RESUMEN
<p><b>OBJECTIVE</b>To distinguish trochlear calcification and intraorbital foreign body after eye injury in order to avoid misdiagnosis as well as mistreatment.</p><p><b>METHODS</b>The orbital CT images of 403 patients, who visited the Eye Hospital or the Second Affiliated Hospital of Wenzhou Medical College during May 2005-April 2007, were reviewed. The diagnosis of trochlear calcification and intraorbital foreign body was made together by a skilled radiologist as well as an ophthalmologist. General information and CT characteristics in the patients with trochlear calcification were collected.</p><p><b>RESULTS</b>Using CT scan images, 27 among 403 patients (6.69%) were identified with trochlear calcification. Three patients (3/27, 11.11%) were misdiagnosed by radiologists as intraorbital foreign body. Among the 27 patients with trochlear calcification, 23 (85.19%) were male and 4 (14.81%) were female, with an unilateral calcification in 7 patients (7/27, 25.93%) and bilateral in 20 (74.07%) . The highest occurrence of trochlear calcification was in 31-40 years old group (13/403, 3.23%) which reached to 12.87% (13/101) after age-correction. There were 3 types of trochlear calcification on the basis of CT images: commas, dot and inverted "U".</p><p><b>CONCLUSIONS</b>The trochlear calcification is not an uncommon phenomenon and should not be diagnosed as intraorbital foreign body, especially when it co-exists with eye injury in 31-40 years old group. Injury history and our classification method on the basis of CT images could help to avoid misdiagnosis.</p>