Cartilage tissue engineering: current limitations and solutions.

Articular cartilage repair remains one of the most intensely studied orthopaedic topics. To date the field of tissue engineering has ushered in new methodologies for the treatment of cartilage defects. The authors' 10-year experience using principles of tissue engineering applied to resurfacing of cartilage defects is reported. Which cell type to use, chondrocytes versus chondroprogenitor cells, and their inherent advantages and disadvantages are discussed. Chondrocytes initially were used as the preferred cell type but were shown to have long term disadvantages in models used by the authors. Mesenchymal stem cells can be used effectively to overcome the limitations experienced with the use of differentiated chondrocytes. The use of mesenchymal stem cells as platforms for retroviral transduction of genes useful in cartilage repair introduces the concept of gene modified tissue engineering. The fundamental conditions for promoting and conducting a viable cartilage repair tissue, regardless of which cell type is used, also were studied. Placement of a synthetic porous biodegradable polymer scaffold was found to be a requirement for achieving an organized repair capable of functionally resurfacing a cartilage defect. A new modular device for intraarticular fixation of various graft composites has been developed. This new cartilage repair device is composed of bioabsorbable polymers and is capable of being delivered by the arthroscope.