# 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 **Risk Factors for Progression:** | Factor | Higher Risk | Lower Risk | |--------|-------------|------------| | **Skeletal maturity** | Risser 0-1, open triradiate | Risser 4-5 | | **Curve magnitude** | >25° | <20° | | **Curve pattern** | Double major curves | Single lumbar | | **Age at diagnosis** | Younger (<12 years) | Older (>14 years) | | **Menarche status** | Premenarchal | >2 years postmenarchal | | **Gender** | Female | Male | **Skeletal Maturity Assessment:** **Risser Sign (Iliac Apophysis Ossification):** | Risser | Description | Growth Remaining | |--------|-------------|------------------| | **0** | No ossification | Significant (>2 years) | | **1** | 0-25% lateral ossification | Significant | | **2** | 25-50% ossification | Moderate (1-2 years) | | **3** | 50-75% ossification | Limited | | **4** | 75-100% ossification | Minimal | | **5** | Fusion to ilium | Complete | **Sanders Skeletal Maturity Staging (Hand X-ray):** - Stages 1-3: Peak height velocity not yet reached - Stages 4-5: Peak height velocity occurring - Stages 6-7: Decelerating growth - Stage 8: Skeletal maturity **This Patient:** Risser 1, premenarchal, 50° curve, documented progression - VERY HIGH RISK. Multiple factors indicate surgery is needed now. > **Consultant Tip:** Sanders staging is more accurate than Risser for predicting peak height velocity. A 12-year-old Risser 1 female still has ~3-4 years of growth. **Lenke Classification Components:** **1. Curve Type (1-6):** | Type | Curve Pattern | Primary Curve | |------|---------------|---------------| | **1** | Main Thoracic | Thoracic only structural | | **2** | Double Thoracic | Proximal and main thoracic structural | | **3** | Double Major | Thoracic and lumbar structural | | **4** | Triple Major | Proximal thoracic, main thoracic, lumbar all structural | | **5** | Thoracolumbar/Lumbar | TL/L only structural | | **6** | TL/L - Main Thoracic | TL/L structural, thoracic minor | **Structural Criteria:** - Thoracic: Kyphosis T2-T5 ≥20°, or bending correction <25° or <25° residual - Lumbar: Bending correction <25° or <25° residual **2. Lumbar Modifier (A, B, C):** | Modifier | CSVL Relationship | Description | |----------|-------------------|-------------| | **A** | CSVL between L1-L4 pedicles | Minimal lumbar curve | | **B** | CSVL touches L1-L4 apical pedicle | Moderate lumbar curve | | **C** | CSVL completely medial to L1-L4 | Significant lumbar curve | **3. Sagittal Thoracic Modifier:** | Modifier | T5-T12 Kyphosis | Description | |----------|-----------------|-------------| | **-** | <10° | Hypokyphotic | | **N** | 10-40° | Normal | | **+** | >40° | Hyperkyphotic | **This Patient:** Lenke 1CN - Type 1: Main thoracic only - Lumbar C: Significant lumbar curve - Sagittal N: Normal kyphosis **Surgical Implication:** Fuse thoracic curve only (selective thoracic fusion) - lumbar curve should improve spontaneously. Lowest instrumented vertebra (LIV) is critical. > **Consultant Tip:** Lenke classification guides which curves to fuse. Non-structural curves spontaneously improve when the structural curve is corrected. **Surgical Indications in AIS:** | Indication | Threshold | Rationale | |------------|-----------|-----------| | **Curve magnitude** | ≥45-50° | Natural history: progression in adulthood | | **Progressive curve** | >5°/year | Will reach surgical threshold | | **Failed bracing** | Progression despite brace | Observation no longer viable | | **Patient preference** | Cosmetic concern | After counselling | **This Patient:** 50° curve with documented progression (25° to 50° in 18 months) - meets surgical criteria. **Preoperative Workup:** **Imaging:** - Standing PA and lateral whole spine X-rays (Cobb angles, Risser) - Bending films (flexibility, structural vs non-structural curves) - MRI whole spine (mandatory before surgery - exclude intraspinal abnormality) **MRI Abnormalities to Exclude:** - Chiari malformation - Syringomyelia - Tethered cord - Intraspinal tumour - Diastematomyelia **Clinical Assessment:** - Complete neurological examination - Trunk balance assessment - Shoulder height - Limb lengths - Pulmonary function tests (if thoracic curve >70°) **Preoperative Counselling:** | Topic | Discussion | |-------|------------| | **Goals** | Stop progression, improve cosmesis, maintain balance | | **Correction** | Typically 60-70% correction achievable | | **Fusion levels** | Which segments will be fused (loss of motion) | | **Risks** | Neurological (<0.5%), infection (1-2%), nonunion, implant failure | | **Recovery** | 4-6 weeks off school, 3-6 months no sport, 1 year full recovery | > **Consultant Tip:** MRI is mandatory before AIS surgery. Up to 10% may have occult neural axis abnormality. Left thoracic curves have highest rate of underlying pathology. **Surgical Technique for Posterior Spinal Fusion:** **Positioning:** - Prone on Jackson table or padded frame - Eyes protected, arms carefully positioned - All pressure points padded - Check baseline neuromonitoring (SSEPs and MEPs) **Approach:** - Midline incision - Subperiosteal exposure to tips of transverse processes - Identify levels with intraoperative X-ray **Fusion Levels (Lenke 1 curve):** - Upper Instrumented Vertebra (UIV): Usually T4 or T5 - Lower Instrumented Vertebra (LIV): Stable and neutral vertebra - LIV Selection: Touched by CSVL, neutral rotation, horizontal on bending films **Pedicle Screw Insertion:** **Thoracic