Several new imaging modalities have been found useful in clinical evaluation of patients with rheumatoid arthritis (RA). Magnetic resonance (MR) imaging has proven to be an excellent noninvasive method to evaluate the spine, shoulder, hip, and knees; its use for the evaluation of smaller joints is still being investigated. In patients with RA, MR imaging has been used to evaluate cervical spine instability, rotator cuff tear, osteonecrosis, and osteomyelitis. Patients with RA may have advanced osteoporosis, predisposing to insufficiency fractures. This includes fractures associated with increased activity after hip or knee arthroplasty. Newer methods for measuring the degree of osteoporosis include single photon absorptiometry, dual photon absorptiometry, quantitative computed tomography (CT), and dual-energy projection radiography. It has not yet been determined which of these methods will be most widely used in the future, but quantitative CT and dual-energy projection radiography currently show the most promise. Ultrasonography provides an excellent noninvasive method for the diagnosis of popliteal cysts, and color Doppler sonography can differentiate cyst and popliteal aneurysm. As compared to radiography or conventional CT, high-resolution CT provides an improved method to detect the early changes of RA in the lung parenchyma.

Instability of the glenohumeral joint is a common cause of chronic shoulder pain and disability. One or more episodes of subluxation or dislocation may result in a tear, detachment, or attenuation of the glenoid labrum, stripping of the joint capsule from the scapula, or trauma to the tendons or muscles of the rotator cuff. A series of 27 shoulders examined with magnetic resonance (MR) imaging showed changes of glenohumeral instability, which were confirmed with open or arthroscopic surgery. MR imaging was capable of displaying common types of pathologic conditions resulting from instability, including labral trauma, capsular detachment, and retraction of the subscapularis muscle. MR imaging is a valuable diagnostic tool for the evaluation of glenohumeral instability.

Magnetic resonance (MR) imaging was performed in 17 patients, 11-84 years of age, referred for evaluation of possible osteomyelitis involving the appendicular skeleton. MR imaging permitted successful identification of osteomyelitis in ten patients (four acute, two subacute with Brodie abscess, two chronic, and two acute with septic arthritis) and of cellulitis in the absence of osteomyelitis in four patients, including one with a soft-tissue abscess. Active osteomyelitis was excluded in three patients. Both T1- and T2-weighted spin-echo sequences were needed to evaluate osteomyelitis. T2-weighted images were needed to identify foci of active infection. MR images provided more accurate and detailed information regarding the extent of involvement than did radionuclide bone scans, computed tomographic scans, or standard radiographs. It permitted the differentiation of septic arthritis or cellulitis from osteomyelitis. In this limited series, MR imaging was particularly useful for seeking foci of active infection in areas of chronic osteomyelitis complicated by surgical intervention or fracture.

The shoulder impingement syndrome refers to a condition in which the supraspinatus tendon and subacromial bursa are chronically entrapped between the humeral head inferiorly and either the anterior acromion itself, spurs of the anterior acromion or acromioclavicular joint, or the coracoacromial ligament superiorly. As a result, the space for the bursa and tendon is reduced, and repeated trauma to these structures leads to bursitis and rotator cuff injury. Although pain and limitation of motion are common early findings, the diagnosis is often delayed until a complete tear of the rotator cuff has occurred. In an attempt to determine if MR can be used to depict the abnormalities associated with impingement syndrome (subacromial bursitis, supraspinatus tendinitis, and rotator cuff tear), we reviewed 107 MR scans of painful shoulders. Changes consistent with impingement syndrome were found in 53 patients (50%), 32 of whom underwent subsequent arthrography or surgery. MR was found capable of depicting several soft-tissue and bony abnormalities that have been clinically described in impingement syndrome. In regions of inflammation, we found that the supraspinatus tendon and/or the subacromial bursa were compressed by spurs (25 shoulders), capsular hypertrophy of the acromioclavicular joint (six shoulders), and/or low-lying acromion (14 shoulders). While T1-weighted MR imaging was highly sensitive to abnormalities of the supraspinatus tendon, tendinitis could be differentiated from a small tear of the supraspinatus tendon only with T2-weighted imaging. Large, full-thickness tears, especially if chronic, produced characteristic MR findings on both T1- and T2-weighted images. We conclude that MR can be used to detect several abnormalities associated with the shoulder impingement syndrome.

