Autologous Chondrocyte Implantation (ACI) for Knee Cartilage Defects

* Autologous chondrocyte implantation (ACI) was first developed in the late 1980s for the treatment of articular cartilage defects in the knee. The first generation of ACI utilized a periosteal patch to contain the cultured chondrocyte solution within the defect. Because of issues with periosteal graft hypertrophy, ACI with use of a collagen membrane patch (second-generation ACI) was developed. Finally, the application of chondrocytes within a matrix (third-generation ACI) was created to improve cell delivery, to allow for minimally invasive implantation, to better replicate normal cartilage architecture, and to accelerate patient rehabilitation. As of December 2016, only 1 third-generation ACI product (matrix-induced autologous chondrocyte implantation, or MACI) has been cleared for marketing by the U.S. Food and Drug Administration (FDA) and is available in the United States. * ACI (regardless of generation) is effective for the treatment of high-grade tibiofemoral cartilage defects. However, issues with coronal alignment, ligament laxity/instability, and meniscal deficiency must be addressed or the outcomes following ACI will be poor. * Because of the extended time that is required for graft maturation, special consideration must be given to return-to-play protocols as athletes can regain strength and neuromuscular coordination well before the graft has sufficiently matured.