ABSTRACT
OBJECTIVE@#To explore the stress distribution characteristics of the graft after anterior cruciate ligament (ACL) reconstruction, so as to provide theoretical reference for the surgical plan of ACL reconstruction.@*METHODS@#Based on 3D MRI and CT images, finite element models of the uninjured knee joint and knee joint after ACL reconstruction were established in this study. The uninjured knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL and posterior cruciate ligament. The ACL reconstruction knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL graft and posterior cruciate ligament. Linear elastic material properties were used for both the uninjured and ACL reconstruction models. The elastic modulus of bone tissue was set as 17 GPa and Poisson' s ratio was 0.36. The material properties of ligament tissue and graft were set as elastic modulus 390 MPa and Poisson's ratio 0.4. The femur was fixed as the boundary condition, and the tibia anterior tension of 134 N was applied as the loading condition. The stress states of the ACL of the intact joint and the ACL graft after reconstruction were solved and analyzed, including tension, pressure, shear force and von Mises stress.@*RESULTS@#The maximum compressive stress (6.34 MPa), von Mises stress (5.9 MPa) and shear stress (1.83 MPa) of the reconstructed ACL graft were all at the anterior femoral end. It was consistent with the position of maximum compressive stress (8.77 MPa), von Mises stress (8.88 MPa) and shear stress (3.44 MPa) in the ACL of the intact knee joint. The maximum tensile stress of the graft also appeared at the femoral end, but at the posterior side, which was consistent with the position of the maximum tensile stress of ACL of the uninjured knee joint. More-over, the maximum tensile stress of the graft was only 0.88 MPa, which was less than 2.56 MPa of ACL of the uninjured knee joint.@*CONCLUSION@#The maximum compressive stress, von Mises stress and shear stress of the ACL graft are located in the anterior femoral end, and the maximum tensile stress is located in the posterior femoral end, which is consistent with the position of the maximum tensile stress of the ACL of the uninjured knee joint. The anterior part of ACL and the graft bore higher stresses than the posterior part, which is consistent with the biomechanical characteristics of ACL.
Subject(s)
Humans , Anterior Cruciate Ligament Injuries/surgery , Anterior Cruciate Ligament Reconstruction , Biomechanical Phenomena , Femur/surgery , Finite Element Analysis , Knee Joint/surgery , Tibia/surgeryABSTRACT
OBJECTIVE@#To provide new concepts of anterior cruciate ligament (ACL) reconstruction by anatomical gross observation of ACL tibial insertion and finite element analysis of distribution of ACL mechanical insertion.@*METHODS@#In the anatomical study, ten fresh adult cadaveric knees were dissected, including 6 males and 4 females, all knees were generally observed through standard medial parapatellar approaches, paying attention to the close anatomical relationship of tibial insertion and anterior horn of lateral meniscus, and ACL was exposed and gradually removed from the inside. The shape of tibial insertion of ACL was observed and recorded, and anterior-posterior diameters and left-right diameters of tibial insertion were measured with vernier caliper. For the study of finite element analysis, three-dimensional thin-layer magnetic resonance imaging of normal knee joint was used to establish knee joint model. Three-dimensional reconstruction software MIMICS and finite element analysis software ANSYS were used to establish knee joint model, subsequently, clinical physical examination Lachman test and pivot-shift test were simulated to observe the force distribution of ACL tibial insertion and femoral insertion.@*RESULTS@#The ACL tibial mechanical insertion was rather flat and long similar as an arc shape without a clear separation between anterior medial bundle (AMB) and posterolateral bundle (PLB) in gross observation. The dense fibers lies belonged to the medial intercondylar ridge and ended up anterior with the osseous landmark of anterior ridge. Its average anterior-posterior diameter was (13.8±2.0) mm, the average left-right diameter of midsubstance was (5.3±0.6) mm, and the average left-right diameter of anterior margin was (11.5±1.2) mm. The finite element analysis showed that distribution on the femoral side was oval shape mainly below the residents' ridge, while the tibial side was rather flat mainly along the medial intercondylar ridge, which was consistent with the anatomical observation. The biomechanical characteristics of ACL attachments were verified theoretically.@*CONCLUSION@#Anatomical study and finite element analysis have confirmed the flat arc shape of ACL tibial insertion. The ideal reconstruction technique of ACL should be based on its biomechanical insertion. Based on anatomical study and biomechanical analysis, we have proposed the idea of ACL biomechanical insertion reconstruction (BIR) and established a surgical model with oval femoral tunnel and rounded-rectangle tibial tunnel.