Corticosteroids, Bone Health and Scoliosis in Muscular Dystrophy

Steroids, bones and scoliosis: the trade-off at the centre of Duchenne care

Corticosteroids are the most effective treatment available in Duchenne muscular dystrophy, and they damage bone.

Both of those things are true, and the way Australian families most often encounter them is unbalanced: a strong recommendation to start steroids, delivered with reassurance, followed some years later by a fracture that nobody had prepared them for.

The numbers from the 2018 international care considerations are specific. Between 20 and 60 per cent of boys with Duchenne sustain low-trauma limb fractures. Up to 30 per cent have symptomatic vertebral fractures. And steroid-treated boys had a long-bone fracture rate around 2.6 times that of boys never treated with steroids.

The answer to that is not to avoid steroids — they slow the loss of muscle, prolong walking, and the Australian 50-year cohort study found longer life expectancy among those who used them. The answer is that the bone monitoring plan should be set up before the first dose, and that it is a specific, written schedule rather than a general intention to keep an eye on things.

This guide covers what the steroids do and what they cost, the bone surveillance schedule in detail, vertebral fractures and why they are missed, scoliosis and the surgery question, and the side effects beyond bone that families should be ready for — including one that is a genuine emergency risk and that almost nobody is warned about.

What the steroids do, and the regimens

Prednisolone or deflazacort. Both are used in Australia. They slow the loss of muscle strength, prolong independent walking, and are associated with longer survival.

Why they work is not entirely settled — anti-inflammatory effects, membrane stabilisation, effects on muscle regeneration — and it does not matter much practically. What matters is that this is the one intervention that changes the muscle trajectory rather than managing its consequences.

Timing. Started during the ambulatory phase, typically in early childhood, with the specific timing a clinical judgment made by the neuromuscular team.

Regimens vary, and this is worth knowing because it gives you options when side effects are a problem. Daily dosing is the most studied. Intermittent regimens — ten days on and ten days off, or weekend-only dosing — are used, generally with fewer side effects and possibly less benefit. Dose can be adjusted. The drug can be switched between prednisolone and deflazacort.

Which means the answer to a side effect is usually a change of regimen, not stopping. Families who find the behavioural effects or the weight gain intolerable frequently have options they have not been offered.

On deflazacort specifically: it has historically been promoted as more bone-sparing than prednisolone. The 2018 care considerations note that this claim is now doubted, because fractures remain frequent in deflazacort-treated boys. So the choice between them is made on other grounds, and nobody should be reassured about bone risk on the basis of being on deflazacort.

The bone surveillance schedule

This is the part that should be in place before the steroids start. From the 2018 care considerations:

At baseline, for everybody: a lateral thoracolumbar spine radiograph. Not a DXA scan — an actual X-ray of the spine from the side, because that is what shows vertebral fractures.

Repeat spine radiograph:

• Every one to two years while on corticosteroids
• Every two to three years off corticosteroids
• And additionally if back pain appears, or if the spine bone mineral density Z-score drops by 0.5 standard deviations or more over twelve months

Annually:

• Spine DXA (bone mineral density)
• Serum 25-hydroxyvitamin D
• Review of calcium and vitamin D intake

Treatment thresholds:

• Treat moderate (Genant grade 2) and severe (grade 3) vertebral fractures, even when they are causing no symptoms
• Monitor mild (grade 1) fractures closely for symptoms or height loss

Treatment choice: intravenous bisphosphonates are first-line. Oral bisphosphonates are specifically not recommended for this purpose.

The practical point. This schedule will not deliver itself, particularly in adult services. Keep your own copy. Know when the last spine X-ray was. Ask at each appointment whether the annual DXA and vitamin D have been done. Families who track it get it delivered, and families who assume the clinic is tracking it frequently find a two-year gap.

Vertebral fractures, and why they get missed

The most important single thing in this guide, because the pattern is so consistent.

Vertebral fractures in boys on steroids are frequently silent. The vertebra compresses gradually. There is no moment of injury, no fall, no acute pain. Up to 30 per cent have symptomatic fractures, which implies a larger number with fractures that are not causing symptoms — and a fracture that is not causing symptoms is still a fracture, still progresses, and still warrants treatment at moderate or severe grades.

