ACCURACY OF INTRAOPERATIVE ASSESSMENT OF ACETABULAR PROSTHESIS PLACEMENT

Anteversion and vertical tilt of the acetabular prostheses in 50 conse cutive total hip arthroplasties were prospectively evaluated during su rgery (by the surgeon, using an alignment guide) and radiographically (calculated). From postoperative standardized radiographs vertical til t was measured directly and anteversion was calculated. The mean error of vertical tilt was 5 degrees (range, 0 degrees-20 degrees). The mea n error of version was 9 degrees (range, 0 degrees-24 degrees). The re liability of prosthesis placement in a predetermined zone was examined . Although the surgeons believed that all 50 cups were inside this zon e, radiographic measurements revealed that 21 of the cups were actuall y outside. It is concluded that vertical tilt can be reasonably assess ed during surgery. Anteversion, however, cannot be accurately assessed during surgery, despite use of the alignment guide.