An algorithm for personalized optimal acetabular cup implant positioning based on bony coverage rate and...

In patients with developmental dysplasia of the hip (DDH), complications such as head dislocation and cup instability after total hip arthroplasty (THA) are often caused by poor cup positioning. However, no planning algorithm currently considers both the cup bony coverage rate (BCR) and the hip impingement-free range of motion (IFROM) simultaneously due to the high variability in cup position and the difficulty in parameterizing IFROM after THA. This study proposed an algorithm to efficiently calculate the BCR and IFROM for all potential cup positions, filtering out the cup's optimal implant position. The IFROM evaluation coefficients (EC_IFROM) were calculated based on the maximum IFROM for each cup position. Cup positions meeting the BCR requirement and ranking in the top 10% of EC_IFROM were selected as the optimal implant positions. The algorithm was tested on three bone models with varying degrees of DDH to compare BCR and optimal implant position. The algorithm developed in this study is versatile, reliable, and efficient. Calculations in three patients showed that (1) the roof BCR is usually greater than the 3D BCR, and (2) the EC_IFROM makes it easier to select the optimal implant position of the cup. This method can calculate the BCR and IFROM for all cup positions, providing surgeons with a reference to determine the optimal cup position and whether augmentation is needed to improve cup stability in patients with DDH, thereby reducing the incidence of impingement after THA.