Surgical Approach and Hip Laterality Affect Accuracy of Acetabular Component Placement in Primary Total Hip Arthroplasty

Introduction: Controversy remains if the anterior approach improves acetabular component alignment, and many studies have compared approaches with different surgeons over different timeframes. The purpose of this study was to assess a single surgeon's experience over a one-year timeframe and radiographically compare acetabular component positioning with the direct anterior versus direct lateral approach. Secondarily, this study compares acetabular component position differences between right and left hips for a right-hand dominant surgeon. Materials and Methods: Postoperative radiographs of 289 primary total hip arthroplasties (THAs) performed by a single right-hand dominant surgeon in 2014 were reviewed for abduction, anteversion, and medial cup seating. Component position was compared to surgical approach with 152 direct anterior (DA) THAs (53%) and 137 direct lateral (DL) THAs (47%). The operative side was also compared to surgeon hand dominance. Surgeons target was 40 degrees abduction, 20 degrees anteversion +/- 5 degrees, and seating to the teardrop +/- 5mm. Lewinnek target was also assessed. Results: DA hips had a significantly lower abduction angle (p=0.04), less abduction target outliers (p<0.001), less abduction Lewinnek outliers (p<0.001), less target anteversion outliers (p<0.001), closer seating to teardrop (p<0.001), and less seating outliers (p<0.001). The combined target and Lewinnek safe zone were achieved more often in DA (p<0.001, p=0.042). Controlling for body mass index (BMI), the combined target achievement remained significantly better for DA (p=0.02), but combined Lewinnek was not significant (p=0.07). In the DA approach, right hips had a significantly lower abduction angle (p=0.03), less Lewinnek anteversion outliers (p=0.043), and less combined Lewinnek outliers (p=0.027). In the DL group, right hips had significantly higher anteversion angles (p=0.004) and Lewinnek anteversion outliers (p=0.033). Conclusion: The anterior approach improved target abduction, anteversion, and medialization compared to the direct lateral approach. Significant differences in component positioning were found in both approaches based on the surgeons dominant and non-dominant side.