Introduction Aetiology : unknown Female>male Bone may be affected –Pelvis –Femur –Skull –Spine/vertebral collapse unusual Usually found incidentally/ follow pathological fracture Onset : 10-30 yr old or first decade Prognosis : worse when lesion occurs early in life
Pathology Medullary bone replaced by: Fibrous tissue Cystic containing blood/serous fluid Fibrous tissue undergoes varying degree of abnormal ossification Increase density (dependent on the extent ossification) Patchy Cotton wool appearance Homogenous ground glass appearance
Characteristic Fibrous Dysplasia Location –Diametaphyseal –Bone end may be involved after fusion –In child may Involve epiphysis Found in 2 form: 1.Poliostotic 50% skeleton may be involved Asimetri & distributed unilateral 2.Monostotic More likely to enlarge in adult life
Radiologycal Features Margin –Smooth dense –Well define –Expanded the bone Cortex scalloped & thinned but intact –Tend to be multilocular –Expand down the medulla rather than cause cortical expansion Various degree of central ossification
FD in the Proximal Femur. Fig. 35.47 The lesions are well defined, often with a very thick 'rind' around them, and show various degrees of central mineralisation. The site is typical for fibrous dysplasia.
Fibrous dysplasia Of the Tibia Fig. 35.48. A multilocular, partly cystic, expansile lesion of the midshaft tibia is surrounded by a thick rim of reactive sclerosis.
Polycystic case of FD Fig. 35.51.(A) marked enlargement and deformity of the pelvis and proximal femur. There is marked bony expansion with extensive cyst formation. The shepherd's crook deformity has been stabilised. (B) The CT scan shows the mixed pattern of tissues seen in fibrous dysplasia, ranging from cystic through ground-glass to heavily mineralised tissue.
Fibrous dysplasia. (A) There is thickening with sclerosis of the frontal bone, the floor of the anterior cranial fossa and the base of the skull extending back to the sphenoid sinus, which is replaced by dense amorphous bone. (B) The CT scan shows expanded and abnormally mineralised bone occupying mainly the left side of the skull base. Considerable facial deformity is present.
Resume Fibrous dysplasia 1.Aetiology & Patology 2.Form –Polyostotic –Monostotic 3.Radialogical feature –Location : diametafisial, medulla –Margin Well define, expansion to the cortex (cortex thin, scalloped, but intact) –Center Varying degree central mineral ossification
QUIZ 1.Please describe this pictures! 2.What is the most likely diagnosis for this pictures? Fig. 35.47, PAGE 1131