What is Pathologic Fractures?

Pathologic fractures, or breaks in bones caused by disease, are becoming more common and worrisome in the field of bone cancer. This increase is mainly due to better diagnosis and treatment of cancers that have spread to other parts of the body, resulting in patients living longer. Identifying the disease that caused the fracture is crucial for effective treatment and must be done before any surgical intervention. These fractures take place in areas of the bone weakened by harmful growths, benign growths, the spread of cancer, or metabolic disorders. The common thread among these is that they change the bone’s structure and strength, making it more likely to fracture.

What Causes Pathologic Fractures?

Most fractures caused by cancer (or ‘neoplastic pathologic fractures’) are due to metastatic disease, which means cancer that has spread from its original site to the bones. This is far more common than fractures caused by primary bone cancers, especially in patients over the age of 40. In fact, the likelihood of a fracture occurring in bone affected by metastatic disease is 500 times higher than it being due to a primary bone cancer like sarcoma.

The cancers that most often spread to the bones are lung, breast, thyroid, kidney, and prostate cancer. The most common places in the skeletal system that these cancers reach are the spine, upper leg bone (the femur), and pelvic bone.

While primary bone sarcomas are far less common, ignoring the possibility that a fracture could be the first sign of such a cancer could lead to serious consequences, including the loss of life or a limb.

Risk Factors and Frequency for Pathologic Fractures

Every year in the United States, about 1.7 million people get diagnosed with cancer. About 5% of these individuals will experience severe bone disease due to cancer spreading – this is called Metastatic disease. It’s worth mentioning that the cost of treating these patients is nearly 13 billion dollars annually.

Approximately 8% of these individuals will suffer from a disease-induced fracture in a bone, based on a study covering 1,800 patients with cancer that has spread to the bone.
On a less common scale, conditions known as primary soft tissue and bone sarcomas affect 13,000 and 3,600 people in the U.S. respectively each year.

Signs and Symptoms of Pathologic Fractures

Pathologic fractures are broken bones that happen because of a disease, and they often have specific warning signs. Sometimes, people feel discomfort before the fracture occurs, while in some cases, there are no symptoms until the bone breaks. Patients might or might not experience ‘B’ symptoms, which include unintentional weight loss and fevers. People may also have symptoms related to the specific type of cancer that caused the fracture. For example, kidney cancer could cause abnormalities in urine, and lung cancer might lead to shortness of breath or coughing. Moreover, patients could show signs of a condition known as hypercalcemia of malignancy, which comes from having too much calcium in the blood due to cancer. This can cause various symptoms ranging from slight confusion and problems in the stomach and intestines, to heart rhythm problems and kidney failure.

When someone visits a doctor for a physical exam, the doctor should focus on checking the affected limb or the spine if needed. It’s particularly important for the doctor to examine the nerves and blood vessels, even though problems in these areas are rare in pathologic fractures of the limbs.

Testing for Pathologic Fractures

If a fracture is found to originate from an unknown cause, a thorough examination is needed to figure out the cause and progression of the disease. This might involve examinations of your body and a wide range of lab tests.

Such lab tests could include a complete blood count, a comprehensive metabolic panel (with special inspection of your serum calcium and alkaline phosphatase levels), prothrombin time and INR tests, another test to measure blood clotting, as well as an erythrocyte sedimentation rate test, urinalysis, and tests for proteins in the urine and blood. Disease-specific markers, like prostate-specific antigen (PSA) and carcinoembryonic antigen (CEA), might also be evaluated. The results of these tests could indicate cancer and provide clues to its origin. For instance, a urinalysis could give some hints about the primary ailment. If blood is found in the urine, kidney or urinary tract cancer may be the cause. If a specific type of protein is found, the diagnosis could be multiple myeloma. Women who could be pregnant should also take a pregnancy test before imaging.

