import { OnePagerSummary, ContentSection, ExamWarning, InfoCardGrid, InfoCard, EvidenceCard, ComparisonTable, VivaScenario, MnemonicCard, ExamCheatSheet, Tab, Tabs } from '@/components/mdx' The **anterior retroperitoneal approach to the lumbar spine** provides direct access to the L4-5 and L5-S1 disc spaces for **anterior lumbar interbody fusion (ALIF)**, disc replacement, vertebral body procedures, and vascular surgery. The approach is performed through a retroperitoneal dissection (NOT transperitoneal - bowel remains within peritoneal sac), mobilizing the great vessels (aorta, vena cava, common iliac vessels) laterally to expose the anterior longitudinal ligament (ALL) and disc space. The anterior approach offers SUPERIOR fusion biology compared to posterior approaches (PLIF/TLIF): (1) **Larger graft surface area** - anterior disc space is 30-40% larger than posterior (more bone graft contact, better fusion 90-95% vs 80-85% posterior - Christensen 2018), (2) **Biomechanically advantageous** - anterior column is under COMPRESSION during standing (versus posterior under tension), so anterior grafts are loaded in compression (optimal for bone healing), and (3) **Preserved posterior structures** - posterior longitudinal ligament (PLL), facets, and musculature remain intact (maintains tension band, reduces adjacent segment degeneration compared to posterior fusion). The CRITICAL anatomic structures at risk are: (1) **Vascular structures** (aorta, inferior vena cava, common iliac vessels - 2-8% injury risk, MOST COMMON complication), left common iliac vein crosses midline at L5-S1 (MOST vulnerable - injured in 70% of vascular complications - Inamasu 2005), (2) **Superior hypogastric plexus** (sympathetic plexus for ejaculation - 0.5-5% retrograde ejaculation risk), plexus lies 2-5cm ANTERIOR to L5-S1 disc on midline (injured by bilateral dissection or midline violation - Tiusanen 1995: unilateral dissection 0.5%, bilateral 4-5%), (3) **Psoas muscle** (lateral border of exposure - iliohypogastric and ilioinguinal nerves run within psoas, injury causes groin numbness), and (4) **Ureter** (crosses iliac vessels at pelvic brim - mobilized with peritoneum, rarely injured if retroperitoneal plane maintained). **Australian Clinical Context:** ALIF is increasingly performed in Australia for single-level degenerative lumbar disease (L4-5 and L5-S1), with AOANJRR spine registry showing increasing utilization over posterior approaches (PLIF/TLIF) due to superior fusion rates (90-95% vs 80-85%) and lower reoperation rates (8% at 5 years vs 12-15% posterior). The anterior approach can be performed by spine surgeons alone (most common in Australia) or with vascular surgeon assistance (available at major trauma centers but NOT routinely required - vascular surgeon assists with complex revisions, prior vascular surgery, or obesity). Retrograde ejaculation counseling is MANDATORY for all male patients (medicolegal requirement in Australia - documented consent must address sexual function risks). Medicare covers ALIF for degenerative disc disease with instability (MBS item numbers 50300-50330), typical hospital stay 2-3 days (shorter than posterior fusion 4-6 days). VTE prophylaxis with LMWH (enoxaparin 40mg daily) is standard for 2-3 weeks post-op (PBS-listed). ## Lumbar Spine Anterior Anatomy The lumbar spine consists of 5 vertebrae (L1-L5) and the sacrum, with 5 intervertebral discs (L1-2 through L5-S1). The anterior approach accesses the L4-5 and L5-S1 disc spaces (most common levels for degenerative disease). Higher levels (L2-3, L3-4) are rarely accessed anteriorly due to (1) overlying aorta and IVC (more midline at upper levels, difficult to mobilize), and (2) sympathetic chain coursing along anterolateral vertebral body (injured during upper level access causes bowel dysmotility). **Anterior Disc Space Anatomy:** The