Does the surgical approach influence the implant alignment in total hip arthroplasty? Comparative study between the direct anterior and the anterolateral approaches in the supine position.

<bold>Purpose: </bold>The purpose of this study was to clarify the difference in implant alignment between the direct anterior approach (DAA) and the anterolateral approach in the supine position (ALS).<bold>Methods: </bold>A retrospective comparative study consisted of 215 consecutive primary total hip arthroplasties using tapered polished and straight cemented-stems via two different minimally invasive approaches (DAA group in 106 hips and ALS group in 109 hips).<bold>Results: </bold>The cup radiographic anteversion angle was significantly lower in the ALS group than in the DAA group (12.9° versus 16.9°, p = 0.001). The frequency of the safe zone tended to be more favourable in the ALS group than in the DAA group (95% versus 87%, p = 0.052). Stem alignment in the sagittal plane was significantly better in the ALS group than in the DAA group (84% versus 71%, p = 0.022).<bold>Conclusions: </bold>Both cup and stem alignments were better in the ALS group than the DAA group. [ABSTRACT FROM AUTHOR]