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OP4.1 Automated Acetabular Coverage Calculations for Virtual Periacetabular Osteotomy
Abstract   Peer reviewed

OP4.1 Automated Acetabular Coverage Calculations for Virtual Periacetabular Osteotomy

Dominic Rivas, Holly Aitken, Terry Hayes, Michael Willey and Jessica Goetz
Journal of hip preservation surgery, Vol.12(Suppl 1), pp.i32-i32
03/27/2025
DOI: 10.1093/jhps/hnaf011.100
PMCID: PMC11953803

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Abstract

Objectives : Hip dysplasia is characterized with multiple radiographic measurements which quantify acetabular coverage of the femoral head. The purpose of this study was to use an automated measurement process implemented on digitally reconstructed radiographs (DRRs) to quantify the relationship between acetabular rotations within the coronal, sagittal, and axial planes during a virtual periacetabular osteotomy (PAO) and traditional radiographic metrics of hip coverage. Methods : Virtual PAOs were performed on 3D surface models of 20 patients indicated for PAO. The simulated acetabular PAO fragment was digitally rotated in 2° increments up to 22° in the coronal/sagittal planes to increase lateral and anterior coverage respectively, and 10° in the axial plane to increase acetabular anteversion. AP and false profile DRRs were generated for the preoperative condition and each rotation (n=864 DRRs per hip). A 2D-to-3D projection method was used to project 2D sourcil landmark(s) defined on preoperative DRRs onto the 3D model, track that 3D location during simulated PAO fragment rotation, and then re-project the rotated 3D location onto an updated DRR. The updated sourcil locations combined with landmarks not dependent on the acetabulum were used to automatically calculate LCEA, Tönnis angle, and ACEA associated with the acetabular reorientation. To measure the AWI/PWI, the femoral neck axis (FNA) and a best-fit femoral head circle were manually defined on the preoperative DRR. Intersections between the anterior and posterior acetabular rim on the 3D model and a plane defined by the FNA axis and the DRR source were detected for each simulated PAO rotation. These intersections were then projected back onto the DRR and used with the femoral head radius to calculate the AWI/PWI. Results : One-degree changes in the coronal plane resulted in a 1.04° increase in LCEA and a 0.96° decrease in Tönnis angle. One-degree changes in the sagittal plane resulted in a 0.015 increase in AWI and a 1.05° increase in ACEA, and one-degree changes in the axial plane resulted in a 0.022 decrease in PWI. Conclusion : Knowledge of how rotations in specific anatomic planes affect certain radiographic coverage measurements may assist clinicians with pre-operative planning to correct specific coverage deficiencies.
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