High Yield Overview
NEUROMUSCULAR SCOLIOSIS
Pediatric Spine | CP, DMD, SMA | Pelvic Obliquity | Long Constructs
90%Prevalence in GMFCS V
PelvisMust include in fusion
PulmonaryFunction declines 4% / year (DMD)
InfectionHigher risk than AIS
ETIOLOGY
Upper Motor Neuron
PatternCerebral Palsy, Friedreich's Ataxia, Syringomyelia
TreatmentSpasticity management + Surgery
Lower Motor Neuron
PatternSMA, Polio, Myelomeningocele
TreatmentFlaccidity + Surgery
Myopathic
PatternDuchenne MD
TreatmentEarly surgery (Cobb greater than 20-30)
Critical Must-Knows
- 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).
Examiner's Pearls
- "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.
Cardiopulmonary Risk
Duchenne Cardiomyopathy
Fatal Risk. DMD patients have progressive cardiomyopathy. Must have detailed Echo/Cardiology review. Ejection Fraction determines eligibility.
Pulmonary Reserve
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.
Nutritional Status
Albumin / Transferrin. Malnutrition is rampant (G-tubes often needed). Poor nutrition = Infection + Wound Breakdown.
Seizure Control
Valproate. Ensure levels are therapeutic. Post-op seizures can break rods!
At a Glance: AIS vs Neuromuscular
| Feature | Adolescent Idiopathic | Neuromuscular |
|---|---|---|
| Curve Pattern | Structural S-shape (Right thoracic) | Long C-shape (Thoracolumbar) |
| Pelvic Obliquity | Rare | Common (Needs fixation) |
| Progression | Stops at maturity | Continues after maturity |
| Surgical Goal | Cosmesis + Prevent progression | Sitting balance + Nursing care |
| Fusion Levels | Selective (save motion) | Long (T2-Pelvis) |
Mnemonic
NUTRITIONPre-operative Checklist
N
Nutrition
Albumin greater than 3.5, TLC greater than 1500
U
Urine
Rule out UTI
T
Tone
Baclofen pump? Spasticity?
R
Respiratory
PFTs, Sleep study
I
Infection
Skin, teeth, ears clearance
T
Team
ICU, Peds, Resp, Dietician
I
Imaging
Traction films, Pelvic incidence
O
Osteopenia
Dexa? Bisphosphonates?
N
Neurology
Seizure control
Memory Hook:NUTRITION is the most commonly missed optimization factor.
Mnemonic
BEACHClinical Assessment
B
Balance
Sitting balance / Head control
E
Etiology
CP vs DMD vs SMA
A
Associations
Seizures, cognitive, nutrition
C
Curve
Flexible vs Rigid
H
Hips
Dislocation risk
Memory Hook:Don't forget the BEACH when assessing these kids.
Mnemonic
SITSurgical Goals
S
Sitting Balance
Head centered over pelvis
I
Ischial Pressure
Level pelvis to prevent ulcers
T
Torso Height
Maximize space for lungs/abdomen
Memory Hook:The goal is to help them SIT comfortably.
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.
| Level | Description | Scoliosis Risk |
|---|---|---|
| I | Walks without limits | Low (less than 5%) |
| II | Walks with limitations | Low-Mod |
| III | Walks with handheld mobility | Moderate |
| IV | Self-mobility with limitations (Wheelchair) | High (~50%) |
| V | Transported in manual wheelchair (No head control) | Very High (greater than 90%) |
Clinical Assessment
Pre-operative Assessment
AskHistory
- 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?
Look/FeelExamination
- 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.
PlanSurgical Decision
- 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.
Hip Dislocation
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.
Investigations
Radiographic Parameters
| View | Parameter | Significance |
|---|---|---|
| AP Spine (Sitting) | Cobb Angle | Magnitude of deformity. Greater than 50 deg usually operative. |
| AP Spine (Sitting) | Pelvic Obliquity | Angle of pelvis relative to horizontal. Drives extensions to pelvis. |
| Lateral Spine | Kyphosis/Lordosis | NMS often kyphotic (collapsing). |
| Bending/Traction Films | Flexibility | 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.
Management Algorithm
📊 Management Algorithm
Click to expand
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.
