Verification of optimal position of shelf graft for acetabular dysplasia using finite element analysis and virtual surgery model

Shelf acetabuloplasty for acetabular dysplasia is being reevaluated as a less invasive, joint preservation surgery. However, there are few reports on validation of the proper placement of the grafting shelf. In this study, finite element analysis was performed to examine the optimal location of shelves from the perspective of stress reduction by simulating various shelf installation patterns. Fifteen patients scheduled for shelf acetabuloplasty were included. Using preoperative computed tomography, we created a total of 81 shelf installation models per case. The equivalent stress at loading area of the acetabulum was analyzed, and the stress reduction ratio was calculated based on the preoperative values. Among the 1215 shelf models across 15 cases, 284 (23.3%) demonstrated a stress reduction exceeding 10%. Multiple regression analysis showed that the center-edge angle was the strongest factor associated with postoperative stress reductio n (p < 0.001). Moreover, the equivalent stress values on the acetabulum were significantly lower for lateral shelf placement than the anterior position (p < 0.05). The reduction rate of acetabular stress exhibited a significant correlation with the equivalent stress on the “inner shelf”, the part implanted in the pelvis, (p < 0.0001). The stress on the inner shelf was significantly greater in the lateral position than the anterior position (p < 0.001). Considering load dispersion, lateral installation is advantageous for effective load dispersion. Additionally, stress changes in the acetabulum are influenced by the stresses applied to the inner shelf.