Section II Musculoskeletal Radiology

Transcription

1 Section II Musculoskeletal Radiology Figure You are shown a noncontrast CT (Figure 1) of the thigh. What is the MOST LIKELY diagnosis? A. Synovial sarcoma B. Hemangioma C. Organizing hematoma D. Soft tissue myxoma Synovial sarcomas most often affect the extremities (80-90%). They are usually found near, but not in, large joints. Approximately 30% show eccentric or peripheral calcification.

2 Figure 2 Figure 3 Figure You are shown an AP radiograph of both knees (Figure 2) and axial CT images of the distal femur (Figure 3) and proximal tibia (Figure 4). What is the MOST LIKELY diagnosis? A. Lyme arthritis B. Pigmented villonodular synovitis C. Synovial osteochondromatosis D. Rheumatoid arthritis Erosion is present in approximately 50% of patients. These erosions are well-defined with sclerotic margins reflecting the chronicity of the disorder. The joint space is preserved until late in the course of the disease. There is no inflammatory pannus actively destroying cartilage. PVNS may appear dense on plain films and CT, a result of abundant hemosiderin deposition.

3 Figure You are shown an AP radiograph (Figure 5) of the ankle of a 35-year-old man. What is the MOST LIKELY diagnosis? A. Osteosarcoma B. Chondroblastoma C. Osteoblastoma D. Giant cell tumor The lesion shows all of the classic features: non-sclerotic margin, no internal mineralization, and epiphyseal location. The patient is also of the appropriate age for GCT.

4 Figure 6 Figure You are shown axial T1-weighted (Figure 6) and sagittal inversion recovery (Figure 7) images of the thigh. What is the MOST LIKELY diagnosis? A. Lipoma B. Morel-Lavallée lesion C. Myxoma D. Hematoma The relatively high SI of the lesion on T1W and inversion recovery images is characteristic of subacute (1-12 weeks) hemorrhage at the soft tissues. This is predominantly due to the presence of methemoglobin. Deoxyhemoglobin is present as well and may explain the lower SI at the center of the bleed which is also characteristic. The low SI at the periphery is typical and is due to hemosiderin deposition.

5 Figure 8 Figure You are shown coronal T1-weighted (Figure 8) and inversion recovery (Figure 9) images. What is the MOST LIKELY diagnosis? A. Stress fracture B. Red marrow C. Pathologic fracture D. Paget disease There is diffuse bone marrow infiltration at the pelvis and femur. There is a hypointense fracture line at the femoral neck. This patient with known multiple myeloma experienced the sudden onset of pain.

6 Figure 10 Figure You are shown coronal (Figure 10) and sagittal (Figure 11) T2-weighted images with fat suppression. What is the MOST LIKELY diagnosis? A. Osteopoikilosis B. Synovial chondromatosis C. Lipoma arborescens D. CPPD deposition Synovial chondromatosis is a benign, neoplastic synovial proliferation of cartilage. Multiple cartilage nodules in the synovium protrude or break off into the joint space. Multiple joint bodies may calcify and/or ossify, or coallesce. The MR appearance of multiple intraarticular masses is therefore variable. Fig 12 Fig 13

7 31. You are shown an AP radiograph (Figure 12) and an axial CT (Figure 13) of a 29-year-old man. What is the MOST LIKELY diagnosis? A. Fibrous dysplasia B. Thalassemia major C. Paget disease D. Sarcoidosis Thalassemia major is characterized by extensive, diffuse hematopoiesis throughout the skeleton. The resulting marrow hyperplasia leads to osteopenia, cortical thinning and coarse trabeculation. It is often associated with extramedullary hematopoiesis. 32. Which one of the following ligaments borders the supraspinatus outlet? A. Coracoacromial B. Coracohumeral C. Superior glenohumeral D. Coracoclavicular Coracoacromial The borders of the supraspinatus outlet are the humeral head, acromion, the acromioclavicular joint, and the coracoacromial ligament. The acromion, acromioclavicular joint, and the coracoacromial ligament form the coracoacromial arch, the superior border. 33. Which one of the following may result in supraspinatus muscle atrophy? A. Quadrilateral space mass B. Supracondylar process C. Spinoglenoid notch varix D. Suprascapular notch ganglion cyst Any space occupying process in the suprascapular notch can compress the suprascapular nerve, leading to denervation atrophy of the supraspinatus and infraspinatus muscles. 34. Which one of the following lesions is usually stable? A. Bankart B. Glenoid labrum articular disruption (GLAD) C. Perthes D. Humeral avulsion glenohumeral ligament (HAGL) The GLAD lesion is a superficial anterior inferior labral tear associated with adjacent anterior inferior articular cartilage damage. It does not usually cause anterior instability because the anteroinferior labroligamentous complex, including the scapular periosteum, remains intact. 35. Concerning aneurysmal bone cyst, which one of the following is CORRECT?

