Fibrous dysplasia of bone (FD) is a common benign tumor-like disorder, accounting for approximately 5-7% of benign bone tumors. Etiologically, Fibrous Dysplasia is a congenital, non-genetic disease caused by mutations in the G5α gene of chromosome 20q13.2-13.3 in the somatic cells after conception, resulting in abnormal development of multiple organs such as the skeleton and the endocrine system, and the earlier the mutation occurs, the greater the degree of developmental abnormality. As the mechanical strength of the bones is greatly reduced, fatigue fractures can occur under normal stress, leading to local pain, and in severe cases, pathological fractures can occur, and repeated fatigue fractures and pathological fractures can lead to deformities, which can be manifested in the proximal femur as In the proximal femur, the hip joint may be deformed. Involvement of the skin may result in milk coffee spots, mostly on the trunk and proximal extremities, which are known to resemble the Maine coastline because of the unsmooth edges. Involvement of the endocrine system may result in a variety of changes including precocious puberty, growth hormone hypertrophy, hyperalgesia, hyperthyroidism, and Cush syndrome. Fibrous dysplasia of bone occurs without gender differences and can occur at any age, with most cases detected before the age of 30. Depending on the degree of bone involvement, it is clinically classified as monostotic (Monostotic Fibrous Dysplasia, MFD), polyostotic (Polyostotic Fibrous Dysplasia, PFD), McCune-Albright syndrome (Polyostotic Fibrous Dysplasia of Bone with Endocrine System Disease, MAS) and Mazabraud’s disease ( The natural course of MFD is very different from that of PFD and MAS; MFD generally stops progressing after the cessation of skeletal development and the lesion itself can undergo repair and thus increase in strength. In contrast, PFD and MAS can continue to develop after skeletal maturation and the lesion can continue to increase in size, and the lesion can involve the entire skeleton, so they are prone to pathologic fractures and deformities, which are most likely to occur between 6 and 10 years of age, and these patients can have multiple fractures in multiple sites, while patients with phosphatiduria have earlier pathologic fractures and more fractures. The different natural course of the disease determines the different treatment outcomes. The main clinical manifestations of fibrous dysplasia of bone are: localized pain, claudication, the affected bones may have deformities, pathological fractures, and the limbs may be shortened. Although fibrous dysplasia is a benign tumor-like disorder, due to its complex presentation and lifelong disease, patients often require multiple treatments, and Ennecking even compares its complexity to that of treatment of bone metastases, but treatment of fibrous dysplasia requires a longer time frame. The proximal femur is the most likely site of fibrous dysplasia of the bone, with Harris et al. reporting 92% of PFD cases involving the femur. The proximal femur is prone to fractures and deformities due to the high concentration of stresses, making it a difficult area to treat fibrous dyskeletal bone. The treatment of fibrous dysplasia of bone can be divided into two directions, one for the lesion itself and one for the fracture and deformity caused by the lesion. There is no ideal treatment at the genetic level. As a congenital disorder, treatment is in principle not required for asymptomatic fibrous dysplasia lesions. Pain due to lesion destruction can be relieved by treatment with bisphosphonates. Scraping of the lesion removes the lesion and in combination with bone grafting and internal fixation can greatly improve the local stability. In patients with fractures, although the pathological fracture can be healed by conservative treatment, one needs to be alert for the appearance of deformity healing. For skeletal deformities correction by osteotomy is required, along with the selection of an appropriate internal fixation. Fibrous dysplasia of bone resembles a congenital malformation in that the lesion is present from birth, but it does not cause symptoms per se and most MFDs are discovered inadvertently during other examinations. Therefore, fibrous dysplasia without local symptoms does not require surgical treatment, but the possibility of pathologic fracture and deformity needs to be carefully evaluated, especially in the lower extremity and proximal femur. According to the European Pediatric Orthopaedic Society, even in MFD of the femur, there is still a 50% chance of fracture. There is no specific method to predict the possible growth trend and complications of a particular lesion, so it is essential to take regular radiographs of the lesion. In recent years, bisphosphonates have been shown to