Presentation
Long-standing leg deformity. New pain in mid-tibia.
Patient Data
Diffuse bubble sclerotic and ground glass change involving the proximal and mid-tibial diaphysis with expansion of the medullary cavity, in keeping with known fibrous dysplasia.
A large, bubbly, lytic lesion with mild ground-glass change, up to 9.5 cm in diameter, involving the left iliac wing, is also in keeping with fibrous dysplasia.
Internal fixation of the left femur with and intramedullary nail and proximal and distal cross-bolts is unchanged, transfixing the now healed left femoral mid-shaft fracture.
Conclusion: Changes of polyostotic fibrous dysplasia, as described, predominantly involving the left side (left iliac wing, femur and tibia).
There is extensive marrow abnormality of the left tibia, consisting of multiple confluent nodules. A few small satellite nodules also lie in the lateral tibial plateau in a subchondral location. The nodules vary slightly in the degree of signal intensity, but all have low T1 and high T2, with enhancement. The findings result in expansion of the medullary cavity and thinning of the overlying cortex, in keeping with a long-standing process. In addition, there is some bowing of the proximal tibia. No cortical breach, pathological fracture, extra-osseous soft tissue component or region suspicious for malignant transformation is appreciated. No soft tissue inflammatory change.
Conclusion: Appearances compatible with the known diagnosis of fibrous dysplasia.
RADIOPHARMACEUTICAL: 99mTc MDP, 835 MBq
A triple-phase bone scan of the lower limbs, whole body blood pool images together with delayed whole body images were obtained.
On the dynamic and blood pool phase, intense perfusion involving the left tibia is seen. Intense perfusion to the left femur and acetabulum and left ASIS is also noted.
On the delayed whole body images, focal areas of intense tracer uptake involving the left acetabulum and ASIS, entire left femur and left tibia is identified.
Conclusion: The scintigraphic findings are consistent with fibrous dysplasia involving the left hemipelvis and left lower limb as described.
RADIOPHARMACEUTICAL: 201Tl, 160 MBq
Hemi-body sweeps of the lower half of the body were performed 0.5 and 4 hours following MIBI infusion, these studies were compared to the piror bone scan. The current studies show increased Thallium uptake diffusely in the left tibial shaft and to a lesser extent in the left femoral shaft consistent with the changes seen in the bone scan. Tibial and femoral uptake in the early studies is higher than in the later ones.
Conclusion: Overall impression is that no focus suspicious of malignancy is detected. A diffuse premalignant or malignant change is not totally excluded but is not likely. About one-half of fibrous dysplasias show Thallium uptake.
Case Discussion
In the setting of known fibrous dysplasia, new onset of pain needs careful assessment for complications e.g. fracture or sarcoma. In this instance neither were identified and years of follow-up (not shown) demonstrated stable changes.
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