To better correlate the appearance of avascular necrosis (AVN) of the femoral head on magnetic resonance (MR) images with the stage of disease, MR images of 56 proved AVN lesions were compared with staging from corresponding radiographs (n = 56), Tc-99m scans (n = 41), and grade of symptoms (n = 28). Fractures complicating AVN were seen in 28 (50%) of 56 radiographs (radiographic stages III-V). With long repetition (TR) and echo delay (TE) times, a characteristic "double line sign" consisting of high signal intensity inside a low-intensity peripheral rim was seen in 45 lesions (80%). The central region within the rim was isointense with marrow fat on both short and long TR and TE images in 20 (71%) of 28 lesions uncomplicated by fracture (stages I-II) but in only four (14%) of 28 stage III-V lesions (P less than .001). Symptoms were least severe in lesions isointense with fat and most severe in lesions with low-signal central regions at short and long TRs and TEs. The peripheral double line sign on long TR/TE images may add specificity to the diagnosis of AVN by MR imaging. A chronologic pattern of central MR signal features is presented which may allow staging of AVN by MR imaging.
To determine the diagnostic performance of magnetic resonance (MR) imaging in the evaluation of suspected rotator cuff tears, eight asymptomatic volunteers and 32 patients with rotator cuff tendonopathy who underwent surgery were examined with MR imaging. Twenty-four of these patients also underwent contrast arthrography. The ability of MR imaging to depict the size of cuff tears and the quality of torn tendon edges was also evaluated. The MR imaging and arthrographic studies were reviewed without knowledge of surgical results or of the other studies. A scoring system was developed and a score assigned to each patient's MR study. The sensitivity of MR imaging for all tears (partial and full thickness) was 0.91, and the specificity was 0.88; whereas the sensitivity and specificity of arthrography were each 0.71. The scoring system improved the sensitivity to 1.0 and the specificity to 0.92. Linear regression analysis showed excellent correlation between preoperative assessment of the size of rotator cuff tears and measurement at surgery (r = .95).
To assess the accuracy of magnetic resonance (MR) imaging in the evaluation of the shoulder after surgery, MR examinations were performed in 31 patients before repeated surgery, and MR findings were correlated with the subsequent operative findings. In addition, the MR findings associated with prior surgery were reviewed, including altered structure of the acromion, soft-tissue metal artifacts, a surgical trough in the humeral head, nonvisualization of the subacromial-subdeltoid fat stripe, and intermediate signal intensity within the substance of the rotator cuff on images obtained with all pulse sequences. The MR criteria for full-thickness tears in the shoulder after surgery are the presence of fluidlike signal intensity on T2-weighted images that extends through an area of the rotator cuff or the nonvisualization of a portion of the rotator cuff. With use of these criteria, six of seven full-thickness rotator cuff tears were identified at MR imaging, with an accuracy of 90%. Partial cuff tears were indistinguishable from repaired tendons. Findings at MR imaging were 74% accurate concerning the presence of impingement.
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