What is Osteofibrous Dysplasia?
Osteofibrous dysplasia (OFD) is a harmless condition impacting bone development, most commonly found in the middle of the front part of the tibia (shinbone) in children. It was first recognized in 1921 by Frangenheim, and it’s also known as congenital fibrous dysplasia or ossifying fibroma of the long bones.
The term “osteofibrous dysplasia of the tibia and fibula” was introduced by Camanacci and Laus, referring to how the disease resembles fibrous dysplasia (a bone disorder where normal bone is replaced with fibrous bone tissue) and appears in the tibia. However, the condition can also occur in other bones, such as the fibula (calf bone), radius (forearm bone on the thumb side), and ulna (forearm bone on the pinky side). It’s important to differentiate OFD from adamantinoma, which is a harmful tumor known for distinctive patterns and groups of epithelial cells (cells that cover the body surface) surrounded by a type of cell called a spindle cell.
OFD is categorized into three types: monostotic (affects only one bone), polyostotic (affects multiple bones), and McCune Albright syndrome (causes abnormal bone development and other health issues). Most individuals with monostotic OFD do not have notable symptoms and the condition is often discovered incidentally during an X-ray evaluation. OFD is most commonly seen in people in their thirties.
What Causes Osteofibrous Dysplasia?
Osteofibrous dysplasia is a rare type of bone disorder that usually affects the tibia, which is the larger bone in your lower leg. This disorder is very rare, making up only 0.2% of all primary bone tumors. It’s most commonly found in infants and children, particularly in the part of the tibia that is located in the middle front part of the bone.
In terms of genetics, studies show that it might happen in connection with an extra copy (or “trisomy”) of chromosome 7, 8, 12, or 22. In simple terms, this means that there is an extra copy of one of these chromosomes in the cells, which could contribute to the development of the disorder.
Risk Factors and Frequency for Osteofibrous Dysplasia
Osteofibrous dysplasia is a rare condition that is often seen in children under the age of 10. It affects boys more than girls and is typically found in the first 20 years of a person’s life. This condition usually targets the tibia, a bone in the lower leg, but it can also occasionally involve the fibula, another bone in the same area. The middle part of the tibia is most frequently affected.
This condition doesn’t just limit itself to the lower leg; occurrences in the radius and ulna (the two bones of the forearm) have also been noted. Interestingly, the progression of the condition seems to stop once a person reaches full skeletal growth, which is a pivotal part of growing up.
Signs and Symptoms of Osteofibrous Dysplasia
Osteofibrous dysplasia is a condition that usually doesn’t cause any symptoms. Sometimes, it can lead to a painless swelling on the front or front-side of the tibia, which is the larger bone in your lower leg. If you go to the doctor, they might notice some tenderness when they touch this part of your leg. Some people with osteofibrous dysplasia first realize there’s a problem when they notice their lower leg is swelling or has an abnormal forward curve. In rare cases, the condition could cause the bone to break more easily. Sometimes, doctors discover osteofibrous dysplasia by accident when looking at X-ray images taken for different reasons, like after an injury.
This condition, along with a similar one called adamantinoma, often shows up as pain, swelling, and a forward curve in the tibia. They both usually involve the tibia’s middle part, known as the diaphysis, and osteofibrous dysplasia sticks to an area called the cortex. Osteofibrous dysplasia has also been found in the fibula, ulna, and radius bones apart from the tibia. Adamantinoma is also known to occur in the fibula and a handful of other bones including the calcaneum, femur, ulna, radius, humerus, olecranon, ischium, rib, spine, metatarsals, and capitate. If you have osteofibrous dysplasia, you may more likely suffer from a pathological fracture – a break caused by a disease weakening the bone – than have swelling or a deformity.
Testing for Osteofibrous Dysplasia
If it’s thought that a person, specifically a child younger than 20 years old, may have a condition called osteofibrous dysplasia (OFD), certain x-ray views of the tibia (shin bone) are recommended. These x-rays will look from the front and side at the part of the body where the symptoms are felt. These x-rays can often show particular features, like unusual “holes” in the tibia. A common sign of OFD is if the tibia near the knee has bent forward due to these unusual holes. The main goal of these x-rays is to tell the difference between OFD and a different rare bone illness called adamantinoma.
