Name : Hamidreza
Resident : Payam Asadi
Gender : Male
Age : 28
A 28 Y/O man with decreased hip range of motion
Imaging Procedures and Findings
AP pelvis x-ray shows extensive bone formation at left hemipelvis and proximal femur associated with periosteal reaction . Axial CT scan demonstrate extensive calcification around the femoral head and neck extends to iliac bone . Periosteal reaction is visible . Figure 5 (shaded surface display) reveals articular ankylosis due to severe bone formation . The key point is in figure 2 where you can see peripheral calcification with lucent center. Another key point is Hx of motor car accident and ICU admission in this patient.
The typical radiologic appearance of myositis ossificans is circumferential calcification with a lucent center. This is often best appreciated on a CT scan . A malignant tumor that mimics myositis ossificans has an ill-defined periphery and a calcified or ossific center. Periosteal reaction can be seen with myositis ossificans or with a tumor. Occasionally, the peripheral calcification of myositis ossificans can be too faint to appreciate; in these cases, a CT scan should help, or delayed films 1 or 2 weeks later are recommended. Biopsy should be avoided when myositis ossificans is a clinical consideration. MR can be misleading because the peripheral calcification is not as well seen, and edema in the soft tissues can extend beyond the calcific rim . Myositis ossificans is an example of a lesion that should not undergo biopsy because its aggressive histologic appearance can often mimic a sarcoma. Unfortunately, radical surgery has been performed based on the histologic appearance of myositis ossificans when the radiologic appearance was diagnostic.
Brant WE, Helms CA. Fundamentals of Diagnostic Radiology, 3rd edition. 1169-1170