be effective in the treatment of FD, with Chapurlat, Zacbarin, Lane et al. reporting significant pain reduction, reduced fracture incidence, and increased cortical thickening and ossification in the lesioned area. Plotkin et al. used bisphosphonates for the treatment of FD in children and found significant pain reduction but no significant changes on x-ray, no significant side effects with long-term use, and no signs of osteochondrosis. Focal scraping is a common treatment for fibrous dysplasia of the proximal femur bone, and either allograft or autologous bone grafts can be used to treat the scraped bone defect, and bone healing is often achieved in the short term. In a review of Harris, Stewart, and his own data, Ennecking found that of 25 cases of fibrous dysplasia of the proximal femur that underwent bone grafting with scraped cancellous bone, 12 cases had satisfactory follow-up and 13 cases had local resorption and recurrence of the lesion. Hao Lin et al. reported 11 cases of fibrous dysplasia treated with scraped cancellous bone grafting and found localized bone healing at a mean of 4.5 months, but the specific case data and long-term follow-up results were not further elaborated. After 2 years, it was found that all implants showed complete resorption on radiographs, and all lesions did not disappear or diminish in size, and some showed enlargement. In a group of cases reported by the European Pediatric Orthopaedic Society, five cases of MFD occurring in the femur were treated with cancellous bone grafting, one case had resorption of the graft and a second graft was performed, and one case had an inversion deformity after grafting and was internally fixed with an osteotomy. Ennecking proposed the use of autologous cortical bone grafting because he found that cortical bone is more difficult to be resorbed and crawl replaced compared to cancellous bone. A total of 15 patients with proximal femoral FD were seen for painful fatigue fractures of the femoral neck, 5 with PFD and 10 with MFD, aged 9-22 years, all with lesions located in the femoral neck region, while normal cancellous bone was preserved in the femoral head and greater trochanter region, with no deformity of the femoral neck. The middle of the cortical bone passed through the lesion area and the ends were embedded in normal cancellous bone, thus strengthening the femoral neck. At a mean follow-up of 6 years (2-14 years), all 15 cases showed pain relief and no further deformity of the proximal femur, 2 cases showed local resorption and were reimplanted with cortical bone implants, and 2 implants were locally stable. Guille et al. therefore recommended not to perform prophylactic scraping implants in asymptomatic FD and not to perform scraping implants in FD with initial pain due to fatigue fracture, as this would only further weaken the bone strength Stephenson et al. also recommended effective internal fixation of the fracture by incision without treatment of the lesion, which does not remove the diseased tissue but directly strengthens the local bone and will help to avoid complications such as local fracture or deformity. He reported that 86% (19/22) of the lesions were stabilized by this method for an average of 10 years. Harris et al. found that the healing time of fractures in poorly fibrous bones did not differ from that of normal bones, so non-surgical treatment of fatigue fractures or pathological fractures, such as cast fixation or traction, can achieve fracture healing and thus eliminate pain, but the long-term outcome is affected by the patient’s age, site of origin, and lesion staging. For example, conservative treatment of lesions involving the upper extremities can provide satisfactory long-term results, whereas for lesions in the lower extremities, especially in the proximal femur, conservative treatment is likely to result in malunion or re-fracture. In his report of a group of 32 patients with FD lesions involving the lower extremities, all younger than 18 years of age, who were treated conservatively, with a mean follow-up of 10.4 years, there were 27 patients with PFD, only 4 with stable local symptoms, 19 with pathological fractures, and 3 with progressive deformities; there were 5 patients with MFD, all of whom were treated unsatisfactorily conservatively, 4 with reappearance of pathological fractures, and 1 with increased pain. The European Pediatric Orthopaedic Society showed that 5 cases of MFD were treated conservatively with plaster fixation or lower limb traction with satisfactory long-term follow-up, but 13 patients with PFD or MAS developed severe deformities after conservative treatment and required reoperation. of the hip, while patients who present with multiple fractures have poor local bone strength and poor results of conservative treatment and should be treated