How may an artificial meniscal implant improve pain and functional outcomes?
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An innovative option
Innovation is required in areas of unmet clinical need, and this can be no truer than in the symptomatic post-meniscectomized knee.
While many patients have improvements after meniscectomy, resection can alter joint biomechanics and overload articular cartilage. Long-term, 50% of meniscectomized patients develop symptomatic osteoarthritis due to increased contact pressures, which then leads to pain, recurrent effusions and cartilage damage. While nonoperative management can help, surgical procedures, such as meniscus transplant and cartilage restoration, generally work better in younger knees without arthritis. In painful post-meniscectomy knees with early arthritis, options remain limited.
Therefore, synthetic meniscal implants have been developed to improve joint biomechanics, alleviate pain and potentially minimize degenerative changes. The NUsurface (Active Implants) is an artificial meniscus implant composed of reinforced polycarbonate-urethane. Early patient outcomes in the United States suggest that significant improvements in pain and function can be achieved compared to nonoperative management. Data from Europe also show that the implant can improve kinematics after meniscectomy, which likely leads to improved contact pressures and reduced overload of cartilage. For our patients, this replication of meniscus function can improve pain, increase function and hopefully delay arthritis progression. While the results are encouraging, the FDA continues to review the data, and this implant is not currently available. In my opinion, we need to follow the results carefully, but I remain cautiously optimistic that this may be an innovative option to improve pain and function in select patients following removal of a damaged meniscus.
- References:
- De Coninck T, et al. Clin Biomech (Bristol, Avon). 2014;doi:10.1016/j.clinbiomech.2014.07.001.
- Englund M, et al. Arthritis Rheum. 2003;doi:10.1002/art.11088.
- Zaslav KR, et al. Knee Surg Sports Traumatol Arthrosc. 2021;doi:10.1007/s00167-021-06573-0.
Aaron J. Krych, MD, is co-chair in the division of sports medicine and professor at Mayo Clinic Orthopedic Surgery in Rochester, Minnesota.
Promising for ‘challenging patient population’
Artificial meniscus implantation is an intriguing option for patients with symptomatic meniscus deficiency after partial meniscectomy. Classically, younger and active patients without advanced degenerative changes are reasonable candidates for meniscus allograft transplantation. Older patients with more advanced degenerative change have been shown to benefit from knee arthroplasty. However, there is a void in the treatment algorithm for the growing “tweener” patient population. This gap is particularly notable for the “middle-aged” patients with meniscus deficiency who are not great candidates for osteotomy or cartilage restoration (ie, borderline or no malalignment, inability to comply with rehabilitation, bipolar chondrosis and mild/moderate joint narrowing, elevated BMI, etc.).
Results from the MERCURY study group showed that the NUsurface artificial meniscus implant has promise in improving pain and function in this challenging patient population. Their data demonstrated a significant improvement in KOOS pain and function scores out to 24 months. Data presented at the American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North American Combined Meeting showed there may also be a chondroprotective effect following implantation.
Compared with other surgical options for meniscus deficiency, artificial meniscus implantation has the benefit of being “off the shelf” and readily available, technically easier than meniscus allograft transplantation and with less rigid rehabilitation protocols. In contrast to rehabilitation guidelines after osteotomy and meniscus transplants, these patients are encouraged to progress early to normal weight-bearing and full range of motion. This may allow for more rapid restoration of normal daily life activities and improvement in quality of life.
As with any innovative procedure, longer-term data are necessary to ensure the safety and efficacy of the artificial meniscus implant. It is exciting that evolving indications and novel techniques continue to shift the treatment algorithm for symptomatic meniscus deficiency.
Seth L. Sherman, MD, is an associate professor of orthopedic surgery and sports medicine fellowship director at Stanford University, and Douglas W. Bartels, MD, is an orthopedic sports medicine fellow at Stanford University.
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