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Purpose: To determine the imaging characteristics of lumbar facet joint synovial cysts after percutaneous treatment with steroid injections and distention of the cyst and to correlate these findings with the clinical outcome., Materials and Methods: Clinical outcome and imaging findings were retrospectively studied in 12 patients (four men, eight women) aged 45-79 years (mean, 60 years) with a symptomatic lumbar facet joint synovial cyst treated with percutaneous steroid injections. At varying times after the procedure, patients were contacted for clinical follow-up, and repeat imaging was performed to verify the status of the cyst., Results: Excellent pain relief was achieved in nine (75%) of 12 patients. At follow-up imaging, the cyst completely regressed in six (67%) of these nine patients, partially regressed in two (22%) patients, and was unchanged in one (11%) patient. One (8%) of the 12 patients had transient pain relief, with recurrence of symptoms at short intervals after each of three injections. No pain relief was achieved in two (17%) of 12 patients., Conclusion: Image-guided percutaneous steroid injections are often effective in the treatment of lumbar facet joint synovial cysts and may result in complete regression of the cyst.

Objective: "Thigh splints," also known as the adductor insertion avulsion syndrome, is a painful condition affecting the proximal to mid femur at the insertion of the adductor muscles of the thigh. Scintigraphic findings in this syndrome have been described; we report a spectrum of MR imaging abnormalities involving this portion of the femur in a group of patients presenting with hip, groin, or thigh pain., Conclusion: Symptoms of vague hip, groin, or thigh pain may be associated with stress-related changes in the proximal to mid femoral shaft (thigh splints). When interpreting MR imaging studies of the pelvis in patients presenting with these symptoms, careful attention should be directed to this portion of the femur. This is especially important because the findings may be subtle, and this region is often at the distal edge of most MR imaging studies of the pelvis and hip.

Objective: Signal intensity changes in lumbar pedicles, similar to those described in vertebral body endplates adjacent to degenerated discs, have been described as an ancillary sign of spondylolysis on MRI. The purpose of this study was to determine whether pedicle marrow signal intensity changes also occur in association with facet degenerative joint disease., Design: Eighty-nine lumbar spine MRI examinations without spondylolysis were reviewed for marrow signal intensity changes in pedicles and vertebral bodies as well as for facet degenerative joint disease., Results: Five percent (46/890) of lumbar pedicles in 23 patients had marrow signal intensity changes. Ninety-one percent (42/46) of the abnormal pedicles had adjacent degenerative joint disease of the facets, while only 21% (189/890) of normal pedicles had adjacent facet degenerative joint disease (p<0.001). Eighty-nine percent (41/46) of the pedicles with marrow signal intensity changes had adjacent degenerative disc disease., Conclusions: Pedicle marrow signal intensity changes are not a specific sign of spondylolysis; they are commonly seen with adjacent facet degenerative joint disease in the absence of spondylolysis. Pedicle marrow signal intensity changes are probably a response to abnormal stresses related to abnormal motion or loading caused by the degenerative changes in the spinal segment.

Objective: To evaluate the association of abnormal signal intensity within the sinus tarsi with abnormalities of the posterior tibial tendon (PTT) on MR imaging., Design and Patients: Sinus tarsi abnormalities were identified on 30 ankle MR examinations in 29 patients. The PTT and anterior talofibular ligament were retrospectively analyzed for abnormalities in these same patients., Results and Conclusions: Tears of the anterior talofibular ligament were found in 13 of 30 (43%) ankles. PTT abnormalities (complete tear, partial tear or dislocation) were seen in 14 of 30 (47%) studies, and were distributed relatively equally between those patients with and without lateral ligament tears. Our results provide evidence of an association between abnormalities of the PTT and the sinus tarsi. The finding of abnormal signal intensity within the sinus tarsi on MR imaging should alert the radiologist to potential abnormalities of the PTT.

