Monostotic fibrous dysplasia of the spine is rare, with the cases of fewer than thirty-five patients discussed in the literature. Dahlin and Unni reviewed the cases of 418 patients with monostotic fibrous dysplasia and noted six (1.4%) involving the spine1. In a series reported by Harris et al., one patient with spine involvement was noted in a total of thirteen patients with monostotic fibrous dysplasia2. Most reports have described the case of a single patient with minimal to no follow-up1-23. As a result, the natural history and ideal treatment for this condition remain poorly understood. For example, the prevalence of scoliosis in patients with polyostotic fibrous dysplasia has been found to be up to 40%24, whereas scoliosis in monostotic fibrous dysplasia appears to be quite rare25. The reported treatment of monostotic fibrous dysplasia in the spine also has varied widely, from surgical resection4,5,7,9-19 to biopsy and observation2,21.
We present the cases of a series of seven patients who were diagnosed with monostotic fibrous dysplasia of the spine at our institution. The history, physical examination, and histologic characteristics are described along with the results of clinical follow-up evaluations.
Clinical Series
Seven patients with histologically confirmed fibrous dysplasia were detected (Table I). There were four male and three female patients. The average age at diagnosis was thirty-three years (range, nineteen to fifty-one years). The average duration of follow-up was 9.8 years (range, two to twenty-eight years). Two lesions occurred in the cervical spine; one each, in the thoracic and lumbar spine; and three lesions, in the sacrum. Two patients were asymptomatic at the time of the diagnosis. Five had pain in the spinal region where the lesions were located. No patient presented with neurologic signs or symptoms. No patient had scoliosis.
Two patients received intralesional curettage as treatment. Five individuals received symptomatic treatment and observation. None of the patients were treated with bisphosphonates. The patients were followed on an annual basis, with clinical and radiographic evaluations, for a minimum of two years. Thereafter, patients were followed on an as-needed basis, with repeat imaging as dictated by symptoms or the location of the fibrous dysplasia lesion.
The presenting symptoms resolved in all patients within two years after presentation. In six patients, the fibrous dysplasia lesion remained static over the course of radiographic follow-up. In one patient, who had been treated with curettage and bone-grafting, the fibrous dysplasia lesion was found to be reduced in size on plain radiographs four years following surgery. In the other patient treated surgically, the size of the lesion remained static, even after ten years.
At the time of the final follow-up, all seven patients were asymptomatic and none had development of symptomatic spinal stenosis or nerve compression. Furthermore, none had pathologic fractures or secondary sarcomas develop.
Representative Case
A forty-six-year-old woman presented with an abnormality in the first thoracic vertebra that was noted incidentally on a plain chest radiograph made for unrelated reasons. A computed tomographic scan demonstrated an expansile, destructive lesion within the first rib and the first thoracic vertebral body. A subsequent computed tomography-guided biopsy revealed fibrous dysplasia. Bone scintigraphy did not show any other sites of disease. She received no treatment but was followed on an annual basis with serial radiographs and computed tomography examinations (Figs. 2-A and 2-B). Eleven years following the initial evaluation, she remained asymptomatic.
Literature Search
A search of the literature revealed that the cases of thirty-one patients with monostotic fibrous dysplasia of the spine have been reported previously1-23. The average age of the patients was 37.2 years (range, twelve to sixty-one years), with most individuals presenting between the third and fourth decades of life. There was a relatively equal distribution between male and female individuals, and monostotic fibrous dysplasia lesions were encountered in all regions of the spine. Axial pain in the location of the lesion was the most common presenting complaint, but radicular symptoms were reported by five patients3,4,18,21,22, four of whom had involvement of the cervical spine4,18,21,22. One patient presented with a pathologic fracture through the lesion23, and one patient had paraparesis because of spinal cord compression9. No instance of scoliosis was encountered. One patient who had malignant transformation in the thoracic spine was reported13.
In the cases of nearly all patients for whom treatment was recorded, the patients underwent surgical intervention. In two patients, a successful resolution of the symptoms was achieved with nonoperative management2,21. There were no reports of patients with monostotic fibrous dysplasia of the spine who had been treated with bisphosphonates.