[Increasing the quality of preoperative planning and intraoperative application of computer-assisted systems and...

14 human femurs were scanned by CAT and 3D reconstructed. In every specimen digital documentation of CCD and antetorsion (AT) angle was performed. With a special software package (Orthodoc) virtual preoperative planning for implantation of a cementless total hip alloplasty was undertaken. The specimens were randomised into two groups, one of which had manual and the other one robot implantation of the femoral component. After implantation all specimens were evaluated again by CAT and CCT and AT angle were documented again. The preoperative CCD angle was 126.7 degrees (SD = 4.0) in the manual group and 127.8 degrees (SD = 4.3) in the robodoc group. Postoperatively the angle averaged 131.9 degrees (SD = 0.8) in the manual group and 133.2 degrees (SD = 1.9) in the robodoc group. Significant differences were found for the AT angle in both groups. The preoperative AT angle in the manual group was 31.3 degrees (SD = 8.8), decreasing to 20.5 degrees (SD = 9.5) after implantation. In the robodoc group this angle was 30.9 degrees (SD = 8.0) before and 31.3 degrees (SD = 8.7) after implantation. The difference between pre- and postoperative AT angle averaged 10.8 degrees (SD = 6.4) in the manual group and only 0.4 degree (SD = 0.9) in the robodoc-group.

With the technique used, preoperative planning in hip alloarthroplasty is much more accurate than with the conventional technique with plain X-ray. The virtual preoperative planning can be transferred to the intraoperative setting with high precision. These factors may lead to an increase in outcome quality.