Fibrous Cortical Defect 

Updated: Apr 15, 2019
Author: Bernardo Vargas, MD; Chief Editor: Omohodion (Odion) Binitie, MD 

Overview

Background

Fibrous cortical defect (FCD; also referred to as nonossifying fibroma [NOF] or nonosteogenic fibroma) was first described by Phemister in 1929. Sontag and Pyle reported a radiologic description in 1941,[1] and in 1942, Jaffe and Lichtenstein described clinical and anatomic aspects and the natural history.[2]

FCD probably is the most frequent bony lesion in children, occurring in as many as 30-40%.[3] It is most common in adolescents. The term FCD was coined to describe the smaller variety of NOF[4] ​; for a lesion large enough to encroach on the medullary canal, the term NOF is used. However, no histologic difference exists between these lesions. The authors believe that FCD and NOF should be considered the same entity, and in this article, the two terms are interchangeable. These lesions are, in fact, developmental abnormalities, as opposed to benign neoplasms.

FCD usually is an incidental finding on radiographs. Always benign, it may result in pathologic fracture, though this is is a rare first presentation.[5] These lesions can exist in multiple sites. FCD may be difficult to diagnose in the presence of pain or swelling of soft tissues. It also can be confused with a more aggressive lesion[6, 7] ; therefore, biopsy may be necessary. Fractures and impending fractures are indications for surgical intervention. Association with other bone lesions, such as aneurysmal bone cyst, is rare.[2, 4, 8, 9, 10, 11]

Pathophysiology

The average duration of FCD is in the range of 29-52 months, after which period the lesion spontaneously resolves. FCD may be present during childhood, but lesions tend to disappear in adolescence.

Etiology

The etiology of FCD remains obscure. FCD is a proliferation of benign fibrous tissue, possibly developing as a result of periosteal injury or secondary to abnormalities at the epiphyseal plate. Others postulate that FCD is related to the normal cutback phenomenon seen in maturing physeal plates. Progression of this lesion introduces abnormal tissue into the metaphyseal cortex.

Epidemiology

FCD constitutes 5% of benign tumoral lesions of bone. The true incidence is more likely to be on the order of 30% or more, but because FCD is asymptomatic in most patients, most lesions are never identified. Sontag and Pyle identified this lesion in 54% of boys and 22% of girls in a series of 200 healthy children.[3, 12] These lesions occur in multiple sites in approximately 50% of patients. FCD is rare in children younger than 2 years and is most common in adolescents.

Prognosis

The rarity of FCDs in adults confirms that these lesions regress with time. The prognosis is excellent in those unusual cases where patients require curettage and bone graft.[13]

 

Presentation

History and Physical Examination

Fibrous cortical defect (FCD) is encountered frequently in children and adolescents and is usually asymptomatic.[3, 12, 14]  Pain is rare and, if present, is usually associated with a fracture. FCD typically is localized in long bones. The most common sites are the femur and tibia. On rare occasions, it may be encountered in the vertebrae, clavicle, or bones of the upper limbs. The association of multiple FCDs with café-au-lait spots, multiple nevi, mental retardation, hypogonadism, and ocular and cardiovascular abnormalities is called Jaffe-Campanacci syndrome.[15]

FCD lesions have a typical and relatively distinct radiographic appearance. The lesion is radiolucent and is located eccentrically, usually in the distal metaphysis of a long bone. The cortex is thin, with sclerotic or scalloped margins. Lesions can be uniloculated or multiloculated. The longitudinal axis of FCD tends to be parallel to the axis of involved bone.

Commonly, FCD can be diagnosed by the orthopedic surgeon on the basis of clinical findings and imaging, without need for referral to orthopedic oncology.[16]

 

Workup

Imaging Studies

Plain radiography

Usually, the diagnosis can be established by means of plain radiography (see the images below), and biopsy is not necessary.[17, 18, 19]

Plain radiograph of fibrous cortical defect of the Plain radiograph of fibrous cortical defect of the proximal tibia.
Lateral radiograph demonstrating a solitary fibrou Lateral radiograph demonstrating a solitary fibrous cortical defect in the proximal tibia.

The classic picture is that of an elliptical radiolucent lesion eccentrically located within the metaphyseal cortex of long bones, especially the femur. The margins are sharply demarcated, and the appearance is often septated. In some cases, multiple lesions may develop (see the image below).

Plain radiograph demonstrating multiple fibrous co Plain radiograph demonstrating multiple fibrous cortical defects in multiple bones.

