Fracture is one of the serious complications of fibrous dysplasia. Because of the particularity of its anatomical position, proximal femur is easy to occur deformities and fractures. Many FD patients couldn't predict whether they will have a fracture or not, and they are often hospitalized after a fracture occurs, so they will miss the best opportunity for treatment. Therefore, early prediction of the incidence of fractures in patients with fibrous dysplasia involving the proximal femur, so as to formulate better treatment strategies, which will help to reduce the incidence of fractures. At present, scholars at China and abroad mainly focus on the treatment of proximal femoral fibrous dysplasia. However there are no case reports on the predictive factors of fracture in patients with fibrous dysplasia of proximal femur, so there is no clear standard about it. Majoor BCJ reviewed of 32 patients with FD in the proximal femur. They investigated the surgical treatment methods and efficacies, but did not discuss the the predictive factors of fracture in patients with fibrous dysplasia of proximal femur. In a retrospective analysis of 26 children with proximal femoral FD, Bian investigated the surgical treatment, clinical effect and revision reasons, but did not introduce a clear standard about fracture factors. Therefore, we need to analyze the influencing factors of fractures in patients with proximal femoral fibrous dysplasia to predict the incidence of fractures. And we formulate corresponding intervention programs to reduce the incidence of fracture.
In order to facilitate the research, scholars at home and abroad have classified FD of proximal femur. At present, the mainstream is the following three types: Guille's classification, Ippolit classification, Zhang’s classification. In this study, we chose Guille's classification, which is simple to operate and convenient for clinical application. We found that most patients are type A FD of proximal femur, and the number of type B, type C and type D cases is less. We divided the patients into two groups according to anatomical classification. Type A patients(involving the whole proximal femur) were divided into type 1. Type B, C, and D patients(involving part of proximal femur) were divided into type 2. In the fracture group, there were 14 patients with type 1 FD of proximal femur In multivariate logistic analysis, there was statistically significant in anatomical classification (OR value=8.622, P༜0.05). Type 1 FD of proximal femur is causing extensive bone destruction due to its wide range of lesions. At this time, the supporting force of the proximal femur decreases, which makes it difficult to support the weight of upper body, so it is easy to fracture.
As an important anatomical marker of the proximal femur, femoral neck shaft angle can increase the range of motion of the lower limbs and transmit the strength of the trunk to the wide base. At present, there are few studies on the relationship between femoral neck shaft angle and fracture in fibrous dysplasia of proximal femur.In addition, it is considered that hip varus is easy to lead to proximal femoral fractur. In a study of 37 cases of femoral neck fracture, it was found that FNSA could serve as a predictive factor for the risk of femoral head stress fracture. In our study, all patients received X-ray examination of hip joint and measured the femoral neck shaft angle. Among the 17 patients in the fracture group, there were 13 patients with the femoral neck shaft angle were less than normal (P༜0.05). Therefore, we think that among the patients with fibrous dysplasia of proximal femur, the patients with femoral neck shaft angle less than the normal value are more prone to fracture than the patients within the normal range. And the smaller the femoral neck shaft angle, the greater the risk of fracture.
Bone metabolic index have high reference value for the impact of fracture risk. Osteocalcin is used as an indicator of bone formation and absorption. Osteocalcin is the most abundant non-collagenous protein in bone and is specifically expressed in osteoblasts. It plays an important role in regulating bone calcium metabolism. It is a new biochemical marker to study bone metabolism. It can maintain normal bone mineralization, inhibit abnormal hydroxyapatite crystallization, and directly reflect the activity of osteoblasts and bone formation. Osteocalcin is closely related to bone mineral density, and it is an important marker of hip fracture risk[20–21]. Although osteocalcin is a marker of bone formation, it may also be released from the bone matrix during bone resorption. Therefore, serum osteocalcin can also be regarded as a marker of bone turnover, not just a marker of bone formation. In a study, osteocalcin deficient mice developed rich bones. Therefore, it is considered that the lack of osteocalcin is related to the improvement of bone functional quality, which indicates that osteocalcin is a negative regulator of bone formation, and the expression of osteocalcin in fibrous dysplasia is generally higher than that in other lesions, so it may inhibit bone formation with poor bone fiber structure. Therefore, the higher the osteocalcin index, the lower the quality of bone at this time, and the risk of fracture will increase accordingly. In the fracture group, there were 16 patients’ osteocalcin was higher than normal (P༜0.05). Therefore, the higher the osteocalcin value, the greater the risk of fracture. At this time, we need to formulate corresponding intervention programs to prevent the occurrence of fracture.
In a study, there were 172 fractures in 35 patients with FD were followed up for 14.2 years. They believed that the peak of fracture rate was 6 to 10 years old, and then decreased with age. In a retrospective study, Han thought that the peak age of fractures in patients with proximal femoral fibrous dysplasia was bimodal. The first peak is between 6 and 10 years old, and the second peak is after 36 years old. However, there was no significant correlation with age in our study. Perhaps due to the small number of samples, age did not become a predictive factor of fracture in patients with fibrous dysplasia of proximal femur. Now there is a lack of corresponding research on the impact of gender factors on fractures in patients with proximal femoral fibrous dysplasia, so it is not used as an influencing factor. The incidence rate of MFD is 8 to 10 times that of PFD. In a multicenter study of 14 patients with MFD of the proximal femur, half of these patients eventually developed disease and fracture progression. In many studies, BMI is considered to be closely related to fracture. They believe that low BMI is a risk factor for fracture[27–28], and there was few study on the relationship between fibrous dysplasia fracture of proximal femur and BMI. In our study, the p-value of clinical classification and BMI were more than 0.05, and there were no statistical significance.
In other studies, the risk of fracture was significantly increased in patients with endocrine diseases. Hyperthyroidism can increase the loss of bone mass and destruction of bone structure, so it will increase the risk of fracture[29–30]. However, we did not choose to include patients with endocrine diseases. This study also has some limitations. Firstly, the number of patients smoking and drinking is small, so they are not included in the study. Meanwhile, the fracture rate will also be affected by external factors (including environment, behavior,etc). In addition, because some patients failed to follow up on time and the clinical data were incomplete, the sample size of this study is insufficient. Large sample cost research is needed in the future. We also need to study the pathophysiology of FD of proximal femur deeply, and make timely and comprehensive therapeutic regimen for patients to prevent the occurrence of fractures.