Imaging features of glenoid bare spot in a pediatric population

The bare spot (BaS) is a central, well-circumscribed focal defect in the glenoid articular surface, with reported adult incidence of 1-2%. We aimed to reassess MRI features of BaS in the pediatric population and determine its etiology.

A retrospective search of our database from June 2014 to October 2015 was performed for shoulder MRI in patients between 5 and 25 years and then subdivided into four groups: group 1, 5-10 years; group 2, 10-15 years; group 3, 15-18 years; group 4, 20-25 years. BaS was defined as a well-marginated, central defect of increased signal in the articular surface of the glenoid, seen on at least two planes, without evidence of underlying glenoid pathology. Presence, location and size along with clinical indications were documented.

A final cohort of 253 patients revealed 23 BaS, 3.5% in group 1, 20% in group 2, 5% in group 3 and 4% in group 4. There was a significantly higher incidence in group 2 (p = 0.007) compared to group 3 and p = 0.002 compared to group 4. Location was mainly central. Mean size was significantly bigger in group 2 compared to group 3 and 4. Distribution showed the highest number at 14-15 years of age. Instability was higher in groups 3 and 4.

Incidence of BaS in group 2 was significantly higher than in other age groups and higher than in adults. BaS was also larger compared to other populations. These findings support a developmental theory, explained by the centripetal ossification of the glenoid.