Paget Disease Imaging
- Author: Mitchell J Kline, MD; Chief Editor: Felix S Chew, MD, MBA, EdM more...
Overview
Paget disease of the bone (osteitis deformans) is a metabolic disorder characterized by abnormal osseous remodeling. Sir James Paget first described Paget disease in 1877 as a chronic inflammatory remodeling disease of bones. He termed the condition osteitis deformans.[1, 2] Paget disease is depicted in the images below.
Lateral radiograph of the tibia in a patient with Paget sarcoma reveals a destructive bone-forming mass in the proximal tibia (osteosarcoma).
Lateral skull radiograph in a patient with Paget disease demonstrates a large, well-circumscribed lytic lesion (arrows) in the frontal and parietal bones (osteoporosis circumscripta).
CT image of the first sacral vertebra demonstrates marked cortical thickening (arrows) and trabecular coarsening. Courtesy of Lee F. Rogers.
Axial T1-weighted MRI of the knee in a patient with Paget disease reveals prominent dark lines in the medullary bone, indicating trabecular coarsening (arrows). Courtesy of Lee F. Rogers.
Whole-body bone scan in a patient with polyostotic Paget disease reveals intense uptake of radiopharmaceutical in the femur, pelvis, spine, and proximal right humerus. The cortical discontinuity of the proximal right humerus represents an insufficiency fracture (arrow). Courtesy of Lee F. Rogers. Paget disease evolves through 3 stages: (1) an early lytic or hot phase; (2) an intermediate or mixed phase; and (3) a final or cold phase, marked by dense bone formation
Paget disease rarely is diagnosed in the initial lytic phase. At this early point of the disease, osteoclastic activity is predominant. Paget disease usually begins at the end of a bone, except when it occurs in the tibia. A characteristic sharply demarcated zone of osteolysis may begin in the subcortical bone and advance along the diaphysis. Osteoblastic activity lags behind; thus, radiolucent fibrous tissue replaces normal bone.
The intermediate or mixed phase reveals evidence of osteolytic and disorganized osteoblastic activity. New bone forms abnormally and demonstrates characteristically coarsened trabecula and cortical thickening in the cancellous and compact bone, respectively. Characteristic intracytoplasmic inclusions may be observed microscopically, supporting evidence for the viral etiology theory.
The final or cold phase demonstrates less evidence of continual osseous remodeling. Previously laid down woven bone is converted to dense lamellar bone. Histologic features of disorganized bone are prominent. The intersecting lines of remodeled bone have a characteristic mosaic pattern histologically.
Insufficiency fractures in patients with Paget disease may present with pain that can last up to several weeks. If pain is focal and severe, it may be a sign of an impending, complete fracture, and radiographic evaluation is warranted. Insufficiency fractures most frequently affect the femur and tibia. Involvement in critical weight-bearing locations may lead to fracture or severe secondary arthritis.[3, 4, 5] See the images below.
Anteroposterior radiograph of the hip in a patient with Paget disease demonstrates dense sclerosis involving the femoral head and neck (arrows). This is a high-risk area for insufficiency fracture.
Anteroposterior radiograph of the femur in a patient with late-stage Paget disease reveals a transverse insufficiency fracture through the proximal femoral shaft (banana fracture). Preferred examination
The radiographic findings of Paget disease are diagnostic in many patients. The lytic stage most commonly is observed in the skull and long bones. The typical appearance in the long bones is osteolysis, which begins in the epiphysis and advances along the diaphysis. Trabecular coarsening and distortion and cortical thickening are observed in the sclerotic phase, typically involving the axial skeleton.
Limitations of techniques
Radiographic findings in Paget disease often are pathognomonic, particularly in the lytic phase. However, given the variable imaging appearance of Paget disease in different stages, as well as the many different bones involved, the differential diagnosis may vary substantially among patients.
Radiography
Characteristic radiographic findings include the following:
In the skull, the lytic phase (osteoporosis circumscripta) typically involves the frontal or occipital bones and progresses to a mixed pattern with multifocal sclerotic patches in the intermediate stage of the disease, referred to as a cotton wool appearance. See the images below.
Anteroposterior radiograph of the femur in a patient with late-stage Paget disease reveals a transverse insufficiency fracture through the proximal femoral shaft (banana fracture).
Lateral radiograph of the calvarium in a patient with Paget disease reveals multiple patches of sclerotic bone in the calvarium (cotton wool appearance). The vertebral bodies typically become enlarged with a prominent cortical margin (picture frame vertebrae) or become densely sclerotic, mimicking lymphoma or metastatic disease (ivory vertebra). See the images below.
Lateral radiograph of the lumbar spine in a patient with Paget disease demonstrates enlargement of an involved vertebral body (arrow), with sclerosis more prominent at the vertebral endplates (picture frame vertebra).
Lateral radiograph of the upper thoracic spine reveals a densely sclerotic vertebral body (ivory vertebra) caused by Paget disease (arrow). The appearance mimics findings that can be observed with malignant neoplasm such as lymphoma or metastatic disease. In the pelvis, typical findings include thickening of the iliopectineal line in early stages, progressing to patchy sclerosis and lucency in later stages. See the image below.
