import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Within sacral canal and exiting through dorsal foramina **Protection**: Careful dissection over sacral ala, avoid violation of sacral canal unless decompression indicated, identify fracture fragments compressing neural elements **Location**: Crosses sacral ala at S1 pedicle level, 15-20mm from midline **Protection**: Identify transverse process and ala junction, stay subperiosteal, avoid aggressive lateral retraction during L5 pedicle screw placement **Location**: Exits greater sciatic notch at piriformis superior border, crosses iliac wing medially **Protection**: Stay posterior and superior to sciatic notch during iliac dissection, control bleeding with bone wax or bipolar, avoid penetrating anterior cortex with iliac screws **Location**: Anterior to sacrum between periosteum and presacral fascia **Protection**: Maintain subperiosteal dissection, avoid anterior cortex breach during S2AI screw placement, have hemostatic agents available, consider preoperative embolization if displaced fracture **Location**: Often compromised by high-energy trauma, edema, degloving **Protection**: Delay surgery 5-7 days if significant swelling, use modified incisions for open wounds, avoid excessive undermining, consider staged approach with external fixation first ## Indications for Lumbopelvic Fixation ### Absolute Indications - **U-type sacral fractures** (bilateral vertical + horizontal component) - **H-type sacral fractures** (bilateral vertical fractures through sacral foramina) - **Spinopelvic dissociation** with vertical shear instability - **Denis Zone III bilateral fractures** with neurological deficit - **Roy-Camille Type III** transverse fractures at L5-S1 level ### Relative Indications - **Unilateral Denis Zone III** fracture with neurological deficit requiring decompression - **Lumbosacral kyphotic deformity** greater than 20° post-injury - **Bilateral Denis Zone II** fractures with vertical displacement greater than 1cm - **Failed nonoperative management** of U-type or H-type fractures - **Polytrauma patients** requiring early mobilization with unstable sacral fractures ### Contraindications **Absolute** - Active infection at surgical site - Medical instability precluding prolonged surgery - Severe osteoporosis preventing adequate screw purchase **Relative** - Extensive soft tissue injury requiring delay - Neurologically intact patient with minimally displaced fracture - Advanced age with low functional demand ## Preoperative Planning ### Imaging Requirements - **AP pelvis radiograph** - assess pelvic ring disruption and vertical displacement - **Inlet view** - evaluate posterior displacement and sacral kyphosis - **Outlet view** - assess cranial-caudal displacement and transverse fracture - **CT scan with 3D reconstruction** - define fracture pattern, canal compromise - **MRI sacrum** - evaluate neural compression, disc injury, soft tissue injury ### Classification Systems **Denis Classification** (Sacral Fracture Zones) - Zone I: Lateral to foramina (sacral ala) - 6% neurological injury - Zone II: Through foramina - 28% neurological injury - Zone III: Central canal involvement - 57% neurological injury **Roy-Camille Classification** (Transverse Sacral Fractures) - Type I: Flexion injury, distal fragment flexed - Type II: Extension injury, distal fragment extended - Type III: Comminuted, associated with spinopelvic dissociation **AO/OTA Classification** - 61-C3: Complete pelvic ring disruption with sacral involvement - 12-C: Posterior arch injury with spinopelvic dissociation ### Templating - Measure sacral alar width and iliac corridor on axial CT - Plan pedicle screw trajectory at L4/L5 based on pedicle dimensions - Template S2AI screw trajectory: insertion point, angulation, length - Identify safe zones avoiding L5 and S1 nerve roots - Plan reduction maneuvers for kyphotic deformity ## Surgical Anatomy ### Bony Landmarks **Lumbar Spine** - **L4 pedicle**: 10-15mm transverse width, 15-20mm height, medial angulation 10-15° - **L5 pedicle**: 15-20mm width, 20-25mm height, medial angulation 25-35° - **L5 transverse process**: attachment for iliolumbar ligament, lateral boundary **Sacrum** - **S1 pedicle**: largest sacral pedicle, 20-25mm diameter - **S1 dorsal foramen**: 15-20mm from midline, landmark for S2AI entry - **Sacral ala**: lateral mass between L5-S1 facet and SI joint - **Sacral