Name : Akbar
Affiliation : Temple University School of Medicine
Academic Degree: Emeritus Professor of Radiology and Former professor of Orthopedic Surgery
Three patients with different diagnosis but a common radiographic sign!
Imaging Procedures and Findings
Femoral ??ShepherdÃ¢??s crookÃ¢?Â deformity is present on all images. Image-1 demonstrates dense sclerosis with considerable irregularity and thickening in proximal femur suggesting involucrum and sequestration in Chronic Osteomyelitis. Image-2 shows cortical thinning, ground-glass-opacity within the medullary cavity of the femur and concomitant increased girth. These findings are consistent with Fibrous Dysplasia. Image-3 reveals abnormal proximal femoral bowing and shortening with pseudarthrosis in a patient with Proximal Femoral Focal Deficiency (PFFD).
The earliest radiographic signs of bone infection are soft-tissue edema and loss of fascial planes. These are usually encountered within 24 to 48 hours of the onset of infection. The earliest changes in the bone are evidence of a destructive lytic lesion and periosteal reaction, usually within 7 to 10 days after the onset of infection and a positive radionuclide bone scan. Within 2 to 6 weeks, there is progressive destruction of cortical and medullary bone, an increased endosteal sclerosis indicating reactive new bone formation, and a periosteal reaction. In 6 to 8 weeks, sequestra indicating areas of necrotic bone usually become apparent; they are surrounded by a dense involucrum, representing a sheath of periosteal new bone. The sequestra and involucra develop as the result of an accumulation of inflammatory exudates (pus), which penetrates the cortex and strips it of periosteum, thus stimulating the inner layer to form new bone. At this stage, termed chronic osteomyelitis, a draining sinus tract often forms.
Fibrous dysplasia is a fibroosseous lesion that some authorities classify among the group of developmental dysplasias. It may affect one bone (monostotic form) or several bones (polyostotic form). Monostotic fibrous dysplasia most commonly affects the femur particularly the femoral neck as well as the tibia and ribs. The lesion arises centrally in the bone, usually sparing the epiphysis in children, and it is very rarely seen in the articular end of the bone in adults. As the lesion enlarges, it expands the medullary cavity. The radiographic appearance of monostotic fibrous dysplasia varies, depending on the proportion of osseous-to-fibrous content. Lesions with greater osseous content are more dense and sclerotic, whereas those with greater fibrous content are more radiolucent, with a characteristic ground-glass appearance. Although radiographically similar to the monostotic form, polyostotic fibrous dysplasia is a more aggressive disorder. It also has a different distribution in the skeleton and a striking predilection for one side of the body a tendency that has been noted in more than 90% of cases.
Proximal femoral focal deficiency (PFFD) is a congenital anomaly characterized by dysgenesis and hypoplasia of variable segments of the proximal femur. The defect ranges in severity from femoral shortening associated with a varus deformity of the neck to the formation of only a small stub of distal femur. Conventional radiography is usually sufficient to make a diagnosis of proximal femoral focal deficiency. The femur is short, and the proximal segment is displaced superior, posterior, and lateral to the iliac crest; ossification of the femoral epiphysis is invariably delayed.
Shepherd's Crook Deformity
1-Bonakdarpour, A., Reinus, W.R., Khurana, J.S. Diagnostic Imaging of Musculoskeletal Diseases A Systematic Approach, Springer, 2010, 551-554 and 363-384.
2-Greenspan A: Orthopedic Imaging a practical approach, 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2004, PP 630-635, 902-903, 789-790.