|Simulator developed by researchers at Clemson University is being used to investigate the effects of different UKA alignment and ligament configurations on the movement and contact pressure distributions on the knee.|
In an effort to investigate the effects of different unicompartmental knee arthroplasty (UKA) alignment and ligament configurations on the movement and contact pressure distributions on the knee, researchers at Clemson University (Clemson, SC) have designed and constructed a knee simulator in which cadaveric specimens can be mounted for study. By better understanding the causes of UKA failures, the researchers hope to improve implant designs, surgical techniques, and patient selection criteria. At the same time, they seek to provide patients with better information about possible postoperative or rehabilitation risks.
UKA is a surgical procedure that is used for treating osteoarthritis when the damage is only limited to one compartment of the knee. The main advantages of this procedure over a total knee replacement include preservation of bone stock, more physiological joint movement, improved proprioception (awareness of the position of the body), increased range of motion, and faster recovery times.
Despite its reported success rates (87 to 98% survivorship at ten years), UKA has not gained universal recognition as the appropriate procedure for treating arthritis afflicting a single condyle. Some of the procedure's failure modes include progression of arthritis in the nonoperated compartment, polyethylene wear, aseptic loosening, fracture, and the need for revision surgery because of pain. These failure modes are believed to be associated with poor implant design, patient selection, and alignment during surgery and with a mismatch in compliance between soft tissues and implant material. All of these factors can result in abnormal loading distributions on the knee, which are thought to accelerate degradation and lead to increased rates of clinical failure.
In addition to performing a reasonable simulation of the body's entire lower extremity during such activities as rising from a seated or a crouching position, the machine allows the scientists to measure internal loadings (contact pressures), which cannot not be performed accurately in living patients. The researchers also use a motion-tracking system enabling 3-D position tracking of knee movement during simulation. The contact pressure and area of the articulating surfaces are measured using paper-thin film pressure sensors that can be inserted between the knee joint.