Fig. 2. Examples of discrepancy between simple radiography and computed tomography (CT). (A) The simple radiograph of a 67-year-old female patient at 1 year after surgery exhibited large heterotopic ossification between the glenosphere and proximal humerus (white arrow), which appeared as a bony island unconnected to the glenoid (white dotted arrow; modified Brooker’s classification, grade I). However, the CT image demonstrated the same ossifying lesion projecting from the posterior glenoid neck (B, white dotted arrow) as a grade II lesion. (C) The simple radiograph of a 67-year-old male patient showed a faint radio-opaque lesion below the scapular neck (black dotted arrow), but it was not clear due to the overlapped ribs. It was read as grade I by observer 1 and grade 0 by observer 2. However, the CT image clearly visualized the grade II heterotopic ossification projecting from the inferior glenoid neck (D, white arrow).
