35. Fibrous Dysplasia
Definition
Fibrous dysplasia is a dysplastic bone disorder wherein immature woven bone forms directly from abnormal fibrous connective tissue. Fibro-osseous tissue within affected bones expands as a lesion of growing bone. The term “dysplasia” refers to the person’s inability to form mature lamellar bone.
Incidence
The true incidence is not known, but there are estimates that about 10% of benign bone tumors are the result of fibrous dysplasia.
Etiology
Fundamentally fibrous dysplasia appears to be a disorder of postnatal cancellous bone maintenance or an abnormality of bone-forming mesenchyme.
Signs and Symptoms
• Abnormal cutaneous pigmentation
• Albright syndrome
• Cushing’s disease
• Hyperparathyroidism
• Hyperthyroidism
• Hypophosphatemic rickets
• Painful swelling and/or deformity of weakened bone
• Pathologic fracture(s)
• Precocious puberty
Medical Management
Care and management of a patient with fibrous dysplasia are generally conservative, with the primary goal to prevent deformity.
Any associated endocrine anomaly should be managed primarily. These include hyperparathyroidism, hyperthyroidism, and Cushing’s disease.
There is no specific medical treatment for the bone disease. Some data suggest that administration of vitamin D plus bisphosphonates are at least somewhat effective in pain amelioration and reconstitution of lesions with normal bone (after physeal closure has occurred). The bony defect may be surgically treated by curettage and allograft or cortical autograft replacement of the lesion. Both allograft and cortical autograft are more resistant to resorption and substitution by dysplastic bone.
Bone deformities, especially of long bones and weight-bearing bones, generally require stabilization. Stabilization is optimally achieved using intramedullary nail fixation. At times, expendable bones with lesions and/or deformities may be treated appropriately by excision.
Complications
• Autonomic hyperreflexia
• Deformity
• Fractures
• Malignant transformation
Anesthesia Implications
Underlying endocrine disorder/dysfunction should be ascertained preoperatively. Appropriate anesthesia concerns will be predicated on the underlying endocrine dysfunction.
Maxillary and/or mandibular involvement may be extensive. Craniofacial deformities may be grotesque. As a result, airway management may be precarious and difficult. Direct laryngoscopy may be difficult to impossible to perform, particularly in a patient with extensive dysplasia of the maxilla and/or mandible. Even fiberoptic laryngoscopy may prove difficult. It is prudent to have a surgeon standing by to surgically secure the airway if necessary.
The patient’s bones are extremely fragile—fractures may occur with even the slightest trauma. Correct positioning and adequate padding of the extremities are essential.
Regional anesthesia techniques may be used, but extreme caution must be taken with a patient who has spinal cord lesions.
Autonomic hyperreflexia is possible in a patient with spinal cord lesions, and can give rise to a host of potential anesthesia implications and concerns.