OFD can cause a thinning (lytic lesion) in the main body (diaphysis) of the tibia bone that has clear edges and maybe surrounded by a hardened (sclerotic) zone. Sometimes several of these lytic lesions may be seen with hardened areas around them. These changes might make the affected part of the tibia look wider. It’s very rare to see the body’s natural response to injury (periosteal reaction) with OFD. The symptoms of OFD usually stop getting worse once the person has finished growing.
The x-rays of OFD often show clear lytic lesions with hardened edges on the front side of the tibia bone. As the disease gets worse, it can spread along the bone, sometimes even making the bone swell and get into the center of the bone (intramedullary). These changes can lead to bending forward of the tibia. OFD symptoms seen on x-rays are well known, but the changes seen on magnetic resonance imaging (MRI) are not fully described in medical research.
On MRI, a different type of imaging test, OFD typically appears as an area of lytic lesions that look like bubbles with clear, hardened edges. It usually affects the main body of the tibia or fibula bones, particularly the front part, and can lead to the nearby bone being swollen. As the disease progresses, it can spread into the center of the bone and cause bending of the tibia.
On MRI, OFD shows a medium signal on images using a technology called T1 and a medium to high signal on T2-weighted images. These effects are caused by changes in the makeup of the cells and tissue and the minerals found in the bone. Changes in the amount of bleeding, the makeup of the tissue, and even the difference in types of tissue can modify the signal on T2-weighted images. However, OFD doesn’t always show these different signals and can look the same as other tumors with fibroblastic stroma, a specific type of tissue. These distinctive patterns can be seen on a type of MRI image that helps us see the blood flow and small parts of tissues and is similar to patterns seen in other fibrous tumors.
MRI can also help in distinguishing OFD from other problems that look the same on x-rays. These can include osteoid osteoma, a kind of bone tumor, abscesses in the bone, and blood vessel tumors, to name a few. Other possible diseases that might look like OFD include adamantinoma, aneurysmal bone cyst, fibrous dysplasia within the bone, and osteoblastoma.
It could be difficult to tell these conditions apart because they may show similar symptoms. For example, both OFD and adamantinoma show nearly identical signs on x-rays. However, MRI might provide additional information to help doctors tell these conditions apart.
OFD can show a variety of signs that range from those limited to the immediate area of the bone to more aggressive signs with full involvement of the bone marrow or surrounding bone. The varied MRI findings of OFD may help diagnose OFD and distinguish it from adamantinoma and other problems that may look like OFD.
Treatment Options for Osteofibrous Dysplasia
Ossifying fibrous defect (OFD) is a rare condition, and the best way to treat it is still up for debate. The problem is OFD is typically a harmless disorder that does not get worse after someone’s growth period, which usually ends during their teenage years. Some doctors recommend simply watching it over time without performing any operations, except maybe taking a sample tissue for further examination. Wearing a brace could also help to keep the defect from getting worse and prevent bone fractures.
Surgery seems to have a high chance of the disorder reappearing if it’s done before puberty for OFD cases. It is generally recommended only for extreme cases where the OFD is too large, is causing a change in the normal shape of a part of the body, or has led to a bone fracture.
However, many OFD cases are benign, meaning they don’t lead to symptoms or problems. However, in some cases, the defect can become large enough to interfere with walking or cause pathological fractures, which are breaks in bones that have been weakened by disease. In such cases, an operation may be required. There are a few surgical methods to treat OFD, including curettage (the process of cleaning out a bone defect) and localized subperiosteal excision (removing the affected part of the bone), but these carry the risk of the OFD coming back. Radical excision, which is complete removal of the affected bone part and reconstruction, carries its own risks, such as pseudarthrosis, which is the failure of a broken bone to heal properly.
If the OFD has caused a deformity, surgery is necessary, but usually only after the patient is fully grown. The usual methods include curettage and bone grafting, which is when the surgeon takes a piece of bone from another part of the body to replace the bone that was taken out. After curettage, the cavity often needs to be filled with something like acrylic cement or a bone graft to keep it stable. However, keep in mind that OFD can become more active after an operation, and there is a significant chance of it coming back. Therefore, many doctors agree that surgery should be put off until absolutely necessary and should be limited to extensive cases.