Study Design: One-group discriminant analysis., Objective: To determine whether 1 MHz of continuous ultrasound can identify tibial stress fractures in subjects., Background: Stress fractures can lead to loss of function or to more serious nonunion fractures. Early diagnosis is important to reduce the risk of further injury and to assure a safe return to activity. Therapeutic ultrasound has been reported to be an accessible, less expensive alternative in diagnosing stress fractures compared with other diagnostic techniques., Methods and Measures: Twenty-six subjects (12 men, 20.33 +/- 1.37 years; 14 women, 20.78 +/- 3.8 years) with unilateral tibia pain for less than 2 weeks volunteered to participate in the study. Continuous, 1 MHz ultrasound was applied to the uninvolved and involved tibias at 7 increasing intensities for 30 seconds each. Subjects completed a visual analog scale after the application of each intensity to assess the pain response to ultrasound. Results from the visual analog scale were compared to magnetic resonance imaging (MRI) findings to determine if continuous ultrasound could predict whether subjects had a normal MRI, increased bone remodeling, or advanced bone remodeling consistent with a stress fracture., Results: Discriminant analysis on the visual analog scale correctly classified subjects into 1 of 3 clinical classification groups in 42.31% of the cases. None of the subjects found to have a stress fracture by MRI were correctly identified by continuous ultrasound. This resulted in a predicted sensitivity of 0% and a predicted specificity of 100%., Conclusions: A protocol using visual analog scores after the application of 1 MHz continuous ultrasound is not sensitive for identifying subjects with tibial stress fractures.

Objective: To our knowledge, this article is the first to describe a series of patients with avulsion fractures of the base of the fifth metatarsal that were not seen on conventional radiography using the standard three views of the foot but that were seen on radiography of the ankle., Conclusion: Because routine radiographs of the foot may fail to reveal an avulsion fracture of the base of the fifth metatarsal, an additional projection should be obtained to better assess this region in the symptomatic patient. The additional view should be an anteroposterior radiograph of the ankle that includes the base of the fifth metatarsal because this projection has been shown to help in the diagnosis of this avulsion fracture.

The authors performed fluoroscopy-guided sacroiliac (SI) joint injections. With the patient prone and the x-ray tube perpendicular to the fluoroscopic table, the skin was marked over the distal 1 cm of the SI joint. With the tube angled 20 degrees - 25 degrees cephalad, a 22-gauge needle was inserted at the skin mark and advanced perpendicular to the fluoroscopic table toward the posterior joint. Nonionic contrast material was injected to confirm the intraarticular position of the needle. Of 31 SI joint injections, 30 (97%) were intraarticular. Mean procedure time was 108 seconds. This technique is safe, rapid, and reproducible.

A thorough understanding of compartmental anatomy is essential for accurate staging of a suspected musculoskeletal tumor with MR imaging and for avoiding potentially devastating biopsy-related complications. Imaging-guided, percutaneous needle biopsy is a safe and cost-effective technique but requires careful planning in conjunction with the surgeon who will perform the definitive surgery because it constitutes the final step in the staging process and the first step in surgical therapy.

Purpose: To determine if there are any predictable patterns of internal derangement associated with a bone contusion of the posterior lip of the medial tibial plateau at magnetic resonance (MR) imaging and to offer a biomechanical explanation for the findings., Materials and Methods: A retrospective review of 215 consecutive MR examinations for knee trauma was conducted to identify contusions of the posterior lip of the medial tibial plateau. Any additional contusions and internal derangements were documented in the cases with these contusions. Medical charts and arthroscopic results, when available, were reviewed for mechanisms of injury., Results: The specific medial tibial contusion was demonstrated in 25 of 215 (12%) knee MR examinations. Associated anterior cruciate ligament (ACL) tears were found in 25 of the 25 (100%) examinations. Injury to the meniscocapsular junction (14 of 25) or a peripheral tear of the posterior horn of the medial meniscus (10 of 25) occurred in a combined 96% of the cases. Lateral compartment contusions were noted in 24 (96%) cases. Pivot, twisting, or valgus forces were reported mechanisms of injury., Conclusion: Contusions involving the posterior lip of the medial tibial plateau may result from a contrecoup impaction injury directly following an ACL tear, as the knee reduces. These contusions are almost always associated with a far peripheral meniscal tear or with a meniscocapsular junction injury affecting the posterior horn of the medial meniscus.

