Pediatric Spine | CP, DMD, SMA | Pelvic Obliquity | Long Constructs
- Definition: Scoliosis caused by neuropathic or myopathic disorders leading to trunk muscle imbalance.
- Pattern: Typically long, C-shaped thoracolumbar curve with pelvic obliquity.
- Goal: A straight spine over a level pelvis to allow comfortable sitting (and nursing care).
- Pre-Op Optimization: Nutrition (Pre-albumin), Pulmonary function, Seizure control, Bowel regimen.
- Fixation: Generally T2/T3 to Pelvis (Galveston / Iliac screws).
- “In Duchenne (DMD), fuse EARLY (Cobb greater than 20°) to preserve lung function. Don't wait for 50°.
- “Pelvic Obliquity causes ischial pressure sores on the 'down' side.
- “GMFCS Level correlates directly with scoliosis risk (Level I less than 5%, Level V = 90%).
- “Beware of 'Malignant Hyperthermia' in myopathic conditions.
Fatal Risk. DMD patients have progressive cardiomyopathy. Must have detailed Echo/Cardiology review. Ejection Fraction determines eligibility.
FVC less than 30%. Patients with forced vital capacity less than 30% predicted need post-op ventilation planning and have high risk of pneumonia/death.
Albumin / Transferrin. Malnutrition is rampant (G-tubes often needed). Poor nutrition = Infection + Wound Breakdown.
Valproate. Ensure levels are therapeutic. Post-op seizures can break rods!
- Adolescent Idiopathic
- Structural S-shape (Right thoracic)
- Neuromuscular
- Long C-shape (Thoracolumbar)
- Adolescent Idiopathic
- Rare
- Neuromuscular
- Common (Needs fixation)
- Adolescent Idiopathic
- Stops at maturity
- Neuromuscular
- Continues after maturity
- Adolescent Idiopathic
- Cosmesis + Prevent progression
- Neuromuscular
- Sitting balance + Nursing care
- Adolescent Idiopathic
- Selective (save motion)
- Neuromuscular
- Long (T2-Pelvis)
Overview and Epidemiology
Neuromuscular Scoliosis (NMS) is a spinal deformity associated with a heterogeneous group of disorders including Cerebral Palsy (CP), Duchenne Muscular Dystrophy (DMD), Spinal Muscular Atrophy (SMA), and Spina Bifida.
Key Characteristics:
- Onsent: Often early (less than 10 years).
- Use: Most patients are wheelchair-bound (non-ambulatory).
- Progression: Unlike idiopathic scoliosis, NMS curves continue to progress after skeletal maturity due to loss of trunk control and gravity.
- Impact: Severe curves compromise sitting balance (hands needed for support), cause pelvic obliquity (pressure sores), and restrict pulmonary function (pneumonia risk).
Pathophysiology and Biomechanics
Pathomechancis:
- The primary driver is muscle weakness (DMD/SMA) or spasticity (CP).
- Unlike AIS (rotation driver), NMS is often a collapsing deformity under gravity.
- Pelvic Obliquity: The "foundation" of the spine acts like a tilted table.
- Causes: Suprapelvic (spine curve) or Infrapelvic (hip contracture).
- Consequence: Pressure ulcers on the low side, hip dislocation on the high side.
Classification
Gross Motor Function Classification System (CP)
The risk of scoliosis directly correlates with GMFCS level.
- Description
- Walks without limits
- Scoliosis Risk
- Low (less than 5%)
- Description
- Walks with limitations
- Scoliosis Risk
- Low-Mod
- Description
- Walks with handheld mobility
- Scoliosis Risk
- Moderate
- Description
- Self-mobility with limitations (Wheelchair)
- Scoliosis Risk
- High (~50%)
- Description
- Transported in manual wheelchair (No head control)
- Scoliosis Risk
- Very High (greater than 90%)
Clinical Assessment
Pre-operative Assessment
- Function: Can they sit? Do they use hands for support?
- Pain: Is the curve painful? (Rare in NMS, look for hip dislocation).
- Pulmonary: History of pneumonia? ICU admissions? CPAP?
- Seizures: Frequency? Medications?
- Nutrition: Feeding tube (PEG)? Weight loss?
