import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Posterior in spinal canal, 2-3mm anterior to lamina **Protection**: Avoid laminar violation during dissection, confirm all pedicle screws extra-canal with probe (all 4 walls), monitor SSEP/MEP during correction **Location**: Exit through neural foramina below each pedicle, 2-5mm inferior to pedicle screw trajectory **Protection**: Probe pedicle inferior wall to confirm no breach, avoid foraminal dissection, careful with L5 screws (steep trajectory) **Location**: Aorta 15-25mm anterior to vertebral body, vena cava 10-20mm anterior on right **Protection**: Limit screw depth to measured pedicle length minus 5mm, fluoroscopy confirms no anterior breach, probe anterior wall resistance **Location**: Enters spinal canal T9-L2 (left side 80%), supplies anterior spinal cord **Protection**: Maintain MAP >85 mmHg during correction, avoid aggressive osteotomies T9-L2, monitor SSEPs (ischemia indicator) **Location**: Exits greater sciatic notch 2-3cm from PSIS, runs between iliac tables posteriorly **Protection**: Iliac screw trajectory aims ANTERIOR (toward AIIS), not posterior, fluoroscopy confirms trajectory, avoid excessive posterior angulation ## Patient Positioning **Position**: Prone on Jackson table or chest rolls - Arms alongside body or on arm boards at <90° abduction (shoulder contractures) - Head in neutral or slight extension (avoid excessive flexion - airway compromise) - Chest rolls allow abdomen to hang free (reduces IVC compression, decreases venous bleeding) **Critical Padding Points** (DMD has fragile skin, osteoporotic bones): - Forehead (avoid globe pressure) - Chest (chest rolls, avoid rib compression fractures) - Iliac crests (prominent, high pressure risk) - Knees and anterior shins - Arms and elbows **Monitoring Setup**: - Neuromonitoring (SSEP, MEP) - note MEPs often poor/absent in DMD - Foley catheter (long surgery, fluid monitoring) - Arterial line (anticipated blood loss, tight BP control needed) - Core temperature monitoring **Positioning Pearl**: Check abdomen hangs free (reduces venous engorgement → less blood loss). DMD patients have fragile skin (pressure ulcer risk), osteoporotic ribs (fracture risk), contractures (limited ROM). Meticulous padding prevents complications in 5-8 hour surgery. ## Surgical Exposure **Incision**: Posterior midline from T2 spinous process to sacrum/upper buttock (40-50cm) - Incise skin, subcutaneous tissue (fatty in DMD - minimal muscle), posterior fascia - Plan for subcutaneous closure as main strength layer (muscle atrophy limits fascial closure) **Subperiosteal Dissection** (T2 to pelvis): - Use Cobb elevator to strip paraspinal muscles off spinous processes, laminae, transverse processes bilaterally - Expose entire posterior elements: spinous processes, laminae, facets, transverse processes, pars - At pelvis: expose sacrum and posterior iliac wings bilaterally (for iliac screw insertion) - Place self-retaining retractors (Taylor, Schofield) - Excessive blood loss (long dissection, osteoporotic bone oozes, fatty tissue bleeds) - Use thrombin-soaked sponges, bipolar cautery, bone wax - Inadequate exposure leads to missed fusion levels or screw malposition ## Thoracic Pedicle Screws (T2-T12) **Entry Point**: Junction of transverse process and superior articular process, 2-3mm lateral to facet - Thoracic pedicles small (4-6mm), angulated medially - Use high-speed burr to create pilot hole **Trajectory**: Converge medially 10-15°, aim toward vertebral body center - Probe all 4 walls with ball-tip probe (medial wall breach = cord injury) - Insert polyaxial screws (4.5-5.5mm diameter, 35-45mm length) **Critical Principle**: Screws at EVERY level (no skipped levels in osteoporotic DMD bone) **Thoracic Screw Pearl**: Medial breach is most dangerous (spinal cord injury). Probe all 4 walls before screw insertion. Use fluoroscopy/navigation if available. T2-T4 pedicles smallest (highest malposition risk). Polyaxial screws allow rod contouring flexibility. ## Lumbar Pedicle Screws (L1-L5) **Entry Point**: Junction of transverse process and superior facet, slightly more lateral than thoracic - Lumbar pedicles larger (8-15mm) - Trajectory converges 10-15° medially **L5 Screws** (special considerations): - Steep trajectory (45-50° caudal angulation) - Aim toward sacral promontory - Check with lateral fluoroscopy (screw should parallel superior endplate) ## Sacral and Iliac Fixation **S1 Screws**: - Entry: S1 lateral mass (junction of facet and ala) - Trajectory: Anterior and lateral toward promontory - Large screws (7.5-8.5mm, 45-55mm) - Bicortical purchase if possible **Iliac Screws** (MANDATORY in neuromuscular scoliosis): - Entry: