Imaging Technique

0278-5919/06/$ - see front matter doi:10.1016/j.csm.2006.03.003

© 2006 Elsevier Inc. All rights reserved. sequence requires relocalization and can lengthen image time; however, it is useful when evaluating failed Bankart repairs. Unfortunately, the position can be uncomfortable and occasionally, in the surgically unstable shoulder, anterior dislocation can be provoked.

Susceptibility Artifact Considerations

A major problem with postoperative imaging is susceptibility artifact from the screws, sutures, tacks, suture anchors, and shavings. The foreign material causes intravoxel dephasing, which leads to loss of signal intensity. Most evident on gradient echo images, the artifact can be reduced by using fast spinecho techniques, which use multiple 180 degree refocusing pulses [1,3-6]. Frequency-selective fat saturation technique is highly dependent on uniform field homogeneity, which becomes distorted by surgical hardware leading to poor fat saturation. Short tau inversion recovery (STIR) can be substituted for frequency-selective fat saturation; however, the drawback is reduced signal-to-noise [1,3,4,6,7]. Other parameters that can improve image quality include increasing the receiver bandwidth and decreasing voxel size [1,4,5,7,8].

MR Arthrography

Many initial studies on postoperative shoulder imaging were performed without MR arthrography [1,9-14]. Subsequent studies have advocated the use of direct MR arthrography in the postoperative shoulder, and direct MR arthrog-raphy is used in all postoperative patients at our institution [1-3,5,7]. MR ar-thrography improves the identification of rotator and labral retears. Several studies have shown that partial tears of the rotator cuff cannot be distinguished adequately from granulation tissue in the tendon from the healing response [3,6,7,9]. In these cases MR arthrography can be particularly useful, because contrast can be seen extending into the partial tear and can help define the margins of the tendon for preoperative planning [6]. One pitfall is that in the operated shoulder the presence of contrast in the subacromial-subdeltoid space does not indicate a full-thickness rotator cuff tear as it would in the nonoperated shoulder. The joint is no longer watertight following surgery [3,5,6,11]. Conversely, the absence of contrast in the subacromial-subdeltoid space does not exclude a full-thickness tear, because scar tissue may prevent contrast from extending through the entire defect [5,6,11]. Arthrography also distends the capsule, allowing for evaluation of the capsular anatomy and the anterior band of the inferior glenohumeral ligament (AIGHL) [2,3,6,15].

The arthrogram portion of the procedure is performed under fluoroscopy. Once the needle tip is documented to be intra-articular with several milliliters of iodinated contrast, or air if allergy is present, a volume of a mixture of gadolinium in normal saline is injected. For a 1.5 T magnet the usual concentration is 1 mL in 250 mL of normal saline. For lower field strength magnets, the concentration can be doubled to 2 mL in 250 mL of normal saline. The effect of shortening the relaxation time of the water produces a bright signal on a T1-weighted fat-suppressed image. The movement of the gadolinium-water complex into an adjacent space is consistent with a rotator cuff tear.

Over the last 15 years, the Yale group has performed more than 6000 MR arthrograms. There have been four major complications, including three cases of suspected infection requiring washout. Only two of the three cases grew a pathogen. The other case appeared to be reflex sympathetic dystrophy that slowly resolved with time.

Was this article helpful?

0 0
Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

Get My Free Ebook

Post a comment