Purpose Curved varus osteotomy (CVO) is a joint-preserving procedure used to prevent progression of the collapse of osteonecrosis of the femoral head (ONFH). During the procedure, the necrotic lesion is moved from a weight-bearing position to a non-weight-bearing position by rotating it into the varus position. Therefore, accurate osteotomy and sufficient lesion movement are essential for favorable outcomes. This study aimed to determine whether a CT-based navigation system helps surgeons perform osteotomies and move necrotic lesions more accurately and effectively than the conventional fluoroscopic technique. Method The subjects were eight patients who underwent CVO using the CT-based navigation system (navigation group) and fifteen patients who underwent CVO using the fluoroscopic technique (conventional group). The intact ratio, which is defined as the proportion of the transposed intact articular surface of the femoral head to the weight-bearing acetabular surface on the postoperative radiograph, is a key indicator of successful CVO outcomes. A minimum value of 34% is reportedly required to prevent progression of collapse of the lesion. We evaluated the postoperative intact ratio, osteotomy accuracy on a transverse plane relative to the femoral neck axis, and varus angle accuracy using postoperative X-rays and 3D CT images. Results Although there was no significant difference in the postoperative intact ratio, its variability was significantly reduced in the navigation group. In four patients in the conventional group, the postoperative intact ratio did not reach 34%. The navigation group achieved a more accurate transverse osteotomy relative to the femoral neck axis than the conventional group. However, the varus angle accuracy was similar in both groups. Conclusion CT-based navigation decreased variability in the postoperative intact ratio and improved osteotomy accuracy on the transverse plane in CVO.
Kutsuna et al. (Thu,) studied this question.