Does Total Hip Arthroplasty Influence Pelvic Version? A Retrospective Case Control Study Using the Sacro-Femoro-Pubic Angle in Osteoarthritis and Fracture Patients

Background and Objectives: Spinopelvic alignment may affect the outcomes of total hip arthroplasty (THA), with pelvic version influencing the risk of mechanical complications occurring after surgery. On the other hand, THA surgery itself may contribute to the modification of pelvis version. The sacro-femoro-pubic (SFP) angle is measured on anteroposterior (AP) radiographs of the pelvis in a supine position, and is used to estimate pelvic tilt (PT), representative of pelvic version, which requires lateral views of the sacrum for its calculation; however, these X rays are not routinely performed in the preoperative setting of hip surgery. This study aims to analyze how THA determines changes in the pelvic version of operated patients; the SFP angle will be used to assess pelvic version on standard AP radiographs. Materials and Methods: This retrospective study included 182 consecutive patients undergoing THA for unilateral primary degenerative hip osteoarthritis (HOA-study group, n = 104) or femoral neck fracture (FNF-control group, n = 78) at the author's institution. The SFP angle was measured on AP pelvic radiographs of the non-replaced hip preoperatively, postoperatively, and at the last follow-up. PT values were derived from SFP angles. Pre- and postoperative PT and its variations Delta PT were assessed. Study groups were compared in terms of native and postoperative variations of pelvic version. Results: The average absolute value of Delta PT was 2.99 degrees +/- 3.07 degrees in the HOA group and 3.57 degrees +/- 2.92 degrees in FNF group. There was no significant overall difference in preoperative or postoperative PT values between groups. In both groups, THA surgery led to a certain improvement, still not significant, in pelvic orientation, with FNF patients presenting a greater tendency toward retroversion. No significant differences in complication rates were found comparing patients with different pelvic orientations. Conclusions: THA can lead to a "normalization" of pelvic version in a certain number of patients with preoperative anteversion or retroversion. Although statistically non-significant, this observation may have clinical implications for spinopelvic balance and could support prioritizing THA in patients with concurrent spinal disease. Further research is needed to confirm these findings and to evaluate the long-term impact of THA on spinopelvic alignment.