European Journal of Radiology 52 (2004) 310–319 Definition of pertinent parameters for the evaluation of articular cartilage repair tissue with high-resolution magnetic resonance imaging Stefan Marlovits a,∗ , Gabriele Striessnig a , Christoph T. Resinger a , Silke M. Aldrian a , Vilmos Vecsei a , Herwig Imhof b , Siegfried Trattnig b a Department of Traumatology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria b Department of Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria Abstract To evaluate articular cartilage repair tissue after biological cartilage repair, we propose a new technique of non-invasive, high-resolution magnetic resonance imaging (MRI) and define a new classification system. For the definition of pertinent variables the repair tissue of 45 patients treated with three different techniques for cartilage repair (microfracture, autologous osteochondral transplantation, and autologous chondrocyte transplantation) was analyzed 6 and 12 months after the procedure. High-resolution imaging was obtained with a surface phased array coil placed over the knee compartment of interest and adapted sequences were used on a 1T MRI scanner. The analysis of the repair tissue included the definition and rating of nine pertinent variables: the degree of filling of the defect, the integration to the border zone, the description of the surface and structure, the signal intensity, the status of the subchondral lamina and subchondral bone, the appearance of adhesions and the presence of synovitis. High-resolution MRI, using a surface phased array coil and specific sequences, can be used on every standard 1 or 1.5 T MRI scanner according to the in-house standard protocols for knee imaging in patients who have had cartilage repair procedures without substantially prolonging the total imaging time. The new classification and grading system allows a subtle description and suitable assessment of the articular cartilage repair tissue. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Cartilage repair; Magnetic resonance imaging; High resolution; Classification 1. Introduction Articular cartilage injuries are one of the most common types of injuries seen in orthopedic practice [1]. In a retro- spective review of 31,510 knee arthroscopies, the incidence of chondral lesions was 63%. Full-thickness articular carti- lage lesions with exposed bone were noted in 20% of pa- tients, with 5% of these occurring in patients less than 40 years old [1]. Traditional techniques for the operative treat- ment of acute and chronic chondral lesions include debride- ment of the chondral flap, perforation of the subchondral bone by drilling, abrasion, or microfracture [2]. More re- cently, the implantation of autologous chondrocytes as well as mosaicplasty have stimulated new interest in the treat- ment of chondral injuries [3–5]. This interest has resulted in an increasing demand for an accurate, reproducible, and, ∗ Corresponding author. Tel.: +43-1-40400-5964; fax: +43-1-40400-5947. E-mail address: stefan.marlovits@akh-wien.ac.at (S. Marlovits). ideally, non-invasive method for subsequent monitoring af- ter operative treatment. A non-invasive technique for the characterization of the repair tissue after biological cartilage repair would be very helpful and facilitate the description of the longitudinal follow-up of the repair tissue and enable the comparison of different surgical treatment techniques. Magnetic res- onance imaging (MRI) is very useful for the evaluation of the morphologic status of cartilage defects and the re- pair tissue throughout the postoperative period [6–14]. With the introduction of fat-suppressed gradient echo (3D-GRE) and fast-spin echo (FSE) sequences in clini- cal practice, magnetic resonance visualization of hyaline articular cartilage is routinely possible. However, the de- tection of subtle cartilage abnormalities by MRI requires high-resolution imaging, which is not provided by these standard sequences. With the use of a surface coil placed over the knee compartment of interest, high-resolution imaging is possible on routinely used 1 or 1.5 T MRI units by performing fast-spin echo imaging. This technique 0720-048X/$ – see front matter © 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2004.03.014