Clinical results and MRI findings after Collagen Meniscus Implant CMI

Aim: To report clinical results and MRI findings observed in 50 patients, who underwent collagen meniscus implant (CMI) between March 2001 and June 2003. Methods and materials: Fifty patients, who were affected by irreparable meniscal lesions or had previously undergone partial medial meniscectomy, were arthroscopically treated with CMI, a tissue engineering technique designed to promote meniscal regeneration. Average age at the time of surgery was 38.4 years. The average size of the lesion/defect was 4.3 cm. Additional procedures included 16 ACL reconstruction, 8 high tibial osteotomy and 2 autologous chondrocyte implantation. All knees were evaluated according to the Lysholm II and Tegner activity scales. MRI (FSE Fat-Sat T2, SE T1, GRE T2) was performed 6, 12 and 24 months postoperatively. Six arthroscopic examinations of the implant were performed at different times (6 to 16 months postoperatively). Results: Postoperative complications included saphenus neuroapraxia in 3 patients and CMI rupture in 1 patient who presented persistent knee swelling. Follow up averaged 15.7 months, with a minimum of 6 months. At most recent evaluation, 46 patients showed improvement of the clinical scores. MRI was useful to document healing of CMI to the meniscal stump and parameniscus, followed by tissue invasion and ingrowth inside the scaffold. A progression toward a more homogeneous signal was detected in the implants with a two-year follow-up. At second arthroscopic look, free fragments of the implant were observed in the knee of the patient, who suffered CMI rupture. In another patient, partial resorption of CMI was observed at the posterior horn. The remaining four arthroscopic examinations demonstrated regeneration of meniscal-like tissue with healing of the implants to the parameniscus and to the residual meniscal stump; good consistency and stability was detected by probing. Conclusions: Clinical results achieved with CMI are promising, once correct indications are respected and patients are compliant with rehabilitation program. MRI demonstrated to be an effective tool for monitoring the evolution of the implant and showed good correlation with clinical outcomes and arthroscopic findings at follow up.