What is Osteoporosis in Spinal Cord Injuries?
Osteoporosis is a condition that refers to weakened bones due to changes in their small-scale structure. It’s typically tied to a decrease in the bone’s mineral density (BMD), which is essentially a measure of how solid and strong the bone is. It’s important to note that spinal cord injuries (SCIs) can have diverse effects on a person’s health and their ability to function day to day. Such injuries can seriously hamper their quality of life.
Notably, SCIs have been identified as a major factor leading to osteoporosis. Doctors are urged to identify and understand the similar yet subtly different aspects of osteoporosis caused by SCIs. This type of osteoporosis is considered a unique subset of the more generalized osteoporosis diagnosis.
What Causes Osteoporosis in Spinal Cord Injuries?
Spinal cord injuries (SCIs) usually follow a certain pattern, typically seen in two different age groups.
Younger individuals often get these injuries from high-energy incidents such as motor vehicle accidents, falls, gunshot wounds, sports injuries, and medical procedures. Here’s a rough estimate of how often these incidents cause SCIs:
* Motor Vehicle Accidents – 50% to 75%
* Falls – 10% to 15%
* Gunshot wounds – 10% to 15%
* Sports – 10% to 15%
* Injuries during medical procedures – 3% to 25%, often because the spine wasn’t properly stabilized or the patient wasn’t moved carefully.
On the other hand, older people usually get SCIs from minor accidents or falls. This is largely because as we age, our spine naturally wears down and becomes narrower, a condition known as spinal stenosis. This makes the spine more vulnerable to injury.
Risk Factors and Frequency for Osteoporosis in Spinal Cord Injuries
The number of Spinal Cord Injuries (SCIs) in the United States has gone up by 30% from 1994 to 2012. In 2016, it was estimated that around 17,000 new cases of SCI occurred, which is about 54 cases per million people. There is also a high occurrence of osteoporosis in the country, affecting around 10 million people. Additionally, about 34 million people are potentially at risk of developing osteoporosis and have been diagnosed with osteopenia. Osteopenia is a condition where bone density is lower than normal but not low enough to be classified as osteoporosis.
These trends show that over 50% of patients with a complete SCI will develop osteoporosis within a year after the injury. If observed in the long term, this number increases to more than 80%. The biggest concern for these patients is the risk of fragility fracture due to osteoporosis. In the long run, over half of these patients will end up with at least one low-impact fracture after the SCI.
Signs and Symptoms of Osteoporosis in Spinal Cord Injuries
When a person with a history of Spinal Cord Injury (SCI) visits a healthcare provider, the time passed since the original injury is significant, especially the first two weeks, as it’s a critical period for bone mineral density (BMD) loss.
General health history should include any conditions that may already jeopardize their BMD levels. For instance, older SCI patients may have been diagnosed with osteoporosis or osteopenia before the injury, which puts them at a higher risk of spontaneous fractures.
A thorough history should consider the following points:
- Previous fragile bone breaks like hip or spine fractures
- Existing chronic illnesses such as eating disorders, lung disease, cancer, inflammatory diseases and hormonal irregularities
- Medication uses like anti-seizure drugs, prolonged use of steroids, certain acid reducers (proton-pump inhibitors), and chemotherapy (methotrexate)
- For women, early menopause or being post-menopausal
- Prior treatments for osteoporosis
The lifestyle factors that could accelerate bone loss are also essential to assess. The doctor will note whether the person smokes or drinks alcohol heavily, their nutritional status and any calcium and vitamin D supplements they take. A family history of osteoporosis and past fractures, especially after reaching 40 years and those caused by minor falls are important indicators as well.
During the physical exam, the healthcare provider will carefully analyze the patient’s condition based on the SCI level and category. These categories include Paraplegia, Tetraplegia, Complete SCI, and Incomplete SCI.
- Paraplegia: SCI that causes issues from the trunk or pelvic area to the lower limbs but leaves the upper limbs functional.
- Tetraplegia: Cervical spine SCI causing dysfunction in the upper body, trunk, and lower body. These patients are at high risk of continuous BMD loss and spontaneous spine fractures.
- Complete SCI: This diagnosis is made after the spinal shock has passed. These patients have no motor or sensory function below the injury level.
