FIBROUS DYSPLASIA

Dr/ Hytham Nafady

Definition

replacement of the normal lamellar cancellous bone by abnormal fibrous tissue.

Types of fibrous dysplasia

Demographics

Age: 3-30. Sex: F > M.

Natural history

Polystotic FDis more aggressive than monostotic FD.

The lesions usually progress in number till the end of skeletal maturation, by then they become quiescent

in only about 5% of cases it continue to enlarge after that.

Complications of fibrous dysplasia

1. Pathological fracture.2. Bone deformity.3. Massive cartilage hyperplasia.4. Accelerated bone growth.5. Sarcomatous degeneration.

Pathological fracture

Shepherd crock deformity

Sarcomatous degeneration

is very rear, it may occur spontaneously or following radiation therapy.

Radiological Criteria: Cortical destruction. Extraosseous soft tissue

component.

Radiological criteria

Location : Long bones specially the neck of femur Skull (including calvarium, skull base, facial

bones & mandible), Pelvis Ribs (fibrous dysplasia is the most common

cause of rib expansion).Distribution: Unilateral or rarely bilateral asymmetrical.

Long bone fibrous dysplasia

Meta-diaphyseal. The epiphysis is usually spared. Central May be expansile. Cortex thinned or scalloped with no cortical break through or

periosteal reaction (smooth outer cortex).Density: depend upon the ratio between the fibrous & osseous

tissues, Sclerotic (increased osseous content), or Lytic (increased fibrous content) or Ground glass, (relatively equal ratios between fibrous & osseous

content).Margin: Well defined sclerotic margin (Geographic bone

destruction). The sclerotic margin may be thick (rind sign).

Pelvis fibrous dysplasia

Expansile, lytic, bubbly lesion. The degree of expansion & the bubbly nature

are quite marked in the pelvis rather than long bones.

Rib fibrous dysplasia

Expansile lytic lesion with no rib destruction.

Calvarium Skull base Facial bones

Widening of the diploic space.Displacement of the outer table.Sparing of the inner table.

Narrowing of the neural foramina.

Facial deformities

Density: •Sclerotic or Ground glass, •Common

•Lytic or mixed •Rare

DDx: Paget disease Skull base tumors Ossifying fibroma

(the inner table is involved). Fibrous dysplasia conforms to the shape of the involved bone.

Special forms of fibrous dysplasia

Leontiasis ossea. Cherubism. Mc Cune Albright syndrome.

Leontiasis ossea

A special form of polystotic fibrous dysplasia that affects the skull & facial bones.

Cherubism

Familial fibrous dysplasia of the jaws.

Mc Cune Albrightsyndrome

Almost exclusively affect females.

Mc Cune Albright syndrome Neurofibromatosis

Never cross the midline and Cross the midline.

Irregular borders

(coast of Maine)

Smooth borders

(coast of California)