Knee joint orthopaedic testing

Knee joint orthopaedic testing

simVITRO gives flexibility to the knee researcher in that:

  • Loads can be applied directly to the knee joint
  • Both loading styles can be utilised
    • Static Laxity
    • Dynamic simulation of activities of daily living
  • Muscle actuators can be incorporated into the control scheme
    • For higher loads and tracking of patella motion

Below are the maximum load and range of motion values in the cadaveric testing of knees:

Loading values Range of motion
Medial/ lateral Force ˜ 50 N Translation ˜ 20 mm
Anterior/ posterior Force ˜ 200 N Translation ˜ ± 40 mm
Superior/ inferior Compression  ˜ 700 N, with potential to go up to 1200N Translation ˜ ± 20 mm
Varus/ Valgus ˜ 20 Nm Angle ˜ ± 20 °
Internal/ external rotation ˜ 15 Nm Angle ˜ ± 50 °
Muscle actuators for the quadriceps ˜ 1000 N
Flexion angle ˜ 0 – 120 °

Range of motion values relate to the knee joint centre.

Mounting Fixtures

The specimen mounting fixtures for the knee can be the aluminium tubes mounted to the memory lock clamp system. These clamps provide a secure connection of the specimen to the robot. In addition, they allow for easy removal and precise re positioning of a specimen (within 0.0002”) if they need to be removed during the experiment for surgical interventions. The clamps grip the aluminium tubes that are connected to the femur and tibia. The specimen tubes are available in different diameters. This system provides kinematic integrity for multiple specimen/session testing such as when trying to test several specimens in a session or the same specimen over several sessions. One specimen can be mounted on the robot while the others are undergoing surgery. The operator just needs to load the right configuration file for each specimen and can quickly transition to previously tested specimens.

 

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