Fig. 3

Distribution of follow-up interval among different HO categories. The median follow-up interval for class 0 was 353.5 days (range, 89–2746); class 1 was 306 days (range, 76–2296); class 2 was 279 days (range, 94–3049); and class 3+ was 321 days (range, 95–2345). Thus, shortest median follow-up interval was observed with class 2 HO group, and the median follow-up interval was actually shorter for class 3+ group compared to class 0 group