Matrix-assisted autologous chondrocyte transplantation (MACT)
Novocart 3D (Fa. Aesculap)
The matrix of the Novocart 3D consists of a covering membrane and a sponge with a columnar arranged, interconnected pores of a defined size. The pure collagen type I used inside the membrane is derived from the heart sac of oxen. Via a lyophilization process the membrane is firmly connected to the sponge, which consists of collagen type I as well and which was isolated from the rawhide. Via a special preparation process the components are cleaned from non-collagen parts like for example enzymes, fats and non-collagen proteins. The columnar arranged pores of the sponge encourage the stem cell ingrowth into the cartilage defect and thus improve the chances of healing for the resulting cartilage regenerate. The membrane particularly tear-resistant and stable against wetness both prevents the intrusion of unspecific connective tissue cells into the defect area as well as the untargeted dissemination of mesenchymal stem cells beyond the preparated area. Due to its mechanical stability the sponge and the cells inside are additionally protected from shear stress.
First of all one or two cartilage-bone cylinders (biopsies) are extracted with special hollow cutting tools by the company TETEC R AG (Reutlingen Germany). Therefore the hollow cutting tool with a diameter of 4mm is inserted arthroscopically via a second access. Approx. 7-8 mm long cartilage-bone cylinders are extracted from outside the load zone. In case of large defects over 10cm three cartilage-bone cylinders have to be extracted in order to collect enough cartilage cells (chondrocytes). The extracted cylinders are dispatched in small transportation bottles containing sterile nutrient solution.
In the laboratories oft he TETEC R AG the chondrocytes are isolated mechanically and enzymatically from the biopsies. The delivery of the transplant takes place on a polyethylene plate with a metal frame.
After 4 to 6 weeks the MACT-constructs are implanted into the defect area via an open arthrotomy. After the cleansing of the cartilage defect down to the bone the cartilage defect is dissected with the punch, in order to make sure, that the implant fits perfectly into the cartilage defect.
- Chondrospheres (Fa. Codon)
With the latest, third generation of the autologous cartilage cell transplantation (ACT), the so-called spheroids, it has recently become possible to perform the re-insertion of the cultivated, endogenous cartilage cells completely arthroscopically. Therefore the cartilage cells are first of all shaped as three dimensional pellets (spheroids). Every single spheroid contains approx. 200.000 cartilage cells, while each of them has only a size of 0,5 – 0,8 mm.
Another special feature of this procedure is, that the multiplication of the endogenous cartilage cells and the production of the 3D-spheroids are exclusively performed with the patient’s own blood serum. This way foreign proteins and side effects like for example incompatibility and rejection reaction are avoided. As soon as the spheroids contact with the prepared cartilage defect bearing during the arthroscopic re-implantation, their compound molecules (adhesion proteins) can stick mechanically stable to the bone after 10 minutes. Hence an additional bearing is unnecessary in most cases.
Cartilage defects on the back of the kneecap (patellar) can be performed arthroscopically, too. Therefore the patient is placed on his belly during the surgery.
After the cleansing of the cartilage defect the spheroids are evenly inserted into the cartilage defect and spread via applicators. Hereinafter the transplanted cartilage cells grow into the cartilage defect until it is completely filled out. The advantage of this technique is, that the cartilage defects can be treated fully arthroscopically in many cases.