RESUMO
PURPOSE: Os trigonum syndrome is a rare condition, often affecting athletes. A paucity of data exists on the incidence of os trigonum syndrome in nonathletic population. The study aimed to determine the incidence and clinical characteristics of os trigonum syndrome in nonathletic patients with sprained ankles. METHODS: The sample consisted of 798 adolescent and adult patients that attended the emergency department or Foot and Ankle Clinic with acute ankle sprain. Lateral and/or oblique lateral radiographs of the feet were screened for the presence of os trigonum in relation to age and gender. A cohort of 163 patients with os trigonum was followed up prospectively over a 48-month period to correlate the presence of the os trigonum with patient symptomatology. RESULTS: Os trigonum was found in 20.4% (163/798) of sprained ankles. Patients aged 18-35 exhibited most os trigonum [42.3% (69/163)], with higher incidence in females. 5.5% (9/163) of the os trigonum patients developed an os trigonum syndrome after a standard treatment of an ankle sprain [3.8% (3/78) of males and 7.1% (6/85) of females]. Females aged between 18 and 35 years had higher incidence of os trigonum syndrome compared to males of a similar age. CONCLUSION: Os trigonum syndrome should be suspected in nonathletic patients with an ankle sprain unresponsive to standard treatment. About 1.1% of acute ankle sprain patients develop an os trigonum syndrome. This finding can help identify the source of a patient's symptoms, leading to an accurate diagnosis, appropriate treatment and reducing the potential chronic symptoms.