Osteonecrosis - Spectrum of imaging findings Poster No.: C-1861 Congress: ECR 2016 Type: Educational Exhibit Authors: P. Ninitas, A. L. Amado Costa, A. Duarte, I. Távora ; Lisbon/ 1 1 2 1 1 2 PT, Costa Caparica/PT Keywords: Musculoskeletal bone, Musculoskeletal joint, Vascular, CT, MR, Conventional radiography, Education, Ischemia / Infarction, Pathology DOI: 10.1594/ecr2016/C-1861 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 12
Learning objectives - To know the most common and rarer causes of osteonecrosis - To review the imaging findings of osteonecrosis Background Osteonecrosis or avascular necrosis is the result of ischemia of the cellular elements of the bone. The term osteonecrosis applies when there is involvement of epiphyseal or subarticular bone, whereas the term bone infarct is reserved for metaphyseal and diaphyseal involvement (1). Osteonecrosis has numerous causes, the common etiologies are trauma, corticosteroids, alcoholism, sickle cell anemia and collagen vascular disease, however many cases are idiopathic (2,3). Other important uncommon causes are pancreatitis, infection, renal transplantation and vasculitis (3). Femoral head, the knee (distal femur and proximal tibia), humeral head, scaphoid, lunate and talus are the most affected sites (3). The patient symptoms are nonspecific - pain and reduce range of motion. The long term symptoms are dependent of the articular chronic changes, namely the articular collapse (3). The diagnosis relies heavily in the imaging findings. We will make a review of the spectrum of findings in conventional radiography, CT and MRI studies of osteonecrosis. Findings and procedure details Radiography Usually, radiography is the first imaging method used because it is widely available and inexpensive. Although insensitive for the earliest changes of osteonecrosis (require several months to occur), the imaging features are often characteristic (3). The first imaging finding is bone sclerosis, that is relative in nature because is the surrounding bone that is osteopenic. Latter in the process bone formation occurs. The typical Page 2 of 12
appearance is patchy areas of lucency and sclerosis (fig. 1) with a serpentine or undulating morphology, being the sclerosis characteristically about the lesion rim (1,3). Early changes of articular collapse typically occur at the junction of the serpentine sclerotic rim and the articular surface, where stress is maximally exerted (fig. 2) (3). The classic crescent sign (a crescent subchondral lucency) is the result of a subchondral fracture, represents collapse of the subchondral bone and separation from the overlying cartilage and attached subchondral bone plate (fig. 3) (1,3). The width of the joint space is usually preserved because the most of the times the articular cartilage is not affected (fig. 4) (4). Secondary osteoarthritis may occur latter on the course of the disease and is the consequence of progressive subchondral fragmentation, flattening and deformity of the joint (2). The radiographic differentiation of primary osteoarthritis from osteonecrosis with secondary joint degeneration can be extremely difficult (1). Computed Tomography (CT) CT is good method in the evaluation of the later changes of osteonecrosis and the findings are similar to the radiography: serpentine or undulating sclerotic margin (fig. 5). Early changes are better depicted with MR, but CT is able to delineate subtle alterations in bone when routine radiographs are normal, namely subtle alteration of the normal trabeculation pattern (1,3). Epiphyseal extension of osteonecrosis is well assessed on CT studies (fig. 6) and that information is particularly important in surgical planning for rotational arthroplasty. CT is usually the technique of choice for detection of subchondral fractures that appear as curvilinear or irregular subchondral low density line with variable extension (can breach the articular surface). Articular collapse, or secondary degenerative changes can be well characterized by CT (fig. 7) (1,3,5). So, the major roles for CT are in determining the severity of articular collapse and its location and evidence of early secondary degenerative joint disease (6). Magnetic Resonance (MR) MR is the most sensitive and specific imaging study for detection of osteonecrosis, including early disease (3,6). The initial findings in early osteonecrosis are bandlike lesions, ringlike lesions, or diffuse decreased signal intensity with a dark band, with or without collapse (7). The most common MR imaging pattern seen in osteonecrosis is a serpiginous or undulating low-signal-intensity line of uniform width on T1-weighted images (fig. 8) and T2-weighted images, with an adjacent rim of increased signal intensity on T2-weighted imaging (double-line) that is virtually pathognomonic of osteonecrosis (fig. 9). In the Page 3 of 12
