Case 41
Presentation:
Clinical history: 70-year-old male, metastatic prostate cancer on treatment. Bone scan requested for restaging. The patient has a bone scan from 1 year ago, demonstrated osseus metastases involving the lower lumbosacral spine and pelvis and proximal left femur. Describe findings in the current bone scan:
Compare the findings with prior bone scan (upper row).
What is your opinion?
Findings: Reduction in uptake intensity in multilevel lumbar vertebral bodies, sacrum, Bilateral sacroiliac joints, Posterior and anterior iliac bones, Acetabulum bilaterally, with more prominent disease on the right side. New focal uptake in the lateral aspect of Right proximal femur within the soft tissue. Interval increase uptake in the Right femoral head and neck. Interval increase in uptake of bilateral acromioclavicular and sternoclavicular joints favored degenerative changes.
Correlation is made with recent diagnostic CT:
New focal activity in the soft tissue, lateral to the proximal right femur is corresponding to a densely calcified focus in the superficial muscular compartment on recent diagnostic CT scan. CT also showed Interval distortion and destructive changes and vascular necrosis, correspomding to increase uptake in the right femoral head and neck.
Opinion:
Significant interval improvement of uptake intensity involving the multiple lower lumbar spine, sacrum and bilateral pelvic bone.
Interval destruction of the right hip joint and femoral head neck.
Finding in the soft tissue as described likely heterotopic ossification/myositis ossificans.
Discussion:
Heterotopic ossification:
Heterotopic ossification refers to the formation of bone in soft tissues where bone is normally absent. Lesions can vary in size, ranging from small, clinically insignificant ossifications to larger deposits that cause pain and functional impairment.
Myositis ossificans:
Myositis ossificans (MO) is a rare condition involving non-neoplastic heterotopic ossification in extraskeletal soft tissues. It may occur spontaneously or 4–12 weeks after trauma. MO is most common in young, athletic males, typically in their second or third decade of life.
Acquired heterotopic ossification can be secondary to:
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Musculoskeletal Trauma
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Spinal Cord Injury
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Burns
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Traumatic Brain Injury
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Postoperative
Mainly seen post joint replacement (approximately 90% of hip joint replacement patients may have heterotopic ossification) , often forms adjacent to metal hardware