Os Trigonum Syndrome

摘要

In 1804, Rosenmuller first described the os trigonum as an accessory ossicle that failed to fuse to the posterolateral talar process.1 Literature indicates that the prevalence of os trigonum syndrome ranges from 1.7% to 7%.2 The talus bone has 2 posterior tubercles with a central groove. Lateral tubercle of the posterior talus, or Stieda process, is larger in comparison to the medial tubercle. A secondary center of ossification of the lateral talar tubercle develops in the embryo during the second month of human gestation and becomes visible on radiographs at age 8 to 10 years in girls and 11 to 13 in boys. Secondary ossification center of this accessory ossicle typically fuse in the same year it becomes visible. Os trigonum is a name given to an unfused secondary ossification center of the posterolateral talar tubercle. This failure of fusion of the secondary ossification center is reported to occur in 1.7% to 49% of the general population.2,3 Os trigonum can also result from an acute fracture of the Stieda process also known as a Shepherd fracture. Os trigonum syndrome can also be referred to as posterior ankle syndrome and can be defined as an unfused secondary ossification center that becomes symptomatic from repetitive use or an injury. This syndrome can result from an overuse injury owing to repetitive plantar flexion stresses. Overuse or traumatic injury can lead to a fracture