Infection Prevention
NMS has 5-10x higher infection rate than AIS. Vancomycin Powder in the wound. Betadine Irrigation. Optimize Nutrition. Minimize OR Traffic.
Complications
Complication Profile
| Complication | Rate | Management / Prevention |
|---|---|---|
| Deep Infection (SSI) | 5-15% (High) | Debridement, Antibiotics, Remove hardware if chronically infected. Prevention is key. |
| Pulmonary Failure | Variable | Prolonged intubation common. Pre-op PFTs mandatory. |
| Pseudoarthrosis | 5-10% | Poor bone stock. Use aggressive grafting. |
| Implant Prominence | Common | Thin patients. Use low profile screws. Cut rod ends flush. |
| Superior Mesenteric Artery Syndrome | Rare | Loss of mesenteric fat pad after straightening. Watch for vomiting. |
Postoperative Care and Rehabilitation
Recovery Pathway
Days 1-3ICU
- Ventilator wean (crucial in DMD).
- Pain control (epidural or PCA).
- Fluid balance.
Days 4-7Ward
- Mobilize to wheelchair.
- Resume bowel regimen.
- Check fitting of wheelchair (back support might need modification).
Day 7+Discharge
- 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.
Evidence Base
GMFCS Level and Scoliosis Risk
Persson-Bunke M et al • J Bone Joint Surg Am (2012)
Key Findings:
- Total population survey of CP children
- Risk of scoliosis correlates with GMFCS
- GMFCS IV and V have 50-90% risk
- GMFCS I and II have low risk
Clinical Implication: Surveillance must be aggressive for GMFCS IV/V.
Limitation: Registry data
Operative vs Nonoperative Management
Bridwell KH et al • J Bone Joint Surg Am (1999)
Key Findings:
- Surgery reliably corrects deformity and pelvic obliquity
- Non-op patients had progression of curve and loss of sitting ability
- Complication rate high in surgical group but satisfaction higher
Clinical Implication: Surgery works for the deformity. Natural history is progressive deformity.
Limitation: Retrospective
DMD: Early Surgery
Kennedy JD et al • Arch Dis Child (1995)
Key Findings:
- Surgery when Cobb greater than 20 deg and FVC greater than 40%
- Prevented severe deformity
- Slowed rate of pulmonary decline
- Increased longevity compared to historical controls
Clinical Implication: In DMD, do NOT wait for the curve to get bad. Fix it while the lungs allow.
Limitation: Cohort study
Infection Rates in NMS
Sponseller PD et al • J Bone Joint Surg Am (2000)
Key Findings:
- Infection rate ~10-15% in NMS vs less than 1% in AIS
- Risk factors: Incontinence, poor nutrition, lack of fascia
- Gram negative organisms more common
Clinical Implication: Counsel parents about the high infection risk (1 in 10).
Limitation: Retrospective
Unit Rod vs Screws
Tsirikos AI et al • Spine (2008)
Key Findings:
- Pedicle screws offer better correction of pelvic obliquity than unit rods
- Lower rate of pseudarthrosis with screws
- Higher cost but better radiographic outcome
Clinical Implication: Pedicle screws / S2AI have largely replaced the Unit Rod.
Limitation: Retrospective comparison
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
EXAMINER
"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."
VIVA Q&A
Q1:What are the goals of surgery for this patient?
The primary goals are to: 1. Level the pelvis (correct pelvic obliquity) to prevent pressure sores. 2. Restore a straight spine centered over the pelvis to improve sitting balance. 3. Maximize thoracic volume (prevent contact between ribs and pelvis). 4. Ease nursing care.
Q2:What levels would you fuse?
Long fusion is standard. Upper instrumented vertebra (UIV) typically T2 or T3 to prevent proximal kyphosis. Lower instrumented vertebra (LIV) must be into the Pelvis (Iliac/S2AI) to correct and control the pelvic obliquity.
Q3:What pre-operative nutritional marker would you check?
Albumin and Pre-albumin/Transferrin. Albumin less than 3.5 g/dL is a significant risk factor for wound dehiscence and deep infection. Optimising nutrition (often via PEG) is mandatory before surgery.
