Navigator-assisted total hip replacement

Aim. To carry out a comparative study of the acetabular inclination angle when a prosthetic cup is put in place using computer-assisted surgery and when it is implanted by means of conventional surgery. Materials and methods. This was a comparative, retrospective study of 42 patients that underwent total hip replacement (THR). In a group of 21 patients a surgical navigation system was used to determine the placement of the acetabular prosthesis and in another group, also made up of 21 patients, the standard technique of manual alignment of the prosthesis was used. Using X-rays and CAT scans the acetabular inclination angle was measured in both groups. Results. In the group in which a navigator was used the average angle measured intraoperatively was 44.14° (standard deviation [SD] 1.35). Measured using conventional X-rays it was 44.57° (SD 1.88) and measured with a CAT scan it was 44.81° (SD 2.06). These differences were not significant. In the group that underwent conventional surgery, though the average inclination angle values did not differ with reference to the group operated with the use of a navigator, the dispersion seen was significantly greater (p=0.005). No significant increase was seen in OR time nor in postoperative complications. Conclusions. The use of a navigation system to implant an acetabular prosthesis in hip surgery decreases the scatter index and makes it possible to place the implant in a position closer to the ideal one.