Is Combined Anteversion Equally Affected by Acetabular Cup and Femoral Stem Anteversion?
Résumé
Introduction
To create a safe zone, an understanding of the combined femoral and acetabular mating during hip motion is required. We investigated the position of the femoral head inside the acetabular liner during simulated hip motion. We hypothesized that cup and stem anteversion do not equally affect hip motion and combined hip anteversion.
Methods
Hip implant motion was simulated in standing, sitting, sit-to-stand, bending forward, squatting, and pivoting positions using the MATLAB software. A line passing through the center of the stem neck and the center of the prosthetic head exits at the polar axis (PA) of the prosthetic head. When the prosthetic head and liner are parallel, the PA faces the center of the liner (PA position = 0,0). By simulating hip motion in 1-degree increments, the maximum distance of the PA from the liner center and the direction of its movement was measured (polar coordination system).
Results
The effect of modifying cup and stem anteversion on the direction and distance of the PA’s change inside the acetabular liner were different. Stem anteversion influenced the PA position inside the liner more than cup anteversion during sitting, sit-to-stand, squatting, and bending forward (p = 0.0001). This effect was evident even when comparing stems with different neck angles (p = 0.0001).
Conclusion
Cup anteversion, stem anteversion, and stem neck-shaft angle affected the PA position inside the liner and combined anteversion in different ways. Thus, focusing on cup orientation alone when assessing hip motion during different daily activities is inadequate.
Domaines
Sciences du Vivant [q-bio]Origine | Publication financée par une institution |
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