Study On The Effect Of Varus Deformity Of Knee Osteoarthritis On The Ankle Joint

Part One Effect of total knee arthroplasty on alignment of lower extre- mities in patients with knee varus osteoarthritisObjective:To study the effect of total knee arthroplasty(TKA)on the alignment of lower extremities in patients with varus deformity of knee osteoarthritis.Methods:The changes of alignment of lower extremities in 77 patients with varus deformity of knee osteoarthritis after TKA were studied retros-pectively.1.Based on the full-length anterior and posterior X-ray films of both lower extremities in the standing position,the following radiological para-meters were measured:Hip-Knee-Ankle Angle(HKA),Hip-Ankle Line and Tibia Angle(HATA),Medial Proximal Tibial Angle(MPTA),Tibial Anterior Surface Angle(TASA),Tibial Talar Surface Angle(TTSA),Talar Tilt Angle(TTA),Angle between the Ground and the upper Surface of talus(GSA),Tibiotalar Joint Space(TTJS),Medial Ankle Clear Space(MACS);2.Comparison of radiological parameters of lower extremities after TKA;3.To analyze the correlation between the changes of the alignment and space of ankle and the alignment of knee joint after TKA.Results:1.TKA can effectively improve the alignment of knee joint.After TKA,HKA decreased from 12.2°(8.6°,16.2°)to 2.4°(1.0°,4.2°),HATA decreased from 6.5°(4.8°,8.8°)to 1.1°(0.4°,2.4°),and MPTA increa-sed from 83.2°(81.1°,85.6°)to 90°(88.9°,90.1°).The differences were statistically significant(P<0.001).2.TKA can effectively improve the alignment of ankle joint.After total knee arthroplasty,TASA decreased from 91.4°±3.6°to 90.6°±3.4°,TTA decreased from 1.0°(0.2°,2.2°)to 0.8°(-0.9°,1.7°),GSA decreased from 9.4°±4.8°to 4.1°±3.7°,the differences were statistically significant(P<0.05).3.TKA can effectively improve the ankle space.After TKA,the TTJS increased from 2.8 mm(2.6 mm,3.0 mm)to 2.9mm(2.7 mm,3.2 mm),the difference was statistically significant(P<0.05).4.There is a poor correlation between the changes of the alignment and space of ankle joint and the change of the alignment of knee joint.In this study,only△GSA had a moderate correlation with△HKA,while△TASA,△TTSA,△TTA,△TTJS and△MACS had poor correlations with△HKA.Conclusions:1.TKA can effectively improve the alignment of knee joint;2.TKA can effectively improve the alignment and space of ankle joint;3.There was a poor correlation between the change of alignment and space of ankle joint and the change of alignment of knee joint.Part Two Finite element analysis of the influence of knee varus defor- mity on the contact characteristics of ankle jointObjective:To explore the influence of knee varus on ankle joint and to explain the cause of ankle arthritis caused by abnormal alignment of knee joint by comparing the stress distribution and fretting characteristics of talus surface under different knee varus angles.Methods:1.Construct the finite element model of lower extremity based on Mimics,Geomagic,Solid Works and ANSYS and then verify the validity of the model;2.Comparison of stress distribution on talus surface under different varus states of knee joint;3.The fretting of the talus surface in different varus states of the knee joint was compared.Results:1.In this study,the finite element model of lower extremity is success-fully constructed,and it is proved that the model is effective;2.When the knee joint was in neutral position,the peak value of equiva-lent stress appeared in the anterolateral side of talus(area 3),while when the angle of knee varus≥5°,the peak value of equivalent stress appeared in the anteromedial side of talus(area 9).With the increase of varus angle,the peak value of equivalent stress on the surface of talus increases gradually;3.When the knee varus angle is 5°,the fretting of talus surface(2.00μm)is less than that in the neutral position(2.54μm),while when the knee varus angle is≥10°,the fretting is larger than that in the neutral position,and with the increase of the knee varus angle,the fretting increases gradually.Conclusions:1.When the knee joint is in the neutral position,the peak equivalent stress on the talus surface is located at the anterolateral side;2.When the knee varus deformity occurs,the peak value of the equiva-lent stress on the talus surface is transferred to the anteromedial side,and the peak value of the equivalent stress on the talus surface increases with the increase of the varus angle of the knee joint;3.When the varus angle of the knee≥10°,the fretting of talus surface gradually increased with the increase of the knee varus angle;4.When the knee joint is slightly varus,it will not have a significant adverse effect on the ankle joint.However,when the knee joint is seriously varus,it will have a serious impact on the ankle joint,especially in the medial area of the ankle joint.Part Three Analysis of risk factors of foot and ankle pain before and after total knee arthroplasty in patients with varus defor-mity of knee osteoarthritisObjective:To investigate the risk factors of foot and ankle pain(FAP)in patients with varus deformity of knee osteoarthritis after total knee arthroplasty,so as to provide some reference for the prevention and treatment of FAP.Methods:The relationship between the risk factors and FAP in 77patients with varus deformity of knee osteoarthritis who underwent total knee arthroplasty were studied retrospectively.1.Based on the full-length anterior and posterior X-ray films of both lower extremities in the standing position,the following radiological para-meters were measured:HKA,HATA,MPTA,TASA,TTSA,TTA,GSA,TTJS and MACS(as in the first part of this article);2.Groups were divided according to age(<60 years old,≥60 years old),sex(female and male),body mass index(<25 Kg/m~2,25～30 Kg/m~2,>30Kg/m~2),knee varus angle(<6°,6°～10°,≥10°),pre-existing ankle osteoarthritis(yes and no),PAP aggravation(yes and no)after total knee arthroplasty;3.Intra-group comparison of risk factors related to preoperative FAP;4.The risk factors of FAP were analyzed by Logistic Regression;5.Study on the relationship between the changes of radiological para-meters and the aggravation of FAP.Results:1.The results of intra-group comparison of risk factors related to FAP before operation showed that gender,body mass index,knee varus angle and preoperative osteoarthritis of ankle joint had influence on the incidence of FAP(P<0.05),while age and extremity side had no effect on the incidence of FAP(P>0.05);2.The results of Logistic Regression showed that the female population would increase the risk of FAP(OR:9.022,95%CI:1.458～55.809,P<0.05),and high BMI would also increase the risk of FAP(OR:9.612,95%CI:2.270～40.701,P<0.05).In addition,the severity of knee varus deformity(OR:31.111,95%CI:3.233～299.405,P<0.05)and the presence of OA in ankle joint before operation(OR:6.158,95%CI:1.314～28.860,P<0.05)also increased the risk of FAP;3.There was no significant difference in radiological parameters between groups of FAP aggravation and non-FAP aggravation(P>0.05).Conclusions:1.Female,high body mass index,severe knee varus deformity and a history of ankle osteoarthritis are risk factors for FAP in patients with knee varus osteoarthritis;2.Total knee arthroplasty can correct the alignment of knee joint and ankle joint at the same time.3.There may be no significant correlation between postoperative FAP aggravation and the degree of correction of deformities after total knee arthroplasty,but it may be related to the mechanical environment of the ankle itself after total knee arthroplasty.