The Effect Of Sectioning The Posterolateral Corner On The Biomechanics Of The Posterior Cruciate Ligament: A Finite Element Analysis With Validation

BackgroundThe posterolateral corner has been shown to play an important role in the prevention of varus angulation, external rotation, and posterior translation. Clinically, undiagnosed and thereby untreated posterolateral corner injury is one of the factors which associated with cruciate ligaments reconstruction failure. As many as 60% of posterior cruciate ligament injuries are combined with injury of the posterolateral corner , though isolated injuries to the posterolateral corner represent less than 2% of all knee ligamentous injuries.In the past few decades, some experimental efforts have been made to the field of posterolateral corner, but experimental measurement which through cadaveric human specimens has been limited in conducting parametric studies of the factors in combined injury of posterior cruciate ligament and reconstruction. The validated finite element model is a powerful tool to obtain data which would be difficult to gain by cadaveric human specimens measurement. However such date can help us understand the mechanism of posterior cruciate ligament reconstruction failure and design improved surgical procedures following posterolateral corner and posterior cruciate ligament injuries.To our knowledge, no finite element model include the posterolateral corner and no data describing the stress distribution within the posterior cruciate ligament has been reported. The objective of this paper was to determine the feasibility of developing a finite element model containing the main structures of posterolateral corner and the stress distribution within the posterior cruciate ligament in response to a 134-N posterior tibial load, a 5-N.m external tibial torque and a 5-N.m varus moment with the knee at 0°,30°,60°and 90°flexion angles. The model was validated using experimental data of knee kinematics from different specimens under previous loading conditions. Objective1. To reconstruct a finite element model containing the main structures of posterolateral corner and validate using experimental data from different specimens2. To analyse the effect of sectioning the posterolateral corner on the biomechanics of the posterior cruciate ligament and calculate the stress distribution within the posterior cruciate ligament.MethodsThe knee joint finite element model was developed based on a volunteer (male, 25 years old). The geometrical model of the knee joint, including bones and ligaments, was developed using CT images and MR data in Mimics 10.0 software. Then the geometriacal model, in―IGES‖format, was sent into Hpyermesh software for meshing. The load definition and was set based on the cadaver test. In software Ls-dyna,the knee kinematics were measured by the model with posterior tibial load, external tibial torque, varus moment at 0°,30°,60°and 90°of knee flexion and compared with those measured from different specimens. Generally, the model predictions were within the range of experimental results. Then the model was used to calculate the stress distribution within the posterior cruciate ligament in response to previous loads with the knee at multiple flexion angles.Results1.A finite element model that firstly consists of the main structures of posterolateral corner was constructed. the whole model contained 4193 nodes, 4278 elements. The results predicted by the model were compared to those obtained experimentally and, in general, were within the range of the experimental data measured from different specimens.2.In response to the 134-N posterior tibial load, With posterolateral corner deficiency,the stress increased significantly at lower flexion angels and the largest increase was 24.9 MPa at full extension. There is no obvious diference in the area of maximum stress between the intactknee and posterolateral corner deficient knee.3.With posterolateral corner deficiency, in response to the 5-Nm external tibial torque, the stress increased significantly at lower flexion angles and the largest increase was 22.6MPa at 30°of knee flexion. The areas of maximum stress were displaced and localized in the ligament body of the posterior cruciate ligament at 30°and 90°of flexion.4.With posterolateral corner deficiency, in response to the 5-Nm varus moment, the stress increased significantly at all flexion angles and the largest increase was 22.2MPa at full extension; the areas of maximum stress localized near the femoral insertion site at full extension, while those near the femoral insertion site, the tibial insertion site and in the mid-substance of the posterior cruciate ligament at 30°of flexion.Conclusions1 The finite element model that firstly consists of the main structures of posterolateral corner is validated and can be used for further research of the behaviors of the posterolateral corner.2. With the deficiency of posterolateral corner, the peak stress in the posterior cruciate ligament was found to be increased significantly under the three loading conditions at lower knee flexions angles.3. The stress distribution within the posterior cruciate ligament are influenced by multiple factors including load, knee flexion angles and integrity of posterolateral corner. Our data suggest that injuries of the posterolateral corner can increase the risk of the posterior cruciate ligament for injury.