Myositis Ossificans of the Thenar Eminence mimicking a Fracture of an Accessory Trapezium: A Case Report.

Abstract

Introduction: Myositis ossificans (MO) is a rare condition characterized by heterotopic ossification within muscle tissue, often mimicking more common pathologies. We present a case of MO involving the thenar eminence, initially suspected and managed as an accessory trapezium fracture.

Case report: A 66-year-old male presented with acute pain and swelling in the base of his left thumb. Initial imaging suggested a possible accessory trapezium fracture, prompting immobilization and conservative management. Subsequent clinical course and imaging over weeks revealed resorption of the calcification on follow-up radiographs, consistent with MO rather than a fracture.

Discussion: This case highlights the diagnostic challenges posed by MO in the upper extremities and underscores the importance of serial imaging and clinical correlation in distinguishing it from other conditions, particularly fractures, to guide appropriate management.

Conclusion: Physicians are encouraged to consider MO as a possible diagnosis for soft-tissue swelling of the hand.