July 26, 2012 -- Unicompartmental knee arthroplasty (UKA) is a surgical procedure used to treat osteoarthritis when the damage is only limited to one compartment of the knee. The main advantages of this procedure over the total knee replacement (TKR) include preservation of bone stock, more physiologic joint movement, improved proprioception, increased range of motion (ROM), and faster recovery time.
Despite its reported success rates, (87 to 98% survivorship at ten years) UKA has not gained universal recognition as the appropriate procedure of arthritis of a single condyle. This is mainly due to its more complex procedure and a reported slightly lower success rates compared to TKA.
Progression of arthritis in the non-operated compartment, polyethylene wear, aseptic loosening, fracture, and revision due to pain are some of the reported failure modes of UKA. These failure modes are believed to be associated with poor implant design, patient selection, and alignment during surgery, and a mismatch in compliance between soft tissues and implant material. All these could result in abnormal loading distributions on the knee, which are thought to accelerate degradation and lead to increased rates of clinical failure.
Our research focuses on investigating the effects of different UKA alignment and ligament configurations on the movement and contact pressure distributions on the knee. The knowledge obtained from the current and future studies performed using the rig may help physicians and researchers to improve implant designs, surgical techniques, patient selection criteria, or better inform the patient about possible post-operative or rehabilitation risks.
Due to measurement limitations on the patient study, we have designed and constructed Clemson knee simulator in which cadaveric specimens can be mounted for the study. The cadaveric specimens will be obtained in collaboration with our clinical partners from the Greenville Hospital System (GHS), Grenville, SC. The rig has the advantages of being a reasonable simulation of the entire lower extremity in activities such as rising from a seated or crouching position while allowing measurements of internal loadings (contact pressures), which could not be performed accurately in a living patient. We are utilizing a motion tracking system that allows 3-D position tracking of the knee movement during simulation. The contact pressure and area of the articulating surfaces are measured using paper-thin film pressure sensors which can be inserted in between the knee joint.
We are currently working on validating the simulator to ensure its ability to capture the key motion characteristics of a normal knee with artificial bones and implant. The funding that we have recently received from OREF (Orthopaedic Research & Education Foundation) in collaboration with our clinical partners will be used to obtain cadaveric specimens needed to perform the stated UKA study. The results from the experiment will be analyzed and used to better understand the underlying causes of UKA failures, which will eventually lead to improvement in implant designs, surgical techniques, patient selection criteria and etc.
Research to improve knee implant design, surgical techniques, and patient selection criteria is taking place at the Frank H. Stelling and C. Dayton Riddle Orthopaedic Education and Research Laboratory located on the Clemson University Biomedical Engineering Innovation Campus (CUBEInC).
Roy Junius Rusly is a PhD student, teaching assistant, and research assistant at Clemson University’s College of Engineering and Science. Rusly’s PhD advisor is John D. DesJardins, assistant professor and director of Bioengineering Abroad Programs in the Department of Bioengineering.