IMAGING-FREE NAVIGATION OF THE ANTERIOR CRUCIATE LIGAMENT: 50 OPERATED KNEES

Abstract

Purpose: Anterior cruciate ligament plasty requires an anatomic and isometric implantation avoiding all notch conflict. This requires appropriate position of the bone holes. Recent studies have shown that hole placement is a key problem. In order to attempt to solve this problem, we examined the possibility of imaging-free navigation.

Material and methods: We elaborated a navigation system based on the bone morphing a concept where a static model of the knee is displayed on the screen. The system uses a 3D optic localiser which records the relative positions of five rigid bodies equipped with reflectors fixed on the femur, the tibia, the palper, the femoral aiming devise and the tibial aiming device. The arthroscopic operative technique is based on bone morphing. The operator navigates from the tibial articular hole drawn as a circle around the point T for which the computer maps on the notch the corresponding femoral isometry. On this isometry map, the surgeon navigates to the femoral articular hole drawn as a circle around the point F. The transplant is then fixed in place. The computer searches for a possible transplant-notch conflict and indicates where notch plasty would be necessary. The system was evaluated by comparing the points T and F indicated by the conventional method and by the computer. We compared the frequency of notch plasty with conventional and navigation surgery.

Results: The navigation system was used for 50 knees. The navigated T points were more anterior and more medial than those indicated by the conventional technique. With the conventional method, the anisometry of the central fibre can vary 3 to 13 mm for a given knee, depending on the F point determined. The computer optimises this point. There were less than 5% notch plasties with the navigation method and more than 50% with the conventional method.

Discussion: Bone morphing allows the operator to navigate in the knee, monitoring the operation on the screen model. The computer helps optimise bore hole position but does not indicate the exact position, which is determined by the operator. The computer can provide real time information helping the surgeon determine the ideal hole position in comparison with the conventional method.