Background Total knee arthroplasty (TKA) is a successful procedure in treatment of degenerative disease of the knee, and optimal component placement is essential for long-term implant survival. The purpose of this study was to compare the accuracy of the accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of the femoral and tibial components in TKA in a Chinese population. Methods A total of 123 (37 conventional and 86 KA2) cases of elective primary TKA were reviewed. Hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and anatomical lateral distal femoral angle (aLDFA) were measured from hip-to-ankle EOS radiographs. Accuracy of conventional alignment and KA2 navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of the components for each respective case. Results There was no significant difference between conventional alignment methods and KA2 navigation in achieving a neutral mechanical alignment of the lower limb. KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of the tibial component in both the coronal and sagittal plane, while no significant difference between the two groups was appreciated in the positioning of the femoral component in the coronal plane. Conclusions TKA using the accelerometer-based KA2 system was found to offer a high degree of accuracy in component alignment, and in particular, significantly improved tibial component alignment in comparison with conventional alignment methods in a Chinese population. However, no significant improvements were observed in neutral mechanical axis of the lower limb alignment and femoral component placement in the coronal plane.

Background:Optimal alignment is crucial for long-term outcomes after Total knee arthroplasty (TKA). Computer-assisted surgical (CAS) techniques provide an alternative method of navigation, using a tracking device and arrays attached to bone to allow tracking of bone position in virtual space, avoiding the need for violation of intramedullary canal. The purpose of this study was to compare the accuracy of accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of femoral and tibial components in TKA.Methods:Thirty-seven and 86 consecutive cases of primary TKA were performed with either conventional or accelerometer-based navigation (ABN) system respectively. Accuracy of femoral and tibial component alignments were measured by femoral or tibial component varus/valgus angle respectively. Accuracy of tibial component alignment in the sagittal plane was measured by posterior slope of tibial component. Accuracy of conventional alignment and navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of components.Results:No statistical difference was found in preoperative mechanical alignments of lower limb between the 2 groups. Both conventional alignment and navigation groups were able to achieve a neutral postoperative mechanical axis of the lower limb. The KA2 navigation group’s tibial component alignment in both the coronal and the sagittal planes were significantly more accurate comparing to the conventional alignment group, while there was no significant difference between the 2 groups in the femoral component alignment in the coronal plane. Mean posterior slope value within the accepted range was significantly achieved in navigation group (43%) than conventional group (16%) (p = 0.004).Conclusions:KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of tibial component in both coronal and sagittal plane. KA2 navigation system was able to achieve such accuracy for tibial component in the sagittal plane. Both conventional alignment and KA2 navigation were able to achieve a neutral mechanical axis of lower limb, and satisfactory placement of femoral and tibial component placement in coronal plane. However, only KA2 navigation system was able to achieve such accuracy for tibial component in the sagittal plane.Trial registration: Not applicable