Which is why the baseline and repeat spine radiographs matter so much. You cannot detect these by asking whether anything hurts.

Signs that should prompt imaging immediately rather than waiting for the scheduled interval:

• Any new back pain. In a boy on long-term steroids, new back pain is a vertebral fracture until proven otherwise, and it should be imaged rather than treated with analgesia and reassurance.
• Loss of height, or a change in sitting height
• A new or worsening curve in the back
• A drop in spine bone mineral density Z-score of 0.5 standard deviations or more over a year

And long-bone fractures. Twenty to sixty per cent of boys with Duchenne sustain low-trauma limb fractures, at around 2.6 times the rate in untreated boys. A fracture of the femur in an ambulatory boy is a serious event beyond the fracture itself, because a period of immobility can cost walking ability permanently — which is why fracture prevention is not a side issue.

What prevention looks like: adequate calcium and vitamin D with levels actually measured rather than assumed; weight-bearing and standing where possible, including standing frames in non-ambulatory boys; physiotherapy; falls prevention in the home; and bisphosphonate treatment where indicated. Hip protectors are worth considering in boys who fall.

Scoliosis

Why it happens. Once somebody stops walking, the trunk muscles that hold the spine in alignment can no longer do so, and a curve develops. Corticosteroids reduce the incidence and severity of scoliosis — one of their underappreciated benefits — but do not prevent it.

Why it matters beyond appearance. A progressive curve causes pain, makes seating difficult, produces pelvic obliquity that creates pressure injury risk, interferes with hand function and the use of a wheelchair control, and reduces lung volumes independently of muscle weakness. It is a functional and respiratory problem as much as an orthopaedic one.

The surveillance schedule, from the care considerations:

While walking: scoliosis assessment at least annually by visual inspection, with radiographs only if a curve is seen or inspection is inadequate.

Early non-ambulatory stage: inspect the spine every six months, and obtain a radiograph when the person first becomes non-ambulatory. If a curve is present, repeat radiographs every six months if skeletally immature, or at least annually if skeletally mature.

Referral to an orthopaedic surgeon for curves of 20 degrees or more.

Late non-ambulatory stage: yearly upright anteroposterior radiographs where progression is a concern.

The surgical question. Posterior spinal fusion is recommended for sitting curves over 20 to 30 degrees in prepubertal boys not on steroids. For steroid-treated boys, the guidance is to observe for clear progression before intervening, because steroids slow curve development and the natural history is different. Fusion into the pelvis is advised when pelvic obliquity exceeds 15 degrees.

Spinal orthoses — braces — are specifically not recommended in this population. They do not prevent progression and they restrict respiratory function. If a brace is proposed, ask about this.

And before any spinal surgery: cardiology and respiratory consultation. This is not a formality. Spinal fusion in somebody with reduced ejection fraction and reduced respiratory reserve is a substantially higher-risk procedure, and the cardiac and respiratory status determines both whether and when it should happen. The care considerations make this explicit, and it is one of the strongest arguments for having the surveillance up to date rather than scrambling for an echocardiogram when a surgeon wants to operate.

What surgery does and does not achieve. It stabilises the spine, improves sitting posture and comfort, makes seating easier to configure, and prevents further progression. It does not improve muscle strength, and the evidence that it improves respiratory function is mixed — it generally slows further decline rather than reversing it. Recovery is significant. Families who go into it expecting comfort, posture and seating gains are usually satisfied; families expecting a functional transformation are not.

The other steroid side effects

Bone is the most serious but not the only one, and knowing what is coming makes it manageable.

Weight gain, which matters mechanically as well as metabolically — extra weight on weakening muscle costs function, and it makes transfers and hoisting harder. Dietetic input from the start rather than after twenty kilos is the right approach, and it is a legitimate NDIS or health referral.

Growth suppression and delayed puberty. Boys on long-term steroids are shorter than they would have been and puberty is frequently delayed. This needs an endocrinologist, not watchful waiting — testosterone treatment for delayed puberty is available and matters for bone density, muscle, mood and a teenager’s experience of adolescence. Ask for the referral; it is frequently not offered.

