Fibrous Cortical Defect/Nonossifying Fibroma

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
> Table of Contents > Fibrous Cortical Defect/Nonossifying Fibroma

Fibrous Cortical Defect/Nonossifying Fibroma
Frank J. Frassica MD
  • NOF is a common developmental abnormality in children and adolescents with open physes; it is not seen in adults (1).
    • Despite the name, this condition mineralizes and disappears with skeletal maturity.
    • When the lesion is very small, it is called a “fibrous cortical defect.”
    • Occurs eccentrically in the metaphyses of long bones, most commonly in the distal femur, proximal tibia, or distal tibia
  • The lesion is seen in children and adolescents, but not in adults.
  • Staging (as with other benign lesions) (2):
    • Stage 1: Latent (~96%)
    • Stage 2: Active (~2–3%)
    • Stage 3: Aggressive (<1%)
  • Natural history:
    • Active stage 2 during childhood
    • Becoming latent stage 1 at skeletal maturation
  • Synonyms: Benign metaphyseal cortical defect; Metaphyseal fibrous defect; Benign fibrous histiocytoma; Fibrous xanthoma
A common skeletal lesion
Estimated to occur in 35% of healthy children with open physes (3)
The cause is hypothesized to be a focal area of increased periosteal resorption during growth.
Associated Conditions
  • NF:
    • NOF-appearing lesions may be found (~5%) (3).
  • Jaffe-Campanacci syndrome (3):
    • Rare, congenital disorder
    • Multiple NOFs (widespread and symmetric)
    • Café-au-lait pigmentation
    • Nonskeletal abnormalities
    • Mental retardation
Signs and Symptoms
  • Most lesions are asymptomatic and are found incidentally on radiographs.
  • Occasionally, the condition is painful if a pathologic fracture occurs through the lesion or if such a fracture is impending.
Physical Exam
  • Usually, the lesion is nontender.
  • No swelling or tenderness should be present with weightbearing, unless a fracture is impending.
  • NOF-like lesions may occur in NF.
  • Jaffe-Campanacci syndrome
  • On plain radiographs, a lytic
    (radiolucent) lesion is seen eccentrically in the metaphyses of long
    bones (usually the distal femur, proximal tibia, or distal tibia).
    • Based in the cortex
    • Overlying cortex if thinned
    • Surrounded by a scalloped, reactive rim of sclerotic (radiopaque) bone
    • Often appears multiloculated, producing a “bubbling” appearance
    • Ranges in size from a few millimeters to a few centimeters
    • Usually solitary
    • If a bone scan is obtained, the lesion will appear “hot” early on from the reactive rim of bone.
      • As the lesion heals, the bone scan will become normal.
Pathological Findings
  • The lesion is filled with fibrous connective tissue arranged in a whirled, “starry night” pattern.
  • Also seen are multinucleated giant cells, foam-filled histiocytes, and hemosiderin pigmentation.
  • Cystic spaces are not typical.
Differential Diagnosis
  • Chondromyxoid fibroma
  • Giant cell tumor
  • Fibrous dysplasia
General Measures
  • In general, full, unrestricted activity is allowed.
  • If weightbearing pain develops, AP and lateral radiographs should be obtained to look for stress fractures.
  • MRI is effective in detecting stress fractures.
  • The treatment for large lesions is
    radiographic monitoring according to the physician’s judgment because
    the lesion is self-healing at skeletal maturity.
  • Patients with large lesions should be seen every 6 months.
    • This monitoring may continue until growth is complete.
  • If >50% of the cortex is involved, and the patient is symptomatic (pain), a pathologic fracture is possible.
    • In this case, treatment is surgery with curettage and bone grafting.
    • If the lesion is small and asymptomatic (<25% of the width of the cortex), no monitoring is needed.
  • No restrictions are placed on activity
    unless a pathologic fracture is impending (>50% of the cortex is
    involved in a symptomatic child), in which case the child should be
    nonweightbearing or have protected weightbearing on the affected
  • For impending pathologic fracture,
    curettage (scraping the lesion) followed by bone grafting (placing bone
    graft into the lesion) should be performed.
  • Internal fixation usually is not necessary.


All these lesions are self-healing at skeletal maturity.
  • Pathologic fracture is seen rarely.
  • Pathologic fractures usually occur only
    in lesions involving >50% of the cortex in symptomatic patients or
    in patients who have had severe trauma.
Patient Monitoring
  • Serial radiography:
    • AP and lateral views of the affected part
1. Enneking
WF. Benign skeletal lesions. In: Clinical Musculoskeletal Pathology,
3rd ed. Gainsville, FL: University of Florida Press, 1990:302–357.
2. McCarthy
EF, Frassica FJ. Primary bone tumors. In: Pathology of Bone and Joint
Disorders: With Clinical and Radiographic Correlation. Philadelphia: WB
Saunders, 1998:195–275.
3. Dorfman HD, Czerniak B. Fibrous and fibrohistiocytic lesions. In: Bone Tumors. St. Louis: Mosby, Inc, 1998:492–558.
Additional Reading
Frassica FJ, Frassica DA, McCarthy EF, Jr. Orthopaedic pathology. In: Miller MD, ed. Review of Orthopaedics, 3rd ed. Philadelphia: WB Saunders, 2000:379–441.
213.9 Fibrous cortical defect
Patient Teaching
  • Tell children that they must report pain or limp to their parents.
  • Reassure the child and parents regarding
    the benign nature of the lesion, the natural course of self-healing,
    and the prevalence of the lesion in healthy children (35%).
  • If the lesion is small, no follow-up is needed.
  • If it is large, follow-up should be obtained every 6–12 months.
Q: If a child has a large NOF and is completely asymptomatic, is protected weightbearing or surgery necessary?
In general, if the child is completely asymptomatic, protected
weightbearing is not necessary. A small risk of fracture is likely with
trauma. Surgery is not necessary.
Q: What are the disadvantages of surgery?
A: A major disadvantage is the scar and the need for protected weightbearing for 3–6 months after surgery.

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