Screws:** - Entry point: Junction of transverse process and superior facet - Trajectory: Medial-to-lateral (straight ahead or slight convergence) - Smaller pedicle diameter (5.5-6.5mm screws typical) **Lumbar Screws:** - Entry point: Intersection of transverse process, pars, mammillary process - Trajectory: Medial convergence ~10-15° - Larger pedicles (6.5-7.5mm screws) **Technique:** 1. Create entry point with awl 2. Probe pedicle with gear shift (pedicle finder) 3. Sound walls with ball-tip probe - medial breach most dangerous 4. Tap (undersized) 5. Insert screw, confirm position **Reduction and Correction:** - Rod contouring to desired sagittal profile - Sequential rod insertion and correction - Derotation manoeuvres - In situ bending - Compression/distraction as needed **Fusion:** - Decorticate laminae and transverse processes - Local bone graft from facet osteotomies - Consider allograft supplementation **Closure:** - Haemostasis - No drain typically (enhanced recovery) - Layered closure > **Consultant Tip:** Neuromonitoring is mandatory. Check SSEPs and MEPs after positioning, after exposure, after each correction manoeuvre, and at closure. Any change = wake-up test or reverse manoeuvre. **Neuromonitoring Signal Loss - Emergency Protocol:** **Types of Neuromonitoring:** | Type | What It Monitors | Pathway | |------|------------------|---------| | **SSEPs** | Sensory function | Dorsal columns | | **MEPs** | Motor function | Corticospinal tracts | | **EMG** | Nerve root irritation | Individual roots | **Alert Criteria:** - SSEP: >50% amplitude decrease or >10% latency increase - MEP: Complete loss or >80% amplitude decrease **Algorithm for Signal Loss:** **Step 1: Rule Out Technical Causes** - Check electrodes - Check anaesthetic agents (propofol, avoid volatile agents) - Check blood pressure (MAP >65 mmHg) - Check patient temperature - Check position (no pressure on brachial plexus, etc.) **Step 2: Reverse Last Manoeuvre** - Remove last screw - Release correction - Remove rod - Reduce distraction **Step 3: Optimise Physiology** - Increase MAP to 80-90 mmHg - Transfuse if Hb <80 - Warm patient - Correct acidosis **Step 4: Wait and Reassess** - Allow 15-20 minutes - Repeat monitoring - If signals return → proceed cautiously - If signals do not return → consider Stagnara wake-up test **Step 5: Stagnara Wake-Up Test** - Reduce anaesthesia - Ask patient to move feet - Confirms clinical motor function - If no movement → remove all instrumentation and abort **Step 6: If Deficit Confirmed** - Consider high-dose methylprednisolone (controversial) - Urgent postoperative MRI - Document thoroughly > **Consultant Tip:** Most signal changes are reversible with prompt intervention. Have a checklist ready. The anaesthetist is your ally - ensure they avoid agents that affect monitoring. **Complications of Posterior Spinal Fusion for AIS:** **Neurological Complications:** | Complication | Incidence | Notes | |--------------|-----------|-------| | **Spinal cord injury** | 0.3-0.5% | Neuromonitoring reduces risk | | **Nerve root injury** | 1-2% | Usually recovers | | **Dural tear** | 1-2% | Primary repair | **Implant-Related:** | Complication | Incidence | Management | |--------------|-----------|------------| | **Screw malposition** | 5-15% | Usually asymptomatic, revise if symptomatic | | **Rod fracture** | 1-3% | Revise if symptomatic, observe if healed | | **Proximal junctional kyphosis** | 5-10% | May require extension of fusion | | **Adding-on distally** | 3-5% | Extension of fusion | **Infection:** | Type | Incidence | Management | |------|-----------|------------| | **Superficial** | 1-2% | Antibiotics | | **Deep** | 1-2% | Debridement, keep hardware if early, antibiotics | **Other Complications:** - Blood loss requiring transfusion: 5-15% - Pseudarthrosis: 1-5% - Flatback syndrome (loss of lumbar lordosis) - Chronic pain - Pulmonary complications (rare) **Counselling Points for Family:** **Expected Outcomes:** - Curve correction typically 60-70% - Stop progression - Improved cosmesis (shoulder balance, waist crease, rib prominence) - High satisfaction rates (>90%) **What to Expect Postoperatively:** - Hospital stay 4-7 days - Walking day 1-2 postoperatively - Return to school 4-6 weeks - Light activity 3 months - Full activity (including sports) 6-12 months - No contact sports involving spinal loading for 12 months **Long-Term:** - Hardware typically stays permanently - Most patients report no significant functional limitations - Long-term back pain similar to general population - Pregnancy and delivery normal - Adjacent segment disease uncommon in adolescents > **Consultant Tip:** Parents are most concerned about paralysis. Explain that with modern neuromonitoring and technique, the risk is less than 1 in 200, and most changes are detected and reversible. --- ## 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 1. **Risser sign guides prognosis** - Risser 0-1 has significant growth and progression risk 2. **Lenke classification guides surgery** - determines which curves to fuse 3. **MRI is mandatory preoperatively** - exclude intraspinal pathology 4. **Neuromonitoring is mandatory** - SSEP and MEP monitoring 5. **LIV selection is critical** - wrong choice leads to adding-on or imbalance 6. **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: 1. **Stable vertebra** - touched by CSVL 2. **Neutral vertebra** - no rotation 3. **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