MR imaging of the foot and ankle.

MR imaging provides significant anatomic detail for the evaluation of disorders of the osseous and soft tissue structures of the foot and ankle. This article describes the normal anatomy and post-traumatic conditions of the ligaments and tendons of the ankle. Other disorders of the soft tissues and osseous structures discussed include plantar fasciitis, Morton's neuroma, ganglions, plantar fibromatosis, hemangiomas and other neoplasms, fractures and stress fractures, arthritides, and osteomyelitis.

Rotator cuff: evaluation with US and MR imaging.

Magnetic resonance (MR) and ultrasound (US) imaging are currently touted for assessment of rotator cuff disease. Optimum clinical imaging techniques include use of (a) a 1.5-T MR imaging unit with small planar coils, proton-density-weighted and T2-weighted fast spin-echo sequences, and 10-12-cm fields of view (yielding 400-470 x 500-625-microm in-plane spatial resolution) and (b) a state-of-the-art commercial US unit with insonation frequencies of 9-13 MHz (yielding 200-400-microm axial and lateral resolution). Proper diagnosis requires familiarity with normal anatomic characteristics and imaging pitfalls. Care must be taken to avoid sonographic tendon anisotropy and MR imaging magic angle effects, which can be misinterpreted as rotator cuff tear. At MR imaging, a complete cuff tear typically appears as either a hyperintense defect or a tendinous avulsion that extends from the bursal to the articular side of the cuff; a partial cuff tear typically appears as a focal hyperintense region that contacts only one surface of the cuff. Complete and partial tears manifest with a wide spectrum of findings at US. MR imaging and US are effective for evaluating rotator cuff injuries, with high reported accuracies for detection of complete tears but more disparate results for detection of partial tears.

Detection of osteomyelitis in the neuropathic foot: nuclear medicine, MRI and conventional radiography.

The diagnostic efficacy of (1) combined three-phase bone scintigraphy and In-111 labeled WBC scintigraphy (Bone/WBC), (2) MRI, and (3) conventional radiography in detecting osteomyelitis of the neuropathic foot was compared. Conventional radiography was comparable to MRI for detection of osteomyelitis. MRI best depicted the presence of osteomyelitis in the forefoot. Particularly in the setting of Charcot joints, Bone/WBC was more specific than conventional radiography or MRI.

Optimal computed tomography imaging of the midfoot: an improved technique.

A new protocol for computed tomography (CT) imaging of the midfoot is described. This imaging technique places the CT cuts parallel to and perpendicular to the talus-first metatarsal axis, as viewed on the lateral CT scout image. For imaging the midfoot, this technique is an improvement over previously described hindfoot or midfoot protocols.

MR imaging diagnosis of triangular fibrocartilage pathology with arthroscopic correlation.

OBJECTIVE: The goal of this study was to compare MR imaging with arthroscopy in evaluating triangular fibrocartilage (TFC) pathology. MATERIALS AND METHODS: The results of 178 MR imaging examinations of the wrist were independently reviewed by two musculoskeletal radiologists who were unaware of the the clinical history, including any subsequent surgery. One hundred forty-nine of these studies were obtained from symptomatic patients. Of these patients, 56 underwent arthroscopic evaluation of the TFC. The remaining 29 studies were obtained from control volunteers and duplicate cases to reduce bias. The data were divided into categories based on Palmer's classification of TFC injury. Diagnostic sensitivity, specificity, and accuracy were calculated for each category. RESULTS: Of the 56 patients who underwent arthroscopic evaluation of the TFC, 27 had TFCs that were intact at surgery. Also, 27 complete perforations and two partial defects were found at surgery. Sensitivity for detecting central degenerative perforations was 91% for both observers I and II. Sensitivity for detecting radial slitlike tears was 100% and 86% for observers I and II, respectively. Sensitivity for detecting ulnar-sided avulsions was 25% and 50% for observers I and II, respectively. CONCLUSION: MR imaging is accurate in revealing TFC perforations.

MR imaging of injuries to the small joints.

This article describes MR imaging of acute and chronic injuries of the ankle and foot, elbow, and hand and wrist. Conditions discussed include ligament and tendon injuries, fractures and bone bruises, osteochondral defects, foreign bodies, and posttraumatic ganglions. Other topics covered include fasciitis, nerve and muscle injuries about the elbow, and triangular fibrocartilage tears.

Diagnostic bone scanning in oncology.

