Aim: Matrix-guided autologous chondrocyte implantation (MACI) was compared with microfracture (MFX) to demonstrate the reconstitution of cartilage over a two-year period using the morphological capabilities of MRI.
Patients and methods: 27 patients (9 females and 18 males, mean age 33 years) underwent MACI on the knee joint. The defects originated from trauma (15 cases), osteochondritis dissecans (8 cases) and chronic repetitive trauma (4 cases) and were localized at the condyles (24 cases) or patella (3 cases). All patients were examined postoperatively after 1, 3, 6, 12 and 24 months with a 1,5 T unit (Gyroscan, Philips) using proton- and T2w spinecho and T1w fatsuppressed 3D gradientecho sequences. We measured the signal intensities of the implant and neighbouring cartilage to calculate the contrast-to-noise ratio (CNR), and the thickness of cartilage and implant layers to define the defect filling rate. Finally, partial and complete remission was defined on MRI and compared with clinical data and morphology on MRI. Additionally, 7 patients were treated with MFX and, subsequently examined on MRI with the same protocol.
Results: After MACI, MRI showed a partial but no complete equilibration of signal intensities of implant and adjacent cartilage over the 1 and 2 year follow-up periods which was shown by reduction of CNR from 21 to 10 on 3D-GE and from 26 to 9 on T2w SE sequences. Continuous growth of the implants resulted in an increased filling of the defects starting at 40% after 0.5 year to 85% after 1 or 2 years. Complete remission was found on MRI in 17/27 cases, and remission rate was influenced by etiology of cartilage defect but not by age and gender of patients or size and location of defects. The Lysholm-Gillquist score improved from 49.7 to 97.3. After MFX equilibration of signal intensities and growth of the regenerating fibrous cartilage was less pronounced and complete remission was found in only 2/7 cases. In addition, the clinical score improved from 45.5 to 74.2.
Conclusion: Direct imaging of cartilage with MRI and assessment of clinical scores allowed improved documentation of the outcome after MACI and MFX. MRI showed that MACI is superior to MFX concerning rate of complete remissions and filling of the defect with regenerating tissue. Clinical examinations showed better scores for MACI than for MFX.