import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Main blood supply to femoral head** arising from MFCA. Run along posterior-superior femoral neck. **Highest AVN risk** if damaged by posterior screw malposition. Protection: verify center-center on lateral view, avoid posterior cortex penetration. **Subchondral bone penetration** causes chondrolysis (acute cartilage necrosis). Presents 2-12 months post-op with stiffness and joint space narrowing. Protection: screw tip 5mm from subchondral bone on **both** AP and lateral views. **Multiple passes** through physis increases trauma and chondrolysis risk. **Inadequate thread engagement** allows continued slip. Protection: single-pass technique, ALL threads across physis, partially threaded screw for compression. **Emerges medial to ASIS**, courses to anterolateral thigh. Risk with lateral thigh incision for percutaneous approach. Protection: incision distal to vastus ridge (more inferior), blunt dissection through muscle. **Absolute Indications:** - All SUFE regardless of severity (prevents further slip) - Unstable SUFE: emergency surgery within 24 hours - Stable SUFE: semi-urgent surgery within days **Prophylactic Contralateral Pinning Indications:** - Age less than 10 years (60% bilateral risk) - Endocrine/metabolic cause: - Hypothyroidism (50% bilateral) - Renal osteodystrophy (60% bilateral) - Growth hormone deficiency (30-50% bilateral) - Unable to reliably follow-up (remote, non-compliant) - Symptomatic contralateral hip without visible slip **Contraindications to In Situ Pinning:** - None absolute (even severe slips pinned in situ by most) - Relative: severe slip greater than 50 degrees in unstable acute SUFE at experienced centre - consider modified Dunn procedure **Essential Imaging:** - AP pelvis: both hips (20-40% bilateral) - Frog-lateral both hips: best view for posterior slip - Klein's line assessment: should intersect lateral epiphysis - Southwick angle measurement (frog-lateral) **Classification:** | Classification | Definition | AVN Risk | |---------------|------------|----------| | **Loder Stable** | Can weight-bear ± crutches | Less than 5% | | **Loder Unstable** | Cannot weight-bear at all | 20-50% | | **Southwick Mild** | Angle less than 30 degrees | Low | | **Southwick Moderate** | Angle 30-50 degrees | Moderate | | **Southwick Severe** | Angle greater than 50 degrees | High | **Screw Selection:** - Partially threaded cannulated screw 7.0-7.3mm diameter - Length typically 80-110mm in adolescents - Thread length: must exceed epiphyseal thickness (10-20mm) **Timing:** - Unstable SUFE: theatre within 24 hours (orthopaedic emergency) - Stable SUFE: theatre within 3-5 days **Procedure-Specific Risks:** - AVN of femoral head: 0.5-5% (stable), 20-50% (unstable) - Chondrolysis: 1-5% (joint stiffness, early arthritis) - Screw penetration requiring revision: 1-3% - Contralateral slip if not pinned: 20-40% - Slip progression: 1-3% - FAI in adulthood: 30-70% (severity dependent) - Need for screw removal (after physeal closure) - Need for further surgery (osteotomy if severe) **General Surgical Risks:** - Infection: less than 1% - DVT/PE: rare in adolescents - Femoral nerve palsy: less than 0.5% (traction-related) **Specific Points to Discuss:** - Weight-bearing restrictions (6 weeks) - Activity restrictions (3-6 months) - Long-term monitoring until skeletal maturity - Risk of early-onset arthritis (severe slips) - Possible contralateral hip involvement **Essential Equipment:** - Radiolucent fracture table (Jackson or OSI) - C-arm fluoroscopy unit - Cannulated screw set (7.0mm or 7.3mm partially threaded) - Guidewires (2.4mm or 2.8mm) - Cannulated drill bit (matching screw diameter) - Depth gauge - Power drill **Patient Setup:** - Supine on fracture table - Affected leg in traction boot - Hip: 10-15 degrees flexion, 10-20 degrees abduction, neutral rotation - Contralateral leg abducted (scissor position) - Well-padded perineal post - C-arm positioned between legs for biplanar imaging **Critical Check:** Confirm ability to obtain perfect AP and lateral views BEFORE prepping ### Step 1: Patient Positioning and Imaging Setup Position supine on radiolucent fracture table. Apply **gentle** longitudinal traction through traction boot - DO NOT attempt forceful reduction (risks AVN). Hip position: 10-15 degrees flexion, 10-20 degrees abduction, neutral rotation (avoid internal rotation). Contralateral leg abducted widely for C-arm access. **Critical:** Verify ability to obtain TRUE AP (femoral neck perpendicular to beam, lesser trochanter barely visible