Postoperative Evaluation of the Knee after Autologous Chondrocyte Implantation: What Radiologists Need to Know

Articular cartilage lesions occur commonly. Cartilage is relatively avascular and is unable to self-repair. A chondral lesion may become symptomatic. It may lead to osteoarthritis and increased morbidity. The aim of cartilage repair is to restore hyaline cartilage. There are many types of cartilage repair surgery, most of which result in fibrocartilage repair tissue that is suboptimal. Autologous chondrocyte implantation has been shown to produce hyaline-type repair tissue. Magnetic resonance (MR) imaging is performed preoperatively to define the ulcer and postoperatively to evaluate the technical success of implantation and the state of cartilage healing and to identify potential complications. Features of the autologous chondrocyte implantation graft that are assessed include the degree of filling by repair tissue, its integration with native cartilage and subchondral bone, the character of the graft substance and surface, and the underlying bone. MR arthrography is superior to unenhanced MR imaging because intraarticular contrast material allows the recipient site to be physically separated from adjacent structures so that it can be characterized more accurately. MR imaging and arthroscopy are complementary investigations in the follow-up of an autologous chondrocyte implantation in the knee. The appearance of the knee after autologous chondrocyte implantation varies among individuals and according to the time-course of healing. Familiarity with the surgical procedure and imaging appearance is essential for an accurate postsurgical assessment.