Abstract
Introduction
The efficacy and accuracy of computer navigation systems in total knee arthroplasty (TKA) have been proven in recent years. However, potential disadvantages associated with navigation systems, such as increased surgical time and registration errors, have been reported. Currently, we use a navigation system only for the femoral side. We use the conventional extramedullary guide system for the tibial side (hybrid navigation method) because we have increased the accuracy of tibial positioning in the coronal plane with the conventional system by considering the following key points. (1) Set the extramedullary alignment guide to avoid the rotational mismatch between the proximal part of the tibia and the ankle joint. (2) Insert the tibial component along the AP axis of the resected surface. (3) Remove the protruding bone at the antero-lateral edge of the tibia to obtain the flat, resected surface of the tibia. The purpose of this study was to determine the accuracy of the hybrid navigation method.
Methods
We compared the postoperative alignment of 60 TKAs implanted using the conventional alignment guide system with 30 TKAs implanted using the hybrid image-free navigation method. The average age was 74.2 (range, 50 to 85) years in the conventional group and 73.6 (range, 51 to 84) years in the hybrid group. The intramedullary alignment guide was used for the femur in the conventional group. The knees were evaluated using full-length, weight-bearing anteroposterior radiographs.
Results
For the conventional group, the mean coronal tibial component angle was 89.9 ± 1.09 degrees (range, 88.0 to 92.0 degrees) (Fig. 1b). The ideal angle within 3 degrees for the tibial component was obtained in 100% of the cases. The mean posterior inclination angle was 83.7 degrees. The mean coronal femoral angle was 90.5 ± 2.06 degrees (range, 84.0 to 96.0 degrees) (Fig. 1a). The ideal angle within 3 degrees for the femoral component was obtained in 85.0% of the cases. For the hybrid navigation group, the mean coronal tibial component angle was 89.6 ± 0.73 degrees (range, 88.0 to 91.0 degrees) (Fig. 2b). The ideal angle within 3 degrees for the tibial component was obtained in 100% of the cases. The mean coronal femoral component angle was 89.4 degrees (range, 86.0 to 92.0 degrees) (Fig. 2a). The ideal coronal angle within 3 degrees for the femoral component was obtained in 96.7% of the cases.
Discussion and Conclusion
Our results demonstrated the accuracy of coronal tibial component positioning with the conventional extramedullary alignment guide system by considering the key points described above. However, the accuracy of femoral component positioning with the conventional intramedullary rod is limited. Therefore, the hybrid navigation method could be an alternative to reduce surgical time while maintaining the accuracy of the tibial component positioning. In conclusion, we recommend the hybrid navigation method in total knee arthroplasty.