Magnetic resonance (MR) imaging was performed in 17 patients, 11-84 years of age, referred for evaluation of possible osteomyelitis involving the appendicular skeleton. MR imaging permitted successful identification of osteomyelitis in ten patients (four acute, two subactue with Brodie abscess, two chronic, and two acute with septic arthritis) and of cellulitis in the absence of osteomyelitis in four patients, including one with a soft-tissue abscess. Active osteomyelitis was excluded in three patients. Both T1- and T2-weighted spin-echo sequences were needed to evaluate osteomyelitis. T2-weighted images were needed to identify foci of active infection. MR images provided more accurate and detailed information regarding the extent of involvement than did radionuclide bone scans, computed tomographic scans, or standard radiographs. It permitted the differentiation of septic arthritis or cellulitis from osteomyelitis. In this limited series, MR imaging was particularly useful for seeking foci of active infection in areas of chronic osteomyelitis complicated by surgical intervention or fracture.

Decisions regarding the surgical approach in osteosarcoma require accurate assessment of tumor extent. In order to determine whether enhancement with gadopentetate dimeglumine could add clinically significant information to that available with unenhanced MR imaging, 21 patients with osteosarcoma underwent preoperative MR imaging. T1- and T2-weighted spin-echo MR images obtained before and after administration of IV gadopentetate dimeglumine were evaluated to determine the conspicuity of marrow and soft-tissue extent of tumor, including tumor involvement of major neurovascular bundles and adjacent joints. MR results were correlated with tumor margins found at surgery. In some instances, use of gadopentetate dimeglumine obscured differentiation of tumor from normal marrow or tumor infiltration into perineurovascular fat, and tumor extension through pseudocapsule could not be differentiated from peritumoral edema after contrast administration. Contrast enhancement did assist in differentiation of intraarticular tumor from effusion; however, synovial invasion could be identified on unenhanced T1-weighted images by loss of synovial fat and cortical disruption. These results indicate that gadopentetate dimeglumine does not assist in defining tumor margins of osteosarcoma.

Magnetic resonance imaging (MRI) is noninvasive and provides images with higher soft tissue contrast than possible with any other imaging modality. Unlike CT which depicts anatomy in the axial plane, MRI is capable of producing images in thin cross sections acquired directly in any plane, usually axial, coronal or sagittal planes. The use of diagnostic MR images is facilitated by an understanding of the detailed anatomy that is depicted. The purpose of this study was to identify anatomical structures in coronal and sagittal cryomicrosections of the hip region. Thin cryosections of the hips of fresh-frozen cadavers were obtained by a method developed by one of the authors (WR). These sections were matched with thin-section, high resolution MR images of a normal volunteer. The complex anatomy of the hip and its surrounding muscles, tendons and ligaments was exquisitely depicted on both the cadaver microcryosections and the matched MRT images.

The authors reviewed 610 consecutive magnetic resonance (MR) examinations of patients with suspected internal derangements of the knee, paying special attention to the posterior cruciate ligament (PCL). The normal PCL shows a low MR signal intensity and an arcuate shape. An accessory anterior or posterior meniscofemoral ligament was identified in 58.5% of examinations. Among 202 patients who underwent arthroscopy or arthrotomy, MR imaging depicted 11 PCL injuries: eight complete or incomplete ligament disruptions and three avulsions. All were confirmed by means of arthroscopy or arthrotomy. MR findings of PCL injury were anatomic disruption, increased signal intensity in the ligament, and redundancy of an avulsed ligament. Of the 11 PCL injuries, four were not detected at initial clinical examination. In none of the 202 patients in whom arthroscopy or surgery was performed was an abnormal PCL identified in the presence of a normal MR examination. MR imaging is a reliable method for the detection of PCL injuries.

The complex anatomy and the requirement to image in the peripheral magnetic field have made the shoulder difficult to examine with MR. However, the use of high-resolution scanning techniques and specialized surface coils has improved the quality of MR images obtained. Seventy-five scans of the shoulders of normal volunteers were correlated with multiplanar cryomicrosections of six cadaver shoulders to study the MR appearance of normal structures. MR was shown to provide excellent depiction of shoulder anatomy.