| Objective:To analyze the knee biomechanics change of recurrent patellar dislocation frozen cadavers model after the operation of extensor mechanics realignment with bone anchors with DICM and pressure sensitive film technology.To establish the 3D finite element models of normal frozen cadaver knee,and then analyze the knee biomechanical character of frozen cadaver models of recurrent patellar dislocation after proximal and distal extensor mechanism realignment with bone anchors by 3D finite element methods.On clinic,to explore the clinical curative effect of knee proximal and distal extensor mechanism realignment for recurrent patellar dislocation with bone anchors and to investigate the surgical indication for this operation and analyze the knee joint kinematics data of ipsilateral knee joint at pre-operation and 12 months postoperation of proximal and distal extensor mechanism realignment for recurrent patellar dislocation with bone anchors.Methods:8 cadavers(16 lower limbs)form the Kunming medical university(male 6 cases,female 2 cases.aged from 38 to 56 years old,on the average of 48±3.6 years old)were included in this study.12 limbs were first made into the recurrent patellar dislocation models with tibial tubercle osteotomy and lateral movement,at the same time,MPFL excision to made into models(pathological knees)as TT-TG value more than 2.00cm,they were then divided into 3 groups randomly and averagely.Group A:proximal extensor realignment with bone anchor,Group B:distal extensor realignment with bone anchor,Group C:proximal and distal extensor realignment with bone anchors.Group D was normal knee.70 N axial tensile force was put on the femoral quadriceps(for group A and C,7 N axial tensile force was put on the transferred proximal extensor mechanics.pressure sensitive film was used to detected the pressure of the patellofemoral joint when the knees were flexed at the 0“,30°,60°,90°,120° respectively,and then,under this condition,20 N force was put on the middle of the patella for lateral dislocation,the DICM technology was used to detected the lateral shift of the patella.Four knees(male one,female one)were selected with the same criteria as part 1,the model and the operation were established and carried out on the knees with the same methods as part 1 respectively,the knees were scanned with CT and MRI for 3D finite element models on the intact condition and after the operation,data were collected,and the software including mimics,ABAQUS,Geomagic Studio2017,solidwork were used sequentially,and at last four 3D finite element models with MPFL,simplified lateral retinaculum of patella were established.(2)on this models an axial 70N force was put on the femoral quadriceps(for normal knee)and the 7 N axial tensile force with the same direction of the transferred proximal extensor mechanics(for the knee after the operation of proximal and distal extensor mechanism realignment with bone anchors),the pressure of the patellofemoral joint were analyzed.From January of 2016 to July of 2018,84 patients with recurrent patellar dislocation were accepted proximal and distal extensor mechanism realignment with bone anchors and followed up.There were 46 male patients and 38 female patients,the age ranged from 6 to 43 years old,average age was 22.7±5.2 years old,all patients were received Lysholm and Kujula knee scores and Insall criterion before and 12 months postoperation;the imaging examination and the clinical results were evaluated.The age,TT-TG,The lateral femoral condyle angle and Insall index of the patients were employed for the logistic analysis with the curative effect.From January of 2016 to July of 2018,32 patients were accepted in this study.Data of average amount of steps,lengths of steps,maximum extension and flexion angles,varus and valgus angles,internal and external rotation angles,anterior and posterior subluxation,medial and lateral subluxation,up and down subluxation of the patients had been recorded and statistics analyzed pre-operation and 12 months post-operation,and the data of 12 months post-operation were compared with the date from the healthy volunteers in the same age group and with the average BMI had no statistic difference.Reulsts:(1)when the knees were flexed at 0°,30°,60°,90°,120°,there was no statistic difference of the pressure of the patellofemoral joint between group A,B and group C,D(p>0.05),but there was statistic difference between group A and group C,D(p<0.05),there was statistic difference between group B and group C,D(p<0.05).(2)when the knees were flexed at 0°,30°,60°,90°,120°,there was no statistic difference of the patellar lateral shift between group A,B and group C,D(p>0.05),but there was statistic difference between group A and group C,D(p<0.05),there was statistic difference between group B and group C,D(p<0.05).(3)Based on CT and MRI scan image,Four 3D element finite models include distal part of femur include MPFL,simplified lateral retinaculum of patella were set up rapidly and efficiently.(4)There was no statistic difference with these data from 3D element finite models and the corresponding data from part 1(p>0.05).)(5)The patients had significant improvement on the Lysholm knee scores and the Kujula scores(p<0.05).The Insall Criterion evaluation results showed:57 patients were "Excellent",10 patients were "Good",9 patients were "Fair",8 patients were "poor",excellent and good rate was 79.8%.(6)There were statistics significance for average maximum extension angles,average amount of steps,average length of steps between pre-operation and 12 months postoperation.Average maximum extension angle became lessened at 12 months postoperation(p<0.05).average amount of steps became lessened at 12 months postoperation(p<0.05),average length of steps elongated at 12 months postoperation(p<0.05).(7)The data of knee joint kinematics analysis 12 months postoperation had no statistic difference with the normal health group(p>0.05).Conclusions:(1)In these models,the pressure of the patellofemoral joint after proximal and distal extensor mechanics realignment was the lowest in the three kinds of operation and similar with the normal knee,(2)In these models,the lateral shiftof patella after proximal and distal extensor mechanics realignment was the least in the three kinds of operation and similar with the normal knee.(3)These 3D finite element models of the knee could measure the variation of the knee biomechanics accurately,the pressure of the patellofemoral joint calculated by the 3D finite element models had no statistic difference with these data and the corresponding data from part 1(p>0.05).(4)Proximal and distal extensor mechanism realignment assisted by bone anchors was a single and reliable way to treat recurrent patellar dislocation,with a satisfactory early clinical effect and less complications,however,its long-term clinical results were required a further follow-up analysis.(5)This kind of operation had better to carry out on the adolescents,patella alta and TT-TG value more than 2.00cm was not the contradiction for this operation and flat lateral femoral condyle has few influence on the result.(6)There was satisfied early knee function recovery after proximal and distal extensor mechanism realignment for recurrent patellar dislocation with bone anchors.(7)Knee joint kinematics analysis could assess the situation of the knee movements more objectively at pre-operation and postoperation.It showed greater instruction for clinical outcomes. |
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