Double-contrast arthrography of the knee.

Abstract

DOUBLE-CONTRAST arthrography of the knee allows radiological assessment of the menisci, the articular cartilages, the synovium, and the ligaments. Adequate assessment of knee joint pathology requires that all these structures be visualized, and this visualization is not possible with single-contrast arthrography. Space does not permit a detailed review of our technic of arthrography nor the presentation of a large number of illustrative examples. Instead, we shall attempt to present the reasons behind and the principles governing the technic and the interpretation of knee arthrography. Technic Many technics of double-contrast arthrography have been described, and any method which insures good detailed films with high contrast and full demonstration of all the structures of interest is, of course, acceptable. Several minor points of technic make the procedure easier for both the radiologist and the patient, and these can be learned from experience. For example, we have found that the use of a combination of carbon dioxide and air allows the patient to return home with a knee that is not at all swollen, and yet there is sufficient negative contrast left that further films can be obtained, if necessary, after an initial review of the films. With Puncture and Injection: The knee is prepared with iodine solution and draped with a sterile towel. Puncture is performed for the most convenient site, usually the lateral approach. A No. 22 needle is adequate, and all synovial fluid should be aspirated. Once the needle is well within the joint, the knee is then inflated with 20 to 30 cc of air and 60 to 80 cc of carbon dioxide. Slightly smaller amounts are found necessary in the female and considerably larger amounts may be required in a knee which has suffered previous damage. The tension in the suprapatellar bursa can be used as an index of filling. Filling should be complete. No more than 5 cc of radiopaque contrast material is injected. Following injection, the knee is exercised either passively or, preferably, actively, with weight-bearing and knee flexion. Following filming, the patient is mobile and may easily go home. We feel that there is one major point of technic which must be mentioned and that is that television fluoroscopic control and spot-filming are absolutely essential. If sufficient detail is to be obtained with this method, a small-focus under-couch tube and low kVp are necessary. These adaptations can be easily mad.e on any standard fluoroscopic equipment. We find that fluoroscopic control is essential for the following reasons: a. Although in the relatively normal knee the menisci can be partially demonstrated with nonfluoroscopic technic, the entire meniscus is not visualized. In addition, patients with locked knees, abnormal tibial plateaux, gross deformities, and associated injuries cannot be adequately examined.