In terms of radiology, analysis of fractures begins with two directional X-ray examinations of both the fracture site and the entire affected bone. X-rays can provide a lot of information about a pathologic lesion. Certain features that could suggest a pathologic lesion include a lesion that’s bigger than 5 cm, a break in the bone’s outer layer, a reactive bone, and a fracture associated with a disease. X-ray examination of the chest and other imaging techniques like CT scans of the chest, abdomen and pelvis could give more details for staging purposes. Whole-body bone scans are particularly useful for detecting bone-forming activity. If the lab tests confirm a diagnosis of multiple myeloma, a skeletal survey could replace a bone scan, which may not identify the extent of bone breakdown in other sites.

In addition to these tests, if there’s a concern about primary bone sarcoma or if surgery is likely, more detailed imaging of the limb might be necessary to evaluate the extent of bone destruction and to better understand the 3-dimensional anatomy of the lesions, particularly in areas with complex anatomy such as the pelvis. MRI of the limb might be needed to evaluate the degree of soft-tissue involvement as well as vascular involvement. Consider mammography for certain patients when breast cancer can’t be ruled out. Positron emission tomography is becoming more popular for its high sensitivity for identifying infection and cancerous tumours. It has a lower accuracy on its own, but that improves when combined with CT scans.

After all these tests, depending on the results, a biopsy may be performed. A biopsy is an examination of tissue removed from the living body to discover the presence, cause, or extent of a disease. There are six accepted reasons for doing a staging evaluation before a biopsy:

The tumor might be a primary bone sarcoma and doing a staging evaluation will ensure the biopsy isn’t poorly placed.
An additional site of disease spread that’s easier to access or has fewer complications than the site of the pathologic fracture might be located.
Pre-surgical blockage of blood supply might be needed to control bleeding during surgery.
Unnecessary biopsies might be avoided entirely if the diagnosis can be made by lab analysis alone, like with multiple myeloma.
Historically, examining tissue only identifies the source in a very small number of cases.

There are three types of biopsy: fine-needle aspiration, core-needle biopsy, and open biopsy. All three have their pros and cons. Open biopsies can further be classified as either incisional or excisional. There are well-documented principles to adhere to when performing a biopsy, these include making the biopsy through a single capsule via a longitudinal incision without damaging vascular structures, in line with the planned surgical incision while maintaining control of bleeding throughout. Any deviation from these guidelines will lead to unnecessary spread of the tumor in the surgical field.

Treatment Options for Pathologic Fractures

There are set methods for dealing with both impending and actual fractures that are caused by diseases such as cancer. These methods generally involve surgery and are accompanied by chemotherapy or radiation therapy.

Impending fractures are areas within the bone that are considerably weakened due to a disease-related lesion. These areas can fracture or break more easily, sometimes just from normal weight-bearing activities. In some cases, these impending fractures may require preventative surgery to stop an actual fracture from happening. This could involve some kind of internal fixation, which strengthens the weak bone and helps to avoid any future breakages.

There are two recognized systems for classifying impending fractures. The first is called Harrington criteria, which was first identified in 1980. This system uses factors such as the size and level of pain of the lesion in the bone to decide whether preventive internal fixation is needed. But this system doesn’t apply to all areas of the bone, and it doesn’t take into account the details of the disease causing the issue.

The second system, known as Mirel classification, was identified in 1989 and is used to determine the need for preventative fixation. Recently, there has been an interest in new scoring systems that use CT scans to determine the rigidity of the bone and predict impending fractures. An example of this is the CT-based structural rigidity analysis (CTRA).

The benefits of surgically addressing an impending fracture include pain relief and a decrease in the associated health issues that might otherwise come with an actual pathologic fracture. This approach also makes surgical management easier.

A pathologic, or disease-related, fracture is typically the result of certain diseases such as benign lesions, various types of cancer, or metabolic bone abnormalities. The treatment for these fractures depends on the underlying cause of the fracture and the expected life expectancy of the individual.

