Adolescent Idiopathic Scoliosis - Progressive Curve
CIM Case: Adolescent Idiopathic Scoliosis - Progressive Curve
Clinical Scenario
Patient: 12-year-old girl Presentation: Referred with progressive right thoracic scoliosis, initially observed with 25° curve 18 months ago, now 50° on follow-up X-rays Relevant history: No back pain, no neurological symptoms, no history of trauma or infection, premenarchal, healthy otherwise, family history of scoliosis (aunt had spinal fusion) Examination findings:
- Visible right thoracic rib prominence on forward bend (Adams test positive)
- Right shoulder higher than left
- Left waist crease more prominent than right
- No café-au-lait spots or axillary freckling
- No midline dimples, hairy patches, or skin abnormalities
- Full range of spinal motion
- Neurological examination completely normal (power 5/5, sensation intact, reflexes 2+ symmetrical)
- No limb length discrepancy
- No foot deformity
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| N/A | - | - | Bloods not routinely required for AIS |
Imaging
Image 1: Standing PA and Lateral Whole Spine Radiographs
Radiological features:
- Right thoracic curve with Cobb angle 50° (T5-T12)
- Apex at T8-9
- Curve pattern: Lenke 1 (main thoracic)
- Lumbar modifier: C (lumbar curve crosses CSVL)
- Thoracic sagittal modifier: N (normal kyphosis 10-40°)
- Risser sign: 1 (early ossification of iliac apophysis)
- Triradiate cartilage: Closed
- No congenital anomalies
- No significant coronal imbalance
Image 2: MRI Whole Spine (if obtained)
MRI indications in AIS (atypical features):
- Left thoracic curve (right-sided is typical)
- Juvenile onset (<10 years)
- Rapid progression (>1° per month)
- Abnormal neurological signs
- Male patient with AIS
- Significant pain
- Would obtain in this patient due to surgical planning
Questions & Model Answers
What are the risk factors for curve progression in AIS and how do you assess skeletal maturity?
Describe the Lenke classification and how it guides surgical planning.
When is surgery indicated, and what is your preoperative workup?
Describe your surgical technique for posterior spinal fusion.
What if you lose neuromonitoring signals during surgery?
What are the complications of AIS surgery and how would you counsel the family?
Key Teaching Points
Pattern Recognition
This pattern suggests AIS requiring surgery:
- Adolescent female with thoracic scoliosis
- Risser 0-2 (significant growth remaining)
- Curve magnitude ≥45-50°
- Documented progression despite observation/bracing
- No underlying cause identified (idiopathic)
- Normal neurological examination
Red Flags for Non-Idiopathic Scoliosis:
| Red Flag | Consider |
|---|---|
| Left thoracic curve | Syringomyelia, Chiari |
| Juvenile onset (<10 years) | Intraspinal pathology |
| Male with scoliosis | Higher rate of underlying cause |
| Back pain | Tumour, infection, spondylolisthesis |
| Neurological signs | Cord pathology |
| Rapid progression (>1°/month) | Neurological cause |
| Café-au-lait spots | Neurofibromatosis |
Critical Management Points
- Risser sign guides prognosis - Risser 0-1 has significant growth and progression risk
- Lenke classification guides surgery - determines which curves to fuse
- MRI is mandatory preoperatively - exclude intraspinal pathology
- Neuromonitoring is mandatory - SSEP and MEP monitoring
- LIV selection is critical - wrong choice leads to adding-on or imbalance
- Balance over correction - a balanced spine is more important than maximal correction
Common Examiner Follow-ups
Q: "Why not brace this patient?"
Bracing indications:
- Risser 0-2 with significant growth remaining
- Curve 25-45°
- Skeletally immature
This patient has a 50° curve - bracing will NOT reduce the curve, only potentially slow progression. With a curve this size, surgery is indicated. Bracing is for curves 25-45° in growing children to prevent progression to surgical threshold.
Q: "What is the natural history of untreated AIS?"
| Curve at Maturity | Natural History |
|---|---|
| <30° | Unlikely to progress in adulthood |
| 30-50° | May progress 0.5-1° per year |
| >50° | Will progress 1-2° per year |
| >70° thoracic | Pulmonary function affected |
Untreated 50° curves will progress throughout life, potentially causing:
- Cosmetic deterioration
- Chronic back pain
- Reduced pulmonary function (if thoracic curve increases)
- Reduced quality of life
Q: "What about anterior surgery?"
Anterior spinal fusion (ASF) for AIS:
- Historically used for thoracolumbar/lumbar curves
- Advantages: Fewer levels fused, better correction in coronal plane
- Disadvantages: Thoracotomy/thoracoabdominal approach, pulmonary morbidity, chest tube, longer recovery
Modern Practice: Posterior-only surgery with pedicle screws achieves excellent correction for almost all curve types. Anterior surgery is rarely needed now with modern instrumentation.
Q: "How do you decide the lowest instrumented vertebra?"
LIV Selection Criteria:
- Stable vertebra - touched by CSVL
- Neutral vertebra - no rotation
- Horizontal on bending films - disc below should open symmetrically
For Lenke 1C curves, the LIV is typically L1-L3 depending on flexibility. Ending too proximally risks adding-on (curve progression below fusion). Ending too distally sacrifices lumbar motion unnecessarily.
Related Topics
- Congenital Scoliosis
- Neuromuscular Scoliosis
- Scheuermann's Kyphosis
- Spinal Cord Injury
- Pedicle Screw Placement
- Spinal Fusion Techniques