Fibrous Cortical Defect/Nonossifying Fibroma

By admin On Jan 20, 2024

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

Basics

Description

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

Epidemiology

A common skeletal lesion

Incidence

Estimated to occur in 35% of healthy children with open physes (3)

Etiology

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

Diagnosis

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

Tests

Imaging

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

Treatment

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.

Medication

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
extremity.

Surgery

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.

P.133

Follow-up

Prognosis

All these lesions are self-healing at skeletal maturity.

Complications

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

References

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.

Miscellaneous

Codes

ICD9-CM

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.

FAQ

Q: If a child has a large NOF and is completely asymptomatic, is protected weightbearing or surgery necessary?

A:
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.