Autologous chondrocyte implantation
The autologous chondrocyte transplantation (ACT), also referred to as autologous chondrocyte transplantation or autologous chondrocyte implantation is a method for the treatment of cartilage injuries. This autologous, ie autologous cartilage cells (chondrocytes ) can be removed, expanded in a nutrient solution and placed into the cartilage defect. The goal of ACT is to prevent the emergence of a (secondary) osteoarthritis. The method is still not for the treatment of an existing osteoarthritis.
Method
In a first operation, first cartilage cells are removed from a lightly loaded region of the articular cartilage. These will now be propagated in vitro in a nutrient solution. After about two weeks enough cartilage cells have been grown to implant these into the cartilage damage. For this, the cartilage damage must first be closed with a periosteal flap (or an artificial membrane ). Care is taken that it is waterproof sutured to the surrounding cartilage. Thereafter, the suspension of the approaching cultured cartilage cells can be injected under the periosteal flap. The present in the solution chondrocytes develop after some time hyaline cartilage and the existing damage is completely filled by the newly formed cartilage.
The procedure was developed in Gothenburg (Sweden) and first applied after successful testing in animal models at the beginning of the nineties in humans. The first results of this tissue engineering application were published in 1994. The process is now in Germany also by the professional associations (eg the German Society for Orthopaedics and Orthopaedic Surgery; DGOOC ) is recommended and assumed the costs since January 1, 2007, by the statutory health insurance under certain conditions.
From a medical point of view, in large area of cartilage lesions in the knee joint from a size of 4 cm ² ( for untreated cartilage damage) and from about 2.5 cm ² (for cartilage damage, which were previously treated with an alternative method without success) the indication for ACT.
Developments
Since the introduction of the method, the technology has been continuously developed. So initially was to cover the cartilage cell suspension, a bone flap of skin, which with a second - albeit small - was taken surgery is usually of the tibia leading edge was used. Later, this was a porcine ( = the pig -derived ) collagen membrane, which is not only the removal of the periosteum flap made redundant, but also the occurrence of an overgrowth of the graft, which was frequently observed in the use of bone flap of skin, makes rare. Finally, the matrix -associated transplantation procedures ( MACI ) was introduced, in which cartilage cells can be applied to a collagen carrier material in the laboratory just before transplantation or in the operating room. Although no scientific data concerning an improved efficiency of these products are available, such developments have led to a simpler application and application with a shortening of the operation time.
Other developments related to the isolation of chondrocytes. So chondrocytes are offered by some companies already, which are grown without the patient's own serum. This leads to a standardization of cell culture conditions and makes blood sampling the patients for the cultivation of cartilage cells unnecessary. Other manufacturers are working to select cartilage cells with particularly high cartilage synthesis performance. Improved therapeutic results by this ACT procedures are not yet occupied.
The matrix substances used during the development of the ACT (eg 3 -D collagen fleeces ) are recently introduced and cell- free ( AMIC ). To the method of the basic defect is broken with an awl and excited to bleeding, which he dismisses abundant endogenous cellular material with the blood. This blood -cell mixture is then collected in the coated nonwovens and encouraged there to differentiate into cartilage -like cells. It is a modification of the successful small cartilage defects microfracture technique. Advantage is the saving of the critical and costly cell culture process. Thus, the method can also be carried out at short notice and no preparation for incidental findings during arthroscopy.
Treatment success
The results of treatment of the ACT method are dependent on the site of the defect, the defect configuration, and the suitability of the patient between 80 and 90%. Meanwhile, there are also individual studies reporting on satisfactory long -term results. Contrary to the application of the knee, where the therapy with autologous cartilage cells usually will be reimbursed by both private as well as public health insurance companies in Germany, make applications to other joints so far represents the exception