Normal variants and pitfalls in MR imaging of the ankle and foot.

Normal anatomic variants may erroneously be interpreted as pathologic conditions on MR imaging of the ankle and foot. Therefore, sufficient knowledge of the normal anatomy and its variations is crucial for accurate diagnostic analysis of such images. This article will focus on outlining variants and MR imaging interpretation pitfalls of the tendons, ligaments, muscles, bones, and other miscellaneous structures of the foot and ankle.

MR imaging of tendon abnormalities of the foot and ankle.

MR imaging, with its unique soft-tissue contrast resolution, noninvasiveness, and multiplanar capabilities, has been applied to the assessment of tendon abnormalities of the foot and the ankle.

MR imaging features of diseases of the peroneal tendons.

Injuries of the peroneal tendons including peritendinosis/tenosynovitis, tendinosis, rupture, dislocation are being detected with greater frequency since the advent of MR imaging. This article focuses on the normal as well as pathologic MR features of the peroneal tendons.

MR imaging and CT in the assessment of osseous abnormalities of the ankle and foot.

This article focuses on the contributions of MR imaging and CT toward the evaluation of painful osseous abnormalities of the foot and ankle. Inconclusive findings on conventional radiographs often mandate further work up with the more advanced cross-sectional imaging techniques. Often, however, the radiologist remains unsure, which modality, CT or MR imaging, should be used. Based on our experience, CT and MR imaging play a complementary role in the assessment of these disorders.

Traumatic musculotendinous injuries of the knee: diagnosis with MR imaging.

Magnetic resonance (MR) imaging is the imaging modality of choice for evaluation of acute traumatic musculotendinous injuries of the knee. Three discrete categories of acute injuries to the musculotendinous unit can be defined: muscle contusion, myotendinous strain, and tendon avulsion. Among the quadriceps muscles, the rectus femoris is the most susceptible to injury at the myotendinous junction due to its superficial location, predominance of type II fibers, eccentric muscle action, and extension across two joints. Among the muscles of the pes anserinus, the sartorius is the most susceptible to strain injury due to its superficial location and biarticular course. The classic fusiform configuration of the semimembranosus along with a propensity for eccentric actions also make it prone to strain injury. MR imaging findings associated with rupture of the iliotibial tract include discontinuity and edema, which are best noted on coronal images. The same mechanism of injury that tears the arcuate ligament from its fibular insertion can also result in avulsion injury of the biceps femoris. The gastrocnemius muscle is prone to strain injury due to its action across two joints and its superficial location. Injuries of the muscle belly and myotendinous junction of the popliteus are far more common than tendinous injuries.

From the RSNA Refresher Courses. Radiological Society of North America. MR imaging of the ankle and foot.

Magnetic resonance (MR) imaging has opened new horizons in the diagnosis and treatment of many musculoskeletal diseases of the ankle and foot. It demonstrates abnormalities in the bones and soft tissues before they become evident at other imaging modalities. The exquisite soft-tissue contrast resolution, noninvasive nature, and multiplanar capabilities of MR imaging make it especially valuable for the detection and assessment of a variety of soft-tissue disorders of the ligaments (eg, sprain), tendons (tendinosis, peritendinosis, tenosynovitis, entrapment, rupture, dislocation), and other soft-tissue structures (eg, anterolateral impingement syndrome, sinus tarsi syndrome, compressive neuropathies [eg, tarsal tunnel syndrome, Morton neuroma], synovial disorders). MR imaging has also been shown to be highly sensitive in the detection and staging of a number of musculoskeletal infections including cellulitis, soft-tissue abscesses, and osteomyelitis. In addition, MR imaging is excellent for the early detection and assessment of a number of osseous abnormalities such as bone contusions, stress and insufficiency fractures, osteochondral fractures, osteonecrosis, and transient bone marrow edema. MR imaging is increasingly being recognized as the modality of choice for assessment of pathologic conditions of the ankle and foot.

Superior labrum anterior-posterior lesions: diagnosis with MR arthrography of the shoulder.

PURPOSE: To determine the accuracy of magnetic resonance (MR) arthrography in the diagnosis of superior labrum anterior-posterior (SLAP) lesions of the shoulder. MATERIALS AND METHODS: From January 1995 to June 1998, MR arthrography of the shoulder was performed in 159 patients with a history of chronic shoulder pain or instability. Fifty-two patients underwent arthroscopy or open surgery 12 days to 5 months after MR arthrography. Diagnostic criteria for SLAP lesion included marked fraying of the articular aspect of the labrum, biceps anchor avulsion, inferiorly displaced bucket handle fragment, and extension of the tear into the biceps tendon fibers. Surgical findings were correlated with those from MR arthrography. RESULTS: SLAP injuries were diagnosed at surgery in 19 of the 52 patients (37%). Six of the 19 lesions (32%) were classified as type I, nine (47%) as type II, one (5%) as type III, and three (16%) as type IV. MR arthrography had a sensitivity of 89% (17 of 19 patients), a specificity of 91% (30 of 33 patients), and an accuracy of 90% (47 of 52 patients). The MR arthrographic classification showed correlation with the arthroscopic or surgical classification in 13 of 17 patients (76%) in whom SLAP lesions were diagnosed at MR arthrography. CONCLUSION: MR arthrography is a useful and accurate technique in the diagnosis of SLAP lesions of the shoulder. MR arthrography provides pertinent preoperative information with regard to the exact location of tears and grade of involvement of the biceps tendon.