Over the last several decades bone scanning has been used extensively in the evaluation of oncology patients to detect bone involvement. It can provide information about disease location, prognosis, and the effect of therapy. Bone scanning offers the advantages of whole body evaluation and the detection of lesions earlier than other techniques. However, as newer diagnostic tools become available, indications for bone scanning must be revised and the results combined with these other tests in order to provide optimum patient care. Advances in instrumentation and the subsequent improvement in image quality have allowed nuclear medicine physicians to provide more accurate bone scan interpretations. By optimizing image acquisition, it is often possible to determine lesion characteristics, which are more likely to represent malignancy. Knowledge of disease pathophysiology and other specific properties of the patient's primary tumor, along with subsequent correlation of scan abnormalities to patient history, physical examination, previous studies, and other radiological examinations, is essential for determining lesion significance. The differential diagnosis of a scan abnormality should also include consideration of both false normal and abnormal causes. The final interpretation should be clearly communicated to the clinician with appropriate recommendations for further evaluation. Only through careful attention to the patient, the clinician, and appropriate study acquisition parameters will bone scanning maintain its place in the evaluation of oncology patients.

MR imaging of the wrist: normal findings that may simulate disease.

Twenty-six normal wrists in young adults were studied with magnetic resonance (MR) imaging. The following conclusions were drawn regarding normal anatomic features: (a) Multiple slips of the abductor pollicis longus tendon simulate longitudinal tears; (b) the extensor pollicis longus and extensor carpi ulnaris tendons normally demonstrate increased signal intensity simulating tendinitis; (c) small quantities of fluid in the extensor tendon sheaths may be normal and not indicative of tenosynovitis; (d) the triangular fibrocartilage normally demonstrates increased signal intensity simulating tears at its radial and ulnar attachment sites; (e) the volar ulnocarpal ligaments are often indistinct, thereby simulating injury; and (f) the median nerve has signal intensity equivalent to that of fat, nor of muscle as commonly believed. Awareness of these normal features is critical in making the correct interpretation of MR images of the wrist.

MR imaging of the painful wrist.

Magnetic resonance (MR) imaging is an effective method for helping determine the cause of wrist pain by demonstrating a broad spectrum of abnormalities, including those of bone, cartilage, ligaments, and tendons. MR imaging is useful in the detection, characterization, and staging of osseous injury and disease, although computed tomography provides superior detail in the depiction of bone. MR imaging may demonstrate irregular cartilage loss in noninflammatory arthropathies such as osteoarthritis, and its superior soft-tissue contrast makes it the method of choice for evaluating the synovial processes. Although arthrography remains the standard of reference in the detection of perforations of the principal intrinsic ligaments of the wrist, three-dimensional MR imaging has shown promise in depicting the small interosseous ligaments. Tendinitis, tenosynovitis, ganglia, and anatomic variants can be diagnosed and accurately assessed with MR imaging. Radiologists need to be aware of the full spectrum of wrist abnormalities and the characteristic MR imaging findings that accompany them.

MR imaging interpretation of the Palmer classification of triangular fibrocartilage complex lesions.

The triangular fibrocartilage complex (TFCC) is a complex anatomic and biomechanical structure. Injury to the TFCC is a recognized cause of ulnar wrist pain. The TFCC may be injured in its horizontal portion, in its peripheral portions, or at its attachments. In the Palmer classification, TFCC lesions are categorized as traumatic or degenerative. Traumatic lesions are subclassified according to the location of the injury; degenerative lesions are subclassified according to the extent of degeneration. This classification is helpful in determining the mechanism of injury and directing clinical management. Magnetic resonance (MR) imaging may be more useful than arthrography in prospective evaluation of TFCC lesions. MR images accurately demonstrate the structural abnormalities that contribute to ulnocarpal instability and pain. The presence or absence of chondromalacia is a factor in the Palmer classification and is also considered in treatment planning. However, only advanced cases of chondromalacia are reliably detected with MR imaging.

Increased signal in the normal supraspinatus tendon on MR imaging: diagnostic pitfall caused by the magic-angle effect.

OBJECTIVE: Increased signal intensity within the distal portion of the supraspinatus tendon during MR imaging is a frequent observation even in healthy subjects. This finding has been variously attributed to the presence of fat, muscle, connective tissue, abnormal vascularity, or degenerative changes. More recently, the effect of tendon orientation in the static magnetic field (Bo) has been implicated. It has been shown that tendons at the magic angle of 55 degrees to Bo show markedly increased signal. This study was designed to determine the contribution of the magic-angle effect to the MR signal in the distal portion of the supraspinatus tendon. SUBJECTS AND METHODS: Five healthy volunteers were imaged in a 1.5-T unit using short TR/TE sequences in standard supine position; they were then reimaged laterally flexed at the waist to reorient the plane of the distal portion of the supraspinatus tendon by approximately 20 degrees relative to Bo. In the second part of the study, three cadaveric shoulders were similarly imaged, first in standard position and then reoriented approximately 35 degrees by simple rotation of the specimen. The supraspinatus tendon was evaluated in each subject by noting the length of the segment with increased signal and the position of this segment relative to the insertion of the tendon on the greater tuberosity. Comparisons were made for each live and cadaveric subject between neutral and rotated positions. RESULTS: Segments of increased signal changed in length and position for each live and cadaveric subject from the neutral to the reoriented position. CONCLUSION: Our study suggests that tendon orientation contributes significantly to the presence of increased signal within the supraspinatus tendon, as caused by the magic-angle effect. Failure to recognize this effect may lead to diagnostic inaccuracy when evaluating the rotator cuff on short TR/TE sequences.

