Increasing serum alkaline phosphatase is associated with bone deformity progression for patients with polyostotic fibrous dysplasia

BACKGROUND: Fibrous dysplasia (FD) is a rare bone disorder in which normal intramedullary bone is replaced by fibro-osseous tissue, which is complicated by the progression of Shepherd’s crook deformity. How to predict the progression of Shepherd’s crook deformity is still a challenging for the orthopedic surgeon. METHODS: A total of 159 cases were reviewed in the retrospective study between January 2000 and September 2016. Clinical and monitoring data were collected. We analyzed the correlationship between the bone turnover markers and other parameters (age, gender, FD type, deformity, BMI, and lesion location). RESULTS: Age, gender, lesion location, lesion type, and shepherd’s crook deformity had a close relationship with preoperative ALP level in the univariate analysis, and the multivariate analysis showed age, gender, lesion type, and shepherd’s crook deformity had the significant relationship with the preoperative serum ALP level. The surgery could remove the bone lesion and suppressed the abnormal bone metabolism. Furthermore, the preoperative ALP level of FD patients with the shepherd’s crook deformity was obviously higher than that without deformity, and the preoperative calcium and phosphorus levels of FD patients with deformity were significantly lower than that without deformity. Notably, for some patients with progression of the shepherd’s crook deformity during the follow-up, ALP increased to the high level and at that time X-ray showed the shepherd’s crook deformity severely progressing. CONCLUSIONS: PFD with higher serum ALP level has obvious tendency to progress severely, and risk factors of progression to the deformity are the condition of bony metabolism and FD type. The deformity of PFD may be related to high speed of bone turnover, which is exactly reflected by the levels of serum ALP and calcium. Evaluation of patients with FD should include a thorough evaluation of calcium/phosphate metabolism and bone turnover.