Fig. 4A–C.

(A) CA ranging from 30° to 50° satisfied the required ROM without using the modular necks in the case at 20° anteversion. (B) At 60° anteversion, ER was less than 10° even when the acetabular component was set at 10° retroversion owing to the posterior bone impingement. (C) At 20° retroversion, the anterior bone and implant impingement led to the insufficient Flex and IR. ER = external rotation at 0° extension and abduction; IR = internal rotation at 90° flexion and 0° abduction; Flex = flexion at 0° adduction and abduction; required ROM = required range of motion; B = bone to bone impingement; I = implant to implant impingement; CA = combined anteversion.