Virginia Research Day 2025

Medical Student Research Biomedical

05 Mechanical Simulation of Patellar Deformation and Stress in Variable Patellar Ligament Attachment Scenarios

Megan Birmingham; Jonathan Millard, PhD Corresponding author: mpresley@vt.vcom.edu

Edward Via College of Osteopathic Medicine - Virginia Campus

where a finite element model of the patella was built using muscle insertion angles and average force productions for each of the muscles of the quadriceps femoris group. The location of the patellar ligament was modified for three different biomechanical simulations: anterior apical attachment, posterior apical attachment, and both anterior and posterior apical attachment. Patterns of total deformation, measured in millimeters (mm), and Von Mises stress, measured in megaPascals (MPa), were compared for each simulation to assess how variable patellar ligament attachments influence force patterns moving through the patella. Results: The posterior apical attachment model performed similarly to the anterior and posterior apical attachment model, demonstrating deformation maxima (0.013 mm and 0.010 mm) focused on a locale of deformation laterally on the patellar base. These models demonstrate lower maximum stress (54.22 MPa and 43.81 MPa) with relatively even patterns of stress distribution. Deformation of the

anterior apical attachment model was over three times greater than the other models (0.045 mm) heavily focalized over a wider portion of the patellar base. The anterior apical attachment had a maximum stress of 91.22 MPa with stresses occurring on the anterior surface, close to its attachment. Conclusions: Variation in the attachment footprint of the patellar ligament influences patellar biomechanics, which represents a reasonable proxy for PF joint stability. Ligaments which include posterior apical attachments result in forces traveling in an oblique direction, whereas anterior apical attachments result in forces moving more uniformly through the patella. Most research in this domain focuses on quadriceps force production and muscle fascicle angle, our results suggest that patellar ligament attachment location (in isolation) has a significant effect on the directions of force exerted by the quadriceps muscles, thereby influencing joint stability.

Introduction: Patellar instability is characterized by malalignment of the patellofemoral (PF) joint. The incidence of PF instability is 29 per 100,000 in children between 10-17 years old, and issues with the extensor mechanism/PF congruence remain the primary non-infectious indication for revision after total knee arthroplasty with recent complication rates reported as high as 20%. Most biomechanical studies aim to evaluate how variable forces contributed from each quadriceps muscle affect stability at the joint. Fewer studies have examined the distal mechanism. Our objective was to use three biomechanical simulations to assess how variation in the location of the patellar ligament’s attachment/”footprint” affects patellar response to forces produced in an anatomically accurate finite element model. Methods: One patella from an anatomical donor was scanned with a Bruker Skyscan 1276 at 50 µm resolution. 3DSlicer (v5.6.2) was used to create a three-dimensional segmentation of the patella. The segmentation was imported into ANSYS Mechanical

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