To determine whether fatty marrow conversion of the proximal femoral metaphysis is related to osteonecrosis of the femoral head using a marrow conversion index ([signal intensity of the proximal femoral metaphysis/signal intensity of the greater trochanter] x 100 in T1 weighted magnetic resonance images), a case control study was conducted on 42 osteonecrotic hips in 28 patients. The 28 patients (42 osteonecrotic hips) were matched with 84 control patients (84 normal hips) for gender, age (5-year range), and time of presentation (1-year range). The marrow conversion index was measured in each hip studied. The index was 90.2% (standard deviation, 8.2%) in osteonecrotic hips and 75.1% (standard deviation, 9.1%) in matched controls. By conditional logistic regression, a 5% increase in the index was associated with 3.6 times increase of the odds ratio of osteonecrosis and a 10% increase with a 12.9 times increase of the odds ratio. The marrow conversion index, which reflects the ratio of fatty marrow conversion of the proximal femoral metaphysis to that of the greater trochanter measured on T1 weighted magnetic resonance images, is increased in osteonecrotic hips.

Purpose: To describe the magnetic resonance (MR) imaging findings in diabetic patients with muscle infarction and to describe commonly associated clinical features., Materials and Methods: The MR imaging studies of 21 patients with diabetic muscle infarction were reviewed retrospectively. Of the 21 patients, 12 were women, and nine were men; the mean age was 48 years (range, 30-77 years)., Results: Eight patients had bilateral lower-extremity involvement; six had involvement confined to the right lower extremity and seven to the left. The thigh was involved in 17 patients (81%). One or more of the musculi vastus, the most frequently affected muscle group, were affected in 16 patients (76%). Four patients (19%) had isolated calf involvement. MR imaging studies showed diffuse enlargement of involved muscle groups and partial loss of normal fatty intermuscular septa. MR imaging also allowed identification of areas of subfascial fluid in 16 patients (76%) and subcutaneous edema in 19 patients (90%). MR imaging showed involved muscle groups best with T2-weighted, inversion-recovery, and gadolinium-enhanced sequences, where the infarcted muscles appeared diffusely hyperintense compared with adjacent muscles. Comparison of T2-weighted and gadolinium-enhanced MR images of nine patients showed enlarged, enhancing muscles in all patients and small, focal, rim-enhancing fluid collections in six of nine patients (66%)., Conclusion: Diabetic muscle infarction is suggested in diabetic patients with sudden onset of severe pain in the thigh or calf muscles who have MR imaging findings of diffuse edema and swelling of multiple thigh and calf muscles (often in more than one compartment).

MR imaging of the wrist has the unique capability of simultaneously demonstrating bone and soft tissue structures. Its exquisite sensitivity for detecting bone marrow edema makes it and ideal screening tool for diagnosing radiographically occult osseous injuries and areas of AVN. This, together with its ability to provide a comprehensive, non-invasive assessment of the ligaments, tendons, nerves, and components of the TFC make MRI a very powerful tool for evaluating patients with wrist pain of uncertain etiology. Its exact role in the work-up of these patients has not been entirely established, but with further advances in technology and the radiologist's understanding of wrist anatomy and pathology, MRI is assuming a more central role in this clinical setting.