anterior disc space is LARGER than the posterior disc space (anterior vertebral body is wider than posterior - trapezoidal shape). Dimensions: - **L4-5 disc**: 35-40mm anteroposterior (AP) diameter, 45-50mm transverse width, 10-12mm disc height - **L5-S1 disc**: 30-35mm AP diameter, 40-45mm transverse width, 8-10mm disc height (smaller than L4-5) The **anterior longitudinal ligament (ALL)** is a strong band of connective tissue covering the anterior vertebral bodies and discs. The ALL must be incised to access the disc space (provides hemostasis from vertebral body endplate bleeding). The **annulus fibrosus** surrounds the disc - anterior annulus is thicker and stronger than posterior annulus (anterior provides 40% of disc stability - must preserve lateral and posterior annulus during discectomy to prevent instability). **Anatomic Landmarks:** - **Aortic bifurcation**: Divides into common iliac arteries at the L4 vertebral body (variable - L3-L5 in 10-15% of patients) - **Iliolumbar vein**: Crosses anterior to L5-S1 disc space from left to right (MOST VULNERABLE structure for L5-S1 access - see SafetyAlert above) - **Middle sacral artery and vein**: Small vessels arising from aortic bifurcation, descending on midline anterior to L5-S1 disc (must ligate for midline exposure) - **Sympathetic chain**: Runs along anterolateral border of vertebral bodies (L1-L5), gives rise to superior hypogastric plexus at L5-S1 ## Vascular Anatomy - THREE Danger Zones ### Zone 1: L4-5 Level - Aorta and IVC (Left-Sided Approach STANDARD) At the L4-5 level, the **aorta** lies on the LEFT anterior vertebral body, and the **inferior vena cava (IVC)** lies on the RIGHT. The approach is typically from the patient's LEFT side, mobilizing the aorta and left common iliac artery MEDIALLY (toward midline) to expose the L4-5 disc. **Vascular structures at risk:** - **Aorta**: Thick-walled artery, relatively safe to mobilize (injury rare 0.5-1%), but if injured causes catastrophic hemorrhage (mortality 10-20% - Brau 2004) - **Ascending lumbar veins**: Small veins ascending along left side of vertebral bodies, branch to left common iliac vein, injured during lateral dissection (most common vascular complication at L4-5 - 3-5% injury rate), causes brisk venous bleeding but easily controlled with clips or cautery - **Middle sacral vessels**: Small vessels on midline (aorta to sacral promontory), must ligate for midline exposure **Protection Strategy:** - Use LEFT-SIDED approach for L4-5 (aorta mobilizes easily medially, IVC stays on right side - avoid crossing midline) - Identify and ligate ascending lumbar veins BEFORE mobilization (prevents avulsion) - Keep dissection SUBPERIOSTEAL on vertebral body (stay on bone, avoids vessels) ### Zone 2: L5-S1 Level - Left Common Iliac Vein (Right-Sided Approach PREFERRED) At the L5-S1 level, the aorta has bifurcated into the **left and right common iliac arteries**. The **left common iliac vein** crosses ANTERIOR to the L5-S1 disc from RIGHT to LEFT to join the IVC (draining left leg → IVC). This is the MOST VULNERABLE structure in anterior lumbar surgery. **Left Common Iliac Vein Anatomy:** - Crosses anterior to L5-S1 disc at MIDLINE (variable - 40% of patients have vein 1-2cm left of midline, 60% directly midline) - Lies directly on anterior disc surface with MINIMAL overlying tissue (no fat, no fascia - just vein on disc) - Receives **ascending lumbar vein** from left side of vertebral body (branches into left common iliac vein 1-2cm lateral to midline - THIS is the vessel most commonly injured) - Thin-walled, fragile vessel that tears easily with retraction or manipulation **Vascular injury patterns:** - **Ascending lumbar vein avulsion** (50% of vein injuries): Vein torn from left common iliac vein during lateral dissection, causes immediate brisk venous bleeding - **Left common