EVALUATION OF PATELLOFEMORAL JOINT CONTACT PRESSURE BEFORE AND AFTER MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION USING A PARAMETRIC FINITE ELEMENT MODEL

Abstract

The reconstruction of the medial patellofemoral ligament (MPFL) is the "gold standard" for_x000D_ the treatment of chronic lateral patella instability, that usually affects young people. Many_x000D_ different surgical techniques have been described to perform this reconstruction, with_x000D_ different attachments and different types of graft. The reported short-term results are good,_x000D_ but there is uncertainty regarding the long-term outcome of these MPFL reconstruction_x000D_ techniques, chondropathy and osteoarthritis being a long term complication that could be_x000D_ secondary to an increased patellofemoral joint contact pressure related with an inadequate_x000D_ MPFL reconstruction. An effective way to evaluate the patellofemoral contact pressure_x000D_ throughout the range of motion of the knee after MPFL reconstruction is by using the finite_x000D_ element methodology (FEM)._x000D_ Our two previous studies enabled us to determine what a real anatomic reconstruction was,_x000D_ based on the femoral attachment point of the reconstruction; and how this attachment_x000D_ point influenced the dynamic changes of the plasty during knee flexion. These studies were_x000D_ performed using patients knee 3D-CT reconstructions._x000D_ These length changes of the medial patellofemoral plasty enabled our engineering team to_x000D_ develop the patellofemoral finite element model used in our study to analyze the_x000D_ patellofemoral pressures before and after different reconstruction techniques of the_x000D_ patellofemoral ligament reconstruction, and to calculate the ligament tension, and its_x000D_ consequences on patellofemoral joint pressure._x000D_ Our purpose was the creation of a parametric model of the PFJ where the joint geometry is_x000D_ simplified and can be meshed by means of automatic mesh generation programs with suitable_x000D_ finite element aspect ratios for all meshes. Additionally, our parametric model enabled us to_x000D_ simulate different types of surgical techniques for MPFL reconstruction. We hypothesized that_x000D_ this model will allow us to evaluate the patellofemoral contact pressure and the maximum_x000D_ MPFL-graft stress in each specific reconstruction and at different flexion-extension angles of the_x000D_ knee. Since this is a novel method, we focused our attention on clinical validation. In this way,_x000D_ five clinical cases are presented to demonstrate the accuracy of our model and to show its_x000D_ versatility for predicting challenging clinical cases. An extrapolation of the computational_x000D_ results was performed to provide a qualitative comparison to the clinical outcomes. The_x000D_ contribution of our results is the introduction of FEM in daily clinical practice to optimize_x000D_ surgical procedures by using personalized treatments._x000D_ The main finding of this study is that the use of a parametric 3D finite element model of the_x000D_ PFJ enables us to evaluate different types of surgical techniques for MPFL reconstruction_x000D_ with regard to the effect on the patellofemoral contact pressure, as well as the kinematic_x000D_ behaviour of the MPFL-graft with flexion-extension of the knee and the maximum MPFLgraft_x000D_ stress. In this way, from diagnostic images, for example, a CT, we could simulate_x000D_ different surgical treatments and choose the best optimal technique for each patient. That_x000D_ is, we can customize treatment for individual patients.

Date of Award	21 Jan 2019
Original language	English
Supervisor	Juan Carlos Monllau Garcia (Director) & Vicente Sanchís Alfonso (Director)