- Sitting Balance: Does the patient list to one side?
- Pelvic Obliquity: Palpate iliac crests sitting. Check for ischial sores.
- Hip Contractures: Hip flexion contracture greater than 20 deg exacerbates lumbar lordosis/kyphosis.
- Windswept Hips: One hip abducted, one adducted.
- Skin: Inspect back and buttocks for breakdown.
- Cobb Angle: Surgery typically indicated for Cobb greater than 50 degrees (CP) or greater than 20-30 degrees (DMD).
- Pelvic Obliquity: If greater than 15 degrees, strictly consider fusion to pelvis.
Always check the hips. Pelvic obliquity drives the "high" hip into adduction, leading to subluxation/dislocation. A dislocated hip can be the primary source of pain, not the spine.
BEACHClinical Assessment
Hook:Don't forget the BEACH when assessing these kids.
Investigations
- Parameter
- Cobb Angle
- Significance
- Magnitude of deformity. Greater than 50 deg usually operative.
- Parameter
- Pelvic Obliquity
- Significance
- Angle of pelvis relative to horizontal. Drives extensions to pelvis.
- Parameter
- Kyphosis/Lordosis
- Significance
- NMS often kyphotic (collapsing).
- Parameter
- Flexibility
- Significance
- Determines if anterior release is needed (rare nowadays with pedicle screws).
Blood Work (Optimization):
- Albumin / Pre-albumin: Marker of nutrition. Albumin greater than 3.5 g/dL desired.
- Total Lymphocyte Count: greater than 1500.
- Hematocrit: Optimize pre-op.
- Coagulation Profile: Valproate can affect platelets/factors.
Anaesthetic Risk in Muscular Dystrophy
A high-yield refinement of the "malignant hyperthermia" warning that examiners probe:
Boys with Duchenne/Becker dystrophy are not classically malignant-hyperthermia (RYR1) susceptible, but they are at high risk of an anaesthesia-induced rhabdomyolysis / hyperkalaemic cardiac arrest triggered by suxamethonium (succinylcholine) and the volatile anaesthetic agents - clinically it can look MH-like (hyperkalaemia, rising end-tidal CO2, arrhythmia, dark/myoglobinuric urine).
- Avoid suxamethonium absolutely (risk of hyperkalaemic arrest) and avoid or minimise volatile agents, favouring a total intravenous anaesthetic (TIVA) technique.
- Conditions with a genuine RYR1 link (for example central core disease) are truly MH-susceptible; treat any crisis with dantrolene, cooling and hyperkalaemia management.
- Either way the practical message in theatre is the same: declare the dystrophy, plan a trigger-free anaesthetic, and be ready for hyperkalaemia.
This sits alongside the cardiac (dilated cardiomyopathy - echocardiogram and ejection fraction) and respiratory (plan extubation to non-invasive ventilation with mechanical cough assist when FVC is low) optimisation already required in these patients.
Differential Diagnosis
Not every curved spine in a child with disability is "simple" neuromuscular scoliosis. Distinguish the collapsing C-curve from mimics that change management.
- Curve / Clue
- Structural right thoracic S-curve, normal neurology
- Key Differentiator
- No underlying neuromuscular disease; stops at maturity; rarely needs pelvis
- Curve / Clue
- Short, sharp curve; hemivertebra/bar on X-ray
- Key Differentiator
- Vertebral anomaly from birth; screen for VACTERL, cardiac and renal anomalies
- Curve / Clue
- Variable curve plus systemic features
- Key Differentiator
- Dystrophic ribs/scalloping (NF1), arachnodactyly/lens (Marfan); dural ectasia
- Curve / Clue
- Atypical (left thoracic), painful, or rapidly progressive
- Key Differentiator
- Abnormal abdominal reflexes; MRI mandatory for atypical curves
- Curve / Clue
- Postural lean, not a fixed structural curve
- Key Differentiator
- Resolves when underlying pain treated; hip dislocation is the classic NMS trap
An atypical curve (left thoracic), a painful curve, rapid progression, abnormal abdominal reflexes, or a new neurological sign mandates whole-spine MRI to exclude a syrinx, tethered cord, or intraspinal tumour before attributing the deformity to the underlying neuromuscular condition.