iliac vein laceration** (30%): Main vein lacerated during cage insertion or aggressive retraction - **Left common iliac vein thrombosis** (10-20%): Delayed (2-7 days post-op), patient presents with left leg swelling and pain (DVT), requires anticoagulation **Protection Strategy:** - Use RIGHT-SIDED approach for L5-S1 (avoids crossing left common iliac vein, reduces injury from 8% to 2% - Faciszewski 1995) - If LEFT-SIDED approach used, identify left common iliac vein EARLY, ligate ascending lumbar vein BEFORE mobilizing - Mobilize vein GENTLY to patient's right (NOT left - avulsion risk), use vascular retractors (release every 15-20 minutes) ### Zone 3: Pelvic Brim - Iliac Vessels and Ureter Below L5-S1, the common iliac vessels divide into **external and internal iliac** branches at the pelvic brim (sacroiliac joint level). These vessels are relevant if exposure extends below L5-S1 (rare) or if vascular anatomy is aberrant. **Ureter:** The ureter descends from the kidney, crosses the pelvic brim at the bifurcation of the common iliac artery (anterior to sacroiliac joint), then enters the pelvis. During retroperitoneal dissection, the ureter is mobilized ANTERIORLY with the peritoneal sac (stays within peritoneal reflection), so it is rarely injured IF retroperitoneal plane is maintained. Ureteral injury occurs if: 1. Peritoneum is violated (transperitoneal dissection - WRONG plane) 2. Dissection extends too far anteriorly or caudally (below pelvic brim) 3. Prior surgery or scarring obscures anatomy **Protection Strategy:** - Identify ureter during retroperitoneal mobilization (palpate as peristaltic cord within peritoneum) - Keep ureter within peritoneal sac (mobilize peritoneum anteriorly, ureter goes with it) - Limit dissection to L4-5 and L5-S1 levels (avoid extending below pelvic brim) ## Superior Hypogastric Plexus - Retrograde Ejaculation Risk The **superior hypogastric plexus** is a sympathetic nerve plexus responsible for ejaculation (sympathetic stimulation causes bladder neck closure and seminal vesicle contraction during orgasm - ejaculation OUT the urethra). The plexus is formed by sympathetic fibers from L1-L3 sympathetic chain, descending as a MIDLINE plexus anterior to the L5-S1 disc space (2-5cm anterior to disc), then bifurcating into left and right hypogastric nerves at the sacral promontory (these nerves descend into pelvis for pelvic organ innervation). **Plexus Location:** - 2-5cm ANTERIOR to L5-S1 disc (in pre-sacral soft tissue) - MIDLINE structure (lies between left and right common iliac arteries) - Variable anatomy - 60% of patients have well-defined plexus, 40% have diffuse fibers (no discrete plexus visible) **Injury Mechanism:** - **Bilateral dissection** (dissecting on BOTH left and right sides of L5-S1 disc): Destroys sympathetic fibers bilaterally, causing retrograde ejaculation in 4-5% of males (Tiusanen 1995) - **Midline violation** (dissecting directly in midline anterior to disc): Divides plexus, causing retrograde ejaculation in 2-3% - **Unilateral dissection** (staying on ONE side of disc): Rarely injures plexus, retrograde ejaculation 0.5% **Clinical Consequences:** - **Retrograde ejaculation**: Semen flows backward into bladder instead of out urethra during orgasm (orgasm sensation preserved, but "dry" ejaculation - no visible semen) - **Infertility**: Male cannot conceive naturally (sperm in bladder, not ejaculate) - **Treatment**: No effective treatment (sympathetic nerve injury is permanent), artificial reproductive techniques (sperm retrieval from bladder post-orgasm, intrauterine insemination or IVF) **Protection Strategy:** - Use UNILATERAL dissection for L5-S1 (left OR right, NOT both - maintains one side of sympathetic innervation) - Avoid MIDLINE dissection (stay lateral to plexus) - Limit dissection to disc space (do NOT extend >2cm anterior to