Spine, Hips & Bones

The possible impact of SMA on the spine, hips and bones (orthopaedic problems) may be all too familiar to you and may have been a reason for any number of orthotic and surgical interventions you’ve had over the years. For others of you this won’t be the case – as always with SMA, everyone’s different.

When your medical team is discussing best care and management with you for any orthopaedic problems, they’ll be thinking not just about what your clinical classification was when you were diagnosed (such as SMA Type 1, 2, 3 or 4), but importantly which physical milestones are relevant for you now. For simplicity, they group people with SMA as:

  • non-sitters - those who are unable to sit
  • sitters - those who are able to sit but not walk
  • walkers - those who are able to walk 

They’re not the most user-friendly terms, but they’re used in the International Standards of Care for SMA (SoC) for those with 5qSMA (Types 1, 2, 3 or 4), which is the reference point for all medical professionals.   

The Impact SMA Can Have On Your Spine, Hips & Bones

You may be very familiar with why some people have orthopaedic problems and what these can be, but if not, this recap may be helpful. 

Because SMA causes muscles to get weaker, people with SMA can also have problems with the bones that are supported by the muscles (orthopaedic problems). SMA can weaken the muscles that support the spine which, without this support, can be pulled by gravity and curve. It’s estimated that as they grow, 60-90% of non-sitters and sitters develop a spinal curvature, as do 50% of walkers. When the spine curves sideways into a “C” or “S” shape it’s called a scoliosis. When the spine bends forward it is called a kyphosis. At the same time as the spine curves, there are changes to the chest wall and rib cage which reduce the space available for the lungs to grow and for breathing. 

Weakening muscles can also mean that some people who are sitters and walkers have ‘unstable hips’. How much muscles weaken and what effect this has on anyone’s spine and hips day to day is very individual - no two people are the same. 

Another thing that can be an issue for people who are non-sitters and sitters is not being able to use bones and muscles as much as someone who can walk. Standing has several benefits for health (see section on Posture, Movement & Exercise) but if you’re a non-sitter you won’t be able to stand and if you’re a sitter you’ll find it hard work to stand for a long time, even with support. This makes you more at risk of bone fractures due to what’s called osteoporosis (when bones are weaker and more likely to break). 

Care and Management

Any support you need would be given to you following an assessment, but if you’ve just started to experience difficulties - or if things change for you - talk to your GP or a member of your healthcare team as you may need your care and management reviewed. You can read more about what this might be in Chapter 4 Orthopaedic Management of A Guide to the 2017 International Standards of Care for SMA: www.smauk.org.uk/international-standards-of-care-for-sma

Page last updated: July 2019