Standard proton-density- and T2-weighted magnetic resonance (MR) imaging and MR arthrography were used to depict rotator cuff disease in 36 shoulders in 36 patients; the findings were compared with arthroscopic findings in every patient. In 19 rotator cuffs normal at arthroscopy, MR arthrography revealed no tear in 16 patients, a partial tear in one patient, and a full-thickness tear in two patients. Standard proton-density- and T2-weighted images were normal in 15 of these patients and revealed a partial tear in two patients and a full-thickness tear in two patients. In 13 partial tears found at arthroscopy, MR arthrography showed a partial tear in six patients, no tear in five patients, and a full-thickness tear in two patients; standard MR imaging revealed a partial tear in one patient, no tear in 10 patients, and a full-thickness tear in two patients. All four full-thickness tears proved with arthroscopy were correctly diagnosed with both MR imaging methods. The main advantage of MR arthrography was better depiction of partial tears in the articular surface.

To determine the histopathologic correlates of alterations in the rotator cuff at magnetic resonance (MR) imaging, 13 cadaveric shoulders (in subjects aged 26-83 years at the time of death) underwent MR imaging in the coronal oblique plane at 1.5 T with proton-density- and T2-weighted spin-echo sequences. Areas corresponding to sites of MR imaging alterations were then examined histologically. Increased signal intensity on proton-density-weighted images (without further increased signal intensity on T2-weighted images) and an indistinct margin at the articular side of the supraspinatus tendon corresponded to eosinophilic, fibrillar, and mucoid degeneration and scarring. Areas of increased signal intensity on T2-weighted images were associated with severe degeneration and disruption of the supraspinatus tendon. Although other authors have suggested that certain MR findings are indicative of tendinitis, the histologic data in this study were not those of active inflammation but rather tendon degeneration.

Insufficiency fractures of the sacrum are a commonly recognized form of stress fracture typically occurring in elderly patients. As such patients usually present with low back pain, MR imaging is often performed initially as a means of evaluation. We present 5 patients with sacral insufficiency fractures imaged with MR. Metastatic disease was a leading clinical suspicion as all patients were elderly and three had known primary neoplasms. T1-weighted sequences demonstrated bands of decreased signal intensity, usually paralleling the sacral aspect of the sacroiliac joints and occasionally occurring as a horizontal band across the sacral body. Four of five patients underwent further evaluation with computed tomography (CT) or nuclear bone scanning, which confirmed the diagnosis of sacral insufficiency fracture. We conclude that MRI is sensitive but not specific in detecting sacral insufficiency fractures. As MR imaging is rapidly becoming the method of choice for evaluating back pain, it is important to consider this diagnosis in elderly persons.

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