Management Algorithm
Role of Bracing
- Controversial / Limited Use.
- Bracing does NOT halt progression in neuromuscular curves.
- Purpose: To provide sitting support ("Soft brace" or TLSO) to delay surgery until larger size reached.
- Risk: Pressure sores, restrictive lung defect (compresses ribs).
Wheelchair Modifications
- Custom molded seat backs.
- Wheelchair modifications.
- Lateral trunk supports.
- Tilt-in-space mechanisms.
Bracing is palliative at best.
Surgical Technique
The "Unit Rod" vs Pedicle Screws
Unit Rod (Luque-Galveston):
- Historic gold standard.
- Pre-bent U-shaped rod with sublaminar wires.
- Legs of rod driven into ilium (Galveston technique).
- Pros: Cheap, distributed force (less pullout). Cons: Wire passage risk, limited lordosis control.
All-Pedicle Screw Constructs:
- Modern standard.
- Iliac Screws or S2-Alar-Iliac (S2AI) screws for pelvic fixation.
- Pros: Better correction, 3-column fixation, no canal entry. Cons: Pullout in osteoporotic bone.
Levels:
- Upper: T2 or T3 (prevent proximal kyphosis).
- Lower: Pelvis (if obliquity greater than 15 deg or non-ambulatory). L5 (if ambulatory and pelvis level).
Pelvic fixation is mandatory for obliquity.
NMS has 5-10x higher infection rate than AIS. Vancomycin Powder in the wound. Betadine Irrigation. Optimize Nutrition. Minimize OR Traffic.
SITSurgical Goals
Hook:The goal is to help them SIT comfortably.
Intra-operative Neuromonitoring in Neuromuscular Scoliosis
Neuromonitoring is routine in idiopathic scoliosis, but the examiner wants you to know why it is different here:
- Baseline signals are often unobtainable or unreliable. Many NMS patients (severe cerebral palsy, advanced DMD/SMA, myelomeningocele) have pre-existing motor/sensory deficits, so motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) may be absent or non-reproducible at baseline - in a substantial minority no usable trace can be obtained at all.
- The wake-up test is rarely feasible because of cognitive impairment and inability to follow commands.
- Implications: when signals ARE obtainable they remain valuable and should be used; when they are not, safety rests on meticulous technique, avoiding over-distraction across a rigid deformity, controlled correction, and accepting less-than-anatomic correction rather than risking the cord. Document the patient's monitorability pre-operatively and counsel the family.
- Contrast this with AIS, where reliable MEP/SSEP monitoring is the expected standard and a true alert mandates the rescue checklist (reduce correction, raise blood pressure, warm, recheck) or a wake-up test.
NUTRITIONPre-operative Checklist
Hook:NUTRITION is the most commonly missed optimization factor.
Complications
- Rate
- 5-15% (High)
- Management / Prevention
- Debridement, Antibiotics, Remove hardware if chronically infected. Prevention is key.
- Rate
- Variable
- Management / Prevention
- Prolonged intubation common. Pre-op PFTs mandatory.
- Rate
- 5-10%
- Management / Prevention
- Poor bone stock. Use aggressive grafting.
- Rate
- Common
- Management / Prevention
- Thin patients. Use low profile screws. Cut rod ends flush.
- Rate
- Rare
- Management / Prevention
- Loss of mesenteric fat pad after straightening. Watch for vomiting.
Postoperative Care and Rehabilitation
Recovery Pathway
- Ventilator wean (crucial in DMD).
- Pain control (epidural or PCA).
- Fluid balance.
- Mobilize to wheelchair.
- Resume bowel regimen.
- Check fitting of wheelchair (back support might need modification).
- Home when feeding tolerated and pain controlled.
Outcomes
Quality of Life:
- Parents report high satisfaction primarily due to ease of nursing care (transfers, bathing) and improved sitting tolerance.
- Correction of pelvic obliquity is the most impactful factor for sitting.
Guidelines, Registries & Global Practice
Global Epidemiology:
- Scoliosis affects roughly a quarter of all children with cerebral palsy and the large majority of GMFCS IV-V (non-ambulant) children, with prevalence and severity rising with GMFCS level and age (Persson-Bunke, total-population data).
