Cartilage degeneration in osteoarthrosis (OA) of the knee generally is believed to precede osseous abnormalities. Because cartilage abnormalities are not readily detected by routine radiography, we investigated the role of magnetic resonance imaging (MRI) in assessing cartilage damage in a goat model for OA. Four goats had the anterior cruciate ligament of one knee severed surgically to create instability and accelerate OA. Two goats each were killed at 4 and 6 weeks, respectively, after walking on the unstable knees. MRI of the knees was performed with Hybrid fat suppression sequences. The images were correlated with gross anatomic sections and histologic analysis of the knees. On gross examination, the unstable knees showed rapid development of thinning, surface irregularity, and focal defects of the cartilage. These findings correlated well with abnormalities detected on the MRIs. In addition, areas of decreased signal intensity in cartilage correlated with histologic evidence of degenerative changes in the cartilage substance, including fragmentation, fibrillary and eosinophilic changes, and chondrocyte proliferation, indicating attempted cartilage repair. Precise correlation of pathologic and MRI data, however, was lacking, related in part to inability to match perfectly the level and orientation of the gross section with that on the MRI examination.

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.

The anatomy of the craniovertebral junction, although complex, may be well visualized by routine MR imaging. This essay discusses the anatomy of the complex articulations of the craniovertebral junction. Representative MR images and gross anatomic photographs are presented to illustrate the intricate ligamentous and articular anatomy. Knowledge of the normal anatomy of the occipitoatlantoaxial region is necessary in order to understand the common disorders that affect this area. The most common disorders are trauma and arthropathies, but also include congenital abnormalities and neoplasm. The resultant abnormal mechanics may lead to neurologic sequelae or pain.

A new sign of anterior cruciate ligament (ACL) tear based on secondary changes of the posterior cruciate ligament (PCL) is described. Thirty-one patients with magnetic resonance (MR) examinations of the knee suspicious for ACL injury and 50 normal controls were examined. In each patient a line was drawn adjacent and parallel to the posterior margin of the distal portion of the PCL and was extended proximally. A positive PCL line did not intersect the medullary cavity of the femur. A positive line correctly predicted ACL injury in 19 of 22 patients.

Plain radiographs of 67 acute spinal compression fractures in 49 patients were analysed by subjective and objective criteria, using CT scans as the diagnostic standard for the diagnosis of burst fracture. Discriminant analysis correctly predicted the type of fracture in 88% of cases. Burst fractures, however, were almost as frequently misdiagnosed as being wedge compression fractures using this technique, compared with the reading of 25 films from patients without previous information. A quarter of the injuries would have been misdiagnosed had reliance been placed solely on the plain radiographs. CT scans of all patients with acute spinal compression fractures should be considered to decrease this potentially serious diagnostic error.

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.

Although soft-tissue calcification is common in collagen vascular disease, paraspinal calcification in the cervical spine has not been described before. We studied five women with large, lobulated, predominantly homogeneous calcific masses centered on synovial articulations in the neck. Changes consisting of either osteolysis or erosions were evident. All patients had radiculopathy, focal pain, or stiffness. In two patients, the presence of hydroxyapatite crystals was confirmed on biopsy. Symptomatic cervical paraspinal calcifications in patients with collagen vascular disease cause large soft-tissue masses that mimic tumoral calcinosis.

Abnormalities of the long tendon of the biceps brachii muscle commonly accompany other lesions about the shoulder, especially rotator cuff rupture, and are a frequent cause of a painful shoulder. The spectrum of abnormalities associated with medial displacement of the biceps tendon seen at magnetic resonance (MR) imaging was reviewed in six patients. MR imaging was performed on a 1.5-T system with use of a dedicated surface coil. The findings at MR imaging were correlated with those at surgery. Two types of medial displacement of the biceps tendon were identified. More frequently observed was a defect in the subscapularis apparatus that allowed intraarticular entrapment of the biceps tendon. Less commonly observed was incomplete dislocation, with the biceps tendon lying between a partially disrupted subscapularis tendon. MR imaging enabled accurate identification of medial dislocation of the biceps tendon and entrapment of the tendon within the glenohumeral joint. MR imaging also demonstrated the associated disruption of the subscapularis tendon that must be present to allow the biceps tendon access to the joint space.

We report a patient with a stress fracture in the sacrum. This may be a cause of hip or back pain. In contrast to typically bilateral insufficiency fractures, fatigue fractures are usually unilateral and the appearances are not diagnostic on scintigraphy. As the plain film findings may be subtle and overlooked, computed tomography is more specific in delineating a sclerotic vertical fracture parallel to the sacroiliac joint. Recognition of the characteristic radiographic pattern in sacral fatigue fractures can avoid incorrect diagnosis and unnecessary tests or treatment.