The surgical management of fibrous dysplasia of bone
© Stanton et al; licensee BioMed Central Ltd. 2012
Published: 24 May 2012
The surgical management of Polyostotic Fibrous Dysplasia (FD) of bone is technically demanding. The most effective methods to manage the associated bone deformity remain unclear. The marked variation in the degree and pattern of bone involvement has made it difficult to acquire data to guide the surgeon’s approach to these patients. In light of the paucity of data, but need for guidance, recognized experts in the management of these patients came together at the National Institutes of Health in Bethesda, Maryland as part of an International meeting to address issues related to fibrous dysplasia of bone to discuss and refine their recommendations regarding the surgical indications and preferred methods for the management of these challenging patients. The specific challenges, recommended approaches, and “lessons learned” are presented in hopes that surgeons faced with typical deformities can be guided in the surgical reconstruction of both children and adults with FD.
The initial evaluation of an adult patient with fibrous dysplasia
In the majority of the patients with fibrous dysplasia (FD) in whom the diagnosed is made in adulthood, FD is an incidental finding. Typically a bone lesion is detected on radiographs that were performed to evaluate a common injury, such as a sprain. Occasionally, the adult patient may present with dull, aching pain and subsequent radiographs may detect a bone lesion. As a first step in the evaluation, a full-body 99Tc-methylene diphosphonate (MDP) bone scan is recommended to not only evaluate the biologic activity of the index lesion, but to detect any additional lesions that may exist throughout the skeleton. If the radiographic appearance is typical (thinning of the cortex without periosteal reaction with a matrix appearance that has been characterized as resembling “ground glass”), most often the diagnosis may be rendered without additional imaging studies (i.e. computed tomography (CT), or magnetic resonance imaging (MRI)). Biopsy is indicated for histologic confirmation only in cases that do not present a typical radiographic appearance.
Management of adult monostotic disease
Treatment decisions for adult patients with monostotic disease depend entirely on the presence of symptoms. The typical lesion, which is identified incidentally and remains asymptomatic, should be treated with observation and serial radiographs at an interval determined by consensus between the patient and the surgeon until they are satisfied that the lesion is biologically inactive and mechanically insignificant. When surgical intervention is indicated, monostotic lesions are typically treated with conventional surgical procedures . In the absence of clinical symptoms, typical monostotic disease may be observed without specific intervention. In select patients, surgical management may be indicated for a variety of reasons. In some patients, the fear of malignant disease may be so profound that the surgeon is unable to adequately reassure the patient of the benign nature of the process. In other patients, the lesion may cause a true mechanical deficit that has led to bone pain or fracture and therefore intervention may be indicated. Typical orthopedic procedures to remove the lesion and to graft the defect may be used in these cases. The use of internal fixation should be considered in most cases to aid in immediate weight bearing and to augment the strength of the bone. If recurrent FD results in the resorption of the graft, generally accepted principles of orthopedic tumor surgery are followed. In MFD in adults, one can expect low levels of tumor recurrence.
The initial evaluation of a child with fibrous dysplasia
Typically a child with FD will consult the orthopedic surgeon for complaints of pain, limp, or management of a pathologic fracture through an area of FD. If the child also has café-au-lait macules, the diagnosis of McCune-Albright Syndrome (MAS) is easily made. The classic diagnostic criteria for MAS had been FD, café-au-lait macules, and precocious puberty [2, 3], but better understanding of the molecular and developmental etiology of FD/MAS has led the acceptance of the fact that any combination of one or more of the typical features of MAS (FD, café-au-lait macules, and/or hyperfunctioning endocrinopathies such as gonadotropin-independent precocious puberty, hyperthyroidism, growth hormone excess, etc.) warrants the diagnosis of MAS. In fact, given that the molecular etiology of even monostotic FD (MFD) is the same activating mutation in Gsα as is found in full spectrum MAS , MFD can be considered a forme fruste of MAS.
The consensus of the authors is that the initial evaluation of the child should begin with a 99Tc-MDP bone scan to assess for the presence and/or extent of polyostotic FD (PFD). Before age six, and especially before the age of three, the bone scan may not show all areas that will ultimately be involved with FD, as small foci of FD may not be detected by the bone scan. After age six, affected areas of FD are usually detectable, and the family can be reassured that it is very unlikely that any “new” areas of FD, and certainly no new areas of clinical significance beyond what is already seen, will subsequently appear . However, parents should also be informed that affected areas identified at a young age may progress. All young patients diagnosed with FD, and especially those with PFD require an evaluation by an endocrinologist, even in the absence of history or clinical findings suggestive of endocrine dysfunction. In addition, older patients with MFD, who have any history or clinical findings suggestive of endocrine dysfunction, should be referred for an endocrine evaluation. Patients whose bone scan shows cranial or facial involvement will require an evaluation by a craniofacial specialist. While CT imaging is often necessary to evaluate craniofacial FD, the consensus of the authors is that CT and/or MRI evaluation of long bone and spinal lesions are rarely indicated. Biopsy and/or molecular diagnosis (gene testing for mutations in GNAS) is rarely indicated in polyostotic disease, as the diagnosis can be rendered confidently on the basis of the history, physical examination and radiographs. When surgical procedures are required material may be obtained for histologic and/or molecular diagnostic confirmation or research purposes.
