Abstract
INTRODUCTION
To obtain appropriate joint gap and soft tissue balance, and to correct the lower limb alignment are important factor to achieve success of total knee arthroplasty (TKA). A variety of computer-assisted navigation systems have been developed to implant the component accurately during TKA. Although, the effects of the navigation system on the joint gap and soft tissue balance are unclear. The purpose of the present study was to investigate the influence of accelerometer-based portable navigation system on the intraoperative joint gap and soft tissue balance.
METHODS
Between March 2014 and March 2015, 36 consecutive primary TKAs were performed using a mobile-bearing posterior stabilized (PS) TKA (Vanguard RP; Biomet) for varus osteoarthritis. Of the 36 knees, 26 knees using the accelerometer-based portable computer navigation system (KneeAlign2; OrthAlign) (N group), and 10 knees using conventional alignment guide (femur side; intramedullary rod, tibia side; extramedullary guide) (C group). The intraoperative joint gap and soft tissue balance were measured using tensor device throughout a full range of motion (0°, 30°, 45°, 60°, 90°, 120°and full flexion) at 120N of distraction force. The postoperative component coronal alignment was measured with standing anteroposterior hip-to-ankle radiographs.
RESULTS
The mean joint gaps at each flexion angle were maintained constant in N group, and there was a tendency of the joint gap at midflexion ranges to increase in C group. The joint gaps at 30°and 45°of flexion angle in C group were significantly larger than that of in N group. The mean soft tissue balance at 0°of flexion was significantly varus in N group than that of in C group. Postoperatively, in N group, the mean femoral component alignment was valgus 0.1°± 1.3°(range, varus 2°- valgus 3°), the mean tibial component alignment was valgus 1.1°± 1.7°(range, varus 1°- valgus 3°) to the coronal mechanical axis. In C group, the mean femoral component alignment was varus 2.3°± 1.9°(range, varus 6°- valgus 1°), the mean tibial component alignment was valgus 2.0°± 1.3°(range, 0°- valgus 5°) to the coronal mechanical axis. There was statistically significant difference in femoral component alignment, there was no statistically significant difference in tibial component alignment.
DISCUSSION AND CONCLUSION
The present study demonstrated that navigation-assisted TKA was prevented the joint gaps from increasing at 30°and 45°of flexion. However, it was difficult to achieve soft tissue balance at extension. In conventional TKA, the femoral component alignment was usually varus. In contrast, accelerometer-based portable navigation system is superior to implant the femoral component accurately. However, there were several cases that femoral component alignment is valgus because of a variation in the accuracy of this navigation system. Surgeons should be aware of difficulty to accomplish all of appropriate joint gap and soft tissue balance, and lower limb alignment in navigation-assisted TKA.
