ACTIfit™: 38% Full Resorption at 8 Years in a Cohort of 18 Cases.

BACKGROUND: Preserving meniscal tissue is a major priority in young, physically active patients. Extensive meniscal defects may result in exercise pain and premature osteoarthritis. ACTIfit™ is a synthetic meniscal substitute that may improve short-term functional scores via biological integration with meniscal tissue regeneration. However, long-term data on the lifespan and chondroprotective effect of this newly formed tissue are lacking. The primary objective of this study was to assess the biological integration of ACTIfit™ based on magnetic resonance imaging (MRI) findings. The secondary objective was to evaluate long-term clinical outcomes.

HYPOTHESIS: The ACTIfit™ meniscal substitute undergoes biological integration over time, suggesting chondroprotective potential.

MATERIALS AND METHODS: A 2014 report by Baynat et al. described the 2-year clinical and radiological outcomes of 18 patients after ACTIfit™ implantation at the Clermont-Tonnerre military teaching hospital (Brest, France). The patients had chronic knee pain of at least 6 months' duration after failure of primary meniscal surgery with segmental meniscal defects. Mean age was 34.0±7.9 years. A concomitant procedure was performed in 13 (60%) patients, including osteotomy in 8 and ligament reconstruction in 5. For the current study, the clinical and radiological follow-up was at least 8 years. Assessments were with the Genovese grading scale for substitute morphology on MRI scans, International Cartilage Research Society (ICRS) score for osteoarthritis progression, and Lysholm score for clinical outcome. Failure was defined as total substitute resorption (Genovese morphology grade 1) or revision surgery with implant removal, conversion to meniscus allografting, or arthroplasty.

RESULTS: MRI scans were available for 12 (66%) patients. The reason for not having long-term MRI scans was surgery for substitute removal or arthroplasty in 3 of the remaining 6 patients. Complete implant resorption (Genovese grade 1) was noted in 7/12 (58%) patients and osteoarthritis progression to ICRS grade 3 in 4/12 (33%) patients. At last follow-up, the mean Lysholm score was significantly improved vs. baseline (79±15 vs. 55±13, p=0.005).

CONCLUSION: The frequency of complete ACTIfit™ resorption 8 years after implantation was high. This finding argues against ability of this substitute to induce the regeneration of durable meniscal tissue with a chondroprotective effect. The clinical outcome score was significantly improved at last follow-up. However, no conclusions can be drawn regarding the effectiveness of ACTIfit™ given the high frequency of concomitant surgical procedures.

LEVEL OF EVIDENCE: IV, retrospective observational cohort.