Parametric finite element model of medial patellofemoral ligament reconstruction model development and clinical validation

Abstract

Background Currently, there is uncertainty regarding the long-term outcome of medial patellofemoral ligament reconstructions (MPFLr). Our objectives were: (1) to develop a parametric model of the patellofemoral joint (PFJ) enabling us to simulate different surgical techniques for MPFLr; (2) to determine the negative effects on the PFJ associated with each technique, which could be related to long-term deterioration of the PFJ. Methods A finite element model of the PFJ was created based on CT data from 24 knees with chronic lateral patellar instability. Patella contact pressure and maximum MPFL-graft stress at five angles of knee flexion (0, 30, 60, 90 and 120°) were analysed in three types of MPFLr: anatomic, non-anatomic with physiometric behaviour, and non-anatomic with non-physiometric behaviour. Results An increase in patella contact pressure was observed at 0 and 30° of knee flexion after both anatomic and non-anatomic MPFLr with physiometric behaviour. In both reconstructions, the ligament was tense between 0 and 30° of knee flexion, but at 60, 90 and 120°, it had no tension. In the third reconstruction, the behaviour was completely the opposite. Conclusion A parametric model of the PFJ enables us to evaluate different types of MPFLr throughout the full range of motion of the knee, regarding the effect on the patellofemoral contact pressure, as well as the kinematic behaviour of the MPFL-graft and the maximum MPFL-graft stress. Electronic supplementary material The online version of this article (10.1186/s40634-019-0200-x) contains supplementary material, which is available to authorized users.

Evaluation of Patellar Contact Pressure Changes after Static versus Dynamic Medial Patellofemoral Ligament Reconstructions Using a Finite Element Model

“…A parametric FE model of the PFJ was previously developed [18] based on the geometrical average of 24 knees acquired with a 64-detector multidetector computer tomography (CT) system (Philips, Best, The Netherlands) at the highest spatial resolution, without slice interpolation (0.255 × 0.255 × 0.672 mm 3 ) [13]. The knee geometry was simplified ( Figure 1).…”

“…The main parts of the PFJ were the femoral condyle and patella bones, considered as rigid parts, and the femoral and patellar cartilages, considered as deformable components. A cartilage thickness of 3 mm was assumed [18,25]. Tendon and ligaments were also included to stabilize the patella and support the distribution of the patellar contact pressures better.…”

“…Cartilage degeneration after a static MPFLr has been related to graft overtension or an incorrect femoral attachment point [16,17]. Several biomechanical studies based on the finite element (FE) method have evaluated the MPFLr [18][19][20][21][22][23][24]. Previous studies were mainly based on a single FE model of the knee.…”

“…Previous studies were mainly based on a single FE model of the knee. Sanchis-Alfonso et al [18] recently created a 3D parametric FE model of the patellofemoral joint (PFJ) that allowed for the evaluation of different types of MPFL reconstructions through the full range of motion of the knee. Additionally, the model is patient-specific.…”

“…High patellar pressures would be a risk factor for patellofemoral cartilage degeneration in the long term. This evaluation used a clinically-validated 3D parametric FE model of the PFJ [18].…”