Objective: The purpose of this study was to determine the prevalence and nature of a horizontal cleft in the posterior aspect of Hoffa's infrapatellar fat pad and to show pathologic processes involving this cleft., Materials and Methods: Fifty consecutive MR imaging examinations of the knee were evaluated for the presence and appearance of a cleft in the infrapatellar fat pad. Examples of abnormalities involving the cleft were collected from additional MR studies. MR imaging, gross dissection, and histologic examination of a cadaveric knee were also performed to evaluate the anatomy and histology of the cleft., Results: The cleft in the infrapatellar fat pad was revealed on MR imaging in 45 of 50 knees and had a variable shape, either linear (82%), pipe-shaped (7%), or globular-shaped (11%). Joint effusion or anterior cruciate ligament tear did not affect the appearance of the cleft. The cleft was located anterior to the distal insertion of the anterior cruciate ligament on the tibia. At gross dissection of the cadaveric knee, the roof of the cleft was formed by the ligamentum mucosum (infrapatellar plica), and the cleft was lined with synovium. The prospective evaluation of additional MR imaging examinations of the knee revealed pathologic entities of the cleft such as ganglion cysts, loose bodies, nodular synovitis, and amyloid., Conclusion: A horizontal cleft located in the posterior aspect of the infrapatellar fat pad is a common and normal MR imaging finding with a prevalence of 90%. The horizontal cleft is lined with synovium and its roof is formed by the ligamentum mucosum (infrapatellar plica). This cleft communicates with the knee joint. A distended cleft can form a prominent recess mimicking pathologic processes; conversely, disorders can arise in the cleft.

This article reviews the variety of imaging modalities that are currently being used to evaluate the knee. Nuclear scintigraphy is discussed with emphasis on prosthesis abnormalities. Sonography is discussed with regard to the evaluation of popliteal masses. The uses of computed tomography, especially in the evaluation of the tibial plateau fracture, are discussed, and the role of fluoroscopy, computed tomography, and sonography in image-guided needle procedures are reviewed. Emphasis is placed on the role of MR imaging in knee imaging, with attention to internal derangements, bursal and capsular pathology, and other assorted intra- and extra-articular disorders. The focus of this article is to review the wealth of information that may be obtained by using these imaging modalities.

Purpose: To assess the effect of knee magnetic resonance (MR) imaging on the diagnosis and management of acute knee injury., Materials and Methods: Two orthopedic knee surgeons prospectively completed pre- and post-MR imaging questionnaires on 84 of 91 consecutive patients with acute knee injury. The pre- and post-MR imaging clinical diagnoses, certainty regarding these diagnoses, other diagnostic tests, and subjective impression of the usefulness of MR imaging were determined., Results: Seven hundred thirty-one of 840 pre- and post-MR imaging diagnoses agreed. Agreement was lowest for medial meniscal injuries (54 of 84). Significantly fewer meniscal injuries were suspected after MR imaging (P < .05). In 60 patients, the orthopedist changed at least one of the 10 potential diagnoses after MR imaging. Clinical diagnostic certainty increased by a mean of 14% for all diagnoses. The increase in diagnostic certainty was greatest for medial meniscal injuries (30%), followed by lateral meniscal injuries (21%). The proposed management changed in 41 patients, resulting in significantly fewer arthroscopic procedures (P < .01). The post-MR imaging management plans included 37% (27 of 73) fewer arthroscopic procedures., Conclusion: MR imaging affects the diagnosis and management of acute knee injury by decreasing the number of arthroscopic procedures, improving clinician diagnostic certainty, and assisting in management decisions.

Purpose: To determine the value of injections of local anesthetic and steroids in the foot and ankle in localizing the source of pain and their effect on clinical confidence and decision making., Materials and Methods: In 47 patients, fluoroscopically guided injections of local anesthetic and steroid into the foot and ankle were performed in 106 intra- and extraarticular sites. Questionnaires were completed by the referring surgeon before and after injections to evaluate the level of confidence with regard to the source of pain for each site injected and the proposed treatment plan., Results: Forty-three (91%) patients reported pain relief after injections. The level of confidence that the site injected was the source of pain increased in 68 (64%) sites, decreased in 19 (18%) sites, and remained unaltered in 19 (18%) sites (P < .01). The treatment plan was changed from nonsurgical initially to surgical in three (8%) of 36 patients and was changed from surgical to nonsurgical in three (27%) of 11 patients after injections. Of the remaining eight patients, treatment was altered in three (37%) as a result of pain relief after the injections., Conclusion: Fluoroscopically guided injections of local anesthetic and steroid in the foot and ankle can improve clinical confidence with regard to the site of pain and may be valuable in clinical decision making and patient treatment.

