מהו nof בעצם הטיביה הדיסטאלית?

Nonossifying Fibroma -------------------------------------------------------------------------------- - Discussion: - also known as fibrous cortical defect; - most common bone lesion (40% children); - it results from defect of periosteal cortical bone development which leads to failure of ossification; - natural history: - lesion typically develops in childhood AND adolescence; - during adolescence non ossifying fibroma is an active stage 2 lesion that persists OR enlarges throughout childhood. - w/ skeletal maturation, NOF becomes latent & either regresses OR ultimately ossifies; - when tumor occupies > 50% of diameter of bone, bone is prone to frx; - Radiographic Appearance: - look for well marginated radiolucent lesion, w/ a distinct multilocular appearance; - lesion is usually irregular & is surrounded by reactive rim of bone: - look for benign cortical thinning, erosion, slight expansion; - there are 2 subtypes; - fibrous cortical defect; - more common lesion; - is small < 0.5 cm radiolucency w/ in cortex w/ sharply defined cortex; - metaphyseal defect; - lesion commonly develops in metaphysis of distal femu(90% cases) OR the distal tibia & is eccentrically located; - located within OR adjacent to the cortex; - may be eccentrically located within the medullary cavity; - cortex may bulge over the lesion, as lack of remodleing; - may be surrounded by a well defined thin rim of reactive bone; - no periosteal reaction is seen unless there has been a frx; - Histology: - look for whorled fibrous tissue, foam cells, & occasionally, small elongated giant cells; - diff dx: - malignant fibrous histiocytoma; - osteosarcoma; - histiocytic lymphoma; - eosinophilic granuloma; - pyogenic osteomyelitis; - Frx Management: - nonossifying fibroma can act as a stress riser in bone which can lead to stress frx w/ heavy running; - this will result in pain & increase uptake on bone scan; - in children, closed treatment is the treatment of choice in most cases; - these fractures fractures are expected to heal with a normal amount of callus, but resolution of the fibroma may OR may not occur; - intracapsular curettage is usually sufficient to promote healing of lesion, however, the defect may be supplemented with bone grafts OR other stabilization techniques for frx prophylaxis AND treatment;