OBJECTIVETo distinguish trochlear calcification and intraorbital foreign body after eye injury in order to avoid misdiagnosis as well as mistreatment.

METHODSThe 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.

RESULTSUsing 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".

CONCLUSIONSThe 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.