Management and follow-up of pediatric polyostotic fibrous dysplasia
Fracture and deformity management
Lower extremity fractures will almost always require the use of internal fixation, although selected non-displaced tibia fractures may be managed with casts. Non-weight-bearing management should be avoided whenever possible. Patients with FD frequently have underlying bone fragility due to a combination of FD in other parts of the skeleton, metabolic issues, and diminished activity. Prolonged non-weight-bearing treatment following surgery will only aggravate the preexisting bone weakness. The use of internal fixation devices may allow early weight-bearing and should be considered when feasible. As with the upper extremity, remodeling of angulation may not occur.
Limb length discrepancy is common in PFD and is more likely to occur in patients with severe disease, requiring multiple corrective procedures. Attempts to surgically lengthen bone with FD will result in the formation of more dysplastic bone. Mechanical devices, such as circular frames with thin wire fixation, are not likely to hold in FD bone. Lengthening may be considered if there are bones or bone segments that are of good quality and not involved with FD. Epiphyseodesis of the longer limb at the appropriate time may be considered; however, many FD patients are destined to be of short stature and may not accept a procedure that reduces adult height. A patient and family that have undergone multiple major surgical procedures may prefer to accept the need to wear a permanent shoe lift as a means to deal with a limb length discrepancy, rather than accept another surgical procedure.
Transformation of fibrous dysplasia
Malignant transformation in FD is very rare and most reported cases appeared to be associated with radiation therapy, which was commonly used to treat FD lesions in the past . At this time, there is no indication for the use of radiation therapy in the management of FD of bone.
Bone grafting may be indicated for selected adult patients with monostotic disease . Allograft is preferred to autograft to eliminate donor site morbidity. Bone grafting for patients with PFD is not useful. Attempts to completely remove polyostotic disease with curettage and bone grafting are rarely successful. Such surgery results in significant blood loss, and the FD lesions typically remodel the grafts with FD over time. There may be a limited indication for the use of allograft in conjunction with internal fixation for selected cases where the graft material provides temporary augmentation for the internal fixation. Large whole bone allographs may be used in adult patients as composite reconstructions in association with artificial joint replacement surgery in selected cases. There are always exceptions to any rule, and occasionally the small bones of the hands and fingers may suffer repeated fractures that warrants the use of grafting. These bones can often be treated effectively with curettage and bone grafting without fixation.
Bone infection and blood loss
The majority of FD lesions are richly supplied with blood vessels, and extensive bleeding may be anticipated for patients in whom a lengthy reconstruction is planned. The presence of an ABC in the lesion can also increase the blood loss during surgery. This may become significant, especially for reconstructions where multiple corrective osteotomies are required and where the medullary canal must be reconstituted with drilling and/or reaming prior to the insertion of an IM device. Blood transfusion may be necessary if multiple sites of deformity correction are attempted at one episode of surgery. Therefore we recommend that the surgeon advocate early intervention before the development of significant bone deformity. Bone infection following surgery for FD is uncommon and perhaps less frequent than in similar surgical procedures performed in otherwise normal bone. The rich blood supply of the FD tissue may provide some degree of protection from infection in these patients. The authors have limited experience with infection in FD surgery and suggest that standard orthopedic principles of management be utilized.
In summary, PFD is an extremely complex condition causing fractures and deformity in children. Although relatively standard procedures are effective in adults with MFD, children with PFD require aggressive and innovative intervention if severe deformity is to be avoided. Bone grafting is seldom indicated. The use of intramedullary internal fixation devices is preferred over plate and screw devices whenever possible. The management of each patient must be individualized. The expectations of the parents must be prospectively managed and the patient and parent must be prepared for multiple episodes of reconstructive surgery throughout the growing years.
This article was developed as part of the Proceedings of the International Meeting on Fibrous Dysplasia/McCune-Albright Syndrome and Cherubism that took place at the National Institutes of Health, Bethesda, MD, October 3-5, 2010. The meeting was supported by funding from the National Institute of Dental and Craniofacial Research and Office of Rare Diseases, NIH, and the Fibrous Dysplasia Foundation. The publication of this manuscript was supported by the Fibrous Dysplasia Foundation and an unrestricted grant from Zimmer, Inc.
This article has been published as part of Orphanet Journal of Rare Diseases Volume 7 Supplement 1, 2012: International Meeting on Fibrous Dysplasia/McCune-Albright Syndrome and Cherubism. The full contents of the supplement are available online at http://www.ojrd.com/supplements/7/S1. Publication of the proceedings was funded by the Fibrous Dysplasia Foundation and an unrestricted grant from Zimmer.
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