PSIS or 1-2cm caudal - Trajectory: PSIS → AIIS (between inner and outer iliac tables) - Long screws (7.5-9.5mm diameter, 70-100mm length) - Fluoroscopy confirms trajectory (parallel to iliac crest on AP, caudal on lateral) - Bilateral iliac screws required - Iliac screw medial breach → iliac vessels (catastrophic bleeding) - Superior gluteal artery injury (exits sciatic notch posteriorly) - S1 anterior breach → presacral vessels - Inadequate pelvic fixation → pseudarthrosis, sacral screw pullout ## Posterior Column Releases **Indications**: Stiff neuromuscular curves (typically all DMD cases) **Technique**: 1. **Facetectomies**: Complete removal of facet joints at 4-6 levels around apex - Remove inferior and superior articular processes - Allows curve to "unlock" and correct 2. **Ligamentum Flavum Resection**: - Remove yellow ligament at release levels - Preserve dura (avoid tear) - Control epidural bleeding (bipolar, thrombin-soaked Gelfoam) 3. **Smith-Petersen Osteotomy** (if needed): - V-shaped posterior opening that closes during correction - Hinges at anterior disc - Usually sufficient for neuromuscular curves (less rigid than congenital) **Release Pearl**: Posterior releases usually sufficient in DMD (curves less rigid than congenital). Avoid PSO/VCR (too much cord stretch risk, unnecessary). Facetectomies at 4-6 apical levels allow adequate correction. Monitor epidural bleeding carefully. ## Rod Contouring and Insertion **Rod Selection**: 5.5-6.0mm cobalt-chrome or titanium - Cobalt-chrome: stiffer (better for long constructs) - Titanium: lighter, MRI compatible **Contouring**: - Pre-contour to desired alignment: thoracic kyphosis 35-45°, lumbar lordosis 40-50° - Gradual bends (avoid sharp angles - stress risers) - Contour for entire construct (T2 → pelvis) **Insertion**: - Insert concave rod first (typically easier) - Thread rod into screw heads (start cranial or caudal) - Use reduction tabs on polyaxial screws - Provisionally tighten set screws - Insert convex rod similarly ## Deformity Correction **Techniques** (gradual and stepwise): 1. **Cantilever Correction**: Apply force to rod, reduce screws progressively 2. **Compression/Distraction**: Compress convex side, distract concave side 3. **Derotation**: Apply rotational force to rods (correct rib hump) 4. **Translation**: Shift apical vertebrae toward midline **Goals**: - Coronal curve to <20-30° (don't need perfect correction) - Restore sagittal balance - Maintain lumbar lordosis - Preserve sitting balance - Neurologic injury (spinal cord ischemia from stretch/distraction) - Monitor SSEP/MEP continuously - changes mandate STOP - Release correction if SSEP changes don't recover - Overcorrection causes flat back syndrome, junctional kyphosis - Screw pullout during correction (osteoporotic bone) ## Decortication **Areas to Decorticate** (T2 to pelvis): - Laminae - Facet joints (exposed after facetectomies) - Transverse processes (thoracic) - Pars interarticularis (lumbar) - Sacral ala - Posterior iliac wings **Technique**: - High-speed burr removes outer cortex - Expose bleeding cancellous bone - Large surface area critical (extensive fusion bed) **Decortication Pearl**: Bleeding bone indicates good preparation. DMD has poor bone quality (osteoporosis) - need maximal surface area for fusion. Irrigate during burring (prevents thermal injury to dura/cord). Generous decortication prevents pseudarthrosis. ## Bone Grafting **Graft Options** (DMD has limited autograft): 1. **Autograft**: Limited availability (minimal local bone from spinous processes/facets) - Posterior iliac crest if needed (limited volume, increases morbidity) 2. **Allograft**: PRIMARY graft source - Morselized cancellous allograft (freeze-dried or fresh-frozen) - Large volume available, no donor site morbidity 3. **Bone Graft Substitutes**: - DBM (demineralized bone matrix) - Synthetic grafts (calcium phosphate, hydroxyapatite) 4. **BMP** (controversial): - Consider in DMD (osteoporotic bone, poor fusion potential) - Off-label in spine, potential complications (seroma, ectopic bone) **Application**: Pack graft generously over entire decorticated fusion bed ## Final Fixation **Set Screw Tightening**: - Torque-limiting driver (80-120 in-lbs) - Tighten cranial to caudal, bilateral - Check all screws secure **Cross-Links**: - Apply 2-3 transverse connectors between rods - Locations: proximal thoracic, mid-thoracic, lumbosacral - Increase rotational stability, prevent rod migration **Iliac Connectors**: - Offset connectors link iliac screws to main rods - Iliac screws sit lateral to rod trajectory ## Hemostasis and Closure **Hemostasis** (critical in DMD - high blood loss): - Bipolar cautery for soft tissue - Bone