promontory**: anterior superior edge, risk for L5 nerve root **Pelvis** - **PSIS**: entry point for traditional iliac screws - **AIIS**: target for iliac screw trajectory - **Iliac corridor**: safe zone between inner and outer tables, 8-15mm wide - **Greater sciatic notch**: inferior boundary, contains superior gluteal vessels ### Soft Tissue Anatomy **Posterior Elements** - **Thoracolumbar fascia**: superficial, middle, deep layers - **Paraspinal muscles**: multifidus (medial), longissimus, iliocostalis (lateral) - **Ligamentous complex**: supraspinous, interspinous, ligamentum flavum **Neural Structures** - **Cauda equina**: terminates L1-L2, fills sacral canal - **L5 nerve root**: exits L5-S1 foramen, crosses sacral ala - **Sacral nerve roots**: S1-S5 exit through anterior and posterior foramina - **Coccygeal plexus**: S4-Co1, supplies bladder, bowel, sexual function ### Biomechanical Principles **Instability Patterns** - **Vertical shear**: requires longitudinal fixation spanning injury - **Rotational instability**: requires cross-connectors between bilateral rods - **Kyphotic deformity**: lever arm for progressive collapse without reduction **Fixation Constructs** - **L4-iliac fixation**: for high sacral fractures or osteoporotic bone - **L5-iliac fixation**: standard construct for most spinopelvic dissociations - **S2AI screws**: 30-40% stronger pullout than PSIS iliac screws - **Cross-connectors**: increase torsional rigidity by 45% ## Patient Positioning **Positioning Strategy**: Prone on radiolucent Jackson table or OSI frame. Free abdomen to reduce epidural venous pressure and blood loss. Padding at chest and iliac crests. Arms tucked or on arm boards. Ensure genitalia free in males. All pressure points padded. - Abdominal compression increases venous bleeding - Excessive hip flexion limits sacral reduction - Inadequate padding causes pressure ulcers - Eye/facial injuries from improper headrest ## Operative Steps ### Step 1: Skin Incision and Exposure **Technique**: Midline incision from L4 spinous process to sacral hiatus (approximately 18-22cm). Deepen through skin and subcutaneous tissue with electrocautery. Incise thoracolumbar fascia in midline. Use Cobb elevator to elevate paraspinal muscles subperiosteally from spinous processes bilaterally. **Dissection Plane**: Stay strictly subperiosteal to avoid muscle ischemia and denervation. Identify L4, L5 spinous processes by palpation - L4 intersects iliac crest line. Cauterize muscular branches of lumbar arteries close to bone. - Superficial wound infection risk 8-12% in trauma cases - Excessive undermining causes skin necrosis - Injury to cutaneous nerves causes painful neuromas at incision ### Step 2: Exposure of L4/L5 Pedicles **Technique**: Expose lamina, facets, and transverse processes of L4 and L5. Use Penfield elevator to define pedicle boundaries. L4 pedicle: entry 2-3mm lateral to midpoint of facet line. L5 pedicle: entry at junction of transverse process, superior articular process, and lateral pars. **Pedicle Landmarks**: L5 transverse process is short and stubby. Identify by tracing facet line caudally. Mamillary process marks superior pedicle boundary. Avoid excessive lateral dissection to protect L5 nerve root crossing sacral ala. - L5 nerve root injury from lateral dissection or retractor placement - Facet joint violation compromises future fusion options - Dural tear if dissection extends too far medially ### Step 3: Exposure of Sacral Ala and Iliac Crest **Technique**: Extend subperiosteal dissection laterally over sacral ala to SI joint. Elevate multifidus and erector spinae from posterior sacrum. Expose PSIS bilaterally. If using S2AI screws, identify S1 dorsal foramen (palpable dimple 15-20mm from midline). **Sacral Ala Dissection**: Stay posterior and superior. The superior gluteal artery exits the greater sciatic notch inferior to PIIS. Maintain continuous subperiosteal elevation. Use sponge sticks to control venous ooze from fracture surfaces. - Superior gluteal artery injury causes massive venous bleeding - Anterior cortex penetration risks presacral vessels - Inadequate exposure leads to malpositioned screws ### Step 4: Fracture Pattern Assessment **Technique**: Palpate sacral fracture lines. Assess displacement and instability with gentle manual pressure. Identify comminution. Use intraoperative fluoroscopy: AP pelvis, inlet, outlet views. Evaluate canal compromise