AUTOLOGOUS MATRIX INDUCED CHONDROGENESIS (AMIC®) FOR FOCAL CHONDRAL DEFECTS OF THE KNEE – FIRST RESULTS

Abstract

Introduction: Bone-marrow stimulating techniques like microfracturing for focal chondral defects of the knee joint are widespread utilizing mesenchymal stem cells (MSC) for an autogenous reparation process. Microfracturing shows good results for smaller defects up to 2cm² while larger defects tend to an early secondary degeneration. Autologous Matrix Induced Chondrogenesis (AMIC®) combines microfracturing with application of a porcine collagen type-I/III bilayer matrix to host the MSC and to stabilize the blood clot.

Methods: 32 patients (25m, 7f, mean age 37.4y (18–52y)) with 35 focal chondral defects of the knee joint (ICRS III–IV°) of the condyle, trochlea and/or patella were treated by standardized microfracturing and application of a collagen matrix (Geistlich Biomaterials, Wolhusen, Switzerland). The outcome was evaluated prospectively by clinical scores and MRI with a follow-up of 6 to 24 months. The mean defect size was 3.86 cm² (1.0 – 6.8 cm²). 22 patients (68%) had at least one operation (1–8) on the knee before. 9 defects were caused by trauma. All 7 patients with osteochondritis dissecans had an autologous bone grafting. In 5 patients an ACL stabilization was performed simultaneously.

Results: All patients considered their knee as abnormal (ICRS III° (70%)) or severely abnormal (ICRS IV° (30%)) preoperatively according to the ICRS functional status. The Cincinnati-Score improved from 52.9 to 81.1 points while the Lysholm-Score rose from 60.4 to 85.9 points (each p< 0.001). Pain decreased significantly from 6.1 to 2.2 (10=max.) on the visual analogue scale. 4 biopsies (4–21 months) revealed reasonable results with regard to surface formation, filling and integration in the Brittberg score (∅10.25 pts., 12 pts.=max.) The MRI follow-ups showed an adequate filling of the defect, no prolonged effusion occured.

Conclusion: Microfracturing in combination with a collagen matrix (AMIC®) is a minimal invasive, effective technique for the repair of focal cartilage defects of the knee joint. Not using cultured chondrocytes it can be performed cost-effectively as a single-step procedure. Both primary and secondary treatments are possible. The first results concerning clinical functional improvement, pain reduction and patients’ satisfaction as well as defect filling in MRI are promising.