Faculty Bibliography

Articular cartilage abnormalities of the knee are a cause of significant patient morbidity. Several surgical techniques have been developed to treat these lesions to improve patient symptoms and to delay or prevent the development of osteoarthritis. MRI has been shown to be an accurate non-invasive test for the evaluation of articular cartilage injuries and for evaluating the postoperative knee following chondral repair. As these surgical repair techniques become more commonly performed, is important for radiologists to be familiar with the surgical techniques and the MRI appearance of the postoperative knee including both normal and abnormal findings. In this article, these chondral repair techniques will be reviewed as well those normal and abnormal MRI findings following these surgeries

It is becoming increasingly important for the radiologist to evaluate the appearance and outcome of cartilage repair procedures. MR imaging is currently the best method for such evaluation but it is necessary to use cartilage-specific sequences and to modify those sequences when necessary to minimize artifacts from retained metal within the joint. This article reviews the surgical technique of the more commonly performed cartilage repair procedures, currently recommended techniques for the MR imaging evaluation of articular cartilage and cartilage repair procedures, and the MR imaging appearance of cartilage repair procedures and of the most frequently encountered complications following such procedures

New developments and improvements in ligamentous and meniscal surgery and cartilage repair procedures have led to an increased incidence ot these procedures being performed. Subsequently, there has been a corresponding increase in postoperative imaging studies. and it is imperative for radiologists to be comfortable with the normal imaging appearance of these procedures and associated complications

MR arthrography by virtue of its ability accurately to demonstrate intra-articular structures and abnormalities of these structures has become an important tool for the evaluation of a variety of articular disorders. Although not necessary in all patients, MR arthrography may facilitate the evaluation of patients with suspected intra-articular pathology in whom conventional MRI is not sufficient for an adequate therapy planning. MR arthrography combines the advantages of arthrography, like joint distention and delineation of intra-articular structures, with the superior spatial resolution of MRI. This technique improves diagnostic confidence, particularly in the assessment of subtle lesions and of complex anatomic structures. MR arthrography is of high value in the evaluation of osteochondral defects, loose bodies, previously operated menisci, and acetabular labral lesions

Magnetic resonance (MR) imaging of the postoperative knee has become more common because more arthroscopic repair procedures are being performed. The most common procedures include partial meniscectomy and meniscal repair, anterior cruciate ligament (ACL) reconstruction, and cartilage repair procedures. Specific findings of a retorn meniscus following meniscal repair or partial meniscectomy are increased signal intensity extending through the site of repair on T2-weighted images, displaced meniscal fragments, and abnormal signal intensity at a site distant from the repair. Findings of ACL graft disruption on T2-weighted MR images include absence of intact graft fibers and increased signal intensity similar to that of fluid within the expected region of the graft. Partial tears of the graft appear as areas of increased signal intensity affecting a portion of the graft with some intact fibers still present. An impinged ACL graft may appear to be draped over the anterior inferior edge of the intercondylar roof or be posteriorly bowed. Localized anterior arthrofibrosis appears on T1-weighted MR images as a focal nodular lesion of low signal intensity that is anterior to the ACL graft in the intercondylar notch and is indistinguishable from adjacent joint fluid. On T2-weighted images, the nodule is well differentiated from high-signal-intensity joint fluid. Finally, MR imaging has been shown to be accurate in the evaluation of cartilage repair tissue. Knowledge of the normal MR imaging appearance of the knee after the more common repair procedures will allow radiologists to recognize complications associated with such procedures

Assessment of articular cartilage has become an essential part of magnetic resonance (MR) evaluation of the knee. This has occurred because of recent advances in treatment along with improved accuracy of MR image evaluation of articular cartilage. Detection of articular cartilage defects can provide an explanation for symptoms and allow identification of patients for cartilage therapy and is an important factor for predicting prognosis of patients with knee injury. This review describes the most easily implemented MR techniques for evaluation of articular cartilage and the normal and abnormal appearance of cartilage seen using these techniques. The influence of imaging findings on treatment is described

Magnetic resonance imaging is the optimal modality for assessing articular cartilage because of superior soft tissue contrast, direct visualization of articular cartilage, and multiplanar capability. Despite these advantages, there has been disagreement as to the efficacy of magnetic resonance imaging of articular cartilage. The reason for this controversy is multifactorial but in part is attributable to the lack of the use of optimized pulse sequences for articular cartilage. The current authors will review the current state of the art of magnetic resonance imaging of articular cartilage and cartilage repair procedures, discuss future new directions in imaging strategies and methods being developed to measure cartilage thickness and volume measurements, and propose a magnetic resonance imaging protocol to evaluate cartilage that is achievable on most magnetic resonance scanners, vendor independent, practical (time and cost efficient), and accepted and used by a majority of musculoskeletal radiologists