center of the line there is, usually, an area of yellow marrow (1,3). However, the MR signal intensity in the area of osteonecrosis may show intrinsic characteristics other than adipose tissue: hemorrhage (high signal intensity on T1- and T2-weighted images), cystic areas (low signal intensity on T1-weighted images and high signal intensity on T2-weighted images) (fig. 10), and fibrous tissue (low signal intensity with all pulse sequences). This variability is much more common in epiphyseal areas of osteonecrosis and does not have prognostic significance (3). Subchondral fracture appears on MR as a curvilinear subchondral low-signal-intensity line on T1-weighted images and a high-signal-intensity line on T2-weighted images, frequently better depicted in the last (5). Epiphyseal collapse appears as a focal depression of the subchondral bone area (fig. 11) (8). In the majority of cases the use of contrast-enhanced MR imaging in osteonecrosis is not necessary for diagnosis or assessment (3). MR imaging characteristics of the osteonecrosis are similar or identical in multiple sites: femoral head, knee, humeral head, scaphoid, lunate and talus (1). Images for this section: Page 4 of 12
Fig. 1: Anteroposterior radiography of the pelvis showing a patchy lytic and sclerotic area (arrow) in the right femoral head, representing osteonecrosis; the articular surface is regular and joint space is normal. Page 5 of 12
Fig. 2: Pelvis anteroposterior radiography of a 21 years old man medicated with corticoids. Patchy lytic and sclerotic area (arrows) in the right femoral head with incipient articular colapse. Page 6 of 12
Fig. 3: Crescent sign. Anteroposterior radiography of the pelvis showing a crescent subchondral lucency (arrow) in the right femoral head. Fig. 4: Anteroposterior radiography of the pelvis, showing an epiphyseal fracture in the left femoral head (arrow in A.). A arthroplasty was performed (B.) Page 7 of 12
Fig. 5: Bilateral osteonecrosis. Coronal (A.) and Axial (B.) CT showing smal subchondral lytic lesions with sclerotic margin (arrows), representing osteonecrosis. Fig. 6: Axial CT showing a lytic area in the right femoral head with sclerotic margin, representing osteonecrosis. Page 8 of 12
Fig. 7: Axial (A.) and coronal (B.) CT showing typical left femoral head osteonecrosis, an undulating sclerotic margin (arrow in A.) with incipient signs of degenerative changes (joint space reduction and flattening of the femoral head) (B.) Page 9 of 12
Fig. 8: Same patient that figure 5. MR T1 weighted image showing bilateral femoral heads osteonecrosis (arrows): low-signal-intensity line of uniform width in a subchondral location. Fig. 9: Bilateral osteonecrosis. Axial T1 weighted image (A.) and T2 weighted image showing bilateral double line sign (arrows) - serpiginous low-signal-intensity line of uniform width on T1-weighted image and T2-weighted image, with an adjacent rim of increased signal intensity on T2-weighted imaging Fig. 10: Osteonecrosis of the right femoral head. Axial T1 weighted image (A.) and T2 weighted image showing undulating low-signal-intensity line of uniform width on T1 weighted image (arrow in A.) and T2 weighted image. In the center of the line there is a low signal on A and high signal on B., representing a cystic area. Page 10 of 12
Fig. 11: Epiphyseal collapse. Coronal T1 weighted image showing osteonecrosis of the right femoral head with a focal depression of the subchondral bone (arrow). Page 11 of 12
Conclusion Osteonecrosis has some characteristic imaging findings that every radiologist must know. MR is the most sensitive imaging study for the diagnosis of osteonecrosis. A serpiginous or undulating sclerotic rim on radiography and CT and a serpentine or undulating rim of low signal intensity surrounding a region of maintained fat signal intensity on MR are the most common patterns. Personal information References 1. 2. rd Resnick D and Kransdorf MJ. BONE AND JOINT IMAGING. 3 edition, 2005. Elsevier Saunders. Philadelphia.pp1067-1088 Manaster BJ, May DA, and Disler DG. Musculoskeletal Imaging: The th 3. 4. 5. 6. 7. 8. Requisites. 4 edition, 2013. Elsevier Saunders. Philadelphia.pp305-312 Murphey MD, Foreman KL, Klassen-Fischer MK, et al. Imaging of Osteonecrosis: Radiologic-Pathologic Correlation. RadioGraphics 2014; 34:1003-1028 th Greenspan A, and Beltran J. Orthopedic Imaging: A Practical Approach. 6 edition, 2014. LWW pp81-85 Stevens K, Tao C, Lee S.U, et al. Subchondral Fractures in Osteonecrosis of the Femoral Head: Comparison of Radiography, CT, and MR Imaging. AJR 2003;180:363-368 Murphey MD, Roberts CC, et al. OSTEONECROSIS OF THE HIP. ACR Appropriateness Criteria. Date of origin: 1995. Last review date: 2015 Ito H, Matsuno T, Minami A. Relationship Between Bone Marrow Edema and Development of Symptoms in Patients With Osteonecrosis of the Femoral Head. AJR 2006; 186:1761-1770 Vande Berg BE, Malgbem JJ, Labaisse MA, et al. MR Imaging of Avascular Necrosis and Transient Marrow Edema of the Femoral Head. RadioGraphics 1993; 13:501-520 Page 12 of 12