CT Arthrography


Scannogram demonstrating two cancellous screws and washers through a healed lateral tibial plateau fracture		Coronal reconstruction at the level of the body of the medial and lateral menisci. Notice the small geode coinciding with a full-thickness cartilage defect a the level of the lateral tibial plateau fracture. The menisci are clearly normal. The washer from the first screw is visible at the lateral aspect of the lateral tibial plateau.


Sagittal reconstruction showing the same cartilage divot and normal anterior and posterior horns of the lateral meniscus.		Sagittal reconstruction showing the same cartilage normal anterior and posterior horns of the medial meniscus.


Sagittal reconstruction through the intercondylar notch demonstrating Hoffa's recesses, the anterior cruciate ligament, and the PCL recess.

Comments

In the evaluation of post-operative menisci, several MR techniques have been proposed, including direct and indirect MR Arthrography. However, a common problem intrinsic to MR is the fact that the superior tissue characterization afforded by MR brings out to light signal abnormalities within the operated menisci that may not represent true tears. After a partial-meniscectomy, the segment of torn menicus is resected, exposing to the articular surface intrameniscal degenerative changes that otherwise would not reach through the surface. Although gadolinium may be of help, results have been mixed, probably because of the difficulty in differentiating signal from gadolinium entering the meniscus from areas of increased T1 signal in relation to exposed degenerative intrameniscal changes.

In this setting, the availability of multidetector CT technology affords an alternative solution. Thanks to its relative compensation for streak artifacts, MDCT can provide exquisite images of the menisci after the injection of undiluted intraarticular iodinated contrast. The result is a study with increased dynamic range, where the menisci appear homogeneously dark unless there are any true defects or re-tears, in which case, contrast extends into the substance of the meniscus.

In the case above, the patient was injected 20 cc. of Visapaque mixed with a coating of epinephrine in the syringe. The reason for the examination was the presence of screws through a tibial plateau fracture precluding the performance of an MRI. The CT Arthrogram was obtained on a 64-slice scanner with 0.65 spiral slice at 50% of overlap.