| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | |
| IMAGE QUIZ ARCHIVE | ||||||
| Image Quiz | ||
| An Ossifying Popliteal Mass1 (continued) | ||
| Answer: Idiopathic heterotopic ossification within the tibial nerve. | ||
| Radiographic examination showed a ring-like ossification in the right popliteal fossa and a well-outlined spindle-shaped ossifying mass (Fig. 1). A technetium-99 radionuclide bone scan revealed an oval area of increased uptake in the right popliteal fossa. Computed tomography of the right popliteal fossa demonstrated an ossifying lesion near the tibial nerve at the proximal tibial level (Fig. 2). Magnetic resonance imaging demonstrated a soft-tissue mass in the right popliteal fossa, which showed slightly higher signal intensity in the central portion in comparison with that of muscle on the T1-weighted images, inhomogeneous high signal intensity on the T2-weighted images, and strong enhancement in the central portion along the tibial nerve. The tibial nerve was noted to be distorted (Fig. 3). | ||
 Fig. 1 |
Fig. 1 Lateral radiograph of the right knee, showing a ring-like ossifying mass (arrow) in the popliteal fossa. For larger view, click on image |
|
 Fig. 2 |
Fig. 2 On a transverse computed tomography scan of the popliteal fossa, a soft-tissue lesion with ring-like ossification is noted near the tibial nerve. For larger view, click on image |
|
 Fig. 3 |
Fig. 3 A T2-weighted image shows a lesion with high central signal intensity and a low-signal-intensity rim (arrowheads). The tibial nerve is distorted; apparently, it is being flattened by compression of the mass (arrow). For larger view, click on image |
|
| A surgical exploration was performed. Histologically, the specimen consisted of three zones surrounded by fascicular nerve and interfascicular connective tissue (Fig. 4). The innermost zone of the lesion was composed of immature, vascular fibroblastic tissue similar to nodular fasciitis. Bordering this area was an intermediate zone in which the cells became condensed into ill-defined trabeculae. Further toward the periphery, the osteoid evolved into mature bone. Bone formation was prominent at the margin of the lesion. | ||
 Fig. 4 |
Fig. 4 Photomicrograph showing that the specimen consisted of three zones surrounded by fascicular nerve (arrowheads) and interfascicular connective tissue. The innermost zone (small arrow) appears similar to nodular fasciitis. In the intermediate zone (intermediate-sized arrow), the cells become condensed into ill-defined trabeculae. Mature bone is prominent in the peripheral zone (large arrow) (hematoxylin and eosin, ×40). For larger view, click on image |
|
| Discussion | ||
| Heterotopic calcification in or around peripheral nerves is related to nerve-fiber breakdown and to the local presence of lipids in the perineurium. The origin of the lipids may be senescent cells or degrading myelin. Our patient had a myositis ossificans-like lesion arising within the peripheral nerve. Heterotopic ossification within the peripheral nerves is quite rare. | ||
| In our patient, radiographic examination showed a ring-like ossification in the right popliteal fossa and a well-outlined spindle-shaped mass, which suggested intraneural ossification of the tibial nerve. In addition, magnetic resonance imaging demonstrated that the tibial nerve was distorted as a result of compression by the mass. | ||
| The pattern and shape of the lesion and the findings on magnetic resonance imaging were very helpful in the clinical diagnosis of the lesion. Histologic examination confirmed the typical appearance of heterotopic ossification. | ||
| Reference | ||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |