Computer-aided planning of reconstructive surgery of the innominate bone: automated correction proposals

In cases of complex reconstructive surgery of the innominate bone, it is difficult to draw up a good surgical plan; manual planning of a 3D reconstruction is highly demanding and time-consuming. This paper presents and validates methodology to automatically generate 3D correction proposals for reconstructive surgery of the innominate bone, and illustrates its use with clinical applications. The developed Matlab methodology starts from CT-based outer surface representations of the patient's bone, which allow straightforward mirror and matching implementations for automated reconstruction procedures. The validation on 9 cadavers was two-fold: the geometrical deviations of the intact original with respect to the reconstructed surface meshes were assessed, and the characteristics of both original and reconstructed acetabular cup regions were determined. Eighteen healthy and thus, it was assumed, spherical acetabula were automatically reconstructed with mean accuracies of 3.2 +/- 2.2 mm, 0.1 +/- 1.0 mm and 3.8 +/- 2.9 degrees for the hip joint centerpoint, joint radius and cup orientation, respectively. As a demonstration, a triflange cup acetabular implant was rapidly designed, starting from the correction proposal. A highly automated, computer-aided approach to surgical planning for pelvic bone defects was developed and sample applications demonstrated. Validation results for healthy acetabula were superior to those obtained in real surgery. The generated virtual correction proposals can be used as targets in surgical planning and cup navigation applications, or in the design of customized implants with complex shapes.