Use of synthetic meniscal implant maintains cartilage, is linked with reduced pain
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NASHVILLE, Tenn. — An artificial meniscal implant helped maintain articular knee cartilage in patients with 2-year minimum follow-up vs. nonsurgical treatment and was linked with reduced pain starting at 6 months, according to a presenter.
Wayne K. Gersoff, MD, who presented the findings at the American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America Combined Meeting, here, said the data for the NUsurface medial meniscus implant (Active Implants) included results mainly in men aged 50 years, in patients with grade 2 or 3 knee cartilage, as well as in some patients who underwent multiple previous meniscal procedures.
Used after partial meniscectomy
The implant is intended for patients with persistent or recurrent pain following partial arthroscopic meniscectomy.
Gersoff told Healio Orthopedics in an interview, “The biggest thing to me, and I think to all the people involved in this study, is that this fills such a void in our treatment bag.”
At the meeting, Gersoff discussed the Verifying the Effectiveness of the NUsurface System (VENUS) study completed in June 2020, a randomized controlled trial of 61 patients who received the implant vs. 66 control patients, and the SUN study, a single-arm study in which 115 patients were implanted with the device.
Patients in both U.S. trials were poolable as the MERCURY study, which included 30 U.S. surgeons at 22 clinical sites, according to the abstract.
KOOS scores for pain, function assessment
Patients eligible for these studies had persistent knee pain and a minimum of one previous partial meniscectomy performed at least 6 months prior to entry into the trial. Patients in the implant group were followed up at 1 month and 6 months, 1 year and 2 years postoperatively. The KOOS was used to assess patient-reported knee pain, function and quality of life in both groups.
“The baseline KOOS score in pain for the SUN trial was 53.4 ± 2.5. In the VENUS trial, the baseline was 52.1 ± 2.8,” Gersoff told Healio Orthopedics.
Concerning baseline KOOS scores for overall function, he said these were 46.6 ± 2.6 and 47.6 ± 3.2 in the SUN and VENUS trials, respectively.
The MERCURY study results “showed that patients who received the NUsurface implant experienced statistically superior pain relief as early as 6 months that continued through the 2-year study period, compared to patients receiving non-surgical care alone,” Gersoff said in a press release.
In the study, 84% of patients treated with the synthetic meniscal implant experienced a 10-point improvement from baseline in KOOS pain, which is considered the minimum clinically relevant improvement in pain and function, according to the release.
In addition, 69% of patients who received the implant met the 20-point improvement threshold vs. 35% of controls, based on the abstract.
Device under FDA review
“What we used as a guideline was to have at least a 20-point improvement would be kind of the most clinically meaningful improvement,” Gersoff told Healio Orthopedics.
“I think the only important statistic is that over the course of 2 years, when we evaluated these data, that clinically significant difference — [the fact that] improvement in the KOOS score was maintained — I think was fairly significant,” he said.
After the knee is prepared arthroscopically to ensure no significant cartilage defects exist and the remnant of the medial meniscus is sufficiently trimmed, implantation of the polymeric implant is done through a mini-arthrotomy.
The NUsurface implant is under review by the FDA.
“The endpoint of the overall study is going to be 5 years,” Gersoff said.
Perspective
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There remains an important clinical need to address meniscal attrition and resultant symptomatic post-meniscectomy syndrome with overload in patients who may fail nonoperative treatment. At the recent 2021 Combined AOSSM and AANA meeting in Nashville, 2-year aggregate prospective outcome data were presented on a novel interpositional meniscus replacement prosthesis. This innovative NUsurface device was studied as part of a larger combined trial compiling results from two U.S. multicenter clinical trials (30 surgeons at 23 sites) including a prospective series of 115 patients and a randomized controlled trial of 61 patients and 66 control patients.
The 2-year outcomes using KOOS pain and overall score assessments revealed clinically meaningful improvements in select patients. MRI imaging and arthroscopic evaluation found that chondral breakdown and degeneration did not occur in patients who received NUsurface as compared with controls.
Over the course of follow-up, 10% of patients required device removal and 21% underwent device exchange replacement, likely attributed to implant instability. These adverse events remain a concern in light of past negative experiences with metallic spacers and Teflon prosthetics. More recent technique refinements have been introduced including more precise preoperative analysis of intercondylar notch and condylar morphology, sculpting a greater residual meniscal stump and device materials enhancement, and these advances may serve to mitigate potential complications.
Continued focus though is needed to best define the optimal patients who may benefit from the procedure (malalignment limitations, ipsilateral chondral wear thresholds and counseling the expectations of higher-impact active patients). The future relevance and benefit of NUsurface as a valuable addition to our treatment armamentarium is promising but many would agree that our approach should be cautiously optimistic as the FDA continues to review the data and our European colleagues continue to report on their clinical experience and longer-term outcomes.
Perspective
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A well-done comparative study demonstrating that an artificial implant in a meniscectomized knee is better than no treatment all. It raises hope that people with knee pain may be able to return to activities without further damage.
The concerns, though, are significant since the history of orthopedics demonstrates that no artificial material has ever been placed against normal articular cartilage without eventually causing degeneration and, if this implant were to be placed against damaged cartilage, the damage to the knee and to the implant naturally would be expected to be accelerated. So, while the 2-year data are encouraging, nothing ruins results like long-term follow-up.
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Gersoff WK, et al. Paper 15. Presented at: American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America Combined Meeting; July 7-11, 2021; Nashville, Tennessee.
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