Patients with hip and knee replacements can now determine over time how the implant is interacting with their body thanks to a new tracking system being used by Midwest Orthopaedics at Rush (MOR) physicians.

Drs. Scott Sporer and Wayne Paprosky, MOR hip and knee orthopaedic surgeons, are the first in the country to implant all compliant patients with radiostereometric analysis (RSA) beads, which monitor if a replacement implant is wearing down or moving.

The procedure, performed at Central DuPage Hospital, part of Cadence Health, also provides the world’s first RSA registry for implants that allows scientists to collect data on materials and designs used for hip and knee replacement prostheses. A recently published study conducted in the Netherlands showed a 22 to 35 percent reduction in the number of revisions of RSA-tested total knee replacements as compared with non-RSA-tested total knee replacements in the national joint registries.

The use of RSA in joint replacement patients comes at a crucial time. A pending bill in the U.S. Senate requires manufacturers to track the performance of all medical devices used for hip and knee replacements.

RSA is a groundbreaking technology that allows x-rays to be taken from different angles creating a “stereo,” three-dimensional image. Using beads as markers around the implant, RSA helps physicians determine a hip and knee patient’s progress and provides research for future implant design and technology. It also provides insight into the safest and most durable materials for implants.

“RSA will let us track relative motion of different implant materials such as metal, plastic and ceramic and provide us data about the safety and efficacy of these devices,” explains Dr. Sporer. ”Although research shows that very few hip and knee replacement patients experience failure (less than 10 percent), now we have data to determine the success of each patient’s implant.”

However, researchers point to a growing concern of failed implants, particularly all-metal artificial hips that need to be replaced prematurely. ”This groundbreaking RSA technology allows us to identify problematic implants before they fail and develop an individualized course of action for patients depending on the situation,” says Dr. Paprosky.

“For example, if a patient complains of pain, we compare a recent RSA scan to the original scan. If we notice instability, we can intervene, by possibly performing a surgery to stabilize the implant before more complications develop.”

The RSA analysis process is a team effort between the physicians and Halifax Biomedical, a Canadian based biomedical company that developed the stereo radiography technology. Once the beads, or biomarkers, have been inserted by the physicians into the bone surrounding the implant, two or more pairs of stereo x-ray images are taken and sent to Halifax Biomedical.

Technicians use visual assessment software to monitor the position of the biomarkers in relation to the implants. Over the years, if a patient experiences pain, another x-ray of the patient’s joint is taken and compared to the original one to determine the relative motion of implants with respect to the bone. A detailed report is then generated showing the stability of the implant.

Other medical facilities in the U.S. and Europe have utilized RSA in clinical trials, but Drs. Sporer and Paprosky are the first in the world to use this monitoring system on all elective joint replacement patients.

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