Matrix-induced autologous chondrocyte implantation (MACI): high-resolution-MRI study at medium term follow-up

Objective: Evaluation of articular cartilage repair after Matrix-induced autologous chondrocyte implantation (MACI) by high-resolution standard MRI and arthro-MRI. Material and methods: Thirty patients with a minimum of 5 years follow-up (mean 67 months, range 60 to 84 months) were evaluated with a high-resolution standard MRI and arthro-MRI (1.5-T unit, using GE, T2*, spin-echo T1, FatSat fast spin-echo DP and T2-weighted sequences). The results were classified according to the grading system described by Marlovits that considered the degree of defect repair in width and length, surface, structure and signal intensity of the repair tissue, and status of the subchondral lamina and bone. A score higher than 50 points (max: 100 points) was assumed as a successful repair. The results were then compared to the most common clinical rating scales (ICRS, Lysholm II, Tegner, Cincinnati) to evaluate the possible correspondence. Results: In 18 patients we observed a complete filling of the defect. Implant integration was evident in 17 cases. Intact surface was found in 18 cases. Arthro-MRI revealed 7 cases of superficial fibrillations and fissures. In 23 implants the signal was isointense and similar to native cartilage. Oedema or cysts were individuated in 9 cases. In 23 patients we recorded an overall value higher than 50 points. Four cases were associated with a clinical failure while 3 cases were not associated. Conclusions: High-resolution MRI provides a useful tool for studying articular cartilage repair tissue. Arthro-MRI can improve the sensibility of the study to detect any clefts between native cartilage and regenerated tissue and any superficial implant fibrillations. It has to be demonstrated if MRI can be predictive of future clinical failures. Only an higher number of cases and long term studies will allow to confirm these observations.