disc - plexus is 2-5cm anterior) - Use RIGHT-SIDED approach for L5-S1 (standard - avoids left common iliac vein AND stays away from plexus on right side) **MANDATORY Consent in Australia:** All male patients must be counseled pre-operatively about retrograde ejaculation risk (0.5-5%) and infertility potential. This is a MEDICOLEGAL requirement in Australia - documented informed consent must address sexual function and fertility risks. Consider sperm banking for young males desiring future fertility. ## Indications The LEFT-SIDED retroperitoneal approach is the STANDARD approach for **L4-5 ALIF** because: 1. Aorta is LEFT of midline at L4-5 (mobilizes easily medially, exposing disc) 2. IVC is RIGHT of midline (stays out of field, not mobilized) 3. Ascending lumbar veins on left are smaller at L4-5 compared to L5-S1 (lower bleeding risk) **Contraindications:** - Prior left retroperitoneal surgery (scarring obscures planes) - Left kidney pathology or prior left nephrectomy (difficult retroperitoneal mobilization) - Abdominal aortic aneurysm (AAA) - vascular surgery required first ## Patient Positioning - **Supine** with left side elevated 15-20° (right hip down, left hip up - opens left retroperitoneal space) - **OR** true right lateral decubitus (right side down, left side up - gravity assists peritoneal mobilization) - **Bump under left hip** (if supine with rotation - creates oblique position) - **Arms positioned** on arm boards or across chest (OUT of surgical field) - **Fluoroscopy positioned** for AP and lateral lumbar spine views (confirm level before incision) **Australian Practice Note:** General anesthesia ONLY (NOT regional - patient must be completely still for vascular dissection). Urinary catheter placed (monitor urine output, decompress bladder during pelvic dissection). ## Skin Incision and Retroperitoneal Access ### Step 1: Mark Incision Palpate LEFT anterior superior iliac spine (ASIS). The incision extends from 2-3cm MEDIAL to ASIS, curving obliquely toward umbilicus, ending at level of umbilicus (total length 8-12cm). The incision is placed 2-3cm above the inguinal ligament (avoids groin creases, better cosmesis). **Alternative:** Pfannenstiel incision (transverse suprapubic incision, 2-3cm above pubic symphysis) can be used for L5-S1 access in obese patients (better exposure below aortic bifurcation), but NOT for L4-5 (too caudal). ### Step 2: Incise Fascia and Enter Retroperitoneum Incise skin and subcutaneous tissue down to **external oblique fascia**. Identify and split external oblique fascia in line with fibers (parallel to inguinal ligament, running inferolateral to superomedial). Deep to external oblique, identify **internal oblique** and **transversus abdominis** muscles - split these muscles BLUNTLY in line with fibers (avoids denervation - muscles are innervated by iliohypogastric and ilioinguinal nerves running within muscle). **Enter retroperitoneal space:** - After splitting abdominal wall muscles, identify the **peritoneum** (thin glistening membrane containing bowel and intraperitoneal organs) - Use BLUNT dissection (finger or sponge stick) to mobilize peritoneum ANTERIORLY and MEDIALLY (push peritoneum toward midline) - Create retroperitoneal pocket between peritoneum (anterior) and psoas muscle (posterior) - this is the WORKING SPACE for the approach **CRITICAL:** Do NOT violate peritoneum (transperitoneal dissection is WRONG plane, exposes bowel and risks bowel injury). If peritoneum is inadvertently opened, close it with 3-0 absorbable suture and continue retroperitoneally. ### Step 3: Mobilize Peritoneum and Identify Psoas With finger or sponge stick, continue BLUNT mobilization of peritoneum anteriorly and medially (away from surgical field). Palpate the **psoas muscle** posteriorly (firm longitudinal muscle fibers along left side of spine). The ureter runs