KEY POINTS TO SCORE
Goals: Sitting Balance, Pelvic Level
Fusion: T2 to Pelvis
Nutrition is critical
COMMON TRAPS
✗Stopping fusion at L5 (will fail)
✗Ignoring nutrition
LIKELY FOLLOW-UPS
"How do you assess pelvic obliquity on X-ray?"
VIVA SCENARIOStandard
EXAMINER
"A 14-year-old boy with Duchenne Muscular Dystrophy (DMD) has a 25 degree scoliosis. His FVC is 50% predicted."
VIVA Q&A
Q1:The curve is only 25 degrees. Do you observe?
No. In DMD, the recommendation is early surgery once the curve is definitely progressive (greater than 20-30 degrees) and while pulmonary function is still permissible (FVC greater than 30-40%). Waiting for the curve to reach 50 degrees usually means the lungs have deteriorated to a point where surgery is too risky.
Q2:What specific cardiac pathology must be checked?
DMD cardiomyopathy. They develop dilated cardiomyopathy. An Echocardiogram and cardiology clearance are strict requirements. Low Ejection Fraction may contraindicate surgery.
Q3:What anesthesia consideration is critical in myopathic patients?
Malignant Hyperthermia is a risk. Depolarizing muscle relaxants (Succinylcholine) are contraindicated as they can trigger massive rhabdomyolysis and hyperkalemia.
KEY POINTS TO SCORE
DMD = Early Surgery
Lung function window
Cardiomyopathy check
COMMON TRAPS
✗Treating DMD like AIS (waiting for 50 deg)
✗Forgetting the heart
LIKELY FOLLOW-UPS
"What anesthesia precautions are needed in myopathic patients?"
VIVA SCENARIOAdvanced
EXAMINER
"You performed a T2-Pelvis fusion on a CP patient. 3 weeks post-op, the wound is dehiscencing and draining serous fluid."
VIVA Q&A
Q1:What is your management steps?
This is a deep infection until proven otherwise. 1. Admit. 2. Bloods (CRP/ESR/WCC). 3. Contrast CT (check for deep collection). 4. Urgent surgical washout (Debridement). 5. Deep cultures. 6. IV antibiotics. VAC dressing may be needed. Do NOT just give oral antibiotics.
Q2:The hardware is exposed. Do you remove it?
Not initially. If the fusion is not solid (it won't be at 3 weeks), removing hardware leads to loss of correction and 'floppy' spine. We attempt to retain hardware with aggressive debridement and VAC therapy. Removal is a last resort for chronic persistent biofilm infection.
Q3:What organism are you worried about in NMS?
Polymicrobial and Gram Negative organisms (Pseudomonas, E. Coli) are much more common in NMS (from bowel/incontinence) compared to Staph Aureus/Cutibacterium in AIS.
KEY POINTS TO SCORE
Aggressive washout
Retain hardware if possible
Gram negative coverage
COMMON TRAPS
✗Antibiotics without washout
✗Premature hardware removal
LIKELY FOLLOW-UPS
"How does nutritional status impact this complication?"
MCQ Practice Points
DMD Threshold
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).
Fusion Levels
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.
Infection Risk
Q: How does the infection rate of NMS surgery compare to AIS? A: It is significantly higher (5-15% vs less than 1%).
Malignant Hyperthermia
Q: Which neuromuscular condition is associated with Malignant Hyperthermia? A: Duchenne Muscular Dystrophy (and Central Core Disease). Succinylcholine is contraindicated.
Spondylolisthesis Association
Q: Is spondylolisthesis common in NMS? A: No, spondylolisthesis is associated with walking (repetitive stress). NMS patients usually have long kyphoscoliotic C-curves.
Cord Tethering
Q: In which NMS condition is cord tethering most common? A: Myelomeningocele (Spina Bifida). Almost all have tethered cords.
Australian Context
Epidemiology:
- Managed in tertiary pediatric spine units (e.g. Westmead, SCH, RCH).
- High burden of care, NDIS funding essential for postoperative equipment.
Referral:
- Early referral to spinal clinic for monitoring.
- "Hip Surveillance" programs often pick up the scoliosis.
High-Yield Exam Summary
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