MR patterns of involvement of humeral head osteonecrosis.

PURPOSE: To characterize osteonecrosis of the humeral head on coronal and axial MR images. METHODS: We retrospectively reviewed MR examinations in patients with humeral head osteonecrosis. The angle of the entire affected articular surface at three levels was measured and an angle subtended by the margins of osteonecrosis was also measured. RESULTS: The appearance of osteonecrosis is identical to that in the femoral head with signal abnormality (13/13), double-line sign (7/13), and subchondral fractures (3/13). The superior aspect of the humeral head was the most common location of osteonecrosis. The MR staging resulted as follows: stage II (6/13), stage IIIA (1/13), stage IIIB (1/13), and stage IV (5/13). The maximum percentage of involvement of the articular surface demonstrated the following distribution: 0% to 25%, 0/11; 25% to 50%, 1/13; 50% to 75%, 5/13; and 75% to 100%, 7/13. CONCLUSIONS: Quantitative analysis of the percentage of involvement of the humeral head was performed and indicates that in most cases, 75% to 100% of the articular surface at the levels measured was involved.

In vivo high-resolution MR imaging of the carpal tunnel at 8.0 tesla.

OBJECTIVE: To determine the feasibility of acquiring in vivo images of the human carpal tunnel at 8 tesla (T). DESIGN: The wrist of an asymptomatic volunteer was imaged with an 8 T /80 cm magnet. The subject was imaged prone with the arm over the head and the wrist placed in neutral position in a custom-built dedicated shielded wrist coil. Axial two-dimensional gradient-echo (GRE) images of the wrist were acquired. RESULTS: Image contrast and resolution at 8 T are excellent. The infrastructure of the median nerve, particularly the interfascicular epineurium and individual fascicles, is better visualized at 8 T than at 1.5 T. The flexor tendons are well delineated from each other and the surrounding soft tissues, and tertiary tendon fiber bundles are resolved. The boundaries of the carpal tunnel are better defined at 8 T. CONCLUSION: We have obtained the first high-quality in vivo images of the human carpal tunnel at 8 T. The 8 T images demonstrated better contrast and resolution than those obtained at 1.5 T.

The POLPSA lesion: MR imaging findings with arthroscopic correlation in patients with posterior instability.

OBJECTIVE: To evaluate the features of the posterior labrocapsular periosteal sleeve avulsion (POLPSA) lesion on MR imaging in athletes with posterior shoulder instability. DESIGN AND PATIENTS: Six male athletes (age range 19-43 years) with avulsion of the posterior glenoid periosteum were identified on MR imaging. There were four football players, one wrestler, and one competitive weightlifter. The weightlifter had a bilateral condition so that seven shoulders were evaluated. MR imaging was performed with a 1.5 T magnet utilizing conventional and fat-saturated fast spin-echo coronal oblique and sagittal oblique sequences and a 3D-GRE transaxial sequence. Surgical correlation was available in all shoulders. RESULTS: All patients presented with pain and a joint effusion. The size of the periosteal sleeve and redundant joint recess was variable. Fibrous proliferation was noted arthroscopically in four shoulders beneath the sleeve. Although the posterior labrum was detached in all studies, only one labrum had a tear while two showed marked degeneration. CONCLUSION: The POLPSA lesion is an abnormality that can be associated with posterior instability. It differs from a reverse Bankart lesion because the periosteum, although detached, remains intact with the posterior capsule and detached posterior labrum. This lesion may represent an acute form of a Bennett lesion.

In vivo high resolution coronal MRI of the wrist at 8.0 tesla.

The wrists of asymptomatic volunteers were imaged at 8 and 1.5 T. The signal-to-noise ratio, spatial resolution, and soft tissue contrast of the 8 T images were much greater. The increased signal-to-noise ratio available at 8 T allows acquisition of high quality, high resolution images and visualization of intricate anatomy at scan times acceptable for clinical imaging.