Treatment of deep articular cartilage defects of knee and ankle with Matrix-induced Autologous Chondrocyte Implantation (MACI®): early results.

INTRODUCTION. Since 1999 the MACI® (Matrix-induced Autologous Chondrocyte Implantation) technique have been used for the treatment of deep articular cartilage defects at the authors' institution. This method requires seeding of autologous chondrocytes on a type I-III collagene membrane, after their arthroscopic harvesting from the knee and subsequent in vitro expansion of the cellular population using autologous serum. The seeded membrane is implanted in the chondral defect using exclusively fibrin glue, through a limited exposure joint approach. MATERIALS AND METHODS. Membrane structure and its cellular population were investigated by light microscopy, immunohistochemistry, SEM, and electrophoresis (SDS PAGE 7%) before implantation. There was evidence of chondroblasts and type II collagen inside the seeded membrane. The MACI® technique was used for the treatment of 24 patients (17 males and 7 females), with an average age of 35 years (range, 17 to 52 years). As isolated lesions, the sites of the defects were the following: 11 medial femoral condyle, 3 lateral femoral condyle, 1 femoral trochlea, 1 patella, 2 lateral tibial plate, 3 talar dome. As combined lesions, there were 1 medial femoral condyle + patella, 1 lateral tibial plate + patella, 1 kissing lesion in the ankle. The average size of the defects was 3.5 cm2 (range, 2 to 4.5 cm2). The treatment of 2 chondral defects in the lateral tibial plate was performed arthroscopically. MRIs (FSE FAT SAT T2, GE T2, SE T1) were taken before the operation as well as at 6, 12 and 24 months post-operatively. RESULTS. The average follow-up was 11.1 months (range, 3 to 25 months). No complications were observed in the postoperative period. Among the eighteen patients with a minimum follow-up of 6 months (15 knees, 3 ankles), 17 showed an improvement in the clinical and functional status after the operation while the patient with a kissing lesion of the ankle did not improve from his preoperative status. At the latest follow up, the ICRS score was normal in all the knees; modified Cincinnati knee score averaged 8.25/10 points (range, 7-10) from preoperative 3.2/10 points (range, 2-4); Lysholm II and Tegner scales averaged respectively 92.5/100 and 6/10 (range, 81-100 and 5-8) from preoperative 54.8/100 and 2/10 (range, 18-67 and 2-3). The AOFAS (American Orthopaedic Foot and Ankle Society) score was used for the evaluation of the ankles and averaged 72/100 (range, 40-100) from preoperative 41.3/100 (range, 23-63). In all the studied knees, MRIs showed filling of the defect with decreased subchondral bone edema; at 6 months hyaline-like cartilage was evident at the site of implantation; remodelling of the implant persisted for 12 months after the operation. In two ankles, healing of the defects was evident at MRI, while the failed case did not show any cartilage formation. A second arthroscopic look was performed in 1 knee and 1 ankle: recovery of the articular surface with wave-like hyaline tissue was demonstrated. DISCUSSION. There are technical limits related to the traditional ACI technique: a non-homogeneous distribution of chondrocytes in the recipient site and the risk of leaking out in case of inadequate sealing of the periosteal patch. Moreover, complications related to the use of the periosteal patch and to the necessity of a wide exposure of the joint have been reported. The MACI® technique is a tissue engineering technique in which the principle of autologous cell culture is preserved; a tridimensional collagen I-III scaffold is used for improving the structural and biological properties of the implant. The collagen membrane offers some advantages from the surgical point of view, too. It can be applied using exclusively fibrin glue through limited exposures of the affected joints, allowing the surgeon to treat sites in which suturing flaps to the cartilage is almost impossible (posterior femoral condyles, ankle). The surgical procedure is quite simple, requiring short operating times, and has also been performed arthroscopically by the authors. The early results of MACI® are very promising, but the limited number of patients and the short follow up do not allow to draw conclusions on the long-term effectiveness of this method.