- Incomplete SCI: These are categorized into syndromes according to the damaged part of the spinal cord. Each syndrome retains some motor or sensory functionality below the injury level. Such syndromes include anterior cord, posterior cord, central cord, cauda equina, conus medullaris and Brown-Sequard.
Along with a thorough motor and sensory exam, it is crucial to check for any invisible or unexpected fractures. Spontaneous fractures occur typically in the sublesion regions, especially the long bones of the lower limbs.
Early follow-up is advisable for a patient who experienced a fragility fracture, as appropriate treatment needs to start soon. However, it is common for follow-up rates to be very low, even after such fractures. Automated follow-up systems and fracture liaison services can be effective strategies to improve this situation.
Testing for Osteoporosis in Spinal Cord Injuries
Over the last 5 to 10 years, management of osteoporosis (a condition where bones become weak and brittle) has seen many developments. However, the follow-up pattern and treatment recommendations for osteoporosis caused by a spinal cord injury (SCI) is not as advanced. This is made more challenging due to the complexity of SCI and the generally low rate at which people keep up with their osteoporosis treatment.
To evaluate osteoporosis, a special type of x-ray called a dual-energy x-ray absorptiometry (DXA) scan is usually done. This scan is considered the best tool for checking bone mineral density (BMD – a measure of how strong and dense your bones are). The DXA scan uses an x-ray beam to measure the amount of bone in certain areas of your body. These usually include the lumbar spine (lower back), hip, and wrist.
The result of the DXA scan provides two scores: a T-score and a Z-score. The T-score shows how your BMD compares to the average BMD for healthy young adults like yourself. According to the World Health Organization (WHO), if your T-score is between -1 and -2.5, you have low bone density or osteopenia. A score below -2.5 means you have osteoporosis. The Z-score, on the other hand, compares your BMD to what’s expected for someone your age. A Z-score less than -1.5 suggests that you may have secondary osteoporosis, a type of osteoporosis caused by certain medical conditions or treatments, and further tests will be needed.
Next, regular blood tests are used to check levels of various substances like calcium, phosphorus, albumin, and others which give the doctor a better idea about your bone health. Males should also check their free testosterone level to rule out hypogonadism (low testosterone levels).
In some cases, particularly when secondary osteoporosis is suspected, doctors may test bone turnover markers (substances in the blood or urine that reflect the rate at which bone is being broken down).
The WHO designed a tool called the FRAX score which predicts your risk of having a bone fracture within the next 10 years. This tool asks 12 questions on various factors that could affect your bone health, like your age, history of fracture, body mass index, and lifestyle habits like smoking or alcohol consumption. Your DXA scan results can also be included to provide a more comprehensive risk assessment. This FRAX score is particularly useful in helping doctors decide on more aggressive treatments for patients with osteopenia, who although having lesser bone density decrease than those with osteoporosis, make up the majority of fragility fracture cases.
Treatment Options for Osteoporosis in Spinal Cord Injuries
Doctors are encouraged to understand the similarities and differences when treating general osteoporosis patients and those with osteoporosis as a result of a spinal cord injury (SCI). Although some general treatment principles apply to both groups, the treatment approach for SCI-induced osteoporosis is somewhat different and still evolving.
Encouraging weight-bearing activity can help promote healthy bone turnover. This activity can even help reverse the bone weakening process in those with SCI-induced osteoporosis. Studies have shown that the bones can respond positively to periods of activity and rest, rather than continuous activity, which may make the bones less responsive over time.
Vibration therapy can also help with bone formation. These treatment methods have shown promise in lab studies. However, more research is needed to confirm their effectiveness in SCI-induced osteoporosis patients.
Calcium and vitamin D supplementation are crucial for all patients. All patients should be aware of the recommended daily intake for these nutrients. For people over 50, the National Osteoporosis Foundation suggests taking between 1200 to 1500 mg of calcium and 800 to 1000 IUs of vitamin D per day. This recommendation applies to those with SCI-induced osteoporosis as well, regardless of their age.
Drug therapies used for osteoporosis generally work by slowing down bone loss or promoting bone formation. Bisphosphonates are the most commonly prescribed class of drugs for osteoporosis. While they have been successful in treating general osteoporosis patients, they have not been shown to significantly improve bone mineral density (BMD) in patients with SCI-induced osteoporosis.