The rate of fracture healing, the prognosis of the disease, and the activity level of the individual are all important when deciding the best course of treatment. It’s key to recognize that the underlying disease can negatively affect the body’s ability to heal a fracture. This is why a proper diagnosis of the primary disease is crucial to planning the best treatment. For instance, a fracture healed in a patient with kidney cancer requires different treatment than one in a lung cancer patient.

For kidney cancer, removing cancerous tissue as thoroughly as possible generally improves survival time. According to research, the rates of survival at 6 months for prostate, breast, kidney, and lung cancers are 98%, 89%, 51%, and 50% respectively.

Let’s not forget that the individual’s activity level is also a factor. A bed-bound or wheelchair-bound patient will likely have different surgery than a patient who is still walking or weight-bearing on the affected limb.

Recently, advances in technology, especially in artificial intelligence and machine learning, have proven useful in predicting patient survival. For instance, PATHFx 3.0 is an externally validated tool that can estimate a patient’s chances of surviving certain durations after treatment for painful skeletal metastases.

Stress fractures: This happens when the bone weakens or splits due to repeated small injuries or overuse.
Paget’s disease: This is a condition where your body’s normal process of bone recycling doesn’t work properly, leading to spots of weaker, brittle bone mixed with spots of abnormally formed bone.
Avascular necrosis: This is when blood supply to a certain part of the bone gets cut off, causing the bone tissue in that area to die.
Benign fracture: This is a break or crack in your bone but doesn’t involve any cancer.
Infection: This condition happens when harmful bacteria or other small organisms enter your bone and multiply, leading to damage to the bone.

Surgical Treatment of Pathologic Fractures

Deciding to operate on a fracture caused by a disease depends on many factors, but the main one is that the patient’s overall health and the disease itself are well-understood. The surgical procedure is a lot like other internal fixation, in which broken bones are rejoined using devices like metal plates, screws, or pins. However, when treating disease-related fractures, there are some additional guidelines:

Use devices that share the load with the bone rather than bearing all the weight
Choose devices that are durable to last through the disease’s progression
Ensure immediate stability so that the patient can bear weight right away
The size of the device should be long enough to extend across the damaged area by two diameters of the bone
If needed, use bone cement to improve bonding

In terms of the material used for the surgical device, the choice depends on the specific situation. Usually, benign fractures (breaks in healthy bones) are treated with titanium, which is compatible with MRI scans and therefore reduces interference with future imaging. Stainless steel is used for pathological fractures (fractures caused by disease) since it’s stronger than titanium, but it may cause issues with future imaging. Scientists also have been increasingly interested in carbon fiber implants due to their strength, flexibility, and compatibility with MRI scanners.

If it’s necessary to replace a person’s hip joint with an artificial one, there’s a big debate over using bone cement versus press-fit implants. Bone cement provides immediate stability, but can have drawbacks such as lung complications, allergic reactions, and increased surgical time. A study found that both methods have similar results in terms of complications, mortality, blood loss, and function, so it’s mostly up to the doctor to decide.

A procedure called embolization can be used to control bleeding in highly vascular tumors. It involves blocking the blood flow to the tumor, and may be used for cancers that are notorious for major blood loss during surgery – kidney and thyroid cancers, for example. Embolization has been shown to reduce surgical time, blood loss, and the need for blood transfusions.

Primary sarcomas are aggressive tumors that require thorough removal to cure, while fractures due to metastatic disease are treated as part of palliative care. It’s critical to correctly diagnose the type of tumor before surgery to avoid spreading it during the operation.

Treatment options differ based on the location of the tumor. For example, fractures in the upper extremity (arm, forearm, and hand) are less problematic because they are not weight-bearing and under less stress. On the other hand, fractures in the lower extremity (leg and foot) are more concerning as they are essential for weight-bearing. The pelvis, for instance, needs aggressive treatment if the fracture is in a weight-bearing area. Smaller fractures could be managed with radiation therapy or radiofrequency ablation, a procedure that uses heat to kill cancer cells.

