Computer assisted hip surgery by using modular-neck femoral component: principles, technique, advantages and limits

Abstract

The author describes the use of a CT-free navigation system equipped with a software, specifically designed to improve the implantation of a modular-neck anatomic cementless stem and acetabular cup for Total Hip Replacement (THR). When comparing the anatomic parameters measured intraoperatively with the native hip and the prosthetic hip, it appears that the use of the modular-neck allows a better approximation of the native hip lateralization and cranio-podal lowering. Cost and additional time might very well be compensated by the significant outlier reduction. For other technologies (CT-based, Imageless, and virtual fluoroscopy), the average operative time is 20-30 min longer (on the average) as compared to conventional procedure. The image-free systems are not able to navigate dysplastic and revision cases. The CT-based navigation systems are more accurate than imageless navigation for the insertion of the acetabular component in THR, but necessitate preoperative CT-image acquisition. Virtual fluoroscopy is able to navigate hips where CT or CT less images are poor (as in revision THR) and in cases of previous hip fusion (where routine CT registration or point-clouds methods are not possible). Virtual fluoroscopy does not necessitate preoperative CT and planning, but the system has the disadvantage that the procedure is disrupted by the use of fluoroscopy during surgery. Patients with dysplastic hips, especially when osteotomies of the proximal part of the femur have been performed, have significant improvement in function with the use of custom made THR.