Just like a house needs a stable frame, your body needs a stable skeleton. Bone health is important for anyone living with Duchenne, whether walking (ambulatory) or those no longer able to walk without the assistance of a wheelchair or scooter (non-ambulatory). People of all ages living with Duchenne have weak bones, especially if they are taking steroids (corticosteroids). Steroids prevent bones from rebuilding, and cause bone to have a lower bone mineral density and an increase risk of fractures (broken bones) compared to the general population.
Keeping Bones Healthy
Nutrition and exercise are especially helpful in keeping your bones healthy. Eating a diet rich in both calcium and vitamin D are important – make sure you and your dietitian review your diet every year to make sure you are eating healthy amounts of each. You should also have a vitamin D level checked each year. This is done by a blood test called a “25 hydroxy vitamin D level” (or 25 OH-vitD). If your level is low (<30mg/ml), your neuromuscular specialist should prescribe a vitamin D supplement to help boost your levels. Exercise (swimming, standing, walking) will help strengthen your bones as well. It’s important to move everything that you can move, at least once a day!
Close surveillance of bone health is important for people living with Duchenne, especially those taking steroids. It may be recommended that you have a baseline DEXA scan and baseline lateral spine X-ray when corticosteroids are started, or when you become non-ambulatory, and each year thereafter. Baseline imaging of these bones allow your doctor to track any changes that happen over time.
Duel-energy X-ray absorption (or DEXA) scans use a small amount of radiation to take pictures of bone. The DEXA scan measure the thickness, or bone mineral density (BMD), of your bone. A very low BMD can indicate that you may be at higher risk for broken bones, or “fractures.” A DEXA scan is recommended every 2-3 years.
Scoring a DEXA Scan
When your doctor is explaining the results of your DEXA scan, they may mention a “Z-score.” A Z-score is a way your doctor can measure your bone density compared to your peers of similar age and gender. In pediatrics, a Z-score between -1.0 and +1.0 is considered normal. A Z-score of less than or equal to -2.0 is considered abnormal and indicative of osteoporosis (weakening, thinning bones). While DEXA results alone cannot be used to diagnose osteoporosis, these measurements can be helpful tools for your doctor to consider when monitoring your bone health.
Lateral Spine X-rays
A lateral spine X-ray is when an X-ray is taken from the side so a radiologist can evaluate your vertebrae. A lateral spine X-ray is recommended every 1-2 years. If you cannot have both and have the choice of either a DEXA or lateral spine X-ray, choosing the lateral spine X-ray is recommended.
People with Duchenne who are taking steroids are at risk for developing low-trauma vertebral fractures. Many of these fractures are not symptomatic at first – in other words, you may not have any back pain or discomfort at all. However, the presence of these tiny fractures indicates that you may be at higher risk of developing future vertebral fractures. A radiologist will “read” the lateral spine X-ray to detect any small fractures or injuries to the vertebrae. If any problems with your vertebrae are left undiagnosed and untreated, vertebral fractures can lead to chronic back pain and spine deformity.
Scoring a Lumbar Spine X-Ray
The Genant Method is a way your doctors can define your vertebral fractures, or risk for fractures. Each of the vertebrae should look rectangular on X-ray, with a space between it and the next vertebrae. The X-rays will allow the radiologist to measure the shape of the vertebrae and the spaces between them. If vertebrae begin to change their shape, or the space between them starts to shrink, this can be a sign of vertebral compression fractures. The radiologist will use a measure called the Genant Score, to evaluate both the vertebrae and the space between them. The Genant score can be normal (normal shape and space), mild, moderate, or severe (each showing that the vertebral shape and the space between them are changing). If scores are normal or mild, they should be followed each year. Moderate scores should be followed more closely and consideration given to starting bisphosphonate medication. Severe scores should be treated with bisphosphonates. This scoring method allows your doctor to better understand your bone health, the extent of any injuries to the vertebrae bones, and if treatment is indicated.
Bisphosphonates are medications given to treat osteoporosis. In the life cycle of bone, bone is constantly being broken down, reabsorbed and rebuilt. Healthy bones are formed as long as this complete cycle is not interrupted. Steroids, unfortunately, interrupt the cycle by slowing down the building of new bone. Bisphosphonates work to slow down the reabsorption of broken down bone. When bone is not reabsorbed, it breaks the cycle of breaking down bone to build new bone.
Bisphosphonates can be given orally (Fosamax (daily or weekly), Alendronate (weekly), Risedronate (daily, weekly or twice monthly) or by IV infusion (Zolendronate (1-2 infusions/year). IV Zolendronate has been recommended if possible. The goal of bisphosphonate therapy is to increase the density of the bones of the body, including the vertebrae in the spine. Increasing the density of bones puts you at less risk for a fracture.
Risk of Bisphosphonates
The preventative removal of wisdom teeth may not be best for all. In addition to the possible risks of anesthesia and aspiration, osteonecrosis of the jaw can be caused by molar extraction when patients are taking bisphosphonates. Be sure to discuss this risk with your dentist and orthodontist.
Duchenne Care Considerations
The latest update to the Duchenne Care Considerations were released earlier this year, including updates to bone health (found in Part 2). These updates are reflected in this blog. To read the updated Care Considerations, click here.
Share Your Data
Your bone health experiences can help tell the story of bone health in Duchenne and increase the understanding of experts in the field. That’s why we are asking you to update your Bone Health module in the DuchenneConnect Registry. Log into your DuchenneConnect account, go to your profile page, and click on the Bone Health module link. Either complete the survey for the first time, or select “Retake this survey” if you are updating your information.
Not in the Registry? Join today and become a Citizen Scientist, adding your data to the already powerful DuchenneConnect Registry! Please take 10 minutes today to complete this survey and you could win a prize this month, including a new iPad!