Fibrodysplasia (FD) is a benign bone disease in which cancellous bone is replaced by proliferating abnormal fibrous-bone tissue, also known as osteofibrous dysplasia, which accounts for 2.5% of bone tumors and 7% of nonmalignant bone tumors. first reported by Wel in 1921, FD was formally proposed by Licht-entein and Jaffe in 1942 The name of the disease is still unknown. The cause of the disease is still unknown, but most scholars believe that it is caused by abnormal development of the primitive mesenchymal tissue and abnormal proliferation of fibrous tissue in the bone. The disease mostly occurs in adolescence, the onset is latent, the progress is slow, often until youth or middle age can be found, there is no significant difference between male and female onset, about 85% of the onset within 30 years of age, the malignant rate of 2%-3%, the whole body bones can occur, the femur, tibia, craniofacial bone more frequent.
I. Clinical classification.
According to the involvement of the site is generally divided into three types.
1, single bone type (MFD): a single bone offended, craniofacial bone and ribs more frequent.
2, multi-bone type (PFD): multiple bony offenders, with long bones, flat bones more frequent.
3, Ebright syndrome: manifested as a multi-bone FD, with skin pigmentation and endocrine hyperfunction.
Second, X-ray performance classification.
1, cystic expansion type: manifested as multiple cystic bone destruction in the bone marrow cavity, bone cortical expansion and thinning, incomplete bone crests are seen inside, in the shape of tongue or plum petals
2, hairy glass type: manifested as increased density of the bone marrow cavity, hairy glass-like changes, some narrowing of the marrow cavity, and some disappearance of the marrow cavity.
3.Loofah-like type: The bone stem is swollen and thickened, the bone cortex is thinner, and the bone trabeculae are thick and distorted, distributed along the longitudinal axis of the bone, like a loofah, and clearly demarcated from normal bone.
4, worm-like type: manifested as speckled osteolytic destruction, with clear and sharp edges.
5, sclerotic type: manifested as swollen osteophyte sclerosis, irregular narrowing of the marrow cavity, and increased density.
Third, the etiology of the discussion.
1, local trauma theory: FD is one of the fibrous lesion diseases of intraosseous origin, and has a close intrinsic connection with a variety of other named fibrous origin diseases. Reviewing the literature, it is agreed that FD is an abnormal fibrous developmental disease within the bone, which is essentially a structural malformation of the bone, and its etiology is related to local trauma to the skeleton, mostly due to impaired bone formation during the repair response after bone injury.
2, embryonic developmental abnormalities theory: FD is an embryonic primitive mesenchymal developmental abnormality. The disease often starts in early childhood, but often to children or adolescents with symptoms, the pathology develops slowly, and has a tendency to heal spontaneously or quiescence in adulthood. The most basic pathological change is that the lesion area consists mainly of differentially differentiated fibrous and osseous tissues. The ratio of the two varies in different cases or different sites.
3. Gene mutation theory: The current findings support that mutations in the activated Gsα gene and the resulting altered activity of effectors such as cAMP have a decisive role in FD. Recent studies have first confirmed the presence of activating mutations in the activating G protein a subunit (Gsα) gene in patients with MAS; this was later confirmed in patients with MFD and PFD. It was also confirmed that G proteins consist of a.b.r subunits, which play an important role in cellular transmembrane signaling. α subunit is its active subunit, contains GTP and GDP binding sites and has GDPase activity. G proteins are classified into activating and inhibiting types. Mutations in the activating Gsα gene can cause a variety of diseases, such as inhibitory mutations in the activating Gsα gene that decrease its activity to activate adenylate cyclase, which can cause Albright osteodystrophy, and activating mutations in the activating Gsα gene that increase its activating activity and cause FD and MAS. it was found that the mutations in the gene that cause FD are somatic mutations, and activating Gsα The mutation of the activating Gsα gene is not present in all cells, but even in typical lesioned tissues there is a mosaic of mutant and normal cells, and this coexistence of mutant and normal cells is necessary to produce FD lesions, as confirmed by Bianco et al. and Goisis et al. in their in vitro model of FD lesions. The activating Gsα mutation occurs at the embryonic stage, but the time of its occurrence and the size and location of the cell mass at the time of mutation determine the extent and severity of the FD lesion.
IV. Diagnosis and differential diagnosis.
The time between onset and consultation of abnormal bone fiber proliferation often varies from six months to 30 years, mostly 1-10 years. The main symptoms are painless localized slowly proliferating masses of bone, facial deformity, asymmetry, and local pain after long bone activity. The CT features are: varying thickness of bone cortex around the lesion, swelling osteolytic changes in the bone marrow cavity of the lesion, clear boundaries around the lesion, no periosteal reaction, and dense sclerosis at the edge; ECT shows abnormal metabolic activity at the lesion.
