The Influence Of Lateral Femoral Bowing On Coronal Alignment After Primary Total Knee Arthroplasty

ObjectiveExplore the correlation between the femoral valgus correction angle(VCA)and femoral anatomic characteristics,analysis the difference effect of femoral bowing angle(FBA)on coronal alignment after primary total knee arthroplasty,aim on achieving precise coronal alignment after total knee arthroplasty.MethodsA retrospective review of clinical data and X-ray imaging data collected from 78patients(92 knees)received primary total knee arthroplasty in our department between January 2017 to October 2018 was undertaken.Measure the femoral bowing angle(FBA),femoral valgus correction angle(VCA),neck shaft angle(NSA),hip knee ankle angle(HKA),distal femoral valgus resection(DFVR),femoral prosthesis angle and tibial prosthesis angle on long leg X-ray according to the standard method.Patients with lateral femoral bowing can be divided into four group: group A(FBA≤0°),group B(0°<FBA≤3°),group C(3°<FBA≤6°),group D(FBA>6°).Compare the difference of mean angles between different groups,analysis the distribution and correlation of VCA and FBA,explore the influence of lateral femoral bowing on postoperative coronal alignment.Results1.There was no significant difference in terms of patient age,gender,height and BMI between the four cohorts.The mean value of VCA is 6.56°±1.00°(range: 4.20° to 8.90°),The mean value of FBA is 3.97°±3.87°(range:-4.50° to 12.30°),The mean value of NSA is 130.48°±5.89°(range: 113.50° to 146.60°),VCA in group A: 5.69°±0.70°,group B:6.31°±1.02°,group C: 7.04°±0.91°,group D: 6.60°±0.89°.FBA in group A:-2.78°±1.14°,group B: 1.38°±0.81°,group C: 4.57°±0.89°,group D: 8.61°±1.65°.The VCA and FBA were statistically significant differences between groups(P<0.05).2.There was a low positive correlation between VCA and FBA(r=0.296,P<0.05),and a moderate negative correlation between VCA and NSA(r=-0.407,P<0.05).3.The preoperative HKA and postoperative HKA were statistically significant differences among groups(P<0.05).The postoperative HKA between the different groups were significant differences(P<0.05).HKA in group A: 179.53°±4.01°,group B:177.56°±3.20°,group C: 176.45°±3.65°,group D: 176.60°±3.65°.The excellent and good rate of postoperative coronal alignment was 81.81% in group A,68.00% in group B,66.66% in group C,and 46.15% in group D.The postoperative HKA showed significant statistical differences between group A vs group D and group B vs group D(P<0.05).The excellent and good rate of coronal alignment in group A was greater than group D,and group B was similar greater than group D.4.There was a moderate negative correlation between FBA and preoperative HKA(r=-0.544,P<0.05),and a moderate negative correlation between FBA and postoperative HKA(r=-0.544,P<0.05).ConclusionThis study showed that the variation of VCA was relatively large,which was negatively correlated with NSA and positively correlated with FBA.The effect of femoral anatomic structure variation on VCA should be considered before total knee arthroplasty.Different patients have a wide range of changes in the FBA.For patients with large lateral femoral bowing,it is suggested to adopt personalized resection program when performing total knee arthroplasty.The distal femoral resection angle should be increased according to the measurement results,so as to obtain an ideal coronal alignment.