medially) and TRUE lateral (neck in profile, greater trochanter posterior) views before prepping. **EXAM KEY:** Positioning for SUFE is NOT about reduction - it's about visualization. Gentle traction only. Forceful manipulation propagates unstable slips and shears retinacular vessels causing AVN. For unstable acute SUFE, use cross-table lateral (shoot-through) rather than frog-lateral to avoid further displacement. - NEVER forcefully reduce stable chronic slips - Gentle traction only for unstable acute slips - Cross-table lateral for unstable SUFE (frog-lateral risks further displacement) - Protect genitals from perineal post pressure ### Step 2: Fluoroscopic Assessment and Entry Point Planning Before incision, plan screw trajectory on fluoroscopy: **AP View Analysis:** - Identify physeal line - Confirm Klein's line abnormality - Plan entry point: anterolateral femoral neck, 1-2cm distal to vastus ridge **Lateral View Analysis:** - Assess severity of posterior slip - Plan trajectory to center of epiphysis - Account for posterior displacement **Entry Point Marking:** - Place guidewire on skin surface - Adjust until overlying planned entry point on both AP and lateral - Mark skin **Screw Length Estimation:** - Measure from entry point to center of epiphysis - Typical length 80-100mm in adolescents **EXAM KEY:** Center-center positioning is the SINGLE MOST IMPORTANT technical step. Screw must bisect the femoral head exactly in the center on BOTH AP and lateral views. Posterior malposition has highest AVN risk (damages posterior retinacular vessels). Anterior malposition damages anterior retinacular vessels. Superior/inferior malposition causes eccentric loading and early physeal closure. ### Step 3: Percutaneous Approach Make 1-2cm stab incision at marked entry point on anterolateral thigh. Divide skin and subcutaneous tissue. Bluntly spread vastus lateralis muscle fibres with haemostat. Palpate anterolateral femoral neck bone surface. **Limited Open Alternative (if obese or revision):** - 2-3cm longitudinal incision - Incise fascia lata - Split vastus lateralis (safe - nerve enters posteriorly) - Direct palpation of entry point **Percutaneous vs Open Decision:** Percutaneous is standard for primary SUFE in non-obese patients with good fluoroscopy. Limited open preferred if: obese (thick soft tissues), revision surgery, or aspiration needed (unstable SUFE - decompress haemarthrosis to reduce tamponade effect on blood supply). ### Step 4: Guidewire Insertion Advance guidewire (2.4mm or 2.8mm depending on screw system) under continuous biplanar fluoroscopy: **Technique:** 1. Start perpendicular to bone at entry point 2. Angle toward center of epiphysis 3. Advance 2-3mm → check AP → advance 2-3mm → check lateral 4. Repeat iteratively across physis into epiphysis 5. Final position: center-center, perpendicular to physis, tip 5mm from subchondral bone **Common Errors:** - Too posterior (lateral view): highest AVN risk - redirect anteriorly - Too anterior: anterior vessel injury risk - Too superior/inferior: eccentric loading, early physeal closure - Inadequate depth: threads won't engage epiphysis - **Minimize passes:** each physeal pass increases chondrolysis risk - **Avoid posterior:** posterior retinacular vessels are main blood supply - **Monitor subchondral distance:** avoid joint penetration - **Hold guidewire stable:** prevents advancement with screw ### Step 5: Screw Length Measurement With guidewire optimally positioned: - Slide depth gauge over guidewire until seated against bone - Read calibrated depth marks - Select partially threaded cannulated screw (7.0mm or 7.3mm) - Thread length must exceed epiphyseal thickness (typically 16-32mm) **Thread Engagement Critical:** ALL screw threads must cross the physis into the epiphysis. If smooth shank (not threads) crosses the physis, there is NO fixation of the epiphysis and slip can progress. Partially threaded screws compress the physis - threads pull epiphysis toward metaphysis while smooth shank slides through cortex. ### Step 6: Screw Insertion **Drilling (if needed):** - Use cannulated drill over guidewire if bone dense - Drill to 5-10mm short of final length - Avoid plunging into epiphysis **Screw Placement:** - Thread partially threaded cannulated screw over guidewire - Assistant holds guidewire stable (hemostat on wire prevents advancement) - Advance under fluoroscopy until all threads cross physis - Compress by continuing to tighten (physis closes) - Avoid overtightening (strips soft epiphyseal bone) ### Step 7: Final Fluoroscopic Confirmation **AP View Checklist:** - ☐ Screw bisects center of femoral head - ☐ All threads across physis in epiphysis - ☐ Tip 5mm from subchondral bone - ☐ No superior/inferior cortex penetration **Lateral View Checklist:** - ☐ Screw bisects center of femoral head - ☐ Perpendicular or minimally oblique to physis - ☐ Tip 5mm from subchondral bone - ☐ NO posterior cortex penetration (critical!) - ☐ No anterior cortex penetration **Dynamic Test:** - Gently internally rotate and flex hip - Screw should remain stable (no toggling or backing out) ### Step 8: Guidewire Removal - Grasp guidewire with needle driver - Steady screw head to prevent backing out - Withdraw guidewire smoothly - Reconfirm screw position on fluoroscopy ### Step 9: Prophylactic Contralateral Pinning Decision **Consider Prophylactic Pinning If:** - Age less than 10 years (up to 60% bilateral) - Endocrine/metabolic cause identified - Unable to reliably follow-up - Symptomatic contralateral hip - Physeal widening on contralateral side **If Pinning:** - Reposition C-arm to contralateral hip - Identical technique (easier as anatomy normal) - Complete one side fully before starting other **Prophylactic Pinning Controversy:** 20-40% overall risk of contralateral slip if not pinned. Arguments FOR: prevents second surgery, earlier return to activities. Arguments AGAINST: 60-80% never slip (overtreatment), surgical risk. **Consensus:** individualize - definitely pin if age less than 10 or metabolic cause; close monitoring acceptable for older children without risk factors. ### Step 10: Wound Closure - Irrigate with saline - Percutaneous: skin closure only (3-0 or 4-0 absorbable subcuticular) - Limited open: fascia lata (2-0 Vicryl), subcutaneous (3-0 Vicryl), skin - Sterile dressing - Remove from traction table with log roll (avoid twisting) ### Step 11: Post-operative Care **Immediate (24-48 hours):** - Neurovascular checks (femoral nerve palsy rare from traction) - Bed rest for unstable SUFE (allows physeal stabilization) - Mobilize same day for stable SUFE **Weight-Bearing Protocol:** - Touch weight-bearing (TWB) with crutches for 6 weeks - Progress to full weight-bearing at 6 weeks if radiographs stable - Activity restrictions: no running/jumping/contact sports for 3-6 months **Follow-up Schedule:** | Timing | Assessment | |--------|------------| | 2 weeks | Wound, X-ray both hips | | 6 weeks | X-ray, progress to FWB if stable | | 3 months | X-ray, expand activities | | Q3-6 months | Until physeal closure (18-24 months) | | Annually | Until skeletal maturity | ### Step 12: Screw Removal **Timing:** 3-6 months after complete physeal closure **Rationale:** Femoral neck continues to grow in girth after physeal closure - if screw left in place, tip progressively approaches/enters joint causing chondrolysis **Technique:** - Same positioning (fracture table, biplanar fluoroscopy) - Percutaneous over screw head - Unscrew and remove - Protected weight-bearing 6 weeks if large screw or long dwelling time ## References 1. Loder RT, Richards BS, Shapiro PS, et al. Acute slipped capital femoral epiphysis: the importance of physeal stability. J Bone Joint Surg Am. 1993;75(8):1134-40. 2. Southwick WO. Osteotomy through the lesser trochanter for slipped capital femoral epiphysis. J Bone Joint Surg Am. 1967;49(5):807-35. 3. Ziebarth K, Zilkens C, Spencer S, et al. Capital realignment for moderate and severe SCFE using a modified Dunn procedure. Clin Orthop Relat Res. 2009;467(3):704-16. 4. Aronsson DD, Loder RT, Breur GJ, Weinstein SL. Slipped capital femoral epiphysis: current concepts. J Am Acad Orthop Surg. 2006;14(12):666-79. 5. Zaltz I, Baca G, Kim YJ, et al. Complications associated with the modified Dunn procedure for SCFE. J Pediatr Orthop. 2014;34(7):661-7. 6. Lehmann CL, Arons RR, Loder RT, Vitale MG. The epidemiology of slipped capital femoral epiphysis: an update. J Pediatr Orthop. 2006;26(3):286-90. 7. Sankar WN, Vanderhave KL, Matheney T, et al. The modified Dunn procedure for unstable slipped capital femoral epiphysis: a multicenter perspective. J Bone Joint Surg Am. 2013;95(7):585-91. 8. Loder RT, Skopelja EN. The epidemiology and demographics of slipped capital femoral epiphysis. ISRN Orthop. 2011;2011:486512. 9. Imhäuser G. Late results of Imhäuser's osteotomy for slipped capital femoral epiphysis. Z Orthop Ihre Grenzgeb. 1977;115(5):716-25. 10. Kocher MS, Bishop JA, Weed B, et al. Delay in diagnosis of slipped capital femoral epiphysis. Pediatrics. 2004;113(4):e322-5.

SUFE Pinning - In Situ Fixation with Single Central Screw

SUFE Pinning - In Situ Fixation with Single Central Screw