Operative Treatment of Knee Cartilage Injuries: A Review of the Current Literature on Non-Cell-Based and Cell-Based Therapies.

Aims: Cartilage is frequently damaged through injury and disease but shows little or no capacity for repair. Injuries that extend to the subchondral level show some capacity for repair due to the release of bone marrow derived mesenchymal stem cells. Focal articular cartilage defects are challenging clinical problems that may progress to more generalised lesions. We reviewed the literature to analyse the results of available noncell- based and cell-based strategies for the repair of articular cartilage defects in the knee. Study design: Review Article Place and Duration of Study: University College London Institute of Orthopaedics and Musculoskeletal Sciences, Royal National Orthopaedic Hospital, Stanmore, Middlesex, HA7 4LP, United Kingdom Methodology: We reviewed the literature to identify studies on the use of non-cellbased and cell-based strategies for the repair of articular cartilage defects in the knee. Results: Repair techniques that do not utilise cell therapy include bone marrow stimulating techniques such as microfracture that is effective in small well-contained lesions and has the advantages of being performed arthroscopically as a single stage and cheaper costs compared to cell-based therapies. It also associated with no donor site morbidity unlike mosaicplasty, and perichondrial or periosteal grafting. The evidence suggests that none of the techniques described above consistently produce durable results. There are encouraging mid-term results with Autologous Matrix Induced Chondrogenesis (AMIC) procedures in small number of patients. Although microfracture is appropriate for smaller cartilage defects, Autologous Chondrocyte Implantation (ACI) and Matrix-carried Autologous Chondrocyte Implantation (MACI), as well as other cell carrier systems, are currently used to treat larger full thickness chondral defects in the knee. Although the results are fairly similar, MACI and procedures using other cell carrier systems are amenable to be performed arthroscopically or through a more limited approach. There are a small number of studies using mesenchymal stem cells with promising early results bur further in vitro and in vivo studies are needed before this treatment becomes more routinely available. Conclusion: Focal articular cartilage defects are challenging clinical problems that progress to more generalised lesions. Only cartilage injuries that extend to the subchondral level show some capacity for repair due to the release of bone marrow derived mesenchymal stem cells. Bone marrow stimulating techniques such as microfracture are effective in small well-contained lesions (<2cm2) and have the advantages of being performed arthroscopically as a single stage and cheaper costs compared to cell-based therapies. Mosaicplasty, and perichondrial or periosteal grafting are associated with donor site morbidity. Longer term studies on AMIC may help define the role for this procedure. The best form of non-cell-based treatment for focal articular cartilage defects in the long term is still unknown. ACI and MACI, as well as other cell carrier systems, are currently used in clinical practice to treat larger full thickness chondral defects in the knee. There are a small number of studies using mesenchymal stem cells and further in vitro and in vivo studies are needed before this treatment is optimised.