Patellofemoral instability in trochleodysplastic knee joints and the quantitative influence of simulated trochleoplasty - A finite element simulation

Clin Biomech (Bristol, Avon). 2021 Jan;81:105216. doi: 10.1016/j.clinbiomech.2020.105216. Epub 2020 Nov 9.


Background: Patellofemoral instability is a debilitating condition mainly affecting young patients and has been correlated with trochlear dysplasia. It can occur when the patella is insufficiently guided through its range of motion. Currently, there is no literature describing patellofemoral stability in trochleodysplastic knees and the effect of isolated trochleoplasty on patellofemoral stability.

Methods: The effect of isolated trochleoplasty in trochleodysplastic knees of patients with symptomatic patellofemoral instability was investigated using a quasi-static finite element model. MRI data of five healthy knees were segmented, meshed and a finite element analysis was performed in order to validate the model. A second validation was performed by comparing simulated patellofemoral kinematics to in-vivo values obtained from upright- weight bearing CT scans. Subsequently, five trochleodysplastic knees were modelled before and after simulated trochleoplasty. The force necessary to dislocate the patella by 10 mm and to fully dislocate the patella was calculated in various knee flexion angles between 0 and 45°.

Findings: The developed models successfully predicted outcome values within the range of reference values from literature. Lateral stability was significantly lower in trochleodysplastic knees compared to healthy knees. Trochleoplasty was determined to significantly increase the force necessary to dislocate the patella in trochleodysplastic knees to comparable values as in healthy knees.

Interpretation: This is the first study to investigate lateral patellofemoral stability in patients with symptomatic patellofemoral instability and dysplasia of the trochlear groove. We confirm that patellofemoral stability is significantly lower in trochleodysplastic knees than in healthy knees. Trochleoplasty increases patellofemoral stability to levels similar to healthy.

Keywords: Finite element; Model validation; Patellofemoral instability; Trochlear dysplasia; Trochleoplasty.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biomechanical Phenomena
  • Computer Simulation*
  • Female
  • Finite Element Analysis*
  • Humans
  • Joint Instability / diagnostic imaging
  • Joint Instability / pathology
  • Joint Instability / surgery*
  • Knee Joint / diagnostic imaging
  • Knee Joint / pathology
  • Knee Joint / surgery*
  • Magnetic Resonance Imaging
  • Male
  • Patellofemoral Joint / diagnostic imaging
  • Patellofemoral Joint / surgery*
  • Tomography, X-Ray Computed