LAS VEGAS — Cayenne Medical (Scottsdale, Arizona), a private sports medicine device company specializing in the soft tissue based arthroplasty and reconstruction, reported the preliminary two-year results of its study evaluating the Mirror Partial Knee System during the American Association of Orthopedic Surgeons (AAOS; Rosemont, Illinois). The Mirror System is the only partial knee replacement system that utilizes the patient's natural knee motion to position implants while balancing the knee. This patient specific surgical procedure dynamically tensions the patient's own ligaments to guide intra-articular cutters that prepare supporting bone.

"I've done over a thousand of these procedures, but what we wanted to do was go back and see how the people were doing in two years to make sure if everything was OK with the system," Gerard Engh, one of the study investigators, told Medical Device Daily. "When you introduce something new the first thing you want to make sure is that there are no skeletons in the closet so to speak, or something that you didn't anticipate that went wrong."

He added, "we didn't find anything and through our IRB we were able to contact the first 100 people we did this operation with the current implant."

The retrospective study of 100 consecutive partial knee implants with more than two year follow up included 88 partial knee replacements in 83 patients. Knee Society Pain Scores and Oxford Scores were evaluated for these patients finding 94% satisfied, 93% with improved function and 93% with decreased pain. One knee was converted to a total knee replacement due to persistent pain.

"The surgeon doing the revision could find nothing wrong with the implant. It wasn't loose, there wasn't any progression of arthritis. There was a patient that had pain for two years and so she was converted to a total. We don't know why she was having the pain," he said.

Nitin Goyal, of Anderson Orthopedic Clinic (Alexandria, Virginia), and first author of the retrospective study, said that "With regard to survivorship, this data confirms that the Mirror Partial Knee Replacement has short-term outcomes that are equivalent to the most ideal unicompartmental knee arthroplasty results that have been published thus far. The Cayenne Mirror technique of ligament guided bone preparation is exciting because of the potential to create the most balanced knee construct possible today. Uniform ligament tension throughout range of motion could potentially increase patient knee function as well as the longevity of the knee implants. I am looking forward to seeing this technology develop further and hope to see improved patient satisfaction and survivorship in the long-term as compared to conventional knee replacements."

David Springer, CEO of Cayenne Medical, said in a release that "We are pleased with these early clinical results as they reinforce our belief that enabling the surgeon to use the patient's natural knee motion to guide implant placement provides a more anatomic, fast, easy and reproducible surgical procedure without the use of imaging studies, expensive capital equipment, service fees, or custom implants. With our two-year outcome results now available, we have even more confidence in this technology and its future applications vs. competitive offerings."

There are more steps ahead however, Engh told MDD.

"I think there are two things ahead of us, he said. "One is to look at those 100 patients out to five years and make sure everything is holding up well. If something goes wrong in the beginning then the patient usually has persistent pain or they can have early loosening of the implant. We didn't have either of those problems. So when you start looking at five years you start putting in the equation potential problems with progression of arthritis or wearing down of the implant."

Engh added, "the second thing we're currently doing an X-ray study to try to document if we're getting component to component position. "The third thing we hope to do is figure out a way to measure the ligament tension."