抄録
Since 2005, we have performed cementless MIS-THA in a lateral position using a CT-based navigation system. However, in some cases the cup inclination and anteversion differed between the intraoperative navigation measurement values and postoperative CT evaluations. We herein report a comparison of the errors before and after four changes had been made to improve the accuracy of the procedure. The pin inserted into the iliac crest was moved into the wound so that the fixed pins for navigation would not interfere with the retractor. This made it possible to prevent the pin from loosening during the operation. In addition, the setting of the pointer-based registration was changed from the plain surface of the anterosuperior acetabulum, an area which we believed would be minimally affected by osteophyte, to the wider plain surface of the rim of the acetabulum to reduce intraoperative errors. We compared the intraoperative navigation measurement values with the postoperative CT scan evaluations of the cup angle. As a result of our comparison of the margins of error for 30 cases before and after the changes, errors have decreased. By improving the methods of MIS-THA using navigation, it is possible to perform more accurate operations.
