ossicle with tendon reattachment was performed. Postoperatively, she progressed from short-leg casting to gradual weight bearing in a boot, then returned to regular footwear. At final follow-up, she had full, pain-free function with normal gait, strength, and range of motion. Conclusion: This case highlights symptomatic OV as a rare but important differential diagnosis for persistent lateral foot pain in adolescent patients, particularly when presumed fifth metatarsal fractures show no healing by 4-6 weeks. Contralateral radiographs and MRI can help differentiate OV from fractures and guide management. While most cases are treated conservatively, surgical excision with tendon repair can yield excellent short-term outcomes when non-operative measures fail. Given the scarcity of skeletally immature cases and unknown long-term implications for tendon integrity and growth plate behavior, further study is warranted to inform age-specific treatment guidelines.