Patellar tendon elastic properties derived from in vivo loading and kinematics

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Medical Engineering

Background:

• Patellar complications significantly impact total knee arthroplasty (TKA) success.
• Patellar tendon elastic properties are crucial for load transmission but exhibit high variability in existing literature.
• Limited in vivo data exists on patellar tendon mechanics in TKA patients.

Purpose of the Study:

• To report in vivo stiffness, Young's modulus, and forces of the patellar tendon in TKA patients.
• To quantify patellar tendon loading and elongation during functional activities.
• To provide essential data for mechanical simulations of the knee joint post-TKA.

Main Methods:

• Utilized a combined approach of telemetric assessment, fluoroscopy, and motion capture in four TKA patients.
• Integrated data into musculoskeletal multi-body models to calculate patellar tendon forces and elongation.
• Measured tendon properties during squat and sit-stand-sit activities.

Main Results:

• Reported patellar tendon stiffness ranging from 511 to 1166 N/mm and Young's modulus from 259 to 504 MPa.
• Peak patellar tendon forces reached 1.31 to 2.79 times bodyweight during activities.
• Tendon forces were approximately 0.5 times bodyweight below tibio-femoral forces.

Conclusions:

• This study provides the first in vivo measurements of patellar tendon mechanical properties in TKA patients.
• The data offers valuable input for computational models simulating knee biomechanics after arthroplasty.
• Understanding these properties can help mitigate patellar complications and improve TKA outcomes.