## 3 Results
### Influence of Implant Related Factors on ROM for the preoperativelyly Planned Situation  
Figure 6 gives an overview of the ROM concerning the implant-specific design parameters-stem size, CCD-angle, acetabular cup size, prosthetic head size, and femoral neck length for the preoperatively planned situation (n = 19 patients). The results in relation to CCD-angle (Figure 6A) showed that there was a minor decrease in ROM using a higher CCD-angle during flexion (125.3 \(\pm\) 16.1\({}^{\circ}\) for 128\({}^{\circ}\) CCD-angle and 120.6 \(\pm\) 2.5\({}^{\circ}\) for 135\({}^{\circ}\) CCD-angle). Contrarily, the ROM was slightly higher when CCD-angle was increased (101.3\({}^{\circ}\)\(\pm\) 14.7\({}^{\circ}\) for 128\({}^{\circ}\) CCD-angle and 107.6 \(\pm\) 6.0\({}^{\circ}\) for 135\({}^{\circ}\) CCD-angle) during external rotation.  
Figure 5: Comparison of the range of motion using implantation according to preoperatively planned situation for each patient (n = 19) during maximum flexion (maxFlex), internal rotation at 90\({}^{\circ}\) of flexion (IR@90 Flex), and external rotation at 90\({}^{\circ}\) flexion (ER@90 Flex). (**A**) Mean range of motion with standard deviations until impingement during the three movements. Physiological ROM are represented from literature studies for maxFlex and IR@90 Flex [18, 64], and ER@90 Flex [54]. (**B**) Quantity N of impingement type (BBI, bone-to-bone-impingement; II, implant-to-implant-impingement; IBI, implant-to-bone-impingement).  
Figure 6: Results of the ROM analysis depending on implant-specific design parameters during maximum flexion (maxFlex), internal rotation at 90\({}^{\circ}\) flexion (IR@90 Flex), and external rotation at 90\({}^{\circ}\) flexion (ER@90 Flex): (**A**) CCD-angle; (**B**) acetabular cup size; (**C**) prosthetic head size; (**D**) prosthetic head offset.  
It was observed that as the acetabular cup size was increased, progressively more ROM during flexion was achieved (Figure 6B). For instance, impingement occurred at 103.5\({}^{\circ}\)\(\pm\) 0.9\({}^{\circ}\) during flexion in case of a 46 mm cup, while impingement occurred at 145.8\({}^{\circ}\) of flexion in case of a 60 mm cup. A larger cup was also related to a higher maximum internal rotation at 90\({}^{\circ}\) of flexion (increased by up to 130%), whereas no clear trend was observed during external rotation. Figure 6C depicts the ROM depending on the head size, where each patient received a femoral stem equipped with a taper 12/14, which establishes the connection between stem and head. Every stem had, therefore, the same neck diameter, which links the prosthetic head size directly to the head-to-neck ratio. For this patient group, the head-to-neck ratio ranged from 2.07 for a 28 mm head to 2.67 for a 36 mm head (reported in Table 1 for all patients). The ROM until impingement increased with increasing head size. Accordingly, the head size of 28 mm resulted in 103.5\({}^{\circ}\)\(\pm\) 0.9\({}^{\circ}\) and a head size of 36 mm resulted in 129.9\({}^{\circ}\)\(\pm\) 13.9\({}^{\circ}\) during flexion. During internal rotation, the ROM rose from 18\({}^{\circ}\)\(\pm\) 1.8\({}^{\circ}\) (28 mm head size) to 41.7\({}^{\circ}\)\(\pm\) 12.7\({}^{\circ}\) (36 mm head size). A higher head offset (Figure 6D), which was defined by the design of the prosthetic head, was paired with a higher ROM during flexion (114\({}^{\circ}\)\(\pm\) 7.5\({}^{\circ}\) on average for type S vs. 133.8\({}^{\circ}\)\(\pm\) 12.2\({}^{\circ}\) for type XL) with a mean improvement of 19.8\({}^{\circ}\). Likewise, this finding could be observed during internal rotation (33.4\({}^{\circ}\)\(\pm\) 8.7\({}^{\circ}\) on an average for type S and 45.3\({}^{\circ}\)\(\pm\) 14.6\({}^{\circ}\) on an average for type XL) with a mean improvement of 11.9\({}^{\circ}\). Similar to the behavior observed for the prosthetic head size, no influence of the femoral neck length was detected during external rotation.