## 4 Discussion
which is expected to require significant effort; therefore, it should be assigned to possible future work. The results of the present study excluded component-to-component contact but relevant in-depth analysis revealed a positive trend between the head diameter size and StL distance in all motor tasks, though it was not statistically significant; generally, this trend was clearer in the more demanding motor tasks. Comparison with the relevant literature revealed an overall good superimposition of the present ROM at the replaced hip joints with those reported in similar GA studies [18; 22; 55; 56] reporting evaluations during walking, stair ascending/descending, squatting, and sitting, as well as extreme joint motion. However, different from the present study, these studies did not include THAs with large femoral head diameters and relevant evaluations were conducted during the execution of a more limited number of motor tasks, i.e., those related to standard activities of daily living, and thus, not forcing the replaced joint toward the extremes of motion. As for the component-to-component contact, the present StL distances concurred well with those reported in similar VA-based studies [33; 40]; however, again, these studies were not evaluating THAs with large diameters and were limited to chair rising and squatting motor tasks. Several limitations are present in this study. Only a small number of motor tasks were tested, and other extreme joint positions, particularly involving critical combinations of rotations in the three anatomical planes, may still result in StL contact. However, those motor tasks analyzed here are tasks that can be more frequently experienced in standard conditions of daily living; therefore, analysis of these motor tasks is possibly more critical than analyzing special exercises in exceptionally performing THA patients. In addition, due to the specific dynamics of walking, chair rising/sitting, and stair climbing and descending, the hip joint could not be tracked using VA since this was out of the field of view for most the image collection time. Despite this, several ROM values, along with the associated peaks and StL distances observed, concurred with those reported in other similar GA- [18; 22; 55] and VA- [33; 40] based studies. Another limit of the present StL interaction analysis is that the acetabular cup position is known to play a major role. However, the exact estimation of this in these patients would have required additional imaging of the pelvis, and we, together with the consulted ethics committee, decided not to perform this. Another limitation is that the StL distance was calculated using VA, whereas the ROM and peak joint rotations were found using GA; however, one session immediately followed the other, and the same tools (chairs, steps, etc.) were used. Furthermore, in the VA, static postures were analyzed, and in GA, complete cycles of movement were collected, but the instructions to the patient and visual inspection facilitated the consistent performance of these tasks. Finally, the population size was not large but it is very revealing that the patterns of motion were highly consistent over the subjects (Figures 3 and 4), and that not a single StL contact was achieved in any patient in any task (Table 3). In conclusion, this multi-instrumental analysis combining GA- and VA-based examinations revealed that, even for demanding motor tasks with extreme ranges of motion, the hip joints replaced with large femoral head diameters did not experience impingement between the prosthesis components. This is important regarding prosthesis design and rehabilitation for THA. Conceptualization: C.B., A.E., and A.L. ; methodology: C.B., G.L., A.E., S.D., and A.L. ; software: C.B., M.O., F.R., and E.T. ; validation: C.B., G.L., and M.O. ; formal analysis: C.B., F.R., and E.T. ; investigation: C.B., G.L., M.O., A.E., S.D., F.R., and E.T. ; resources: C.B., A.E., and A.L. ; writing--original draft preparation: C.B.