requiring decompression. **Fracture Reduction Assessment**: Measure lumbosacral kyphosis on lateral fluoroscopy (normal 30-45°). Assess vertical displacement on AP and outlet views. Plan reduction maneuvers before instrumentation. May need temporary Schanz pins for manipulation. - Missed injury patterns lead to inadequate fixation - Excessive manipulation causes neurological deterioration - Undisplaced fracture propagation from handling ### Step 5: L4 and/or L5 Pedicle Screw Placement **Technique**: Use anatomic landmarks or image guidance. Create starting point with burr or awl. Palpate pedicle with curved probe (gear shift technique). Confirm 4-wall integrity with ball-tip probe. Tap, measure depth. Insert polyaxial pedicle screws (6.5-7.5mm diameter, 40-50mm length). Confirm position with fluoroscopy and neurophysiological monitoring. **L5 Pedicle Technique**: Convergent medial trajectory 25-35°. Caudal angulation 10-15° to follow endplate. Deeper insertion (45-50mm) provides better purchase. Bicortical purchase not necessary and risks anterior vessel injury. - Nerve root injury 1-3% risk with medial or inferior breach - Dural tear with medial pedicle wall violation - Screw loosening if inadequate purchase in osteoporotic bone - Anterior cortex penetration risks iliac vessels ### Step 6: Iliac Screw Insertion (Traditional Technique) **Technique**: Entry point at PSIS, 1-2mm lateral to lateral edge. Trajectory: 40-45° lateral in axial plane, 20-30° caudal in sagittal plane toward AIIS. Use fluoroscopy to confirm corridor position between inner and outer tables. Drill with 3.2mm bit followed by 4.0mm bit. Measure depth (usually 70-90mm). Tap and insert 7.5-8.5mm diameter screw. **Iliac Corridor Navigation**: Inlet view shows medial-lateral position. Outlet view shows superior-inferior position. Oblique view visualizes full screw trajectory. Feel resistance changes: hard cortex at entry, softer cancellous bone, hard anterior cortex. Do not penetrate anterior cortex. - Superior gluteal artery injury if trajectory too inferior/medial - Iliac crest fracture with excessive force during tapping - Prominent hardware at PSIS causes pain, requires later removal 20-30% - Screw cutout through outer table with incorrect trajectory ### Step 7: S2-Alar-Iliac (S2AI) Screw Placement (Preferred Technique) **Technique**: Entry point 1-2mm lateral to S1 dorsal foramen on sacral slope. Starting trajectory: 40-45° lateral, 20-30° caudal. Palpate S1 and S2 pedicle boundaries. Use guidewire under fluoroscopy. Cannulated drill over wire. Measure depth (90-120mm for bicortical purchase at AIIS). Insert cannulated 7.5-8.5mm screw. **S2AI Advantages Over Traditional Iliac Screws**: (1) Starting point closer to midline allows easier rod contouring, (2) 30-40% greater pullout strength, (3) Lower prominence and pain, (4) Reduced removal rate (5% vs 25%), (5) Crosses SI joint for additional stability, (6) Can be placed percutaneously. - L5 nerve root risk if trajectory too superior/medial - S1 nerve root risk if starting point too medial - Anterior cortex penetration risks presacral vessels - Inadequate length provides suboptimal fixation ### Step 8: Rod Contouring and Placement **Technique**: Measure distance between screw heads. Contour 5.5mm or 6.0mm titanium or cobalt-chromium rods to restore lumbar lordosis and correct sacral kyphosis. Insert rods into screw heads, usually starting caudal and working cephalad. Use rod holders and persuaders. Achieve provisional reduction. **Rod Contouring Strategy**: Pre-bend rods to restore normal lumbosacral alignment (lumbar lordosis 40-60°, sacral slope 30-45°). Create smooth curve without sharp bends (stress risers). S2AI screws require less rod offset than traditional iliac screws, easier to connect. - Excessive force during rod insertion can displace screws - Sharp rod bends create fatigue failure points - Incomplete seating prevents solid connection ### Step 9: Fracture Reduction **Technique**: Use rods as reduction tools. Compress to close vertical fracture gaps. Apply extension force to correct kyphotic deformity. May use temporary Schanz pins in sacrum for manipulation. Confirm reduction with fluoroscopy: AP pelvis (vertical displacement), inlet (posterior displacement), outlet (cranial-caudal displacement), lateral (kyphosis). **Reduction Maneuvers**: For vertical displacement: compression along rod. For kyphosis: extend