Computed tomography

Computed tomography (CT) should not be performed unless a strong doubt about diagnosis is present, except to confirm a pathologic fracture (see the image below). This lesion is located eccentrically, and CT scans should depict a central lucency. CT may confirm a minimally displaced fracture.[17, 18, 19]  It may also be helpful in preoperative planning for FCDs in unusual locations (eg, the femoral neck).

CT scan of the fibrous cortical defect shown in th CT scan of the fibrous cortical defect shown in the plain radiographs in Images 2-3; note the cortical location and the sclerotic rim around the central lucency.

Bone scintigraphy

This study is not indicated for diagnosis. Nevertheless, in some cases, a methylene diphosphonate (MDP) technetium bone scan can help in assessing the biologic activity of the lesion.[17, 18, 19]  Minimal increased uptake can be seen, as in the image below. In associated fractures, this study is not useful.

Methylene diphosphonate technetium bone scan of th Methylene diphosphonate technetium bone scan of the fibrous cortical defect in Images 2-4; uptake is minimally increased at the site of the lesion.

Biopsy

Biopsy is rarely needed, because radiographs typically are diagnostic.[16]

Histologic Findings

Histologic analysis of FCD reveals a predominantly bland fibroblastic component with a few histiocytes, myofibroblast cells, and giant cells (see the image below). The lesion is marked by proliferations of spindle cells arranged in a storiform pattern. Hemosiderin deposits also are found. Around the lesion, some leukocyte infiltration may be present.

Histologic section of a fibrous cortical defect de Histologic section of a fibrous cortical defect demonstrating a bland fibrous stroma in the absence of nuclear atypia or mitoses; a few giant cells are scattered within the stroma.

Fractures through an FCD may change the histologic pattern. In these cases, blood deposits due to the fracture and formation of new bone are seen. Care must be taken not to confuse early callus with osteogenic sarcoma.

 

Treatment

Approach Considerations

The characteristic location and appearance are usually suggestive of a benign lesion and are often pathognomonic for fibrous cortical defect (FCD); thus, no further action is necessary unless a pathologic fracture has occurred or risk of fracture is high.

The following considerations should be kept in mind:

  • Does the lesion involve more than 50% of the transverse diameter of the bone? The risk of fracture is higher in this circumstance, and prophylactic surgery may be indicated
  • Is the lesion becoming larger and more symptomatic? A more aggressive therapy may be considered
  • Is the location of the lesion particularly associated with high risk for pathologic fracture (eg, femoral neck)? Localization around the femoral neck is associated with an increased risk of pathologic fracture, producing avascular necrosis of the femoral head; therefore, stabilization may be indicated

In the pediatric population, casting usually is the most appropriate treatment after pathologic fracture. In unstable fractures or in adolescents, curettage (with or without grafting) and internal fixation are appropriate.

When FCD is near an open physis, surgery should be avoided if possible. With time, the FCD will migrate away from the physis, and risk of damage to the growth plate will be minimized.

Medical Therapy

In the pediatric population, casting usually is the most appropriate treatment after pathologic fracture to avoid injuring the physes during surgery.[3]  FCD may heal spontaneously following fracture. If, after casting and union of the fracture, the lesion does not regress, curettage and grafting are indicated. In unstable fractures or in adolescents, curettage (with or without grafting) and internal fixation are appropriate.

Surgical Therapy

Surgery is recommended in cases involving unstable fractures or a high risk of pathologic fracture.

The surgical approach involves exposing the fracture site and developing a cortical window to curette the tumor. The lesional tissue is gray or brown-yellow. The texture is firm. Bone septa may be present, giving the impression of a multicameral lesion. As mentioned previously, surgery should be delayed, if possible, for lesions abutting a physis. Corticancellous allograft (the author's preference) or autograft may be used, depending on the size of the lesion.

Complications

Injury to the physis and subsequent growth abnormalities are possible adverse effects of surgery for lesions abutting a physis.

Long-Term Monitoring

After first diagnosis

Typical lesions do not require more than one follow-up examination and radiograph (after a 6- to 12-week interval). Large lesions must be followed with plain films every 4-6 months to assess progression. The lesion may increase in size. A lesion that measures more than 50% of the transverse diameter of the bone is susceptible to pathologic fracture. Patients must be instructed to avoid excessive activities in order to prevent acute fractures. Contact sports also must be avoided.

The natural history of nonossifying fibroma (NOF) is one of involution and ossification as puberty is reached. This usually proceeds from the diaphyseal end to the metaphyseal end of the lesion.

After fracture

Immobilization following fracture is continued until union is radiologically evident. At this point, if the lesion is not regressing and is at risk for refracture, curettage with or without internal fixation and grafting may be indicated.