Fig. 1

Summary of the conventional method to calculate penetration. a Radiographs taken immediately following the operation and at the follow-up period. b Detection of circular edges of the cup and head and calculation of their center positions (circle and cross) are semi-automatically performed by the measurement application. c Relative positions of the head center to the cup center are calculated for each radiograph (\(\overrightarrow{{H}_{0}}\) and \(\overrightarrow{{H}_{k}}\)). d The head penetration during the follow-up period can be calculated as \(\left|\overrightarrow{{H}_{k}}-\overrightarrow{{H}_{0}}\right|\) or \(-\left|\overrightarrow{{H}_{k}}-\overrightarrow{{H}_{0}}\right|\)