Bare spot of the glenoid fossa in children: incidence and MRI features.

BACKGROUND: The bare spot of the glenoid fossa is a normal cartilage defect seen frequently in adults. It has been used on arthroscopy as a landmark for the center of the glenoid fossa. There are no reports of this variant in children, but we have noted it on some pediatric clinical shoulder MRI studies. OBJECTIVE: Our main purpose is to evaluate the incidence of the bare spot in children and define location and MRI features. MATERIALS AND METHODS: Shoulder MRI studies (total 570) from 2004 to 2008 were reviewed. Children were divided into two age groups: group 1, 0-10 years (n = 200), group 2, 11-20 years (n = 370). RESULTS: A total of 12 bare spots (2.1%) were identified; all were seen in group 2. Eight (67%) were central and four were eccentric in the glenoid fossa. All showed a well-marginated focal cartilage defect containing hyperintense joint fluid or contrast agent. Three also had air. CONCLUSION: The bare spot is seen in children. The absence in children younger than 10 years and the low incidence in the second decade support the proposed acquired nature. Familiarity with this finding is important so as not to misinterpret it as a pathologic condition.