Comparision Of The Femoral Condylar Ellipses Line And The Surgical Epicondylar Axis

Purpose:In our previous experiment,we published a new method to describe the sagittal femoral condyles shape :ellipse-fitting method.When the MRI-scans direction was perpendicular to the SEA on the axial plane,and was tangent to the distal femoral condyles surface on the coronal plane,A good ellipse-fitting was found on the both medial and lateral femoral condylar cartilage contours.Compared with femoral condyle double circle method and femoral posterior condyle single circle method,ellipse method simplified the description of the sagittal femoral condyle geometry.It accurately reflects the parameter relationship between femoral condyle and femoral trochlea;The relationship between sagittal femoral condyle shape and posterior tibial slope.However,it was unclear that the orientation of the femoral condylar ellipses centers line and the relationship between it and the surgical epicondylar axis.The purpose of this study was to determine the orientation of the centers of the femoral condylar ellipses centers line(CEL),and to analyze the relationship between CEL and the surgical epicondylar axis(SEA)by using 3D reconstruction femoral condylar model from magnetic resonance images(MRI)data.Methods:Total of 80 healthy Chinese volunteers were involved in this study(40 males and 40females),All subjects denied history of trauma,any symptoms on the knees,or congenital diseases.The exclusion criterions were abnormal valgus/varus knees(hip-knee-ankle angles were >-3° and < 3°),discoid meniscus,trochlear dysplasia or cruciate ligaments injury as revealed by MRI images.All signed informed consent forms for MRI examination.Sagittal MRI-scans of the distal femur were performed on each subject’s right knee joint at full extension position using MR scanner(Philips Achieva 3.0 T magnetic resonance imaging system).The scanning direction was perpendicular to the SEA on the axial plane,and was tangent to the distal femoral condyles surface on the coronal plane.3D model of the distal were manually reconstructed respectively.According to Wang’s and Zhang’s methods in determining of the Femoral Condylar Ellipses and according to Akagi’s method in determining the surgical epicondylar axis(SEA).According to Berger’s method in determining of the posterior condylar line(PCL)on the axial plane and distal condylar line(DCL)on the coronal plane.In the 3D model,the angles of SEA-PCL、CEL-PCL、SEA-CEL were measured in axial view,and SEA-DCL 、 CEL-DCL 、 SEA-CEL in coronal view respectively.Measurement of the distance and angle between the outlet points of the medial and lateral condyles of SEA and CEL on sagittal plane of three-dimensional femoral condyle model.SPSS 26.0 statistical software was used for statistical analysis.Measurement data conforming to normal distribution were expressed as mean ±standard deviation.Measurement data that do not conform to normal distribution are expressed by median(quartile spacing).The relationship of SEA-PCL and CEL-PCL,SEA-DCL and CEL-DCL data using correlation regression analysis.Results:A total of 80 healthy Chinese volunteers were involved in this study,including42 males(mean 25.46 ± 1.88 years)and 38 females(mean 26.15 ± 1.35 years).The average height was 174.81 ± 5.53 cm for males,and was 162.06 ± 4..75 cm for females.The mean Body Mass Index(BMI)was 24.66 ± 3.45 kg/m2 for males,and was 20.13±2.57 kg/m2.The average major and minor axis of the medial and lateral ellipses were 55.40 mm on the medial side(standard deviation of 0.51mm)and44.21 mm on the lateral side(standard deviation of 0.43mm).The average eccentricity ratio of the medial and lateral ellipses was 0.60 on the medial side(standard deviation of0.02)and 0.48 on the lateral side(standard deviation of 0.05).The average rotation angle of the lateral ellipses were12.97°(standard deviation of 3.50°).On the axial view of three-dimensional femoral condyle model,CEL-PCL:3.27 ± 1.11 °; SEA-PCL: 2.91±1.40°.There was a significant correlation between CEL-PCL and SEA-PCL(r = 0.731 P < 0.001),and the mean difference was 0.35 ± 0.96°(95 %CI : 0.13-0.58).On the frontal view of the three-dimensional model of the femoral condyle: CEL-DCL: 0.18±0.84°;SEA-DCL:-1.16±1.06°;There was a weakly correlation between CEL-DCL and SEA-DCL,the mean difference was 1.35 ± 1.13°(95 % CI : 1.07 – 1.62).On the medial surface of the three-dimensional model of sagittal femoral condyle,the outlet point of CEL is 76.28 ± 13.17° below the outlet point of SEA,the horizontal distance is 1.01 ± 0.92 mm,and the vertical distance is4.62 ± 1.15 mm.On the lateral surface of the three-dimensional model of the sagittal femoral condyle,the outlet point of CEL is 79.12 ± 22.66° below the outlet point of SEA,the horizontal distance is 0.56 ± 1.17 mm,and the vertical distance is 2.80 ±1.14 mm.Conclusion:The femoral condylar ellipses line points to the femoral attachments of the medial and lateral collateral ligaments on the epicondyles.which is almost coincident with the surgical epicondylar axis at the axial view,and it has 1.35° varus relative with the condylar line at the coronal view.The surgical epicondylar axis may actually be the projection of the femoral condylar ellipses line on the axis view.Therefore,the femoral condylar ellipses centers line(CEL)is more equipped with a theoretical basis for representing the sagittal anatomical morphology of femoral condyles.