within the peritoneal reflection (palpate as a peristaltic cord - keep ureter within peritoneum, mobilize anteriorly with peritoneal sac). **Identify anatomic landmarks:** - **Psoas muscle**: Lateral border of exposure (posterior) - **Iliac vessels**: Palpate pulsations of iliac artery, feel venous hum of iliac vein (medial structures) - **Vertebral body**: Palpate anterior lumbar spine (midline) Place self-retaining retractor (e.g., Omni-Tract, Bookwalter) to hold peritoneum anteriorly and maintain retroperitoneal exposure. ## Vascular Mobilization and Disc Exposure ### Step 4: Identify and Mobilize Aorta and Left Common Iliac Artery Palpate the **aorta** (midline pulsatile structure anterior to L4 vertebral body). The aorta BIFURCATES into left and right common iliac arteries at the L4 level (variable - L3-L5 in 10-15%). Identify the **left common iliac artery** (continuation of aorta on left side, pulsatile). **Mobilize aorta/left common iliac artery MEDIALLY (toward midline):** 1. **Clear overlying tissue**: Use blunt dissection (sponge stick or Kittner) to clear loose areolar tissue off anterior and left lateral surface of aorta (expose vessel wall) 2. **Identify ascending lumbar veins**: Small veins (2-4mm diameter) ascending along LEFT side of vertebral body, draining into left common iliac vein. These veins cross the surgical field during medial mobilization of aorta. **LIGATE these veins BEFORE mobilizing** (use vascular clips or 2-0 silk ties) - prevents avulsion and bleeding. 3. **Place vascular retractor**: Use a handheld vascular retractor (e.g., malleable ribbon retractor, Deaver retractor) to gently retract aorta/left common iliac artery MEDIALLY (toward patient's right side). Have assistant hold retractor - DO NOT use self-retaining retractors on aorta (excessive pressure risks vessel injury). 4. **Expose L4-5 disc**: With aorta mobilized medially, the L4-5 disc space is now visible anteriorly (white anterior longitudinal ligament covering disc) **CRITICAL:** Release vascular retraction every 15-20 minutes (allow vessel perfusion, prevent ischemia to lower limbs). Palpate distal pulses (dorsalis pedis, posterior tibial) periodically to confirm perfusion. ### Step 5: Confirm Disc Level and Mark Disc Space With disc exposed, use fluoroscopy to CONFIRM the level before proceeding: 1. Place radiopaque marker (e.g., spinal needle, instrument) on anterior disc space 2. Obtain **lateral fluoroscopy image** - count vertebrae from L5 (most caudal lumbar vertebra with disc space before sacrum) upward to confirm L4-5 3. Obtain **AP fluoroscopy image** - confirm midline positioning (marker should be at midline of disc, not lateral) **CRITICAL:** Wrong-level surgery is a NEVER EVENT - medicolegal catastrophe. ALWAYS confirm level fluoroscopically before proceeding with discectomy. ### Step 6: Incise Anterior Longitudinal Ligament (ALL) Using electrocautery or scalpel, make a VERTICAL (longitudinal) incision through the ALL over the L4-5 disc space, extending from superior endplate of L5 to inferior endplate of L4 (full height of disc space). The ALL is vascular - cauterize bleeding from ligament and anterior annulus. **Mark superior and inferior vertebral bodies:** Place blunt retractors (e.g., Cloward retractors) above and below the disc space (on L4 inferior endplate and L5 superior endplate) to define disc boundaries and protect adjacent levels during discectomy. ## Discectomy and Endplate Preparation ### Step 7: Perform Complete Discectomy Using pituitary rongeurs, curettes, and angled instruments, remove ALL disc material from the L4-5 disc space: 1. **Remove nucleus pulposus**: Start centrally, remove soft gelatinous nucleus (bulk of disc) 2. **Remove annulus fibrosus**: Extend peripherally, remove annular fibers circumferentially (360° discectomy) - remove ALL cartilaginous tissue down to