Posterior cruciate ligament balancing in total knee arthroplasty: a numerical study with a dynamic force controlled knee model

Abstract

BackgroundAdequate soft tissue balancing is a key factor for a successful result after total knee arthroplasty (TKA). Posterior cruciate ligament (PCL) is the primary restraint to posterior translation of the tibia after cruciate retaining TKA and is also responsible for the amount of joint compression. However, it is complex to quantify the amount of ligament release with its effects on load bearing and kinematics in TKA and limited both in vivo and in vitro. The goal of this study was to create a dynamic and deformable finite element model of a full leg and analyze a stepwise release of the PCL regarding knee kinematics, pressure distribution and ligament stresses.MethodsA dynamic finite element model was developed in Ansys V14.0 based on boundary conditions of an existing knee rig. A cruciate retraining knee prosthesis was virtually implanted. Ligament and muscle structures were simulated with modified spring elements. Linear elastic materials were defined for femoral component, inlay and patella cartilage. A restart algorithm was developed and implemented into the finite element simulation to hold the ground reaction force constant by adapting quadriceps force. After simulating the unreleased PCL model, two models were developed and calculated with the same boundary conditions with a 50% and 75% release of the PCL stiffness.ResultsFrom the beginning of the simulation to approximately 35° of flexion, tibia moves posterior related to the femur and with higher flexion anteriorly. Anterior translation of the tibia ranged from 5.8 mm for unreleased PCL to 3.7 mm for 75% PCL release (4.9 mm 50% release).A decrease of maximum von Mises equivalent stress on the inlay was given with PCL release, especially in higher flexion angles from 11.1 MPa for unreleased PCL to 8.9 MPa for 50% release of the PCL and 7.8 MPa for 75% release.ConclusionsOur study showed that dynamic FEM is an effective method for simulation of PCL balancing in knee arthroplasty. A tight PCL led in silico to more anterior tibia translation, a higher collateral ligament and inlay stress, while retropatellar pressure remained unchanged. Surgeons may take these results in vivo into account.

Partial versus Intact Posterior Cruciate Ligament‐retaining Total Knee Arthroplasty: A Comparative Study of Early Clinical Outcomes

“…PCL tension is an important factor for a successful CRTKA. PCL release can be performed on the tibial or femoral side, as noted in a previous study. In a previous study, we resected the anterolateral bundle of the PCL together with the bone island at the tibial attachment site of the PCL to create more flexion–extension space, retaining and releasing only the posteromedial bundle.…”

The effect of constitutive representations and structural constituents of ligaments on knee joint mechanics

“…Previous numerical knee models have investigated the mechanical behavior of knee joint ligaments under different loading conditions 5 – 16 . For instance, some studies simulated ligaments as nonlinear elastic springs and cartilage and menisci as a simple linear elastic material or rigid 12 , 17 – 19 . Other studies have included realistic geometries of ligaments, but cartilage and menisci were treated as linear elastic materials 14 , 20 .…”

Material Models and Properties in the Finite Element Analysis of Knee Ligaments: A Literature Review

“…In some cases, the authors only stated the use of non-linear elements without any additional information on the constitutive equations (Shin et al, 2009 ; Yoon et al, 2010 ). In contrast, the use of linear 1D elements appears to be very limited in simulation studies (Shin et al, 2007 ; Innocenti et al, 2014 ; Steinbruck et al, 2014 ).…”