Knee arthrography

Knee arthrography - Dennis J.Stoker

The knee is one of the most functionally complex and commonly injured joints. In addition to traumatic injuries, the knee is frequently affected by inflammatory processes, systemic disorders, and neoplasm. Developmental and congenital abnormalities may also afflict the knee. Long before the availability of CT and MR imaging, conventional arthrography was performed to evaluate the joint capsule and other intra-articular structures. Today, the most powerful diagnostic techniques combine CT and MR imaging with arthrography.

Arthrography is derived from the Greek words arthros (joint) and graphie (to write or record), which taken together imply the drawing or delineation of the joint. A multitude of contrast media have been utilized to image the knee joint with reports dating back to 1905.95 Early iodinated contrast media proved too toxic and water-soluble contrast media was subsequently introduced in the 1940s. Single-contrast examinations were initially utilized in which the entire joint recess was filled providing a positive relief to the joint cavity. Once intra-articular structures were outlined by contrast material, diagnostic emphasis was centered on the evaluation of menisci, articular cartilage, loose bodies, and synovial capsule. Double-contrast arthrography was soon to follow, providing a thin radiopaque coating contrasted by air- or gas-distended joint cavities. Double-contrast knee arthrography proved to be the radiologic procedure of choice for evaluation of menisci over the subsequent two decades. Progressive improvements in contrast media, fluoroscopic equipment, and diagnostic techniques led to reported accuracies of 90% or better for the evaluation of meniscal tears.33 Although examiner-dependent, the fine art of knee arthrography was optimized so as to evaluate extrameniscal abnormalities, such as articular cartilage defects, loose bodies, anterior cruciate tears, synovitis, and joint degeneration. Its greatest limitation was its inability to evaluate extrasynovial structures about the knee. For a complete understanding and review of single- and double-contrast knee arthrography, excellent texts authored by Freiberger and Faye37 and Goldman42 are recommended.

Tomographic imaging techniques were frequently combined with arthrography. Plain tomography performed after knee arthrography was first used in the evaluation of articular cartilage defects but was soon replaced by CT due to a marked improvement in anatomic delineation, contrast resolution, and visualization of extrasynovial soft tissues. CT (unenhanced) and CT arthrography of the knee were evaluated intermittently between 1978 and 1987.3,21,63,64,76 Promising early results by Passariello et al77 suggested conventional unenhanced CT of the knee may be competitive with arthrography for the diagnosis of meniscal tears. Blinded studies by Steinbach et al88 were less optimistic and showed variable sensitivities and accuracies dependent on instrumentation utilized. Manco et al64 corroborated accuracy rates of 91.5% for meniscal tears utilizing unenhanced CT of the knee.

The rapid evolution and acceptance of knee MR imaging limited the development of CT as an important tool for assessing intra-articular abnormalities of the knee. At present, MR imaging is the dominant noninvasive imaging technique currently available for evaluation of the knee. Superior soft tissue discrimination, superb spatial resolution, multiplanar capabilities, noninvasive nature, and lack of ionizing radiation have combined to limit single-contrast arthrography to the evaluation of joints with metal prostheses for loosening, wear, or infection, or patients in whom MR imaging is contraindicated. Prior to the advent of open-bore magnets, patients too large to be evaluated by standard 60-cm bores were also forced to undergo single- or double-contrast arthrographic examinations. In the rural or community hospital setting, arthrography of the knee may be rarely performed to document preoperative meniscal abnormalities principally due to unavailability of MR imaging equipment or cost containment.

Currently, MR imaging is the most commonly performed radiologic test in the assessment of intra-articular knee abnormalities. Posttraumatic prearthroscopic MR imaging evaluation, although initially controversial, has proved to be cost-effective.14 Although arthroscopy has revolutionized the diagnosis and treatment of knee disorders, most orthopedists acknowledge the invasiveness of the procedure; limitations in evaluation of extra-articular pathology; cost, and, albeit uncommon, potential complications associated with the procedure. They are receptive to accurate diagnostic imaging complementing their clinical evaluation and providing a global intra-articular and extra-articular assessment of the knee. Clinicians utilize MR imaging to support nonsurgical management or to confirm injuries that benefit from arthroscopic or open surgical treatment. Technical improvements in arthroscopic instrumentation have paralleled the technical advances in MR imaging and have expanded the surgical procedures now performed by arthroscopy. Although it is the clinical assessment that determines therapy, the MR imaging examination complements arthroscopy by providing a noninvasive, painless, and morbidity-free modality for accurate preoperative anatomic assessment that is well accepted by patients.