Fully hydroxyapatite-coated collared femoral stems in direct anterior versus direct lateral hip arthroplasty

Background Total hip arthroplasty (THA) via the direct anterior approach has increased in popularity in the last decade, with research supporting enhanced early recovery; however, some investigators have reported increased early revision rates in direct anterior THA. We examined outcomes from a single institution's experience with a fully hydroxyapatite-coated collared femoral stem implanted via the anterior or the lateral approach. Method Patients who had received fully hydroxyapatite-coated collared femoral stems as part of THA surgery performed by 1 of 3 surgeons between January 2012 and September 2017 were identified from our institutional database. We examined revision rates for the 2 approaches and compared them between the 2 groups. We also analyzed outcomes on plain film radiographs obtained immediately postoperatively and at 1 and 2 years. Results A total of 695 patients received a fully hydroxyapatite-coated collared stem during the study period. Total hip arthroplasty was performed via the direct anterior approach in 281/778 hips (36.1%) and via the direct lateral approach in 497 (63.9%). Nineteen patients (2.5%) underwent subsequent revision surgery; there was no statistically significant difference in the revision rate between the anterior and lateral approaches (2.5% v. 2.4%, p = 0.95). The mean subsidence of the stem at 1 year was 1.68 mm (standard deviation 11.7 mm). No statistically significant differences were observed between the cohorts for any of the radiographic measurements at either follow-up time Conclusion We found no significant difference in revision rates between the direct anterior and direct lateral approach. Stem subsidence levels were in keeping with expected values, and no major changes in stem position occurred during the first postoperative year. Surgical approach did not appear to substantially affect biomechanical stem behaviour.