With high-resolution MR imaging, the collateral ligament of the elbow can be directly evaluated; thus ligamentous injuries can be detected, localized, and graded. The functional anatomy of the ligaments of the elbow is reviewed. The normal appearance of the ligaments on MR images as well as the clinical and MR imaging findings of medial and lateral collateral ligament injury are presented.

Objective: To determine whether anteroposterior (AP) and lateral views of the knee are equivalent to four views in acute fracture detection., Design: Three musculoskeletal radiologists retrospectively interpreted the plain film knee examinations of each patient, establishing ground truth for the presence or absence of a fracture. Cases were presented to four masked senior radiology residents twice--once as a two-view study and again as a four-view study--with 4 weeks separating the two reading sessions to minimize recall bias. Sensitivity, specificity, and diagnostic performance were calculated., Patients: Ninety-two patients presenting to the emergency department with acute knee trauma were evaluated with at least a four-view plain film examination., Results and Conclusions: Mean sensitivity for fracture detection using four views (85%) was significantly higher than that using two views (79%). Mean specificity and receiver operating characteristic curve areas were not significantly different using two or four views. Four views are more sensitive than AP and lateral views alone in detection of acute knee fracture.

Objective: Diagnosing degenerative disk disease (DDD) at the lumbosacral junction (LSJ) on plain films is often difficult, compared with other disk levels. The purpose of this study was to determine whether criteria for diagnosis of DDD at the LSJ can be established for plain films., Design and Patients: We retrospectively reviewed 100 lumbar MRI scans of patients who also had lumbar plain films. Using MRI as the reference standard, the LSJ was classified as normal (n=35) or exhibiting mild (n=45) or severe (n=20) DDD by two radiologists using accepted criteria. Measurements were performed on the plain films by two other radiologists and the average measurements were tabulated according to the three categories of DDD defined by MRI. Plain film measurements included the anterior and posterior disk heights (ADH, PDH), Farfan's ratio, determined by adding ADH to PDH and dividing that number by the measured anteroposterior (AP) length of the inferior end plate of L5 [(ADH+PDH)/AP length of L5], and lumbosacral angle (LSA). Subsequently, five additional radiologists interpreted the radiographs by visual inspection only, for DDD at the LSJ, both before and, several weeks later, after being provided with the quantitative data for normal versus DDD., Results and Conclusion: There was a statistically significant difference between normal disk and increasing severity of DDD on radiographs using the parameters of PDH and Farfan's ratio. There was no statistically significant difference regarding ADH or LSA. Diagnostic accuracy by visual inspection was not significantly altered using the quantitative data for interpretation of DDD (68% correct before, 69.5% correct after). Analysis of results indicates that PDH is the most reliable and easily used criterion for detection of DDD at the LSJ. A PDH < or =5.4 mm on plain lateral film indicates DDD; PDH > or =7.7 mm indicates the absence of DDD on plain film.

Hip dysplasia is a not uncommon feature in adults and can vary from subtle acetabular dysplasia to complex sequelae of developmental dysplasia of the hip. This review article describes the most useful radiographic measurements used to evaluate the adult hip. The frontal projection of the pelvis permits measurement of the center-edge angle (CE angle) and "horizontal toit externe" angle (HTE angle), both of which assess the superior coverage of the acetabulum. The femoral neck-shaft angle (NSA) is also measured on this view. The false profile radiograph of the pelvis is described. It allows measurement of the vertical-center-anterior angle (VCA angle), which determines the anterior acetabular coverage and detects early degenerative hip joint disease. When surgery is contemplated, computed tomography (CT) is useful to better determine the anterior acetabular coverage by use of the anterior acetabular sector angle (AASA), and the posterior acetabular coverage by use of the posterior acetabular sector angle (PASA). CT also permits measurement of femoral anteversion. These measurements are particularly useful in the evaluation of acetabular dysplasia and for the preoperative assessment of the dysplastic hip.