One more aggressive surgical method for OFD is extraperiosteal resection, which removes the outer surface of the bone that has the defect. Based on findings from a small number of patients, a group of researchers suggested that all OFD should be aggressively treated since there’s a chance the OFD could mutate into adamantinoma, which is a rare bone cancer. But because of the lack of larger studies, that idea is not universally agreed upon. Most believe that OFD is benign and as long as the diagnosis is correct, just keeping an eye on it and treating symptoms is enough.
The way to treat adamantinoma that arises from OFD is not well known due to the rarity of cases. Current recommendations include careful observation and symptom treatment. The difference between OFD and adamantinoma that arises from OFD is not only noticed in their appearances under the microscope and on X-ray but also in clinical symptoms- especially the degree of pain. Performing surgery does not increase the risk of it coming back or spreading to other parts of the body.
What else can Osteofibrous Dysplasia be?
When doctors are analyzing a cortical, lytic, and expansive lesion in the bone, they have to consider a variety of potential diagnoses. Here’s a list:
- Fibrous dysplasia
- Unicameral bone cyst
- Osteomyelitis (bone infection)
- Nonossifying fibroma (a benign bone tumor)
- Aneurysmal bone cyst (the existence of a cavity filled with blood in the bone)
- Chondromyxoid fibroma (another benign bone tumor)
- Langerhans cell histiocytosis
- Osteosarcoma (a type of bone cancer)
- Chondrosarcoma (a type of cancer that affects the cartilage)
- Hemangioendothelioma (a rare form of cancer that affects blood vessels)
- Angiosarcoma (another type of cancer that affects blood vessels)
- Metastatic carcinoma (cancer that has spread from another part of the body to the bone)
Knowing information like the patient’s age, medical history, or where the lesion is located on the bone can be very helpful in narrowing down these options.
What to expect with Osteofibrous Dysplasia
Lesions, which are areas of abnormal tissue, typically disappear by adulthood and don’t cause issues. The benign (non-cancerous) lesions, often called OFD, have a great outlook for recovery. However, some studies suggest a connection between OFD and AD, a type of cancer. But, in many large studies with good follow-ups, none of the OFD cases progressed to AD. There are a few reports where OFD has evolved to AD, but these instances might be due to an initial misdiagnosis or a sampling issue during a biopsy.
People who have survived this slowly progressing, low-grade tumor need to be under continued medical supervision for a long time. The tumor may reappear locally, typically between 5 -15 years after diagnosis, although it has been reported as late as 24 – 36 years later. The risk of spreading to other parts of the body remains even years after the successful removal of the tumor, including more than 10 years after the patient was declared disease-free. When this happens, it’s managed through surgery.
Since there isn’t strong evidence that OFD can progress to cancerous adamantinoma, conservative management strategies such as monitoring or scraping of the lesion are often successful for patients with OFD and those with OFD-like adamantinoma. Surgical removal with clear margins (removing all the visible tumor along with a layer of healthy tissue for safety) is necessary for patients with adamantinoma. Adamantinoma, however, often recurs much later, so long-term monitoring is suggested.
Possible Complications When Diagnosed with Osteofibrous Dysplasia
The main complication that can come from Osteofibrous Dysplasia (OFD) is a pathological fracture, which usually happens following a minor injury. Other potential problems include changes in the shape of the bone, the disease coming back, the disease turning into cancer, and severe pain.
Potential complications:
- Pathological fracture, typically after a slight injury
- Bone deformity or changes in shape
- Recurrence of the disease
- Disease turning into a malignant or cancerous state
- Severe, possibly persistent, pain
Preventing Osteofibrous Dysplasia
Osteofibrous dysplasia is a noncancerous bone tumor that usually appears in the tibia, one of the bones in the leg. This condition usually shows up as a painless swelling in the leg and is most commonly found in children. It’s often identified through an X-ray. It’s important for parents to know that this condition could cause a pathological fracture, which is a break in a bone weakened by some other health condition, or a bony deformity, an unusual bone shape. Parents should also understand the necessity of a large tissue sample or biopsy. This is done in order to tell the difference between osteofibrous dysplasia and another condition known as adamantinoma.