vertebral endplates 3. **Preserve posterior longitudinal ligament (PLL)**: The PLL is the posterior boundary of disc space (separates disc from thecal sac) - do NOT violate PLL (causes CSF leak, nerve root injury). Confirm PLL intact by palpating posterior disc space with nerve hook (should feel smooth ligament, NOT pulsatile dura). **Extent of discectomy:** - **Central disc space**: Complete discectomy (remove all disc material) - **Lateral disc space**: Extend discectomy to lateral margins of vertebral body (preserve lateral annulus for stability - do NOT violate lateral annulus completely) - **Posterior disc space**: Discectomy to PLL (do NOT violate PLL) ### Step 8: Prepare Endplates After discectomy, the superior (L5) and inferior (L4) vertebral endplates are visible (cancellous bone with cartilaginous endplate covering). Prepare endplates for fusion: 1. **Remove cartilaginous endplate**: Using curettes or endplate scrapers, remove the thin cartilaginous endplate layer (0.5-1mm thick) from both superior and inferior endplates - exposes bleeding cancellous bone (necessary for bone graft incorporation) 2. **Preserve subchondral bone**: Do NOT remove thick subchondral bone (dense bone beneath cartilaginous endplate) - this provides structural support for cage and prevents subsidence 3. **Create bleeding bone bed**: Endplates should be actively bleeding (confirms viable bone for fusion) **CRITICAL:** Balance endplate preparation - remove cartilage (non-vascular, blocks fusion) but preserve subchondral bone (structural support). Over-aggressive endplate preparation causes SUBSIDENCE (cage migrates into soft cancellous bone - 12% incidence if endplate violated - Malham 2017). ## Interbody Graft Insertion ### Step 9: Size and Insert Interbody Cage Measure disc space height (distance between L4 inferior endplate and L5 superior endplate) and anteroposterior (AP) depth using trial spacers or rulers. Select appropriate cage: - **Height**: Restore disc height to pre-degenerative state (typically 10-12mm at L4-5) - restores foraminal height for nerve root decompression - **AP depth**: Maximum safe depth is 25-30mm (75-80% of vertebral body AP diameter) - NEVER insert cage >30mm (risks posterior cage migration into canal, nerve root injury) - **Lordosis**: Select cage with 6-10° lordosis (restores lumbar lordosis) **Cage types:** - **PEEK (polyetheretherketone) cages**: Most common, radiolucent (allows fusion assessment on X-ray), filled with bone graft (autograft from iliac crest OR allograft) or bone graft substitute (BMP, demineralized bone matrix) - **Titanium cages**: Radiopaque (obscures fusion on X-ray), higher subsidence risk (rigid) - **Expandable cages**: Inserted collapsed then expanded to desired height (less endplate preparation needed, but higher cost) **Insertion technique:** 1. **Pack cage with bone graft**: Fill central cavity of cage with morselized bone graft (autograft from iliac crest if harvested, OR allograft chips, OR bone graft substitute). Compress graft into cage (maximize graft volume). 2. **Insert cage under fluoroscopy**: Using cage holder/inserter, advance cage into disc space under continuous lateral fluoroscopy (ensures cage is positioned centrally in disc space, not posteriorly). Advance cage to appropriate depth (typically 25-28mm from anterior vertebral body). 