- Essentially all boys with Duchenne muscular dystrophy who lose ambulation develop scoliosis; historically up to 90% before routine glucocorticoid use. Long-term daily corticosteroids have markedly reduced both the incidence and severity of DMD scoliosis, so fewer patients now reach surgical thresholds.
- Spinal muscular atrophy (SMA) types I-II carry the highest and earliest scoliosis burden of the flaccid neuromuscular disorders.
Side-by-Side Guidance (where recommendations differ):
- Position relevant to NMS
- Annual spine surveillance once non-ambulant; daily glucocorticoids reduce scoliosis incidence; consider surgery for progressive curves with attention to cardiac and respiratory status
- Position relevant to NMS
- Spine monitoring from diagnosis; growth-friendly instrumentation for early-onset curves; account for nusinersen intrathecal access when planning fusion
- Position relevant to NMS
- Emphasise pre-operative optimisation (nutrition, pulmonary, cardiac) and fusion to the pelvis for non-ambulant patients with pelvic obliquity
- Position relevant to NMS
- Centralised paediatric spinal services; structured cerebral palsy hip and spine surveillance pathways feed early referral
- Position relevant to NMS
- No randomised evidence; surgery decisions individualised with explicit discussion of uncertainty
- Multicentre prospective databases (e.g. the Harms Study Group / CP spine cohorts informing Yaszay 2020) provide the best available complication benchmarks: roughly a one-in-three major complication rate and a 14% spine-related reoperation rate after CP fusion.
- Population-based CP surveillance registries (Sweden's CPUP, and similar UK/Australian/North American programmes) drive GMFCS-based screening intervals.
- High-resource settings: all-pedicle-screw and S2AI constructs, intra-operative neuromonitoring, cell salvage and tranexamic acid, dedicated paediatric ICU, and multidisciplinary pre-optimisation.
- Limited-resource settings: cost-effective segmental constructs (Unit Rod / sublaminar wire systems remain valuable), selective rather than routine neuromonitoring, and greater reliance on careful patient selection where ICU and blood-bank capacity are constrained.
- Referral principle everywhere: structured hip and spine surveillance pathways frequently detect the curve before it becomes symptomatic, enabling timely referral to a spinal service.
Controversies & Areas of Uncertainty
There are no randomised trials of spinal surgery in NMS (Cochrane, DMD). Practice rests on case series and physiological reasoning, so the magnitude of benefit on survival and quality of life is genuinely uncertain.
Pelvic fixation reliably corrects obliquity but adds operative time, blood loss and the risk of S2AI/iliac complications. In ambulant CP with a level pelvis, stopping short of the pelvis can preserve motion; in non-ambulant patients with obliquity, the pelvis is included.
All-pedicle-screw and S2AI constructs dominate modern practice, but no high-level trial proves superiority over the Unit Rod, which remains a cost-effective, well-validated option (Tsirikos: 68% curve and 71% obliquity correction).
Earlier surgery preserves a respiratory window, but glucocorticoids have reduced curve incidence/severity, so fewer boys now reach surgical thresholds and some are managed without fusion. The classic "fuse early, by 20-30 degrees" rule is being re-examined in the steroid era.
Magnetically controlled growing rods reduce repeat lengthening surgeries but carry implant-related and infection risks; intrathecal nusinersen access must be planned around any spinal construct.
Osteopenic, low-volume local bone drives interest in BMP and allograft, but BMP is off-label in children and its safety profile in this population is not established.
MCQ Practice Points
Q: What is the operative threshold for scoliosis in Duchenne Muscular Dystrophy? A: Cobb angle greater than 20-30 degrees (much lower than the 45-50 degrees for AIS).
Q: In a non-ambulatory CP patient with pelvic obliquity, where should the fusion stop distally? A: The Pelvis (Iliac/S2AI screws). Stopping at L5 or S1 has a very high failure rate.
Q: How does the infection rate of NMS surgery compare to AIS? A: It is significantly higher (5-15% vs less than 1%).
Q: Which neuromuscular condition is associated with Malignant Hyperthermia? A: Duchenne Muscular Dystrophy (and Central Core Disease). Succinylcholine is contraindicated.
