%0 Journal Article %T Challenging for cartilage repair %A Mitsuo Ochi %J Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology %D 2009 %I BioMed Central %R 10.1186/1758-2555-1-13 %X The next contribution to our variety of cartilage repair methods, was the minimally invasive approach using a tissue-engineered chondral plug. New scaffolds, consisting of a type I collagen sponge and surrounding PLLA mesh [4] or interconnected porous calcium hydroxyapatite ceramic [5], were demonstrated to comprise an effective minimally invasive approach.The bone marrow stimulating technique under arthroscopy is another minimally invasive technique which is a well accepted procedure for large osteochondral defects. However, there are two potential weak points when inducing hyaline cartilage. One is a compressive overload on the drilled or microfractured area in the early stage after surgery. In order to reduce this early stage overload, we have developed external fixators which allow almost full ROM with joint distraction for clinical cases, based on an animal study [6]. This apparatus has been successfully used for 12 patients, each with a large cartilage defect [7]. Another weak point is a small number of mesenchymal stem cells obtained from drilled holes which are used for chondrogenesis. An injection of cultured MSCs into the joint has been demonstrated to be effective for cartilage defects in rats [8]. The combined approach should be adopted for large defects in the near future.However, the most optimal procedure for the repair cartilage defects is simply an injection of cytokines or growth factors and cells. Our planned novel approach for the future is to use a cell delivery system using an external magnetic field. Our procedure involves using autologous bone marrow mesenchymal stem cells attached to small-sized magnetic beads and an external magnetic field. For successful cartilage repair, it is ideal to effectively attract injected mesenchymal stem cells to a desired portion in the knee joint (osteochondral defect) using an external magnet force [9]. We believe that this novel system is also effective in the treatment of brain or spinal cord injury and for %U http://www.smarttjournal.com/content/1/1/13