Piriformis-Sparing vs. Conventional Posterior Approach in Total Hip Arthroplasty: A Retrospective Analysis of the Functional Outcomes

<i>Background and Objectives:</i> The posterior approach in total hip arthroplasty (THA) is widely used among surgeons. This study compares dislocation rates and functional outcomes between patients using a piriformis tendon-sparing posterior approach (PSPA) and those using a conventional posterior approach (CPA). <i>Materials and Methods:</i> 350 patients who underwent THA between 2016 and 2020 were retrospectively reviewed, with 163 patients receiving a PSPA and 187 receiving a CPA. Dislocation complication and the functional outcomes including the baseline and postoperative sixth-week pain and Oxford Hip Score, sixth-week Ranawat internal rotation test, and sixth-month acetabular inclination and anteversion angle were recorded. Hospital stay and the duration of surgery were also noted. <i>Results:</i> Implant dislocation occurred in three (1.6%) patients only in the CPA group at six weeks postoperatively (<i>p</i> = 0.104). No differences were noted in surgery time, baseline and postoperative pain, or hip function (<i>p</i> < 0.05). The Ranawat internal rotation test was positive in 89.6% of the PSPA group and 40.1% of the CPA group at six weeks (<i>p</i> = 0.001). The inclination angle was better in the PSPA group (<i>p</i> = 0.001), but there was no difference in anteversion angle (<i>p</i> = 0.523) at the sixth month postoperatively. The PSPA group had a shorter hospital stay (mean = 2.14 days) compared to the CPA group (mean = 2.47 days) (<i>p</i> = 0.006). <i>Conclusions:</i> The absence of dislocation cases in the piriformis-sparing approach suggests that the preservation of the piriformis tendon, especially in the early period, may have reduced the risk of prosthesis dislocation by increasing joint stability from a clinical perspective. Further research is needed to evaluate the long-term impact of the piriformis-sparing posterior approach regarding the dislocation rates and functional outcomes.