The Effect Of Anterior Medial Entrance Position On The Femoral Tunnel By 3D Simulating ACLR

Objective The purpose of this study was to observe the optimal flexion angle of knee and low accessory anteromedial portal position effect on femoral tunnel through simulating ACL reconstruction with 3D technique.Methods 280 patients who underwent 3D CT scan of knee in the First affiliated Hospital of University of South China were screened from January 2014 to October 2017,and 20 normal images of knee wereselected.The 3D virtual model was constructed with mimics software to simulate the process of anatomical single bundle anterior cruciate ligament reconstruction(ACLR).The length of ACL femur tunnel was measured at knee flexion 110 °,120 °,130 °and 140°and the anterior medial guide pin located at 0 °,10°and 20 °.The angle between the femoral tunnel and the sagittal and coronal plane was calculated,and the rupture of the posterior wall of the femoral condyle was calculated.Results 1.3D model of knee joint successfully constructedbased on 20 healthy CT data of knees,the length of the femoral tunnel was 34.78 ± 2.90 mm to 38.86 ± 2.47 mm in the range of 0-20 ° and 110-140 °;the length of the femoral tunnel increased with the increase of knee flexion angle.Along with the increase of the AM external rotation angle,the length of the femoral tunnel also increased.According to the analysis of two-factorvariance,there were statistical differences in the length of femoral tunnel between different knee flexion angles and AM external rotation angles(p<0.05).2.The angle between femoral tunnel and sagittal plane ranged from 46.01 ±8.80 °to 63.32±9.58 °.It was statistically different with the AM external rotation angle(p < 0.05);besides,it decreased with the increase of the AM angle.There was no significant difference in the angle between the femoral tunnel and sagittal plane at different knee flexion angles(P>0.05).3.The angle between the femoral tunnel and the coronal plane ranged from 19.86 ±4.67 °to 57.24 ±7.24 ° and the angel was statistically different with knee flexion and AM angle;it went down with the increase of the knee;However,as for the AM angle,the trend was opposite.4.No posterior wall rupture of lateral femoral condyle was found in all patients withreconstructed ACL in thisstudy.Conclusion 1.The length of femoral tunnel was more than 30 mm,which could satisfy the condition of femoral tunnel fixation and the length of tendon bone healing after anatomical reconstruction of ACL in the range of flexion 110-140 °and guide pin 0-20 °.2.According to the angle between ACL and sagittal and coronal planes,and considering the stability of knee joint after reconstruction,it was suggested that the flexion of knee should be close to 140 °and the guide pin was located at 10-20 °;ideal femoral tunnel could be obtained by reconstruction of ACL.It had important guiding significance for ACL reconstruction.