Transition from straight lateral to direct anterior approach in total hip arthroplasty: a retrospective single-centre study

Introduction: The muscle-sparing direct anterior approach (DAA) for total hip arthroplasty (THA) has gained popularity for reduced postoperative pain and faster rehabilitation. The aim of this study was to evaluate the potential benefits of transitioning from straight lateral approach (SLA) THA to DAA THA, and investigate whether these benefits outweigh potential disadvantages of the DAA learning curve. Method: Patients undergoing surgery between 2015 and 2020 (n = 2275) were categorised into three periods: pre-transition period (2015-2016) utilizing SLA exclusively, transition period (2017-2018) incorporating both SLA and DAA, and post-transition period (2019-2020) employing only DAA. The Hip disability and Osteoarthritis Outcome Score - Physical function Short-form (HOOS-PS) was recorded pre-surgery and one-year post-surgery. Furthermore, complications, blood loss, duration of surgery and length of stay were compared between groups. Results: A larger improvement in HOOS-PS score was found for DAA in comparison with SLA (37.13 +/- 18.62 vs. 32.55 +/- 22.83; p < 0.001). Significant improvements were found for the DAA group regarding duration of surgery (70:02 +/- 15:54 min vs. 79:47 +/- 15:03 min; p < 0,001) and length of stay (1.68 +/- 1.80 days vs. 3.39 +/- 1.85 days; p < 0,001) compared to the SLA group. Total number of complications was higher for SLA (n = 87 (9.2%)) compared to DAA (n = 77 (6.5%); p = 0.018), with more femoral fractures for SLA (n = 35 (3.7%) vs. n = 6 (0.5%); p < 0.001) whereas more dislocations were found for DAA (n = 24 (2.0)% vs. n = 7 (0.7%); p = 0.017). More specifically, a higher number of dislocations occurred during the DAA transition period when compared to the SLA pre-transition period (n = 12 (2.7%) vs. n = 4 (0.6%); p = 0.008). Conclusions: Transitioning from SLA to DAA for THA improves patient-reported outcomes but does not seem to result in a higher overall complication rate. Suggesting the advantages of the DAA outweigh the potential disadvantages of the learning curve.