Isabel Guillén-Vicente, Juan Manuel López-Alcorocho, Elena Rodríguez-Iñigo, Marta Guillén-Vicente, Tomás F. Fernández-Jaén, Jesús Manuel Cortés, Steve Abelow, and Pedro Guillén-García. High-Density Autologous Chondrocyte Implantation (HD-ACI) in patients with bilateral knee chondral defects. Journal of Cartilage & Joint Preservation TM 1 (2021) 100013