Abstract
Introduction
Increased long-term survival of TKA is becoming more important. Several studies have confirmed that optimal positioning and alignment of prosthetic components is crucial for the best long-term results. Therefore, the purpose of the current study was to compare the postoperative alignment and sizing of femoral prosthesis among patients performed by 3 different navigation systems.
Methods
Twenty patients who underwent primary TKA (E. motion; B. Braun Aesculap, Tuttlingen, Germany) using a CT-free navigation system (OrthoPilot v 4.2) by modified gap technique were enrolled in this study. The results of this study group were retrospectively compared with those in a control group of 20 matched-paired posterior stabilized TKAs (Triathlon;Stryker; Mahwah, NJ, USA) which were using another CT-free navigation system (Stryker Navigation System) by measured technique and 20 matched-paired posterior stabilized TKAs (Press-fit Condylar prosthesis; DePuy, Tokyo, Japan) using CT-based navigation system (VectorVision) by measured technique. Several parameters were evaluated for each patient using Athena Knee (Softcube Co, Ltd. Osaka, Japan), 3-D image-matching software. The coronal component angles and sagittal component angles were measured in relation to mechanical axis (MA). In addition, axial femoral component angle was measured in relation to surgical epicondylar axis (SEA) and axial tibial component angle was measured in relation to Akagi line.
Results
(Coronal plane alignment)
The coronal femoral component angle (varus) was 1.3° ± 2.7° in the Orthopilot group, 1.1 ± 1.5° in the stryker group and 0.21° ± 2.2°in VectorVisioin group with no sigificant difference. The coronal tibial component angle (varus) was 0.7° ± 2.0° in the Orthopilot group, −0.50° ± 1.4° in the stryker group and −1.0° ± 1.2° in VectorVision group with no significant difference.
(Sagittal plane alignment)
The sagittal femoral component angle (flexion) was 2.7° ± 2.2° in the Orthopilot group, 3.3° ± 2.4° in the stryker group and −0.2° ± 2.9°in VectorVisioin group. The sagittal femoral component angle in VectorVison group is significantly smaller than that in the Orthopilot group and that in the Stryker group. The sagittal tibial component angle (posterior slope) was 4.7° ± 1.9° in the Orthopilot group, 2.6° ± 1.5° in the stryker group and 2.8° ± 1.4° in VectorVision group. The posterior slope was aimed at 5°in Orthopilot group and 3°in stryker group and VectorVision group. Accuracy among 3 groups is no significant difference.
(Axial component angle)
The axial femoral component angle (external rotation) was 2.2° ± 1.9° in the Orthopilot group, 1.2° ± 1.5° in the stryker group and −0.9° ± 2.0°in VectorVisioin group. The axial femoral component angle in Orthopilot group was significantly more external than that in the stryker group and that in the VectorVision group. The axial tibial component angle (external rotation) was 2.4° ± 5.0° in the Orthopilot group, 2.6° ± 5.5° in the stryker group and 2.0° ± 4.2° in VectorVision group with no differnence.
Discussion and Conclusion
We performed primary TKA by 3 different navigation systems and analyzed alignment of component. Accurate alignment was obtained in all 3 different navigation systems. However surgeons should take into account the features in each navigation.
