In vivo tissue engineering of the knee joint meniscus.

Nowadays it is beyond any doubt that menisci are important components of the normal knee joint. Meniscectomy leads to abnormal high stresses on the articular cartilage in the affected compartment, which might lead to articular cartilage degeneration on the longer term. Therefore, we developed a repair technique for tears in the meniscus. We implanted a porous polymer scaffold in a created defect between the capsule and the tear in the non/vascularized zone of the meniscus. After 6 months the tear was healed however the articular cartilage degeneration was not prevented. This technique needs to be improved before clinical implementation may be expected. We developed a porous polymer implant with the shape of the native meniscus to replace the meniscus in case of extensive damage. We replaced the meniscus again in dogs and in the porous polymer new meniscus like tissue developed with fibrocartilage. These results were very promising, however, cartilage degeneration could not completely be prevented. Therefore the prostheses now are produced with a mold to create a smooth surface. Also, a new in vitro loading experiment was developed to evaluate the movements of the meniscus implant after implantation in a human cadaver knee joint and compare it with the movements of the native meniscus by means of rontgen stereophotogrammetric analysis (RSA). These experiments showed that the porous polymer implant mimicked the movements of the native meniscus, however, the excursions of the implant were less than those of the native meniscus. Obviously the gliding characteristics of implant needed to be improved. In the past two decades this meniscus research line has led to promising polymers for meniscal tissue replacements and highly developed analysis methods for the in-vivo and in vitro evaluation of these polymers. Eventually, we hope that this may lead clinical implementation of this technique on the long ter