Selective nerve block (SNB) in the spine is a diagnostic and therapeutic imaging procedure. It consists of placing a needle under fluoroscopic guidance in the epiradicular space, which is formed by extensions of the anterior and posterior epidural membranes. Injection of nonionic contrast will confirm the correct position of the needle. This is followed by injection of a long-acting local anesthetic and/or corticosteroid. Pain reproduction followed by pain relief is recorded. This technique enables one to identify a symptomatic nerve, produce pain relief for a variable period of time, and help select surgical candidates.

Rationale and Objectives: We assessed the impact of ankle radiographs on referring physicians' diagnoses and treatment of acute ankle injuries., Methods: Twenty emergency department physicians prospectively completed questionnaires before and after radiography on 101 patients with acute trauma receiving ankle radiographs. The questionnaires asked physicians to estimate the probability (0-100%) of their most likely diagnosis before and after receiving the radiographic information. We also asked their anticipated and final treatment plans. We calculated the mean gain in diagnostic confidence percentage and the proportion of patients with changed initial diagnoses or anticipated management., Results: The mean gain in diagnostic certainty from ankle radiographs was 34% (95% confidence interval [CI] = 28-40%). Ankle radiographs changed physicians' initial diagnoses in 37% (95% CI = 28-47%) of the patients. Immediate clinical management changed in 30% (95% CI = 22-40%) of the patients., Conclusion: Plain ankle radiographs have considerable impact on referring physicians' diagnoses and treatment of acute ankle trauma.

The authors present a review of the anatomy of the major bursae around the shoulder joint and discuss the use of the different imaging modalities which demonstrate their radiologic features. The calcified subacromial-subdeltoid bursa has a characteristic appearance on plain radiographs. When inflamed it can be visualized by ultrasound and magnetic resonance imaging. Calcific bursitis may involve the subcoracoid bursa. This bursa may mimic adhesive capsulitis of the shoulder or complete rotator cuff tear when injected inadvertently during shoulder arthrography. Less well known are three coracoclavicular ligament bursae. These are also subject to calcific bursitis and have a typical radiologic appearance.

Purpose: To determine how often lateral-compartment bone contusions are seen on magnetic resonance (MR) images of knees in adolescents with intact anterior cruciate ligaments (ACLs)., Materials and Methods: MR images obtained in 53 adolescent patients (30 male, 23 female; aged 10-20 years) were reviewed to detect bone contusions in the posterolateral tibial plateau or the lateral femoral condyle. ACLs were also evaluated with accepted criteria for the diagnosis of ligamental disruption. Only patients referred for evaluation of a knee injury or mechanical symptoms were included., Results: Five patients with bone contusions had an intact ACL at MR imaging. One of the five had arthroscopic confirmation. Fifteen other patients had complete ACL disruptions: 13 of these patients had typical bone contusions; the other two had no bone abnormalities but had chronic ACL tears. Thus, 28% of the 18 patients with typical bone contusions had intact ACLs., Conclusion: Adolescents may have the same pattern of contusions as adults but may maintain an intact ACL owing to increased ligamentous laxity.

This article describes the steps involved in production of a computer teaching module on the radiographic diagnosis of arthritis. The module was part of a research project aimed at producing seven computer teaching modules. Several staff radiologists and residents were involved, as well as a consultant on medical education. A generic shell program was used as a frame for all seven modules. The author of each module then filled in the empty pages of the shell with the appropriate text and images, along with additional short program scripts. The module on the radiographic diagnosis of arthritis described and illustrated the basic radiographic signs of arthritis. Practice cases were also included, and interactive and hypermedia features were implemented. The modules were then evaluated by means of task list tests and interviews. The experience was judged to have been successful, although the amount of time spent by some authors was much more than expected.

