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

Abstract

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.

Is Magnetic Resonance Imaging Reliable in Predicting Clinical Outcome After Articular Cartilage Repair of the Knee?

“…This is underlined by the controversial relationship between clinical and radiological outcome found in the literature. 5,24,26,37,45,55 As such, surgeons mainly rely on expertise when interpreting an MRI scan after cartilage repair. 9 This systematic review sought to evaluate the correlation between MRI and clinical outcome after cartilage repair to elucidate the inconsistency in the literature and to identify parameters that are most important in determining clinical outcome.…”

Imaging of the Postoperative Knee

“…Incomplete filling of the chondral defect or an irregular surface of the graft may lead to suboptimal clinical results. 81,82 Graft hypertrophy is defined by chondral graft that is thicker than the adjacent native hyaline cartilage. If mild, graft hypertrophy may be asymptomatic, but more severe cases may lead to pain or a catching sensation within the knee (Fig.…”

“…Marrow edema that persists >1 year or the development of subchondral cysts underlying the graft may be an indication of graft failure and requires close clinical and imaging follow-up. [80][81][82] Figure 30 Graft hypertrophy following ACI. (A) Coronal T1-and (B) T2-weighted images show graft hypertrophy with the graft protruding (arrows) above the level of the adjacent native articular cartilage.…”

Clinical and MRI Considerations in Sports-Related Knee Joint Cartilage Injury and Cartilage Repair

“…MRI can accurately detect underfilling. 87,88 Occasionally this can be severe enough to indicate further surgery.…”