3. **Confirm position**: Obtain AP and lateral fluoroscopy to confirm: - **Lateral view**: Cage at midline of disc space (anteroposterior), not too posterior (risk of canal encroachment), cage parallel to endplates (not tilted) - **AP view**: Cage centered on disc space (mediolateral), symmetric positioning **CRITICAL:** Under-sizing cage height causes pseudarthrosis (no compression across graft), over-sizing causes subsidence (cage crushes endplate). Use trial spacers to determine optimal height (should require FIRM impaction to insert - slight resistance confirms good endplate contact without over-distraction). ### Step 10: Supplement with Posterior Fixation (Optional) **Stand-alone ALIF** (cage only, no posterior screws/rods): Biomechanically stable for single-level fusion in non-osteoporotic patients with competent facets. Subsidence risk 12% (Malham 2017). **ALIF + posterior fixation** (cage + posterior screws/rods): Indicated for: - Osteoporosis (subsidence risk 28% stand-alone vs 8% with posterior fixation - Malham 2015) - Multi-level fusion (>1 level) - Degenerative spondylolisthesis (instability - requires posterior fixation for stability) If posterior fixation planned, this is performed in SECOND STAGE (patient repositioned prone, posterior approach to lumbar spine, percutaneous pedicle screws placed at L4 and L5, connected with rods). ## Wound Closure 1. **Confirm hemostasis**: Visualize all dissected areas for bleeding (ascending lumbar veins, anterior annulus, ALL) - cauterize or clip any bleeding vessels 2. **Release vascular retraction**: Remove all retractors from aorta/iliac vessels, allow vessels to return to anatomic position 3. **Close retroperitoneal space**: DO NOT attempt to close peritoneum (peritoneum will heal spontaneously) - simply ensure peritoneum is intact (no violation) 4. **Close abdominal wall layers**: Close transversus abdominis, internal oblique, and external oblique fascia in layers using 0 or #1 absorbable suture (Vicryl or PDS) 5. **Close subcutaneous tissue**: Close subcutaneous layer with 2-0 absorbable suture (minimize dead space) 6. **Close skin**: Skin closure with 3-0 or 4-0 absorbable subcuticular suture (monocryl) OR staples (faster, equivalent outcomes) 7. **Drain placement**: Typically NO drain needed (retroperitoneal space is not closed, fluid drains into peritoneal cavity where it's absorbed) - drain only if significant oozing or concern for hematoma **Post-operative immobilization:** LSO (lumbosacral orthosis) brace for 6-12 weeks if stand-alone ALIF (supports fusion), NOT required if supplemental posterior fixation used. ## Indications and Advantages The RIGHT-SIDED retroperitoneal approach is the PREFERRED approach for **L5-S1 ALIF** because: 1. **Avoids left common iliac vein** (most vulnerable structure) - vein stays on left side, not mobilized, reduces vascular injury from 8% to 2% (Faciszewski 1995) 2. **Avoids superior hypogastric plexus** (theoretical advantage - plexus lies on left/midline, right-sided stays away), though retrograde ejaculation rates similar if unilateral dissection used 3. **Simpler vascular anatomy** - right common iliac artery is smaller and more mobile than left iliac vein (safer to retract) **Disadvantage:** - Slightly less familiar for most surgeons (left-sided is traditional) - but evidence supports right-sided as safer ## Surgical Technique - Key Differences from Left-Sided The right-sided approach is SIMILAR to left-sided approach (described above) with these key differences: ### Incision and Retroperitoneal Access - **Incision**: RIGHT lower quadrant (mirror image of left-sided), extending from 2-3cm medial to RIGHT ASIS toward umbilicus - **Muscle splitting**: Split right external oblique, internal oblique, transversus abdominis in line with fibers - **Retroperitoneal mobilization**: Mobilize peritoneum ANTERIORLY and MEDIALLY (toward midline), exposing right psoas muscle and right iliac vessels ### Vascular Mobilization - **Identify right common iliac artery**: Pulsatile vessel on right side (continuation of aorta after bifurcation at L4) - **Identify IVC and right common iliac vein**: IVC lies on RIGHT side of midline, right common iliac vein joins IVC (smaller and less vulnerable than left iliac vein) - **Mobilize RIGHT common iliac artery/vein MEDIALLY**: Retract vessels toward midline (similar to left-sided