MR imaging of the major carpal stabilizing ligaments: normal anatomy and clinical examples.

The integrity of the ligamentous network of the wrist is critical, as disruption of this network may result in carpal instability and pain. The extrinsic (radiocarpal) and intrinsic (intercarpal) ligaments that maintain carpal stability can be evaluated with magnetic resonance (MR) imaging. The major extrinsic ligaments are the radioscaphocapitate, radiolunotriquetral, short radiolunate, and dorsal radiocarpal ligaments. The scapholunate and lunotriquetral ligaments are the most important intrinsic ligaments and the primary wrist stabilizers. The most common causes of carpal instability are unstable fracture of the scaphoid, scapholunate dissociation, and lunotriquetral dissociation. Carpal instability can be diagnosed from the sagittal MR image that includes the capitate, lunate, and radius and from the sagittal MR image that includes the scaphoid and radius. Knowledge of the MR imaging appearances of the major carpal stabilizing ligaments and common patterns of carpal instability allows more precise diagnosis in cases of wrist pain.

Ulnar collateral ligament of the thumb: MR findings in cadavers, volunteers, and patients with ligamentous injury (gamekeeper's thumb).

OBJECTIVE: The ulnar collateral ligament bridges the ulnar aspect of the first metacarpal and the proximal phalanx and functions as a major stabilizer of the first metacarpophalangeal joint. Acute or chronic injury of this ligament is referred to as gamekeeper's thumb. The objectives of this study were to (1) determine the MR appearance of the ulnar collateral ligament of the thumb in cadavers and volunteers and (2) analyze the MR findings in patients with gamekeeper's thumb, especially with regard to the value of MR in detecting clinically significant displacement of the ligament (Stener lesion). MATERIALS AND METHODS: MR imaging of the first metacarpophalangeal joint was performed in three volunteers, two cadaveric specimens, and 11 patients with acute injury. In the patients, the mechanism of injury was an abrupt abductive force on the thumb resulting in rupture of the ulnar collateral ligament. The diagnosis was confirmed by surgery in five patients and by clinical follow-up in the remaining six. Cryomicrotome sectioning of the cadaveric tissue blocks was performed to correlate pathologic and MR findings. Images were interpreted by one radiologist. RESULTS: MR images showed rupture of the ulnar collateral ligament in all 11 patients. Prospectively, Stener lesions (n = 3) could be differentiated from non-Stener lesions (n = 8) in eight of 11 patients. Retrospectively, the correct diagnosis could be made in all 11 patients once the importance of determining the position of the ulnar collateral ligament relative to the adductor aponeurosis was understood. CONCLUSION: MR imaging of the first metacarpophalangeal joint depicts the ulnar collateral ligament and adductor aponeurosis to good advantage. It can also accurately show tears of the ulnar collateral ligament and thus be used to differentiate a rupture without significant retraction from a Stener lesion. This information is important in determining whether surgical or conservative management is indicated.

MR imaging of the ankle and foot: normal structures and anatomic variants that may simulate disease.

In the past, MR imaging of the ankle and foot has been performed by scanning both extremities simultaneously to provide a normal side for comparison. More recently, unilateral imaging with small local coils has been favored to maximize spatial resolution through use of small fields of view or large matrices. Such clarity of detail, however, demands a greater knowledge of normal anatomy and anatomic variants. We illustrate the MR appearances of a number of variants involving muscle, tendons, ligaments, and osseous structures of the foot and ankle. Familiarity with these findings is essential to prevent errors in the interpretation of MR images.

The functional significance of calcification of coronary arteries as detected on CT.

We evaluated the coronary arteries on computed tomography (CT) scans of the chest and on coronary angiograms of 27 patients who underwent both studies. We related the presence or absence of coronary artery calcification on CT to percentage stenosis on angiogram. For the left anterior descending artery (LAD), the likelihood of calcification rose proportionately with degree of stenosis; this was less true for the circumflex, and not true for the right coronary artery (RCA). The sensitivity of CT in detecting coronary artery calcification in patients with angiographic criteria of significant coronary artery disease (CAD) was 78% for the LAD, 63% for the circumflex, and 16% for the RCA. Specificities were 78%, 80%, and 100%, and positive predictive values were 88%, 83%, and 100%. The high positive predictive values suggest that coronary artery calcification diagnosed by chest CT has a high correlation with clinically significant CAD. Therefore, when we detect such calcification in a patient without documented heart disease, we suggest that a cardiac workup is indicated.