Improving Cup Positioning Using a Mechanical Navigation Instrument

Background Although surgical navigation reduces the rate of malpositioned acetabular cups in total hip arthroplasty (THA), its use has not been widely adopted. As a result of our perceived need for simple and efficient methods of navigation, we developed a mechanical navigation device for acetabular cup orientation. Questions/purposes We assessed accuracy of cup orientation (mean error of cup inclination and anteversion) of a novel mechanical navigation device, percentage of outliers, length of operation, and compared the results with a series of CT-based computer-assisted THAs. Methods Cup orientation of 70 THAs performed using the mechanical navigation device was compared with a historical control group of 146 THAs performed using CT-based computer navigation. Postoperative cup orientation was measured using a validated two-dimensional/three-dimensional matching method. An outlier was defined outside a range of +/- 10 degrees from the planned inclination and/or anteversion. Results Using the mechanical navigation device, we observed a decrease in the errors of inclination (1.3 degrees +/- 3.4 degrees [range, -6.6 degrees to 8.2 degrees] versus 3.5 degrees +/- 4.2 degrees [-12.7 degrees to 6.9 degrees]), errors of anteversion (1.0 degrees +/- 4.1 degrees [-8.8 degrees to 9.5 degrees] versus 3.0 degrees +/- 5.8 degrees [-11.8 degrees to 19.6 degrees]), percentages of outliers (0% versus 9.6%), and length of operation (112 +/- 22 [78-184] minutes versus 132 +/- 18 [90-197] minutes) compared with CT-based navigation. Conclusions Compared with CT-based surgical navigation, navigation of acetabular cup orientation using a mechanical device can be performed in less time, lower mean errors, and minimal equipment.