lumbosacral junction (may need prone positioning adjustment). For rotation: de-rotation around bilateral fixation points. Accept up to 5-10mm residual displacement if neurologically intact. - Neurological deterioration from manipulation - Screw pullout with excessive force - Propagation of undisplaced fracture lines - Overcorrection into hyperlordosis ### Step 10: Set Screw Tightening **Technique**: Provisionally tighten all set screws. Recheck reduction and alignment. Definitively tighten set screws sequentially (not alternating) to approximately 8-10 Nm torque. Confirm no screw toggle or rod slippage. **Tightening Sequence**: Start at apex of construct (L5 or S1). Work toward ends (L4 and iliac/S2AI). This prevents locking in malalignment. Recheck reduction after each screw tightened. Final torque 8-10 Nm using torque-limiting driver. - Screw head fracture with excessive torque - Construct failure if undertightened - Rod slippage if not properly seated before tightening ### Step 11: Cross-Connector Application **Technique**: Measure distance between bilateral rods. Apply cross-connectors at two levels (typically proximal and distal). Tighten cross-connector screws. Confirm construct rigidity by gentle manual stress. **Cross-Connector Biomechanics**: Increases torsional rigidity by 45%. Essential for bilateral unstable injuries. Place one connector near top of construct (L4-L5) and one near sacrum. Offset connectors axially for maximum rigidity. Consider multiple connectors for long constructs. - Prominent connectors cause discomfort - Inadequate tightening allows micromotion - Excessive length prevents skin closure ### Step 12: Supplemental SI Screw Fixation **Technique**: If anterior pelvic ring unstable or inadequate lumbopelvic fixation, place percutaneous SI screws. Entry point: lateral sacrum below iliac crest. Trajectory: perpendicular to fracture plane, parallel to S1 superior endplate. Confirm position in inlet, outlet, and lateral views. Insert 7.3mm or 8.0mm cannulated screw across SI joint into S1 body. **SI Screw Indications**: (1) Unilateral fixation requiring contralateral SI stabilization, (2) Comminuted sacral ala fracture, (3) Osteoporotic bone requiring augmentation, (4) Vertical shear pattern requiring compression across SI joint. Start SI screws before lumbopelvic fixation for easier trajectory. - L5 nerve root injury if trajectory too superior (must stay parallel to S1 endplate) - Anterior cortex penetration risks iliac vessels - Screw too short provides inadequate purchase - Dysmorphic sacrum (25% prevalence) requires careful templating ### Step 13: Neural Decompression (If Indicated) **Technique**: If neurological deficit present, perform laminectomy of involved sacral segments. Use Kerrison rongeurs and high-speed burr. Remove bone fragments compressing nerve roots. Decompress central canal and lateral recesses. Preserve posterior tension band if possible. Confirm decompression by visualizing dura and nerve roots. **Decompression Timing**: Acute neurological deficit (less than 8 hours): emergent decompression. Subacute (8-72 hours): urgent decompression improves outcomes. Chronic (greater than 2 weeks): limited recovery potential, decompress for pain. Incomplete cauda equina has better prognosis than complete. - Dural tear requires meticulous repair (high CSF leak risk in sacrum) - Nerve root injury from manipulation - Destabilization if excessive bone removed - Persistent deficit despite adequate decompression ### Step 14: Fluoroscopic Confirmation **Technique**: Obtain AP pelvis, inlet, outlet, and lateral radiographs. Confirm: (1) Screw positions within bone, (2) Adequate reduction, (3) No hardware impingement on neural structures, (4) Restored alignment. Perform final neurophysiological monitoring checks. **Fluoroscopic Assessment Checklist**: AP: screw trajectories, vertical displacement reduced. Inlet: posterior displacement corrected, iliac/S2AI screws in corridor. Outlet: cranial-caudal displacement reduced, transverse sacral screws below L5-S1. Lateral: lumbosacral kyphosis corrected, no anterior screw penetration. - Missed screw malposition causes postoperative neurological deficit - Incomplete reduction leads to progressive deformity - Inadequate documentation for medicolegal purposes ### Step 15: Wound Closure **Technique**: Copious irrigation (3-6 liters with bacitracin or chlorhexidine). Place drains if extensive