The Dynamic Alignment Analyses Of The Lower Extremity During Total Knee Arthroplasty Using Computer Navigation

Objective By means of the research on intraoperative passive dynamic alignment of the lower extremity using computer-assisted navigation in total knee arthroplasty surgery,to explore the correlation between preoperative passive dynamic alignment and the extent of the flexion contracture deformity and the changes of intraoperative passive dynamic alignment between pre and post-implant states, and analyse the influence the influence of the three major bone cuts to the kinematic alignment in total knee arthroplasty.Methods Since October 2013 to December 2015, we prospectively select patients who performed computer-navigated TKAs in Yantaishan Hospital as the object of our study. All the surgeries in our study were performed by the same experienced surgeon.According to inclusion and exclusion criteria, our study inclued data from 133 consecutive computer-navigated TKAs. evaluation criteria mainly consist: the extent of the flexion contracture deformity in the sagittal plane before surgery and Each patient's knee varus-valgus angles in the coronal from maximal extension to 0°,30° 45°, 60°, 90°and maximal flexion.All data was analyzed using stata 12.0 software,the pearson correlation analyses of varus-valgus were performed at various degrees of flexion in whole range of motion,and the differences of varus-valgus preoperative and postoperative were analysed using paired wilcoxon rank test.significant difference used p<0.05.then using three-dimensional mathematical model to reason out the influence of the three major bone cuts to the kinematic alignment.Result 1.The extent of the flexion contracture deformity in the sagittal plane is highly correlated with coronal plane varus deformity. But with the flexion of the knee ,the correlation is gradually decreased. 2. The preoperative and postoperative dynamic alignment of the lower extremity: extension varus-valgus angles is correlated with flexion varus-valgus angles at 30°, 45°,60°and 90°,but the correlation is gradually decreased with the flexion of the knee , there was poor correlation between extension varus-valgus and flexion varus-valgus at 90°.3.For Patients with preoperative severe extension varus (?15°), postoperative knee dynamic alignment in extension (z=4.108,p<0.01)?flexion 300?(z=4.111, p<0.01)?flexion 45°(z=4.110,p<0.01)?flexion 60° (z=4.109,p<0.01) and flexion 900° ( z=3.835, p < 0.01 ) can be significantly improved using computer-assisted navigation in .total knee arthroplasty surgery,the difference was statistically significant(p <0.01 ) .The extension alignment was significantly improved , and with the flexion of the knee ,the improvement of the alignment is becoming less distinct. 4. Different kinds of bone cuts have different influence on the kinematic alignment of the lower extremity in total knee arthroplasty.Conclusions1. The patients who have preoperative varus angular deformity in coronal plane often have corresponding severe flexion contracture deformity in the sagittal plane.2.The extension alignment is gradually decreased with the flexion of the knee at 30°,45°,60°and 90°,this suggests that although the conventional extension alignment is perfect, this does not represent the dynamic alignment is perfect in range of motion.3. There was poor correlation between extension varus-valgus and flexion varus-valgus at 90°, this suggests that The ability to achieve the equalization of flexion-extension gaps with knee at 0° extension and 90° flexion which implies the knee will be balanced is crucial for TKAs.4. For Patients with preoperative severe extension varus (?15°),computer-navigated TKA can improve the dynamic alignment not only in extension but also in flexion of 30°,45°,60° and 90°.5. Different kinds of bone cuts in total knee arthroplasty have different influence on the dynamic alignment of the lower extremity.