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Intrapelvic Landmarks Are Highly Unreliable in Acetabular Cup Positioning Through Direct Anterior and Posterolateral
Fatih Yildiz1, Mustafa Alper Incesoy1, Ahmet Can Erdem1
1Department of Orthopedics, Bezmialem Vakif University Faculty of Medicine, Iskender Pasa District Adnan Menderes Boulevard, Fatih, 34093 Istanbul, Turkey.
Background:
Accurate acetabular cup placement is crucial for the long-term success of total hip arthroplasty (THA). This cadaveric study investigated the reliability of intrapelvic landmarks for cup positioning in conventional THA, examining the influence of surgeon experience, surgical approach (direct anterior and posterolateral), and pelvic positioning.
Methods:
108 conventional THA procedures were performed on 24 hips of 12 lower extremity cadavers by nine surgeons with different surgical experiences (Group I: high volume, group II: intermediate volume and group III: low volume) through a posterolateral (PL) or direct anterior approach (DAA). The anteversion and inclination of the acetabular cups were measured using an image-based robotic arm system. Outliers were defined according to Lewinnek's and Callanan's safe zones and the groups were compared.
Results:
In groups I, II and III, the percentages of cups within the safe zone of Lewinnek for the combined versions were 38.9, 33.3, and 27.8 for DAA (p = 0.12); and 16.7, 27.8, and 16.7 for PL (p = 0.633) approaches, respectively, while the percentage of cups within the safe zone of Callanan for the combined versions was 27.8, 27.8, and 16.7 for DAA (p = 0.667); and 11.1, 16.7, and 11.1 for PL (p = 0.849) approaches, respectively.
Conclusion:
This study demonstrates the unreliability of intrapelvic landmarks for accurate acetabular cup placement in conventional THA, irrespective of surgeon experience. The absence of the trunk in the cadaveric model may have affected pelvic tilt, underscoring the importance of intraoperative pelvic positioning in achieving optimal cup placement. These findings suggest that reliance on intrapelvic landmarks alone may not be sufficient for accurate cup positioning and highlight the potential benefits of alternative techniques, such as robotic-assisted THA.