Abstract
Introduction
Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. The current study assesses the validity of intraoperative assessment using a specialized software to analyze intraoperative radiographs.
Methods
Cup orientation as measured on intraoperative radiography using the RadLink Galileo Positioning System was assessed in 10 patients. These radiographs were measured by personnel trained to support the system. The results were compared to cup orientation measured by CT. Cup orientation on CT was measured by first identifying the Anterior Pelvic Plane Coordinate system landmarks on a 3D surface model. A multiplanar reconstruction module then allowed for the creation of a plane parallel with the opening plane of the acetabulum. The orientation of the cup opening plane in the AP Plane coordinate space was then calculated. The same definition of cup orientation was used for both methodologies.
Results
As compared to direct measurement using CT, the intraoperative radiograph system underestimated anteversion by an average of 8.0 degrees and overestimated cup inclination by 2.9 degrees. The radiographic measurement error in anteversion ranged from −27.4 to +4.0. degrees and for inclination ranged from −2.0 to +5.3 degrees.
Conclusion
The use of an intraoperative radiological assessment system is relatively reliable in estimating the inclination of the acetabular component. Anteversion of the acetabular component is extremely poorly assessed by the system.
