Case Author(s): Stephen Schmitter, M.D. and Keith Fischer, M.D. , 1/30/01 . Rating: #D2, #Q3

Diagnosis: Heterotopic Ossification

Brief history:

23 year-old man with reduced range of motion in both hips

Images:

Anterior Radionuclide Angiographic Images of the Pelvis

View main image(bs) in a separate image viewer

View second image(bs). Anterior Immediate Static Image of the Pelvis

View third image(bs). Delayed Anterior and Posterior Whole Body and Pelvic Spot Images

View fourth image(xr). Plain Radiographs of the Pelvis and Hips

Full history/Diagnosis is available below

Diagnosis: Heterotopic Ossification

Full history:

23 year-old paraplegic man with bilateral heterotopic ossification of the hips. Evaluation of the maturity of bone formation is requested prior to possible surgical resection.

Radiopharmaceutical:

21.6 mCi Tc-99m MDP i.v.

Findings:

Radionuclide angiographic images of the pelvis (main image) demonstrate mild to moderate increased flow to the soft tissues of the hips. The immediate static images (second image) show increased activity in both hip regions extending beyond the confines of the proximal femora. Delayed images (third image) demonstrate markedly increased uptake around both hip joints. Plain radiographs (fourth image) reveal exuberant heterotopic ossification surrounding both hip joints.

Discussion:

Heterotopic ossification is a common complication of CNS and spinal cord disorders, most commonly occurring in patients with spinal cord injuries (16 to 53 percent of cases of spinal cord injury). Its cause is unknown. Heterotopic ossification generally appears 2 to 6 months following injury. Single or multiple sites can be involved. Most common sites are the hips, knees, and shoulders. Clinical manifestations vary. Many have no symptoms or signs, while others develop pain, swelling and decreased range of motion.

Radiographic evalution initially demonstrates ill-defined periarticular radiodensities which enlarge and merge with underlying bone. Eventually these may develop trabecular architecture and cause bridging across the joint.

Bone scintigraphy is often used to evaluate the maturity of ossification prior to surgical intervention. This evaluation is important because resection of immature heterotopic ossification often results in recurrence. Acutely, increased radiopharmaceutical activity may be seen as early as 2 weeks following injury. During the subacute phase, there is a rapid increase in activity. A chronic active immature phase follows in which there is a steady state of increased activity. Finally, there is a chronic mature phase in which the activity decreases and returns to normal. Surgery should not be performed until uptake begins to diminish.

In this particular patient, there is markedly increase uptake of radiopharmaceutical, and thus, surgical intervention should be postponed. The clinical, radiographic and scintigraphic features in this case are characteristic and no other entitities were considered.

Reference:

Resnick D. Neuromuscular Disorders. In: Resnick D, Niwayama G, eds. Diagnosis of Bone and Joint Disorders, 2nd Ed. Philadelphia: WB Saunders, 1988.

ACR Codes and Keywords:

References and General Discussion of Bone Scintigraphy (Anatomic field:Skeletal System, Category:Misc)

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Case number: bs125

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