The spine is a common site for bone metastasis. Deciding on surgical intervention depends on the patient’s pain, stability, and any neurological deficits. This decision must weigh the relief of symptoms against the risks and recovery of surgery.

What to expect with Pathologic Fractures

The survival chances of those suffering from bone disease caused by other cancers will depend largely on the type of cancer that caused it. For example, the 6-month survival rates for common cancers that spread to the bones are: lung cancer 50%, kidney cancer 51%, breast cancer 89%, and prostate cancer 98%.

The 5-year survival rates for localized soft tissue cancers are quite different at 83%, compared to 16% when the disease is spread throughout the body. The five-year survival rate for cancer located in the bone itself is 68%.

There’s a varying rate at which bone fractures, caused by the disease, occur. This depends on the initial cause of the cancer and the overall health of the patient. When these fractures occur in patients with bone cancer, there used to be a belief that they pointed to a worse outcome due to concerns that the broken bone could spread the cancer. However, this has been proven untrue.

Possible Complications When Diagnosed with Pathologic Fractures

Pathologic fractures and their surgical treatment can lead to a wide variety of complications. A main concern after surgery is that the fracture may not heal well or the condition may progress, leading to failure of the surgical repair or reconstruction. Infections related to the surgical hardware can also occur which might require long-term antibiotics or even removal of the hardware. Further complications such as muscle weakening or blood clots can also occur due to reduced mobility during the recovery period. There are also complications specific to the use of endoprostheses (a type of surgical implant) which include:

Type 1: Failure of the soft tissue surrounding the implant.
Type 2: The implant becoming loose without an infection (aseptic loosening).
Type 3: Breakage or other structural failure of the implant.
Type 4: Infection around the implant (periprosthetic infection).
Type 5: Progression of the tumor (if the fracture is due to cancer).

If bone cement is used during the procedure, some patients may experience allergic reactions or lung problems. A phenomenon known as Bone cement implantation syndrome (BCIS) can cause low oxygen levels and low blood pressure shortly after cement is applied within the bone. This syndrome is common in cancer patients undergoing a specific hip surgery and can be life-threatening if not carefully managed.

Recovery from Pathologic Fractures

The primary aim of surgery for fractures caused by disease is to help patients move and function normally as soon as possible. Following this type of surgery, it is ideal for patients to start physical therapy right away. This targeted therapy enables them to start bearing weight whenever they can. Patients who have had surgery on their legs should be given anticoagulation therapy after surgery to prevent blood clots. This may also be considered for patients who have had arm surgery because the presence of a disease can increase the risk of developing blood clots.

For long-term treatment, medicines called bisphosphonates or denosumab should be thought about seriously. These medicines can significantly lower the chance of bone-related events, such as radiation or surgery to the bone, fractures caused by disease, spinal cord compression, or high calcium levels due to the presence of a tumor. Previous studies have shown that people with disease spread to their bones could experience these events whether they show symptoms or not. Without bisphosphonates, there is a high chance of these events occurring.

A review of past medical data has shown that bone-related complications were found in more than half of the patients with breast cancer that had spread to other parts of the body. This rate is similar in patients with the spread of prostate, lung, and myeloma cancers. Another study showed that such complications occur every 3-6 months on an average in patients with spread diseases. The use of bisphosphonates has significantly lowered these complications and increased the time between each event. One study noted a drop in these complications by 31%, 36%, and 41% respectively in patients with lung, prostate and kidney cancer. However, the benefits of using bisphosphonates should be considered against its potential risks, which could include low calcium levels, damage to the jaw bone, and unusual fractures.

Preventing Pathologic Fractures

In the process of determining the level of cancer, it’s crucial to check if the cancer has spread to the bones. This is a part of the standard procedures when examining a cancer patient. It’s also highly important to inform patients about the signs of cancer spread to bones. Early treatment can prevent the bones from breaking due to cancer, which makes the recovery process after surgery easier compared to treating a patient who has experienced a bone break due to cancer.