Femoral components implanted through a direct anterior approach have higher postoperative anteversion compared to those implanted through a posterior approach in total hip arthroplasty

There have been few studies that have investigated the effect of surgical approach on femoral component version in total hip arthroplasty (THA). The purpose of this study was to investigate the influence of the direct anterior approach (DAA) and the posterior approach (PA) on femoral component version in THA. A retrospective database review of 807 THAs in 807 patients who had both preoperative and postoperative CT scans was performed. Femoral component version was measured in the second CT scan and compared to the native neck axis measured in the first CT scan, using the posterior femoral condyles as the reference for both. Operations were performed using either a DAA (n = 291) or a PA (n = 516), with one of four femoral component designs: quadrangular taper, calcar-guided short stem, flat taper, or fit-and-fill. Subgroup analyses investigated changes in version for low (≤ 5°), neutral (5° to 25°), and high (≥ 25°) native version subgroups and for the different femoral component types. Overall, DAA components had more mean anteversion relative to the native neck axis versus PA components (6.0° (SD 9.8°) vs 1.3° (SD 10.1°); p < 0.001). Predictors of increased femoral component anteversion postoperatively on multivariable regression analyses were approach (DAA), decreased native version preoperatively, decreased femoral sagittal bow angle, and component type (quadrangular taper). DAA components had greater mean anteversion relative to native than PA in hips with high native version (3.5° (SD 11.1°) vs -5.8° (SD 10.5°); p < 0.001) and neutral native version (5.2° (SD 9.3°) vs 1.3° (SD 9.4°); p < 0.001), but did not reach significance in the low native version subgroup (9.0° (SD 10.3°) vs 5.9° (SD 9.6°); p = 0.109). Quadrangular taper and calcar-guided short-component types had significantly more mean anteversion than native for DAA versus PA. Femoral components implanted with a DAA had more mean anteversion than those implanted with a PA. Future studies should aim to investigate the effect of femoral component version on postoperative clinical outcomes.