Patient-specific Instrumentation for Acetabular Cup Orientation: Accuracy Analysis in a Pre-clinical Study

Purpose We investigated two major factors which affect the overall accuracy of patient specific instrumentation (PSI) for cup insertion in total hip arthroplasty; 1) the fitting of PSI on the bony surface, and 2) deviation of cup impaction under a linear visual reference. Methods Using 12 cadaveric hips, we inserted Kirschner wire (K-wire) through PSI on the acetabulum for the linear reference to transfer planned cup alignment. Deviation of the K-wire was then measured. With bone models, deviation when aligning an impactor to the K-wire was also measured. Results The mean deviation of the fitting was 1.9° for inclination and 2.0° for anteversion. The mean deviation when aligning the two lines was 1.2° for inclination and 1.4° for anteversion. Discussion This PSI can transfer the pre-operative plan to the operating room with acceptable accuracy.