Anteroposterior radiograph of the pelvis demonstrates thickening of the right iliopectineal line (small arrows), as well as later-stage involvement with Paget disease, including trabecular coarsening and patchy sclerosis (large arrow). Weakening of the pagetic acetabular bone may lead to protrusio acetabuli and insufficiency fracture. See the image below.
Anteroposterior radiograph of the right hip, coned down on the obturator ring, reveals patchy sclerosis and disorganized coarsened trabecula characteristic of late-stage Paget disease. An insufficiency fracture of the ischium inferior to the acetabulum (arrows) is present. In the long bones, early involvement consists of lysis of the subarticular bone, which advances along the diaphysis with the characteristic shape of a blade of grass. Long bones are affected first in the epiphyseal region, with the exception of the tibia, where Paget disease frequently begins in the tubercle.
Later stages of disease show development of enlarged, sclerotic, deformed bones with thickened coarse trabeculae. The weakened femur and tibia eventually may become bowed under the stress of weight bearing. Insufficiency fractures may occur, characteristically involving the convex cortical surface. Conversely, Looser zones of osteomalacia typically occur on the concave cortical surface. See the images below.
Coned down anteroposterior radiograph of the knee demonstrates an abnormal lucency in the distal femur with a flame-shaped or "blade of grass"-shaped proximal margin caused by the advancing lytic phase of Paget disease (black arrows). Courtesy of Lee F. Rogers.
Lateral coned down radiograph of the tibia reveals replacement of the tibial tubercle with pagetic bone that has mixed osteolysis and sclerosis (arrows).
Anteroposterior radiograph of the distal forearm demonstrates mixed-phase Paget disease in the distal radius with lytic disease proximally (white arrows) and coarsened trabeculae more distally (black arrow).
Anteroposterior radiograph of the proximal femur involved with intermediate (mixed phase) Paget disease reveals characteristic insufficiency fractures on the convex surface of the bone (arrow). Development of secondary sarcoma in pagetic bone is the most lethal complication of Paget disease, occurring in 1% or fewer of patients with Paget disease (see the image below). These sarcomas are aggressive and may be multicentric. Short-term interval follow-up and/or cross-sectional imaging may prevent diagnostic errors and initiate prompt attention to a newly developing lesion.[6, 7, 8]
Lateral radiograph of the tibia in a patient with Paget sarcoma reveals a destructive bone-forming mass in the proximal tibia (osteosarcoma). Computed Tomography
Cross-sectional MRI and CT demonstrate enlarged bones with trabecular coarsening and increased cortical thickness. The anatomy is well demonstrated by cross-sectional imaging in complex structures, such as the spine, where spinal or nerve root compression may be an issue. Cross-sectional imaging also helps delineate the pathology in complicated Paget disease, which includes nerve or spinal cord compression, as well as basilar invagination at the skull base and osseous encroachment involving cranial nerve foramina.
Secondary sarcomatous development also is better evaluated with cross-sectional imaging. Additionally, should biopsy be indicated for the diagnosis of sarcoma, CT typically is the guidance modality of choice. See the images below.
CT image of the first sacral vertebra demonstrates marked cortical thickening (arrows) and trabecular coarsening. Courtesy of Lee F. Rogers.
Axial T1-weighted MRI of the knee in a patient with Paget disease reveals prominent dark lines in the medullary bone, indicating trabecular coarsening (arrows). Courtesy of Lee F. Rogers.
Sagittal T1-weighted MRI of the lumbar spine demonstrates enlargement of the fourth lumbar vertebral body with no central canal encroachment (arrows). Courtesy of Lee F. Rogers. Magnetic Resonance Imaging
See CT Scan section.
Nuclear Imaging
Skeletal scintigraphy is useful. Radionuclide bone scans are more sensitive than radiographs for the diagnosis of Paget disease. Additionally, bone scans help survey the different sites of involvement with polyostotic disease.
Characteristically, a marked uptake of radiopharmaceutical in the involved bones is observed. However, late-stage involvement may not reveal intense radiopharmaceutical uptake, and osteoporosis circumscripta may demonstrate only a peripheral rim of increased uptake. Scintigraphy tends to follow the physiologic activity of disease and may monitor treatment.
Polyostotic Paget disease often can be distinguished from multiple metastatic lesions, although occasional difficulties occur. Perform radiographic correlation when this situation arises. Furthermore, the diagnosis of fracture or sarcoma may be challenging, often requiring multimodality correlation. See the images below.
Whole-body bone scan in a patient with polyostotic Paget disease reveals intense uptake of radiopharmaceutical in the femur, pelvis, spine, and proximal right humerus. The cortical discontinuity of the proximal right humerus represents an insufficiency fracture (arrow). Courtesy of Lee F. Rogers.
Anterior image of the thoracic and lumbar spine in a 75-year-old man demonstrates intense radiopharmaceutical uptake in the third lumbar vertebra, which is involved with Paget disease (arrows). Courtesy of Lee F. Rogers. Paget J. On a form of chronic inflammation of bones (osteitis deformans). Med Chir Tr. 1877;60:37.
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