dead space (controversial). Close fascia with #1 absorbable suture in interrupted or running fashion. Close subcutaneous layer with 2-0 absorbable suture. Skin closure with staples or subcuticular suture. Apply sterile dressing. **Closure Considerations**: Fascia closure essential for strength. Avoid excessive tension (use relaxing incisions if needed). Drains may reduce hematoma but increase infection risk - author preference varies. Subcuticular closure improves cosmesis. Negative pressure wound therapy for high-risk wounds. - Wound dehiscence if fascia not properly closed - Deep infection risk 2-8% in trauma setting - Seroma/hematoma if inadequate hemostasis - Skin necrosis from excessive tension ## Complication Management ## Risk Factors for Complications **Patient Factors** - Diabetes mellitus (3x infection risk) - Smoking (2x nonunion risk) - Obesity (BMI greater than 35: 2.5x wound complication risk) - Osteoporosis (increased screw loosening) - Polytrauma/ISS greater than 25 (increased medical complications) **Surgical Factors** - Operative time greater than 4 hours - Estimated blood loss greater than 1000mL - Extensive soft tissue stripping - Inadequate fracture reduction - Suboptimal screw placement **Injury Factors** - Open fracture or degloving injury - Neurological deficit at presentation - Severe comminution - Associated visceral injuries - Delay to fixation greater than 3 weeks (scarring, malunion) ## Immediate Postoperative Management **First 24-48 Hours** - ICU or monitored bed for polytrauma patients - Neurological checks every 2 hours: motor, sensory, bowel/bladder - DVT prophylaxis: chemical (enoxaparin 40mg SC daily) + mechanical (SCDs) - Pain control: multimodal analgesia (PCA, oral narcotics, acetaminophen, gabapentin) - Foley catheter if bowel/bladder dysfunction, otherwise early removal - Incentive spirometry and chest physiotherapy - Early mobilization to chair with physical therapy once hemodynamically stable **Drains** - Remove when output less than 30mL per 8-hour shift (typically 24-48 hours) - Monitor for excessive drainage suggesting CSF leak **Imaging** - Postoperative AP pelvis and lateral lumbosacral radiographs in recovery room - Confirm hardware position and alignment - Obtain CT scan if neurological deficit or concern for malposition ## Mobilization Protocol **Weight-Bearing** - **Weeks 0-6**: Touch-down weight-bearing (TDWB) on crutches or walker - **Weeks 6-12**: Partial weight-bearing (50%) if radiographic healing - **Weeks 12+**: Weight-bearing as tolerated if fracture union progressing **Rationale**: Early weight-bearing causes cyclic loading and potential screw loosening. Sacral fractures heal slowly (12-16 weeks) due to limited soft tissue envelope and high forces. **Exceptions** - Polytrauma requiring early mobilization: accept higher hardware failure risk - S2AI fixation with excellent purchase: may advance WBAT at 8 weeks - Osteoporotic patients: extend protected weight-bearing to 16 weeks ## Bracing **LSO (Lumbosacral Orthosis)** - Indications: Comminuted fractures, osteoporotic patients, questionable fixation stability - Duration: 12 weeks or until radiographic union - Type: Rigid TLSO with thigh extension for vertical shear injuries **Bracing Controversy** - No high-level evidence supporting efficacy after rigid internal fixation - May improve patient comfort and compliance with weight-bearing restrictions - Author preference varies ## Follow-Up Schedule **2 Weeks** - Wound check, suture/staple removal - Assess for infection, dehiscence, hematoma - Repeat neurological exam - Radiographs: AP pelvis, lateral lumbosacral **6 Weeks** - Clinical exam: pain, functional status - Radiographs: assess for hardware loosening, fracture alignment - Advance to partial weight-bearing if healing appropriately - Begin gentle range of motion exercises **12 Weeks** - Radiographs ± CT: assess fracture healing - Advance to full weight-bearing if union evident - Discontinue brace if used - Begin strengthening exercises **6 Months** - Assess functional outcome - Radiographs: confirm union - Address persistent symptoms: hardware prominence, SI pain, neurological deficit **12 Months** - Final assessment for union, alignment, functional recovery - Discuss hardware removal if prominent and symptomatic (after confirmed union) ## Physical Therapy Protocol **Phase 1 (Weeks 0-6): Protection** - Goals: Protect fixation, prevent