Objective: The purpose of this study was to evaluate the MR imaging characteristics of Achilles tendons in patients at risk for tendon xanthomas because of familial hyperlipidemia and to compare these findings with those seen on plain radiographs and physical examination. We also wished to determine if MR imaging could be used to differentiate xanthomas from traumatic tendinopathy in a second group of patients who had no history of hyperlipidemia but who had a history of trauma to the Achilles tendon., Subjects and Methods: We evaluated the MR imaging studies of 26 Achilles tendons in 13 patients with heterozygous familial hypercholesterolemia (n = 11) and type III dysbetalipoproteinemia (n = 2). The size, shape, and signal characteristics of the Achilles tendon were recorded. A tendon was considered abnormal by MR if there was high signal, a convex anterior border, or an anteroposterior measurement greater than 7 mm. Findings on plain radiographs and physical examination of the Achilles tendons were evaluated in the same group of patients. In the group of patients with hyperlipidemia, palpable abnormalities of the Achilles tendon were present in 14 of 26 tendons. Plain radiographs were interpreted as showing abnormalities in 18 of the 26 tendons. In a second group of 21 tendons in patients with no history of hyperlipidemia but with traumatic tendinopathy, studies were evaluated for the size, shape, and signal characteristics of the Achilles tendon., Results: On MR images, 24 of 26 tendons showed signal abnormalities, and 19 of 26 were enlarged. Abnormal signal was a diffuse stippled pattern with many low-signal round structures of equal size surrounded by high-signal material on all pulse sequences. Abnormal signal was seen in tendons of both normal and abnormal size. Bilateral and symmetric changes were found in all but one patient. Tendinopathy in patients without known hyperlipidemia appeared indistinguishable from tendon xanthomas in six (29%) of 21 tendons. The other tendons (71%) were distinctly different from xanthomas without a uniform stippled signal pattern., Conclusion: MR imaging of patients with familial hyperlipidemia showed an abnormal stippled signal pattern with or without enlargement or abnormal configuration of the tendon. MR imaging is a more sensitive method than physical examination and plain films for detecting abnormalities in Achilles tendons of patients with hyperlipidemia. Although the MR signal pattern of xanthomas is often different from that of partial tendon tears, tendon degeneration, or tendinitis, a significant overlap in appearance can be observed and the MR appearance of a xanthoma is not pathognomonic.

Magnetic resonance imaging (MRI) of the knee is the most frequently performed musculoskeletal MRI examination and, after initial study with plain radiographs, has supplanted arthrography and arthroscopy as the imaging procedure of choice in the investigation of internal derangement and arthritic disorders of the knee. Knee MRI is a highly accurate, noninvasive procedure that provides exquisite depiction of the soft tissues and bone marrow. In this article a simplified approach to knee MRI is presented, including a practical discussion on the basics of MRI physics, review of the normal anatomy, and illustration of the most commonly encountered pathologic conditions.

Technical improvements in MR imaging have resulted in the ability to detect soft tissue and bone pathology, with great facility in the elbow joint. This allows application of MRI to the elbow in the same valuable ways it has been used in other joints for a much longer period.

Careful analysis of conventional radiographs remains the first step in the investigation of intra-articular abnormalities. However, other imaging techniques, such as ultrasonography, arthrography, computed tomography and magnetic resonance imaging, may add critical information that allows the correct diagnosis. The authors discuss the evaluation of masses within a joint on the basis of plain film analysis, as well as the contribution of additional imaging techniques to the differential diagnosis.

This article reviews the numerous applications of ultrasound in the musculoskeletal system. Emphasis is made on the important and often under-utilized role of ultrasound in infections, vascular lesions, arthritis, and trauma.

Magnetic resonance imaging (MRI) is the technique of choice to depict normal anatomy and to image internal derangements of the knee. The overall accuracy of this method can reach approximately 94%. MRI can effectively replace diagnostic arthroscopy for evaluation of meniscal and ligamentous tears.

