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Findings: Coronal T1 and sagittal T2 images of the knee show prominent linear areas of persistently very low signal intensity involving the fibula, tibia, femur, and patella. Some are centrally located within the medullary canal while others are clearly cortically based. No evidence of internal derangement was seen.
Diagnosis: : Melorheostosis.
Discussion: Melorheostosis is an uncommon bone disorder which often presents in children or young adults as extremity pain with limited range of motion. The symptoms may be progressive. In general, children are more severely affected and may develop muscle contractures and ligament and tendon shortening. It may be incidentally discovered in asymptomatic adults. Associated disorders have been reported; these include overlying linear scleroderma, osteopoikilosis, osteopathia striata, neurofibromatosis, tuberous sclerosis, vascular lesions, and hypophosphatemic rickets.
The typical distribution is sclerotomal in one or more bones of an extremity. The axial skeleton can also be involved, however, either separately or in conjunction with extremity findings.
Plain film radiography shows characteristic changes:
The MR appearance of wavy, linear areas of signal void along the cortex and in the medullary canal, corresponds to the dense cortical bone seen on plain films and histologically.
References:
Yu JS et al. Melorheostosis with an ossified soft tissue mass: MR features.
Skeletal Radiology. 24:367-70, 1995.
Resnick D and Niwayama G. Enostosis, hyperostosis, and periostitis, In: Diagnosis of Bone
and Joint Disorders, 3rd ed. D Resnick, editor. W.B. Saunders Co., Philadelphia,
1995. Vol. 6, pp 4396-4415.
Acknowledgement: Special thanks to Mr. Martin Rush of Royal Hobart Hospital, Tasmania, Austrailia for constributing this case.
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