Denosumab, an antibody drug that interferes with a protein involved in bone loss, has shown promise in treating SCI-induced osteoporosis. Indeed, one study showed that this drug increased BMD in patients with SCI-induced osteoporosis after a year of treatment.
Other drugs such as teriparatide, which stimulates cells that produce bone, may also prove beneficial for patients with SCI-induced osteoporosis. Additionally, blocking certain agents involved in bone formation and resorption, like activins and cathepsin-K inhibitors, may also benefit these patients. However, more research is needed to confirm their effectiveness.
What else can Osteoporosis in Spinal Cord Injuries be?
To diagnose osteoporosis caused by spinal cord injuries (SCI), doctors need to consider a few key things. First, they have to know how long it’s been since the original SCI injury. Then, they use a test called a DXA scan to establish a starting value for bone mass density (BMD). After that, they continue to monitor the patient closely to watch for any loss of bone mass over time.
They’ll also need to understand where the patient is on a scale of bone loss, according to criteria set by the World Health Organization:
- Normal BMD = t-score of -1.0 or greater (or within 1 standard deviation below the normal, healthy group)
- Osteopenia = t-score between -1.0 and -2.5
- Osteoporosis = t-score below -2.5
Doctors also need to consider if the patient has any pre-existing medical conditions or is using any medication that might have already made them more susceptible to lower BMD levels. Lastly, doctors always need to be on alert for frailty fractures that happen spontaneously, especially in patients with SCI who are in a critical state.
What to expect with Osteoporosis in Spinal Cord Injuries
In general, people with spinal cord injuries (SCI) often experience a faster decline in bone mineral density (BMD) than those with general osteoporosis risk. BMD is a measure of bone strength and a drop in BMD indicates weaker bones.
SCI patients are at high risk for osteoporosis; a bone disease characterized by loss of bone mass, making the bones brittle and prone to fractures. Statistics indicate that within a year of their spinal injury, over half of these patients will have osteoporosis. Furthermore, more than 80% of people with a long-term SCI end up developing osteoporosis.
The effectiveness of treatment for osteoporosis in these patients is also less predictable compared to post-menopausal women who can walk around.
Understanding the timeline for bone health implications in SCI patients can be important:
- Two weeks after a SCI: the patient’s BMD levels could start to decrease rapidly.
- Below the injury level: around a 4% reduction in BMD per month is expected.
- Trabecular BMD loss: Trabecular bones are found at the ends of long bones like the hip and wrist and they can lose around 40% of their density two years after the SCI.
- After 2 to 5 years post-injury: There’s still ongoing debate concerning further BMD decline over the years. Some studies suggest that bone loss may plateau or level out after 3 to 5 years, while others show that BMD continues to decrease chronically.
Possible Complications When Diagnosed with Osteoporosis in Spinal Cord Injuries
The main issue resulting from osteoporosis caused by spinal cord injuries (SCI) is a condition known as fragility fracture. This is a type of broken bone that happens even with minor injuries or, occasionally, no injuries at all.
Notably, these fractures most often happen below the level of the spinal cord injury, especially in long bones – like those in your legs and arms.
A significant concern is that many of these fragility fractures in patients with a SCI can occur without any apparent reason and can often be overlooked or diagnosed late.
Key Points:
- The main concern with osteoporosis caused by spinal cord injuries is fragility fractures.
- These fractures are usually seen under the level of the spinal cord injury, particularly in the long bones.
- Many of these fractures can occur suddenly, and can often be missed or their diagnosis delayed.
Preventing Osteoporosis in Spinal Cord Injuries
Patients who have had a Spinal Cord Injury (SCI) should be informed about their immediate and ongoing risks of reduced Bone Mineral Density (BMD) – which is the amount of bone mineral in your bones, and the potential for fractures from smaller impacts. Particular attention should be given to the period immediately following the SCI, as it is the most vulnerable time.
The main treatment options for patients with weakened bones due to low BMD involve early guidance on how to maintain healthy bone mass levels. This also includes extensive education and advice on the various social, environmental, and lifestyle risk factors that can impact bone health negatively.