In 30 volunteers with normal shoulders, the following conclusions were made with regard to normal anatomic features at magnetic resonance (MR) imaging: (a) The supraspinatus tendon has low signal intensity, except for a 1-cm area with intermediate signal intensity in the region of the "critical zone." (b) The deltoid tendon attachment on the inferior surface of the acromion may simulate a subacromial spur if not imaged in continuity. (c) Fluid in the long head of the biceps tendon sheath is normal if not completely surrounding the tendon. (d) The anterolateral branch of the anterior humeral circumflex vessels in the proximal bicipital groove adjacent to the biceps tendon mimics fluid in the tendon sheath. (e) Continuity or obliteration of the subacromial-subdeltoid bursal fat plane is an unreliable diagnostic sign since the fat plane is often focally absent. (f) Fluid is not detected in subacromial-subdeltoid bursae. (g) Undercutting of the anterior glenoid labrum by hyaline cartilage or a closely apposed middle glenohumeral ligament may simulate an anterior labral tear.

One hundred consecutive magnetic resonance (MR) images of the knee in patients with acute complete anterior cruciate ligament (ACL) tears were reviewed to evaluate the prevalence and patterns of associated occult fractures. Eighty-nine occult fractures were identified in 56 knees. All occult fractures were in the posterior aspect of the lateral tibial plateau. Of these, occult fractures were isolated in 24 cases (43%) and were in combination with fractures in the middle aspect of the lateral femoral condyle in 26 (46%), with fractures in the posterior aspect of the medial tibial plateau in four (7%), and with fractures involving all three areas in one (2%). Disruption of the ACL under valgus stress leads to anterior translation of the tibia and relative external rotation of the femur. This allows impaction of the posterior portion of the lateral tibial plateau against the middle of the lateral femoral condyle and accounts for the unique pattern of occult fractures associated with ACL tears. An occult fracture of the posterior lateral tibial plateau with or without an associated fracture in the lateral femoral condyle ("kissing contusion") is a relatively frequent finding in acute ACL tears and, when present, is highly suggestive of such an associated tear.

A double-blind, prospective study of 45 patients with adhesive capsulitis of the shoulder compared the therapeutic efficacy of distensive and nondistensive arthrography in combination with the intra-articular injection of corticosteroids. After 1 and 3 months there was no significant difference between the two treatments in the degree of pain or of limitation of movement experienced by the patients. More than 80% of the patients who experienced pain at rest and nocturnal pain improved under both treatment regimens. Scapulohumeral mobility increased significantly but only partially within the first month of treatment. Articular capacity and the duration of symptoms before treatment were of no prognostic value.

The authors describe a systematic approach to plain-film diagnosis of joint disease. The major radiologic criteria--soft-tissue swelling, joint-space narrowing, bone erosion, bone sclerosis and osteophytosis, and chondrocalcinosis--are considered first. Assessing the involvement of the minor criteria of joint disease--soft-tissue atrophy or calcification, malalignment, osteoporosis, abnormal growth, intra-articular bony ankylosis, bone fragmentation, periostitis, subperiosteal resorption or acro-osteolysis--narrows the probabilities to the more likely diagnoses. Further analysis includes the distribution of joint injury, whether mono- or polyarticular, symmetrical or asymmetrical. Added to clinical information, this approach leads to a specific or refined differential diagnosis.

Facet joints have a variable anatomic orientation, and their imaging must be adapted to this variation. They have an important role in the stability and mobility of the spine at all levels. They are the sites of microtrauma leading to degenerative changes. Trauma may cause subluxation, dislocation, and fracture. As synovial joints, they manifest inflammatory processes and can present as part of a systemic disease. The facet joints are a component of a trijoint complex at each motion segment and cannot be separated biomechanically. Their visualization and analysis must be integrated with the adjoining soft tissue, and with neural and bone components.

At the Université de Montréal, a four-week rotation in radiology is part of the core curriculum for students in their fifth and final year of medicine. The objective of this undergraduate radiology clerkship is to prepare the future physician to use efficiently the resources of radiology and nuclear medicine in patient care. Specific goals and methods used to achieve them are described and analysed.

Impaction fractures of the femoral head following anterior hip dislocation were noted in eight of 11 patients. This fracture is characterized by a depression or a flattening of the posterosuperior and lateral portion of the femoral head. It is usually seen on the standard anteroposterior view of the pelvis.