Fibrous Dysplasia

By admin On Jan 21, 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 Dysplasia

Fibrous Dysplasia

Frank J. Frassica MD

Basics

Description

Fibrous dysplasia is a benign bone process in which there is a failure to produce mature lamellar bone.
The condition:
- Causes focal defects in bone quality
- Is characterized by multiple, gradual
  bone deformities; a risk of endocrinopathy (in the polyostotic
  variety); and a tendency toward pain in the lesions
Café-au-lait spots are common signs in multifocal disease.
Physical findings require some time to develop.
Precocious puberty may occur as early as the 1st year of life.
Classification:
- Monostotic: Involves only 1 bone
- Polyostotic: Involves multiple bones, usually more on 1 side of the body
Synonym: Osteitis fibrosa cystica

Epidemiology

Incidence

Rare
Occurs equally in males and females

Risk Factors

McCune-Albright syndrome (the triad of polyostotic
fibrous dysplasia, café-au-lait spots, and precocious puberty) is an
age-related risk factor.

Genetics

(See “Etiology”)

Etiology

A defect in the gene occurs for a subunit
of a certain G-protein, a type of protein that couples cell-surface
receptors to extracellular signals and activates intracellular
synthesis of cyclic adenosine monophosphate.
The extent and severity of the disease are related to the period in embryonic life when the mutation occurred.

Associated Conditions

Endocrinopathy
Osteosarcoma
Fibrosarcoma

Diagnosis

The diagnosis is made from the characteristic plain radiograph.

Signs and Symptoms

Signs:
- Progressive distortion of bone, as in the proximal femur, pelvis, and cranium
- Possible neurologic compromise, caused by cranial or spinal deformity
- Café-au-lait spots in the polyostotic form (spots have irregular margins likened to the coast of Maine)
- Pain and a waddling gait
- Scoliosis
Symptoms: Constant aches from bones affected by dysplasia under loading

Physical Exam

Measure the patient’s height.
Check for scoliosis, because sometimes it may develop in this condition.
Measure limb-length and angular deformities.
Check all 4 extremities for bowing.
Document the ROM, especially about the hip.
Palpate tender areas of bone.
Observe the patient’s gait.

Tests

Lab

Specific tests for any of the described endocrinopathies should be performed if clinically indicated.
- May include measurement of growth hormone, thyroid function, and adrenal function

Imaging

Radiography:
- The internal appearance of bone with fibrous dysplasia on radiographs is so homogeneous that it is called “ground glass.”
  - This finding is not surprising, given the histologic findings of multiple small disorganized trabeculae.
- Fibrous dysplasia usually is seen occupying a large segment of the diaphysis, and sometimes the entire diaphysis, of a bone.
- The classic teaching is that fibrous dysplasia is a “long lesion in a long bone” (1).
- A characteristic deformity is the “shepherd’s crook” appearance of the proximal femur:
  - A diffuse, severe bowing of the entire proximal end, secondary to bone weakening
Technetium bone scans may be used to locate other lesions of fibrous dysplasia, if needed.
- The lesions are usually “hot” on bone scans, although not universally so.
CT is useful for imaging cranial or spinal disorders.

Pathological Findings

Bone lesions show multiple small, disorganized bony trabeculae, not organized to provide normal mechanical support.
- Likened to “alphabet soup” in their disorganized appearance
The marrow is filled with fibrous tissue.
Osteoblastic rimming of the trabeculae is absent; the bone forms from fibro-osseous metaplasia.

Differential Diagnosis

Unicameral bone cyst
Fibrous cortical defect
Ollier disease

P.135

Treatment

General Measures

Correct progressive skeletal deformity when painful.
Treat endocrinopathy appropriately.
Perform craniofacial reconstruction in patients with severe deformity.
Manage pain with analgesics, or consult a pain management specialist.
- Early trials of diphosphonate agents are promising.

Special Therapy

Physical Therapy

Therapy is useful for postoperative rehabilitation.
The involvement of multiple limbs often poses special challenges to the therapist.

Medication

Pain should be managed with analgesics, or a pain management specialist should be consulted.
- Early trials of diphosphonates are promising.
No evidence suggests that increasing a patient’s activity level will strengthen the dysplastic bone.
- Generally, pain should be the patient’s guide to what is allowed.
- High-impact or endurance activities pose an increased risk of fracture.

Surgery

Orthopaedic principles:
- A marked bowing deformity should be straightened to minimize additional bending forces.
- In the proximal femur, this procedure involves a valgus osteotomy or a medial displacement osteotomy.
- Diseased bone should be supported with a stronger material, such as cortical bone or a metal implant.
- An intramedullary device usually is
  better than a plate because it can protect the length of the bone and
  is more centrally located and therefore more effective (less subject to
  fatigue fracture).
- Lesions of fibrous dysplasia often recur after simple bone grafting.
Lesions often bleed copiously during surgery.
Autogenous cancellous grafts are not used because this graft material is remodeled quickly into fibrous dysplasia.

Follow-up

Prognosis

Progression of dysplasia and new lesions may occur in adulthood.
About 1/3 of patients have chronic pain.
Life expectancy is shortened in patients
with the polyostotic form because of pneumonia, thrombosis, and
malignant transformation.

Complications

Fracture
Chronic pain
Depression
Malignant transformation, most commonly to osteosarcoma (~1% [2])

Patient Monitoring

Patients should be seen periodically by the same physician or set of specialists to detect progressive deformity.
In particular, this regimen should include yearly visits to the orthopaedic surgeon to track femoral bowing and scoliosis.
Patients also should be told about the risk and warning signs of malignant transformation to sarcoma:
- Increase in pain, size, or warmth of the lesion

References

1. 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.

2. Dorfman HD, Czerniak B. Fibroosseous lesions. In: Bone Tumors. St. Louis: Mosby, 1998:441–491.

Additional Reading

Stephenson RB, London MD, Hankin FM, et al. Fibrous dysplasia. An analysis of options for treatment. J Bone Joint Surg. 1987;69A:400–409.

Miscellaneous

Codes

ICD9-CM

733.29 Monostotic fibrous dysplasia
756.54 Polyostotic fibrous dysplasia

Patient Teaching

Patients should be supported because of the chronic nature of the disease.
Sports restrictions, specific to the patient’s individual lesions, should be discussed.
Career counseling should be given.

Prevention

Avoid irradiation of the lesions because of the risk of malignant transformation.

FAQ

Q: Is the solitary form of fibrous dysplasia painful?

A: In general, no pain is present, but some patients do have unexplained pain.

Q: Is it necessary to perform curettage and bone grafting in patients with no symptoms?

A: Patients who have no symptoms should be treated with observation.

Q: Will the bone heal in fibrous dysplasia after a fracture?

A: Yes, it will heal in ~6–12 weeks. If a marked deformity is present, the risk of repeat fracture is high.