surgically. After repeated microfractures or pathological fractures of the proximal femur FD, a severe hip entropion deformity like a Shepherd’s crook can occur. The surgical treatment of this deformity is a very important aspect of the treatment of proximal femoral FD, and the prevention of recurrence of inversion is a difficult task, and the treatment of PFD and MAS cases is more difficult than that of MFD. Funk et al. reported four cases of PFD involving the femur, in which the progression of the inversion deformity could not be controlled after as many as 19 osteotomies and scraping implants, and the intertrochanteric region where the lesion was located was finally resected. Gullie’s experience was to correct the force line early in the disease with an external osteotomy and internal fixation for cases with more than 10 degrees of valgus, with the internal fixation of the femoral neck reaching as far as possible to the femoral head or through the epiphyseal plate, and with a McMurray internal transfer osteotomy if the lesion involves the femoral spur or if the lesion is too large for internal fixation. Four of the nine cases of MFD involving the proximal femur underwent external osteotomy with internal fixation, and nine of the 13 cases of PFD involving the proximal femur underwent external osteotomy and/or internal displacement osteotomy with an average follow-up of 15 years, except for two cases of PFD with a stem angle of the femoral neck less than 90 degrees. Bray performed a composite osteotomy with Zickel pin fixation in 6 cases of PFD involving the proximal femur, and the inversion deformity did not worsen again at 34.5 months of follow-up. The European Pediatric Orthopaedic Society found that three cases of MFD with internal fixation such as direct plate screws or intramedullary pins without treatment of the lesion tissue were found to achieve lesion stability and good joint function at long-term follow-up, but limb shortening (1-6 cm) occurred in most cases; whereas the eight cases of PFD with pathological fractures fixed with plate screws showed plate fracture and loosening and increased deformity, with additional stresses concentrated on the fixed The distal end of the steel plate, due to the large extent of the lesion, reoccurrence of fracture and inversion deformity at the distal end of the lesion, and inability to ensure long-term stability of the proximal femur, required multiple fixation procedures. For PFD cases with a large extent of the lesion that affects the entire proximal femur, it is recommended to use the direct use of the femoral reconstructive intramedullary pin (Cephalomedullary nailing) fixation technique, which can provide long-term Effective stability can prevent fractures and severe deformities without the need to treat the lesion itself, and this technique has been used in 12 cases with custom-made non-expandable intramedullary pins in 9 cases with a follow-up time of more than 10 years without any increase in deformity or fracture. However, this fixation does not prevent fracture or deformity, and the corresponding conventional intramedullary pin should be replaced as soon as the femur grows to the appropriate diameter, and of course the thinner the pin, the less ability it has to provide long-term prevention of fracture and deformity, and the authors believe that the ideal situation would be to design an adjustable diameter and length intramedullary pin for children, and that this type of fixation would be the best internal fixation for FD treatment in children.Mark O’Sullivan performed a study of 5 Jung ST et al. performed a composite osteotomy in 7 cases of PFD involving the proximal femur, using an intramedullary pin for internal fixation and 2 screws driven into the femoral neck at the same time. The neck stem angle recovered from 92 degrees to 129 degrees. At more than 2 years of follow-up, there was no recurrence of the inversion deformity and no fracture. In conclusion, poor fibrous structure of the bone is most likely to involve the proximal femur and predispose to pain, fracture, and hip internal derangement deformity. No treatment is required for asymptomatic FD. Bisphosphonates can relieve the pain caused by the lesion. Lesion scraping and bone grafting are commonly used to treat fibrous dysplasia of the proximal femur bone; however, resorption of cancellous bone is often present and combined with internal fixation can result in increased local stability. Conservative treatment can achieve fracture healing but is prone to deformity healing. Surgical treatment of hip inversion deformities and pathological fractures requires a combination of appropriate internal fixation methods. Looking forward, treatment from the etiology to promote normal mineralized ossification in the FD lesion area is a promising approach.