A Study Of Isometric Point During The Reconstruction Of Anterior Cruciate Ligament (ACL) With Three Dimensional Reconstruction Models

ObjectiveThe purpose of this article is to investigate the isometric point of anterior cruciate ligament (ACL) with the three dimensional reconstruction of MR. Material and MethodsTen knees of 10 volunteers were underwent the MR scan with the knee at full extension position and at 30°,60°,90°,120°flexion position. All the images obtained were exported into Mimics 10.01. Three dimensional models were established with Mimics in a personal computer. All the mark points were confirmed on femur and tibia. The distance between the femoral mark point and tibial mark point were measured respectively. If the change of the distance is lower than 3mm during knee flexion-extension, the points of this group should be the isometric points.Simulate a cylinder by the MedCAD, which diameter is 7mm, between the isometric points, so we can know whether the impingement of graft on the intercondylar fossa or posterior cruciate ligament should happen.Results10 three dimensional models were established successfully and A1-X, A2-X, B1-Y, B2-Y, C1-Z, C2-Z ,C3-Z were isometric points.During simulating operation, we found that if we reconstruct the ACL at A1-X, A2-X and B1-Y, the impingement of graft on the intercondylar fossa or posterior cruciate ligament should not be avoided. If we reconstruct the ACL at B2-Y, C1-Z, C2-Z and C3-Z, the impingement should not happen mostly. But the graft should be too vertical, which should influence the function of ACL graft, if we reconstruct the ACL at C1-Z, C2-Z and C3-Z.ConclusionThe B2-Y (11 o'clock position in the right knee and 1 o'clock position in the left knee) is the best isometric point of ACL reconstruction.