The correlation of specific orthopaedic features of polyostotic fibrous dysplasia with functional outcome scores in children

Background: Polyostotic fibrous dysplasia has a wide clinical spectrum, with substantial variation between patients in terms of orthopaedic manifestations, including the number of fractures, the degree of deformity of the limbs, and the presence of scoliosis. Data from bone scans, skeletal surveys, and records were correlated with the Pediatric Outcomes Data Collection Instrument scales to examine whether any specific facet of orthopaedic involvement could be related to functional abilities. Methods: All patients who were sixteen years of age or younger and who were part of an ongoing natural history study of polyostotic fibrous dysplasia (including McCune-Albright syndrome) were sent an age-appropriate Pediatric Outcomes Data Collection Instrument outcomes tool. The medical records and radiographs of the patients who returned forms were reviewed. Radiographic measurements of scoliosis, the femoral neck-shaft angle, and limb deformities were then performed. The extent of skeletal involvement with polyostotic fibrous dysplasia (disease burden) was assessed on bone scans with use of a validated tool. A chart review was performed to determine the fracture rate, the use of bisphosphonates, and the endocrine status. These measurements were correlated with the Pediatric Outcomes Data Collection Instrument scores. Results: The outcomes tool was sent to twenty-seven patients and the completed instrument was returned by twenty patients, for a response rate of 74%. The parent-child form was filled out for twelve patients and the parent-adolescent form was filled out for eight patients. The mean standardized Pediatric Outcomes Data Collection Instrument scores for all twenty patients were lowest for sports (62; range, 14 to 100) and happiness (72; range, 25 to 100). Adolescents and parents disagreed with regard to sports (with adolescent scores being higher than parental scores) and pain (with parental scores being higher than adolescent scores). However, the overall global scores correlated well between the parents and the adolescents (r = 0.78, p = 0.03). The femoral neck-shaft angle correlated strongly with the Pediatric Outcomes Data Collection Instrument score for sports (r = 0.46, p = 0.03) but not for transfers. The bone scan scores for the lower extremity disease burden correlated with both the transfer scale (r = 0.76, p = 0.03) and the sports scale (r = 0.77, p = 0.02). Deformity of the limbs, the presence of scoliosis, the prevalence of endocrine dysfunction, and the number of fractures did not correlate with the Pediatric Outcomes Data Collection Instrument scores. Conclusions: In patients with polyostotic fibrous dysplasia, the loss of the normal femoral neck-shaft angle and the disease burden in the lower extremities appear to have the greatest effect on functional activity as measured with the Pediatric Outcomes Data Collection Instrument tool.