1. Single lesion in single bone: it should be differentiated from isolated bone cyst, angiomatous bone cyst, giant cell tumor of bone, fibrosarcoma of bone, osteogenic tumor, etc. Local puncture cytology examination is very important. If yellowish liquid is extracted during puncture, the first consideration is isolated bone cyst; if it is bloody, then angiomatous bone cyst is more likely; when the bone shell around the cystic lesion is thick, the tissue can be drilled with a Kirschner needle and then punctured with an epidural puncture needle (or biopsy puncture needle), and if the tumor tissue is rubbery, grayish, hard and tough connective tissue, and there is a gravelly feeling when dissected, the preliminary diagnosis is FD. Its pathological features are The normal bone tissue and bone marrow are replaced by a large amount of proliferating fibrous tissue, and there are poorly structured bone trabeculae within the fibrous tissue, and the fibrous tissue can be directly transformed into bone.
2, single bone multifocal: single bone multifocal type can sometimes be combined with other lesions, such as long bone enamel cell tumor, hyperparathyroidism causing fibrocystic osteitis, etc.. In this regard, several parts of the puncture biopsy should be done.
3, multi-bone multi-focal: there are more clinical signs and symptoms, x-ray performance of multiple bone multi-focal.
4, Ebright’s syndrome: for multiple bones and multiple lesions, accompanied by skin pigmentation and endocrine hyperfunction. The skin pigmentation spots are usually distributed on the side with bone lesions, and are coffee pigmentation spots with irregular edges; endocrine hyperfunction can be manifested as precocious puberty, hyperthyroidism, Cushing’s syndrome, prolactinoma, excessive secretion of growth hormone, increased cortisol, anti-vitamin D hypophosphatemia, and enlarged parathyroid glands. Precocious puberty is the most common. The disease is sporadic, and the incidence is twice as high in females as in males.
V. Treatment.
In the past, it was thought that the disease was an abnormal developmental disease of the fibers in the bone, or called intraosseous fibrous dysplasia in children, which could heal spontaneously or be quiescent in adulthood, and it was emphasized that the younger the patient was, the higher the recurrence rate after surgery, so surgery was mostly advocated in adulthood. However, in recent years, early and complete surgery is mostly advocated for symptomatic active lesions, and it is not advisable to wait and observe, even in children and adolescents. According to Gross et al, this disease is prone to malignant transformation after radiotherapy, and the rate of malignant transformation of normal bone and other benign bone tumors is increased by nearly 400 times by radiotherapy, so radiotherapy is contraindicated for this disease. Early and complete surgical resection is the most effective treatment for this disease, and surgery should be performed to restore the function of the affected organs.
Surgical methods:
1, weight-bearing bone can be considered for local scraping and bone grafting: surgery to remove the focal bone as much as possible after taking the autologous iliac bone implant. If the FD lesion is large or multiple lesions, simply taking the iliac bone is not enough, it is advisable to take the autologous rib bone implant. Recurrence is closely related to the incompleteness of the surgery, and multiple recurrences are one of the causes of multiple bone spread and malignant transformation. The surgery requires that the bone window should not be too small, and the lesion should be scraped out as much as possible under direct vision, and then the residual cavity should be treated with chemical cautery such as carbolic acid or 50% zinc chloride to inactivate the lesion cells that may remain, and then the bone should be implanted to facilitate healing.
2, non-weight-bearing bone can be considered for excisional bone grafting: the author observed no recurrence and good results. The periosteum should be kept intact during the operation to facilitate postoperative bone regeneration.
3, craniofacial bone can be considered for local excision plastic surgery: surgery should take into account the facial deformity and dysfunction, neurovascular compression, etc. The scope and depth of excision should refer to the healthy side and preoperative CT three-dimensional imaging, surgery to plastic, restore the function of the affected organs as the principle. If there is more bleeding on the bone trauma during surgery, monopolar electrocoagulation and bone wax can be used to stop the bleeding, and local pressure dressing should be applied after surgery. For cranial cap bone, it has been reported that a large range of complete resection of the lesion is used, and the resected bone flap is repaired and shaped into a porous shape, which is inactivated by boiling and then replanted in situ to play a scaffolding and protective role to prevent postoperative recurrence.
In conclusion, osteochondrodysplasia is a benign bone disease of unclear etiology, and its etiology still needs further study.