Behavioural effects. Irritability, mood swings, emotional lability, difficulty settling. Usually most pronounced in the first weeks after starting or after a dose increase, and frequently manageable by changing the dosing schedule — moving to morning dosing, or to an intermittent regimen. Families should know this is a recognised drug effect rather than a behavioural problem, and should raise it rather than absorbing it.

Adrenal suppression, which is the emergency one. Long-term corticosteroids suppress the body’s own cortisol production, which means that during illness, injury, surgery or anything physiologically stressful, the person needs stress dosing — extra steroid — because their adrenal glands cannot mount the normal response. Without it, adrenal crisis is possible: vomiting, low blood pressure, collapse.

What this requires practically: the family, the person, every support worker, and any emergency clinician needs to know. A steroid alert card or medical bracelet. A written plan from the clinic specifying what to do during illness and vomiting. An in-date supply of whatever the clinic recommends for stress dosing. And it should be stated prominently on any summary document and in any chest infection plan.

This is the side effect most likely to be missed in an emergency department, because the staff are focused on the presenting problem and nobody has said the words. Say the words.

Cataracts, particularly with longer-term use, which is why ophthalmology review is part of monitoring.

Raised blood pressure, monitored at each visit.

Glucose intolerance and diabetes, monitored with periodic bloods.

Immune suppression, which means annual inactivated influenza vaccine and pneumococcal vaccination are recommended, and live vaccines are generally avoided. It also means infections need prompter attention.

Skin changes — easy bruising, striae, acne — which matter more to a teenager than clinicians often assume.

What to ask for, and when

Before starting steroids: the monitoring schedule in writing. Baseline spine radiograph, DXA and vitamin D. A dietitian referral. A plan for what happens if behavioural effects are a problem. And the steroid alert card and stress dosing plan.

Annually thereafter: spine DXA, vitamin D, blood pressure, glucose, ophthalmology review, and the spine radiograph on its one-to-two-year cycle.

At any new back pain: imaging, promptly.

At loss of ambulation: a spine radiograph, and the scoliosis surveillance interval halved.

In adolescence: endocrinology referral for delayed puberty, which is one of the most commonly missed items on this list.

Before any surgery: cardiology and respiratory consultation, and confirm the anaesthetist knows about the steroids.

And into adult life: all of the above continues. Fracture risk does not stop at eighteen and vertebral fractures remain silent, but the surveillance frequently stops because nobody is booking it. See Duchenne into adulthood.

The things worth asking before the first dose

Starting corticosteroids is a conversation most families have once, in a clinic appointment, with a great deal else going on. These are the questions that make the next ten years go better, and almost none of them get asked.

“Which drug, which regimen, and why that one?” Prednisolone or deflazacort, daily or intermittent. There is a genuine choice here and the reasoning should be explained rather than assumed.

“What is the monitoring schedule, in writing?” Baseline spine X-ray, spine DXA, vitamin D, blood pressure, glucose, ophthalmology. Ask for it as a document you can keep, with the intervals on it, because in a few years you will be the only person tracking it.

“Who is booking the annual items, and what happens if they are missed?”

“What do we do if the behavioural effects are a problem?” Ask this before it happens, because the answer — change the dosing time, change the schedule, change the drug — is much easier to act on when it has already been discussed.

“Can we have a dietitian referral now?” Weight gain is predictable, and managing it from the start is considerably easier than reversing twenty kilos.

“When should we expect to need endocrinology?” Delayed puberty is a recognised effect and testosterone treatment is available and matters. This referral is one of the most commonly missed in Duchenne care, and asking early means it is already on somebody’s list.

“Can we have the steroid alert card and the written stress dosing plan today?” Not later. The adrenal suppression risk starts with long-term treatment, and the plan needs to exist before the first illness, not after it.

“What is the plan for vitamin D and calcium, and will levels be measured?” Measured, not assumed.

“What would make you reduce or stop the steroids?” Useful to know in advance, so that a side effect does not feel like a crisis with no options.

And: “Can I have all of this in a letter?” Because you will be handing it to a school, a support provider, an emergency department and eventually an adult service, and a letter does the explaining for you.