complications, gentle ROM - Activities: Bed mobility, transfers, TDWB gait training, ankle pumps, quad sets - Restrictions: No hip flexion greater than 90°, no lumbar flexion/rotation **Phase 2 (Weeks 6-12): Progressive Loading** - Goals: Advance weight-bearing, improve ROM, begin strengthening - Activities: WBAT gait training, stationary bike, pool therapy (if wound healed), core stabilization - Restrictions: No running, jumping, twisting **Phase 3 (Weeks 12-24): Strengthening** - Goals: Return to activities of daily living, improve strength and endurance - Activities: Progressive resistance exercises, proprioception training, functional activities - Return to work: Sedentary 12 weeks, light duty 16 weeks, heavy labor 24 weeks **Phase 4 (Months 6-12): Return to Full Activity** - Goals: Return to unrestricted activities - Activities: Sport-specific training, advanced strengthening - Restrictions: High-impact activities (contact sports) may be permanently limited ## Long-Term Monitoring **Annual Follow-Up Years 1-5** - Assess for late complications: hardware failure, SI arthritis, lumbosacral degeneration - Radiographs if symptomatic - Functional outcome scores: Oswestry Disability Index, SF-36, Majeed pelvic score **Hardware Removal** - Indications: Prominent painful hardware, patient request, infection - Timing: Minimum 18-24 months after surgery (ensure solid union) - Technique: Remove iliac/S2AI screws first. Retain pedicle screws/rods unless symptomatic. - Risk: Recurrent instability less than 5% with solid fusion ## References 1. Denis F, Davis S, Comfort T. Sacral fractures: an important problem. Retrospective analysis of 236 cases. Clin Orthop Relat Res. 1988;227:67-81. PMID: 3338224. [Classic paper defining Denis classification zones and neurological injury rates] 2. Roy-Camille R, Saillant G, Gagna G, Mazel C. Transverse fracture of the upper sacrum. Suicidal jumper's fracture. Spine. 1985;10(9):838-845. PMID: 4089659. [Original description of Roy-Camille classification and lumbopelvic fixation technique] 3. Bellabarba C, Schildhauer TA, Vaccaro AR, Chapman JR. Complications associated with surgical stabilization of high-grade sacral fracture dislocations with spino-pelvic instability. Spine. 2006;31(11 Suppl):S80-S88. PMID: 16685241. [Comprehensive analysis of complications in 75 patients with spinopelvic dissociation] 4. Schildhauer TA, Bellabarba C, Nork SE, Barei DP, Routt ML Jr, Chapman JR. Decompression and lumbopelvic fixation for sacral fracture-dislocations with spino-pelvic dissociation. J Orthop Trauma. 2006;20(7):447-457. PMID: 16891935. [Landmark study of lumbopelvic fixation technique and outcomes in 40 patients] 5. O'Brien DP, Luchette FA, Pereira SJ, et al. Pelvic fracture in the elderly is associated with increased mortality. Surgery. 2002;132(4):710-715. PMID: 12407358. [Important epidemiology demonstrating mortality risk and need for aggressive management] 6. Gupta MC, Levine AM, Bosse MJ. Treatment of lumbosacropelvic dissociation associated with sacral fractures. Spine. 2004;29(11):E227-E231. PMID: 15167672. [Case series demonstrating technique and outcomes of lumbopelvic fixation] 7. Gardner MJ, Routt ML Jr. Transiliac-transsacral screws for posterior pelvic stabilization. J Orthop Trauma. 2011;25(6):378-384. PMID: 21577073. [Technical guide for transiliac-transsacral screw placement with radiographic landmarks] 8. Shillingford JN, Laratta JL, Park PJ, Fischer CR, Lehman RA Jr. Human versus robot: a propensity-matched analysis of the accuracy of free-hand versus robotic guidance in placement of S2-alar-iliac (S2AI) screws. Spine. 2018;43(21):E1297-E1304. PMID: 29689040. [Modern study of S2AI screw accuracy and safety] 9. Chang TL, Sponseller PD, Kebaish KM, Fishman EK. Low profile pelvic fixation: anatomic parameters for sacral alar-iliac fixation versus traditional iliac fixation. Spine. 2009;34(5):436-440. PMID: 19247163. [Anatomic study defining S2AI corridor and comparing to traditional iliac screws] 10. Kuklo TR, Potter BK, Ludwig SC, Anderson PA, Lindsey RW, Vaccaro AR. Radiographic measurement techniques for sacral fractures consensus statement of the Spine Trauma Study Group. Spine. 2006;31(5):E118-E126. PMID: 16508541. [Standardized measurement techniques for sacral fracture assessment and reduction evaluation]

Spinopelvic Dissociation - Lumbopelvic Fixation

Spinopelvic Dissociation - Lumbopelvic Fixation