8 A. Giant cell tumor is the most commonly associated neoplasm. B. There is thick sclerosis at the margin of the lesion. C. A preexisting lesion can be found in over 75% of cases. D. Primary lesions are usually epiphyseal. Aneurysmal bone cyst is a non-neoplastic, expansile lesion of bone with thin-walled, blood-filled spaces. The development of some ABC's following trauma led to the notion that changes in local hemodynamics may have a role in their development. This is further supported by the coexistence of numerous neoplasms which, like antecedent trauma, may also disturb local hemodynamics. Whether or not ABC is a reaction to such precursors is, however, not proven. It is customary, therefore, to speak of primary ABC, presumably arising denovo and secondary ABC, associated with neoplsm. Up to 40% of secondary ABC's are associated with giant cell tumor of bone. Other associated lesions are osteoblastoma, chondroblastoma, chondromyxoid fibroma, non-ossifying fibroma, fibrous dysplasia, solitary bone cyst and Langerhan cell granulomatosis. Approximately 15% of giant cell tumors have areas of ABC. 36. Concerning Paget disease of bone, which one of the following is CORRECT? A. The incidence in individuals over 80 years of age is approximately 10%. B. Monostotic disease is more common than polyostotic disease. C. Secondary sarcomas are typically low grade. D. It does not occur in bones formed by intramembranous ossification. The incidence is up to 3-4% of individuals over the age of 40 years, and 10% in individuals over the age of 80 years. 37. Concerning soft tissue hemangioma, which one of the following is CORRECT? A. Phleboliths are seen equally well with MRI and CT. B. Intralesional fat is seen well with MRI and CT. C. Bone involvement is a sign of malignant degeneration. D. The lesion may dramatically decrease in size with pregnancy. MRI and CT both show fat within the lesion. 38. Concerning bone marrow, which of the following is CORRECT? A. Hematopoietically active bone marrow is 5% fat. B. Conversion begins at the metaphysis. C. The epiphyses and apophyses are hematopoietically active throughout life. D.Residual red marrow is common at the proximal and distal femora. Residual red marrow is common at the proximal femora and humerii. It is also common at the distal femora especially in adolescents and menstruating women. This may appear geographic or patchy and therefore may be confused with a tumor. This is particularly the case when viewing an MRI of the knee without the contralateral side for comparison.

9 39. Concerning the MR appearance of a stress fracture, which one of the following is CORRECT? A. Edema may be seen at the bone marrow, periosteal surface, and adjacent soft tissues. B. Bone marrow edema is less prominent on water-sensitive images than on T1-weighted images. C. A hypointense fracture line is the earliest finding. D. Lack of gadolinium enhancement is characteristic. Long before a stress fracture is evident on plain X-ray and before a hypointense fracture line can be detected on MR, edema is present at the bone masrrow, periosteal surface and/or soft tissues with MR imaging of stress reactions. 40. Uniform joint space narrowing is characteristic of which one of the following? A. Osteoarthritis B. Pigmented villonodular synovitis C. Rheumatoid arthritis D. CPPD arthropathy The extensive synovitis and pannus formation of RA or any of the inflammatory arthridities leads to relatively early, uniform destruction of the hyaline articular cartilage and therefore, uniform, concentric, diffuse joint space narrowing. 41. Concerning calcium hydroxyapatite deposition, which one of the following is CORRECT? A. The flexor carpi ulnaris tendon is most commonly involved. B. It most commonly involves the bursa. C. It is associated with tumoral calcinosis. D. It does not occur in the joint. Calcium hydroxyapatite is the most common form of calcium in pathologic calcifications. This may be primary or idiopathic and secondary. The secondary soft tissue calcifications of chronic renal disease, collagen-vascular disease, tumoral calciniosis and hypervitaminosis D, for example, are predominantly hydroxyapatite. 42. Concerning Looser s zones, which one of the following is CORRECT? A. They are associated with Paget disease. B. They are usually unilateral. C. They are considered stress related. D. They progress to a complete fracture. They represent stress related regions of unmineralized osteoid that present as incomplete linear lucencies perpendicular to the cortical surface. They are most common in the scapula, rib, pelvis, femur, and ulna. 43. Which of the following pulse sequences results in the shortest scan time? A. Spin echo B. Gradient echo C. Inversion recovery D. STIR pulse sequence

10 The gold standard in MR imaging is spin echo. It requires full recovery of Mo or Mz. It also requires a 90 degree flip angle and a 180 degree refocusing pulse at TE/2. Gradient echo can use a partial flip angle and requires no 180 degree refocusing pulse. It uses the frequency encoding gradients to refocus. Inversion recovery adds a pre sequence to either gradient echo or spin echo sequences. STIR is a special IR pulse sequence. Therefore, Gradient echo is the shortest. 44. Concerning the arthropathy of systemic lupus erythematosus, which one of the following is CORRECT? A. It is deforming and erosive. B. It is similar to Jaccoud s arthropathy. C. It is characterized by soft tissue calcifications. D. It is an uncommon manifestation. It is similar to Jaccoud s arthropathy. The radiographic manifestations are similar to the post-rheumatic fever arthropathy, non-erosive, and reversible in nature 45. Concerning ankylosing spondylitis, which one of the following is CORRECT? A. Anterior corner osteitis is the hallmark of the disease. B. It is most common in children. C. Ossification predominates at the anterior longitudinal ligament. D. Early erosions occur at the ilium. At the S.I joint, the hyaline articular cartilage is thinner at the ilium and thicker at the sacrum. Thus, erosions occur on the iliac side first in patients with sacroiliitis. 46. Concerning necrotizing fasciitis, which one of the following is CORRECT? A. It is a slow but progressive infection. B. The prevalence has decreased. C. Gas in the subcutaneous tissue is a clue to diagnosis. D. Contrast-enhanced CT shows marked fascial enhancement. A fairly specific indicator of necrotizing fasciitis is the presence of gas in the subcutaneous tissue formed by gasforming anaerobic organisms. This, however, is not always present. Aerobic gram negative organisms are often present as well.