RESUMO
The hand consists of five sesamoids. Two of them are present at the metacarpophalangeal (MCP) joint of the thumb. Fracture of the sesamoid bones of the thumb is a rare injury and the literature on the radial side is seldom reported. We reported a case of a patient with a fracture of the radial sesamoid at the MCP joint of the thumb in order to increase attention regarding this type of injuries. A 44-year-old male, high level gymnastic trainer, was helping one of his athletes during an exercise while he reported a hyperextension trauma to the MCP joint of the right thumb. One week after trauma, he presented to the hand surgeon complaining of a painful thumb at the MCP joint level on its palmar aspect. Standard A-P and lateral X-rays revealed a fracture of the radial sesamoid and the fracture was treated with a splint for 3 weeks. He was able to resumed his entire work 6 weeks after the injury. The sesamoid fractures is an indicator of the magnitude of the hyperextension injury and sometimes associated with tears of the volar plate ligament of the MCP joint. And a failure to recognize the ligament injury may lead to a long-term hyperextension instability on pinching.