P0171 - 16-year-old Female with Persistent Forefoot Pain

Introduction: A 16-year-old female with a history of bilateral flexible pes planus presented to a sports medicine clinic with pain at the plantar surface of her right great toe for two years. The patient was diagnosed with avascular necrosis of the right first metatarsal medial sesamoid. Sesamoid osteonecrosis is a rare condition that is typically idiopathic in nature and treated with surgical excision.

Case Description: At the patient’s initial sports medicine appointment, she reported that her pain was intermittent and exacerbated by activity. Through instruction of her pediatrician, previous treatments including ice, ibuprofen, kinesiology tape, insoles and a walking boot were unhelpful. Aside from right great toe swelling, review of systems were negative. Exam of the right great toe displayed swelling overlying her metatarsophalangeal (MTP) joint. No erythema, skin breakdown or joint effusion were noted. Tenderness to palpation was present on the medial sesamoid. Passive and active range of motion of the first MTP joint were limited due to pain. She was neurovascularly intact. Gait was antalgic. Plain films displayed a bipartite medial sesamoid and magnetic resonance imaging revealed medial sesamoid edema concerning for sesamoiditis (FIGURE 1). She was treated with a medial sesamoid orthotic cut-out and progressive return to activity.

The patient presented three months later with persistent right great toe pain despite use of the orthotic cut-out. Her exam was unchanged from her prior appointment. Computed tomography displayed fragmentation of the right first metatarsal medial sesamoid with central boney absence and surrounding sclerotic bone consistent with osteonecrosis (FIGURE 2). Due to persistence of symptoms and poor prognosis, the patient underwent sesamoidectomy. She was placed in a post-op shoe with slow increase in activity. One month following excision, the patient tolerated full activity without any limitation or pain.

Discussion: A sesamoid is a bone embedded within a tendon or muscle. Sesamoids provide a smooth surface for tendon movement which increases the tendon’s capacity to transfer force similar to a pulley system. Sesamoid bones of the foot are typically located within the FHB tendon, at the lateral and medial side of the first metatarsal head. Nearly 10% of people have a bipartite sesamoid, which is frequently misread as fracture. Sesamoid osteonecrosis is often idiopathic, while other cases are thought to be related to repetitive micro-trauma. Sesamoid osteonecrosis is rare but should remain in the differential diagnosis for chronic forefoot pain. Treatment is typically excision.

Conclusion: The differential diagnosis of chronic forefoot pain at the plantar surface of the great toe near the MTP joint includes sesamoid fracture, flexor hallucis brevis tendinopathy, sesamoiditis, plantar plate injury, MTP joint osteoarthritis and sesamoid osteonecrosis. Sesamoid osteonecrosis is diagnosed through exam and advanced imaging. Treatment is typically surgical excision with gradual return to activity.