DEXA Scans & Lateral Spine X-Rays
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 cause bone to have a lower bone mineral density and an increase risk of fractures (broken bones) compared to the general population. Muscle weakness and decreased mobility are also risk factors for weak bones.
Why does my child need these tests?
Given the high risk for fractures, close surveillance 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.
What is a DEXA scan?
DEXA, or dual-energy X-ray absorption, uses a small amount of radiation to produce pictures of the bone. It is a quick and simple test that is non-invasive and will not hurt. There is no special preparation for this test. However, if you are currently taking a calcium supplement, do not take it for at least 24 hours before the scan. A DEXA scan is recommended each year.
What is your doctor looking for?
The DEXA scan measures bone mineral density (BMD). Your doctor can use the results of your DEXA scan as a tool to evaluate bone health and to help determine if you may be at a higher risk for bone fractures.
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. While DEXA results alone cannot be used to diagnose osteoporosis, they can be a helpful tool for your doctor to consider when monitoring your bone health.
Note: Adult bone densities are measured with a T-score and are not appropriate measurements for pediatric bone health.
Lateral Spine X-rays
What is a lateral spine X-ray?
A lateral spine X-ray is when an X-ray is taken from the side so a radiologist can evaluate your vertebrae. This test is non-invasive and will not hurt. You will usually lie on a table so the radiology tech is able to get a good image. The X-ray is very quick and you will only need to stay still for a short amount of time. A lateral spine X-ray is recommended every 1-2 years. If you have the choice of having either a DEXA or lateral spine X-ray, choosing the lateral spine X-ray is recommended.
What is your doctor looking for?
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. However, the presence of these tiny fractures usually indicate you are at a 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.
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 a 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.