Two new studies have researched the effect of a novel knee system which is, in effect, a first-of-its-kind implantable shock absorber for the knee. Both studies offer evidence that, in cases of chronic knee pain due to osteoarthritis (OA), this novel approach may be a viable alternative to traditional arthroplasty and provide improved pain relief and function.
An older study, from 2019, provided evidence that the implantable shock absorber system (brand named MISHA Knee System) reduced peak forces on the knee by over 30% with every step.
The recently reported Calypso Study (81 patients), provided evidence that when compared to high tibial osteotomy, an implantable knee shock absorber system (MISHA System) was superior at two years.
According to the manufacturer, Fremont, California-based Moximed, Inc., the system is indicated for patients who feel they are too young or active for knee replacement, or for those whose disease is not end-stage OA based on radiographic evidence.
In the Calypso Study, patients receiving the implantable shock absorbers reported an 85.6% composite success rate compared to high tibial osteotomy (65.5%). The system also demonstrated superiority on all secondary endpoints including the time to full weight bearing and improvement of Knee injury and Osteoarthritis Outcome Score-derived Western Ontario and McMaster Universities Arthritis Index pain and function scores at 3 and 24 months.
The Development History of the Knee Shock Absorber Implant System
In 2006 Anton Clifford, Ph.D., now CEO of the manufacturer of the MISHA brand implant, Moximed, was looking for a novel, non-end stage (TKA) treatment for patients suffering from medial knee OA. “I find that this is a very interesting disease because it has both biological and mechanical factors. OA was, and still is, a massive problem and there are no disease-modifying drugs on the horizon.”
Intrigued, Dr. Clifford attended the next meeting of the International Cartilage Regeneration and Joint Preservation Society, where he detected a substantial lack of treatments for OA patients who were not ready for joint replacement. “Either the disease isn’t ready, or the patients are not ready,” he noted to OTW. “The events that weekend, including the slide that said, ’think stress normalization,’ were, well, shocking.”
Playing With the “Unload the Joint” Concept
“As I listened to surgeons describe an osteotomy, I was struck by the simplicity of the goal, to unload the knee, compared to the complexity of the surgery for both surgeons and patients.”
So he sat back and reflected, “How else can we achieve the simple goal of unloading the knee?”
“We knew that the solution was to reduce stress on the joint, whether weight loss, a brace, a cane, etc.,” stated Dr. Clifford to OTW. “But we didn’t have a reliable method of delivering this solution. In 2008, Josh Makower, M.D., of Stanford and the ExploraMed incubator, and I developed the concept of an implantable shock absorber.”
“We spoke with clinicians from sports medicine, joint replacement, and trauma to test numerous concepts on the bench and in animal studies. Ultimately, the true test would be pain relief and patient acceptance.”
“The very first implantable shock absorber designs always provided pain relief to patients, but we had to learn more about how to develop a repeatable surgical procedure and how to implant a robust medical implant in a form factor that was acceptable to patients and surgeons.”
“The first patient, who was part of the OASYS Study in Australia, reported an immediate benefit. The day following surgery we went on rounds, and he voluntarily rose from his chair without assistance. Several surgeries and six weeks later we found that all of the patients were saying that their pain was either gone or massively reduced…so we knew that the therapeutic benefit was there.”
Placement Is OUTSIDE the Joint
While the implant is placed under the skin, says Dr. Clifford, it is alongside the joint. “The genius is in the kinematic spring platform that remains outside the joint—that’s what provides the shock absorption.”
And what provides the staying power? Evolution.
“Over time we have learned who is right (and who is not) for MISHA. Before surgery, the ‘right’ patients are often patients who have exhausted conservative treatments. Interestingly, this is a much larger group of people than those who are appropriate for joint replacement surgery.”
“We estimate that there are around 9 million patients in the U.S. with symptomatic mild to moderate radiographic knee OA, while 18 million Americans suffer from symptomatic knee OA of all severities. The anticipated indication for MISHA is OA of the medial knee in patients aged 65 or under and with a body mass index of less than 35.”
“Another improvement is that we have downsized the implant so that the profile is more anatomically friendly. In addition, due to the concern regarding metal-on-metal implants, we switched to a polymeric-based shock absorber. Even though we had experienced no issues with the metal device, we wanted no possible perception of metal-on-metal problems with MISHA.”
The Patients Who’ve Received a Shock Absorbing Knee Implant
According to Dr. Clifford, “The youngest patient I met who was diagnosed with knee OA was 19 years old and couldn’t walk a flight of stairs without stopping. At 15, she tore her ACL and then underwent numerous surgeries, eventually leading to the OA. She was 22 when she received the implant and MISHA truly gave her a new life to her, she’s now a success ICU nurse.”
“Another patient had mild radiographic OA but could not hike, an activity that was important for her because it was the main way she bonded with her daughter. Her doctor said that what she was experiencing was just part of life and that she should give up hiking and consider arthroplasty.”
“Sensitive to ageism (she was 56) and not satisfied with his idea, she did some research and found out about the implantable shock absorber. Three months after her surgery she sent us a photo of her hiking with her daughter in the Scottish Highlands.”
“The third patient had torn his anterior cruciate ligament (ACL) in high school and then got an infection after the ACL repair. By the age of 33, he couldn’t kick a soccer ball with his 5-year-old son. He tried stem cells, to no avail. He then met a surgeon in Boston who had implanted the implantable shock absorber…he is now fully mobile and pain-free almost six years later.”
When Conservative Treatment Fails, a New Alternative
Whether they specialize in joint replacement or sports medicine, says Dr. Clifford, surgeons are telling us they are frustrated because they are out of options for their patients. “Patients have tried braces, weight loss, acupuncture, etc. for many years. These patients are stuck because they are not ready to make a commitment to knee replacement, but there have been no other solutions. Every day, surgeons are meeting with these patients and feeling helpless to get them back on track.”
The Calypso Study
“The Calypso Study was designed as a noninferiority study to evaluate MISHA compared to high tibial osteotomy, a great procedure with good, reproducible outcomes,” said Dr. Clifford to OTW. “The fact that we have demonstrated superiority at two years is also notable because we did not go against conservative care or another treatment option where the results are variable.”
A surgeon who has participated in three studies of the implantable shock absorber, David R. Diduch, M.D., the A.F. Voshell Professor of Sports Medicine, Department of Sports Medicine at the University of Virginia, added, “These clinical findings are exciting because they demonstrate that the joint-preserving implantable shock absorber has the potential to provide significant benefits compared to high tibial osteotomy.”
“Over 90% of the patients receiving the MISHA Knee System experienced substantial, clinically meaningful pain relief and functional improvement. Without cutting bones or permanently modifying the joint, patients with knee OA may soon have a treatment option that allows them to return to their active lives.”
“We are now in FDA review,” stated Dr. Clifford, “and hope to have a decision regarding our De Novo application in the first half of the year. Then, because we want to reproduce the excellent clinical outcomes through a controlled launch, we will partner with a smaller number of surgeons, train them through our educational program, and provide clinical support for their first cases. Part of this extended education involves wet- and dry-lab training, animated videos, peer-to-peer webinars, and case observation.”
