| Aneurysmal bone
cysts are uncommon benign vascular
bone tumors. Their origin is unknown, but they resemble
intraosseous arteriovenous malformations. They may cause
cortical expansion and thinning, leading to pathologic
fracture. They are more common in females than males, in
young patients (less than 20 years old) and in the lower
extremities, pelvis and spine. The most common treatment
is curettage. One out of five will recur after
curettage. After excision, treatment of the margins with
cryotherapy, phenol or methacrylate may reduce
recurrence. However, if there is structural weakening
from circumferential cortical thinning, cytotoxic
marginal treatment may may be too risky and structural
bone grafting may be required.
The following two cases are each an atypical demographic: elderly, male, upper extremity.
|Click on each image for a larger picture|
Case 1This 75 year old gentleman complained of three months of wrist pain severe enough to prevent playing golf. Plain films showed a well circumscribed lobular lucency in the capitate and STT osteoarthritis.
interpreted as inconclusive, differential including an
intraosseous cyst or giant cell tumor with cortical
thinning but no suggestion of malignancy.
|Dorsal exposure of
the capitate revealed extraosseous extension.
| The dorsal
capitate was windowed and the tumor was removed with
rongeur and curette. Margins were taken back to
subcortical bone with a high speed burr.
Technical point:The irregular texture of cancellous bone makes it difficult to visually inspect the margins, and the use of a small curette only makes this worse. Once the gross tumor is removed, the margins can be "polished" with a large high speed burr - the larger the better. This leaves a a smooth surface and reduces the chance of residual hidden pockets of tumor.
fluoroscopy of the defect after marginal excision with
|and then after the
defect was filled with corticocancellous iliac crest
bone graft to improve structural stability:
|Pressure fit bone
graft in place.
decalcified specimen showed empty spaces, hemorrhage,
stromal elements and multinuclear osteoclasts - not to
be confused with giant cells.
incorporation at 6 months postop.
Case 2This elderly gentleman presented with an enlaging tumor of his thumb tip. He did not know how long it had been present. He complained that it bled frequently, was unstable, and he requested an amputation. He had no lymphadenopathy or evidence of metastatic disease on chest Xray.
|Plain films showed
loss of the distal 2/3 of the distal phalanx.
in the form of an interphalangeal disarticulation:
pathology similar to the prior case, confirming the
diagnosis of aneurysmal bone cyst.
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