Design, Construction, and Validation of a Cadaver Knee Motion Testing Device
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Date
2008-05-14
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Abstract
The knee joint is a complex part of the human body, exhibiting six degrees of freedom, and plays an important role in many everyday activities including walking, running and kneeling, making it vulnerable to a variety of injuries and disorders. Injury to the anterior cruciate ligament (ACL), for example, causes the tibia to slide too far forward relative to the knee and also affects side-to-side rotation of the lower leg. Knee kinematics may also be affected when the joint is diseased, such as by osteoarthritis, which is caused by the breakdown and eventual loss of joint cartilage. Surgical procedures, such as ACL reconstruction and total knee replacement, commonly are required to alleviate pain and restore more normal joint function. In recent years, many research studies have been aimed at discovering how to better restore normal knee motion and function after surgery. A thorough understanding of normal knee kinematics and how surgical procedures affect knee kinematics is required for achieving this goal. Since it is unethical to simulate surgery on human subjects, there is a need for an experimental device which can utilize cadaver knee specimens to simulate motion. The purpose of this project is to design, construct, and validate a cadaver knee motion testing device using passive motion for the purpose of understanding how surgical procedures affect knee kinematics.
The design is based on a continuous passive motion (CPM) machine. A CPM machine is a device often used on patients who have undergone knee surgeries, such as total knee replacement or ACL reconstruction. The device passively flexes and extends the knee at slow speeds, which helps to reduce the swelling that may lead to joint stiffness. I created a custom CPM machine so that it could be easily adapted for both a whole cadaver leg and a transected knee and also so that I could investigate different joint angles and speeds that are not possible with existing CPM machines. The completed device will be capable of moving a cadaver knee through a range of motion of 0 to 120 degrees. The angular velocity at the knee joint can also be varied between 30 and 750 degrees/minute. The design consists of a 4-bar linkage in combination with a slider linkage. I utilized kinematic vector loop equations to determine the required position and speed of the slider to obtain the desired knee flexion angles and angular velocities. The device is powered by a linear slider which is controlled by a custom LabVIEW program. The final construction of the device is expected to be completed by early April. Evaluation of the completed device will take place during the remainder of spring quarter.
Description
Engineering: 3rd Place (The Ohio State University Denman Undergraduate Research Forum)
Keywords
Biomechanics, Knee kinematics, machine design