“…In addition, a number of studies did not report complete data on the outcome of each hip. For example, 32 studies [3, 5, 7-9, 15, 17, 19, 23, 26, 28, 29, 33-35, 38, 40, 44-48, 52, 54-58, 60, 61, 63, 64] reported data only in terms of conversion to THA, and seven reported only in terms of progression of disease [2,4,22,30,39,42,62]. Only 15 studies reported data in terms of both conversion to THA and progression of disease [1,6,11,12,14,16,18,20,21,24,27,49,50,65,66].…”