Q: Is spondylolisthesis common in NMS? A: No, spondylolisthesis is associated with walking (repetitive stress). NMS patients usually have long kyphoscoliotic C-curves.
Q: In which NMS condition is cord tethering most common? A: Myelomeningocele (Spina Bifida). Almost all have tethered cords.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 12-year-old boy with GMFCS V Cerebral Palsy presents with a 60 degree thoracolumbar neuromuscular scoliosis and pelvic obliquity. He is finding it hard to sit in his wheelchair.”
“A 14-year-old boy with Duchenne Muscular Dystrophy (DMD) has a 25 degree scoliosis. His FVC is 50% predicted.”
“You performed a T2-Pelvis fusion on a CP patient. 3 weeks post-op, the wound is dehiscencing and draining serous fluid.”
Optimization Checklist
- Nutrition (Albumin greater than 3.5)
- Lungs (FVC greater than 30%)
- Heart (Echo for DMD)
- Seizures (Controlled)
- Bowels (Regimen)
Surgical Principles
- Fuse T2 to Pelvis
- Correct Pelvic Obliquity
- Use TXA (High blood loss)
- Vancomycin powder (Infection)
Condition Specifics
- CP: GMFCS V most at risk
- DMD: Fuse early (greater than 20 deg)
- SMA: Growing rods often needed
- Myelomeningocele: Latex allergy / Tethering
Evidence Base
GMFCS Level and Scoliosis Risk (Total Population)
- Prospective total-population CP registry of 666 children aged 4-18 years
- 28% had clinical scoliosis (17% mild, 11% moderate/severe)
- Risk of scoliosis rose with GMFCS level and age
- GMFCS IV-V: ~50% risk of moderate/severe scoliosis by age 18; GMFCS I-II: almost no risk
Posterior Fusion Slows Respiratory Decline in DMD
- 56 DMD patients; %FVC tracked before and after posterior spinal fusion
- Whole-cohort rate of FVC decline fell from 4% per year pre-op to 1.75% per year post-op (p less than 0.0001)
- Paired subgroup: decline fell from 8.0% to 3.9% per year
- Fusion did not reverse decline but significantly slowed it
No RCT Evidence for DMD Scoliosis Surgery (Cochrane)
- Systematic review seeking RCTs of spinal surgery for DMD scoliosis
- 47 relevant studies screened; none met inclusion (all case series, no randomised/quasi-randomised trials)
- No evidence-based recommendation could be made for or against surgery
- Benefits on survival, respiratory function and quality of life remain unproven by high-level evidence
Major Complications After Spinal Fusion in Cerebral Palsy
- Prospective multicentre database of 257 CP patients with minimum 2-year follow-up
- 78 patients (30%) had at least one major complication; overall 36% complication rate
- Deep infection 4.7% perioperatively plus 3.1% delayed; prolonged ventilation 8.2%
- Spine-related reoperation rate 14%; 11 patients (4.3%) died during follow-up
Unit Rod Instrumentation for CP Scoliosis
- Retrospective series of 287 CP children treated with Unit Rod instrumentation to the pelvis
- Scoliosis corrected from mean 76 to 25 degrees (68%); pelvic obliquity from 17 to 5 degrees (71%)
- Deep wound infection 4.2% early and 2.5% late; three perioperative deaths
- Caregiver satisfaction 96%
Sacral Alar-Iliac (S2AI) Pelvic Fixation
- Describes the S2-alar-iliac technique: screw one-third in sacral ala, two-thirds in ilium, in line with cephalad anchors
- Low-profile, in-line entry avoids the offset connectors and prominence of classic iliac screws
- Referenced pediatric series reported ~70% pelvic obliquity and ~67% coronal Cobb correction
- Screws of 9 mm or greater outer diameter recommended to prevent breakage
Surgery in Severe DMD With FVC Under 30%
- 14 DMD patients with forced vital capacity under 30% predicted
- Pre-operative inspiratory muscle training raised %FVC before surgery
- All-screw constructs corrected coronal curve and pelvic obliquity, maintained long-term
- Mean %FVC decline 3.6% per year after surgery; high patient and parent satisfaction