wax for bone bleeding - Thrombin-soaked Gelfoam, Floseal - Copious irrigation with antibiotic solution **Drain Placement**: - 2-4 large-bore Jackson-Pratt drains bilaterally - High output expected (reduces hematoma) **Closure Layers**: 1. Thoracolumbar fascia (if adequate tissue - often minimal in DMD) 2. Subcutaneous layer (0 or 2-0 Vicryl) - main closure strength 3. Skin: Running absorbable subcuticular or interrupted nylon 4. Consider VAC dressing if high wound tension - Ongoing bleeding → hematoma (cord compression risk) - Wound dehiscence (poor tissue quality, high tension) - Unrecognized dural tear → CSF leak, meningitis - DMD has minimal muscle for layered closure - subcutaneous is key layer ## ICU Management (ALL DMD patients) **Respiratory Care** (highest priority): - Overnight ventilation often needed - Extubate when awake, strong cough, good tidal volumes - BiPAP if marginal (aids respiration, prevents atelectasis) - Aggressive pulmonary toilet: incentive spirometry, chest PT, frequent suctioning - Early mobilization (sit day 1-2) **Pain Control**: - Multimodal: PCA opioids, gabapentin, acetaminophen - Consider epidural or intrathecal morphine **Cardiac Monitoring**: - Continuous telemetry (cardiomyopathy risk) - Arrhythmia surveillance **Neurologic Surveillance**: - Frequent neuro exams (q2-4h initially) - Check motor/sensory all extremities - Watch for delayed deficits (epidural hematoma) **Drain Management**: - Remove when output <30 mL/8hr (typically day 3-5) **Mobilization**: - Sit day 1-2 - Transfer to wheelchair day 2-3 (most DMD patients wheelchair-dependent) - No brace needed (instrumented fusion stable) **Imaging**: - AP/lateral spine X-rays day 1 (confirm instrumentation intact, alignment maintained) **Post-op Pearl**: Respiratory complications are most common (20-30%). Aggressive pulmonary care prevents failure. ICU stay 1-3 days minimum (longer if respiratory support needed). Most discharge 5-10 days if uncomplicated. Complications occur in 20-40% of cases. ## Long-term Follow-up **Imaging Schedule**: - Discharge - 6 weeks - 3 months - 6 months - 1 year - Then yearly until skeletal maturity - Every 1-2 years after maturity **Monitor For**: - Infection (fever, wound drainage, elevated CRP/ESR) - Pseudarthrosis (pain, loss of correction, nonunion on X-ray/CT) - Instrumentation failure (screw pullout, rod fracture) - Proximal junctional kyphosis (increasing kyphosis above instrumentation) **Functional Goals**: - Improved sitting balance (primary goal) - Maintained pulmonary function - Quality of life preservation - Prevent progression to wheelchair-bound state (if ambulatory) ## References 1. Suk SI, Lee SM, Chung ER, et al. Determination of distal fusion level with segmental pedicle screw fixation in single thoracic idiopathic scoliosis. Spine. 2003;28(5):484-491. 2. Bridwell KH, Lenke LG, Baldus C, Blanke K. Major intraoperative neurologic deficits in pediatric and adult spinal deformity patients. Incidence and etiology at one institution. Spine. 1998;23(3):324-331. 3. Yasui N, Aoki R, Nakazawa T, et al. Major complications of spinal surgery for patients with muscular dystrophy or spinal muscular atrophy: a multicenter study. J Orthop Sci. 2016;21(4):504-508. 4. Bridwell KH, Baldus C, Iffrig TM, et al. Process measures and patient/parent evaluation of surgical management of spinal deformities in patients with progressive flaccid neuromuscular scoliosis (Duchenne's muscular dystrophy and spinal muscular atrophy). Spine. 1999;24(13):1300-1309. 5. Altiok H, Finlayson C, Hassani S, et al. Neuromuscular scoliosis surgical outcomes in patients with Duchenne muscular dystrophy: a 20-year experience. J Pediatr Orthop. 2017;37(2):e94-e99. 6. Garg S, Engel AJ, Grimm JC, et al. Pelvic fixation in neuromuscular scoliosis: comparison of different techniques. Spine. 2007;32(15):E423-E428. 7. Barsdorf AI, Sproule DM, Kaufmann P. Scoliosis surgery in children with neuromuscular disease: findings from the US National Inpatient Sample, 1997 to 2003. Arch Neurol. 2010;67(2):231-235. 8. Shapiro F, Sethna N, Colan S, et al. Spinal fusion in Duchenne muscular dystrophy: a multidisciplinary approach. Muscle Nerve. 1992;15(5):604-614. 9. Sengupta DK, Mehdian SH, McConnell JR, et al. Pelvic or lumbar fixation for the surgical management of scoliosis in Duchenne muscular dystrophy. Spine. 2002;27(18):2072-2079. 10. Miller DJ, Vitale MG, Skaggs DL, et al. Comparison of iliac screw versus S-alar-iliac screw pelvic fixation in patients with neuromuscular scoliosis. J Child Orthop. 2013;7(4):319-323.

Muscular Dystrophy Scoliosis - Posterior Spinal Fusion (T2-Pelvis)

Muscular Dystrophy Scoliosis - Posterior Spinal Fusion (T2-Pelvis)