CupAlign: Computer-Assisted Postoperative Radiographic Measurement of Acetabular Components Following Total Hip Arthroplasty

Clinical problems following total hip replacement surgery, such as dislocation and implant wear, remain as significant clinical problems with many contributing factors. Although it is intuitive to surgeons that acetabular component alignment is one important factor, large clinical series have produced conflicting results with respect to cup alignment as a risk factor in predisposing to dislocation. One reason is that postoperative measurements of alignment are limited to single or biplanar radiographic measurements. However, the radiographic measurements are limited only to radiographic alignment and may not accurately detail true anatomic orientation of the cup. In this paper, software designed to accurately measure radiographic alignment is described. Postoperative measurements using this system are compared to the actual intraoperative measurements of cup orientation determined by the HipNavTM image-guided surgical system to assess the accuracy of radiographic evaluation of cup orientation.