technique), exposing L5-S1 disc space - **Middle sacral vessels**: Small vessels (artery + vein) descending on MIDLINE from aortic bifurcation to sacrum - must LIGATE for midline disc exposure (use vascular clips or ties) **Advantage of right-sided:** - **Left common iliac vein is NOT mobilized** (stays on left side of disc, untouched) - this eliminates risk of left iliac vein avulsion (most common vascular injury at L5-S1) - Right common iliac artery/vein are smaller and more mobile than left iliac vein (safer to retract) ### Disc Exposure and Cage Insertion - **Disc exposure**: After mobilizing right iliac vessels medially, L5-S1 disc space is exposed (same as left-sided) - **Discectomy and endplate preparation**: Identical to left-sided technique - **Cage insertion**: Same technique (under fluoroscopy, 25-28mm depth, centered positioning) **All other steps (discectomy, endplate preparation, cage insertion, wound closure) are IDENTICAL to left-sided approach.** ## Post-operative Protocols **Phase 1 (Days 0-2): Immediate Post-op** - **ICU/HDU monitoring**: Not routinely required (unlike posterior spine surgery with dural exposure) - most patients go to regular ward - **Pain control**: Multimodal analgesia (acetaminophen 1g Q6h, NSAIDs if no contraindication, opioids PRN - typically low opioid requirements with anterior approach) - **Early mobilization**: Out of bed to chair post-op day 0-1 (early mobilization reduces DVT risk, ileus), walking with assistance day 1-2 - **Bowel function**: Ileus common (10-15% incidence - bowel retraction during peritoneal mobilization), usually resolves 2-4 days with conservative management (NPO, NG tube if persistent vomiting) - **Urinary catheter**: Remove day 1 (placed intraoperatively for bladder decompression) - **Discharge**: Typically post-op day 2-3 (shorter than posterior fusion 4-6 days) **Phase 2 (Weeks 0-6): Brace and Activity Modification** - **LSO brace**: If stand-alone ALIF (no posterior fixation) - wear brace for 6-12 weeks during upright activities (supports fusion, prevents excessive motion). NOT required if posterior fixation used. - **Activity**: NO bending, lifting >10 pounds, twisting for 6-12 weeks (until fusion solid) - **Walking**: Unlimited walking encouraged (promotes healing, cardiovascular fitness) - **Driving**: Resume at 2-4 weeks if no opioids and adequate mobility - **Return to sedentary work**: 4-6 weeks (if no brace required), 6-8 weeks (if brace) - **X-rays**: AP and lateral lumbar spine at 2 weeks and 6 weeks (assess hardware position, early subsidence) **Phase 3 (Months 3-6): Progressive Activity** - **Remove brace**: At 3 months if fusion progressing on X-ray (bridging bone across disc space) - **CT scan**: At 3-6 months if fusion questionable on X-ray (CT is gold standard - shows trabecular bone bridging) - **Physical therapy**: Core strengthening, lumbar stabilization exercises (once fusion solid) - **Return to manual labor**: 3-6 months (based on fusion status and functional recovery) - **Return to high-impact activities**: 6-12 months (running, contact sports - only after confirmed solid fusion) **Australian Context:** Outpatient PT is covered under Medicare (5 visits/year for chronic conditions) and private insurance (15-20 visits/year). Return to work: WorkCover coverage for occupational injuries, typical time off 6-12 weeks for sedentary work, 3-6 months for manual labor. Inpatient rehabilitation (2-4 weeks) is rarely required for single-level ALIF (unlike complex posterior fusions or elderly patients). ## Complications ### Intraoperative Complications **1. Vascular Injury (2-8% - MOST COMMON Major Complication)** - **Presentation**: Sudden brisk bleeding from retroperitoneal space (arterial spurting OR venous oozing depending on injury), hypotension if severe - **Vessels injured**: Left common iliac vein 70% (MOST COMMON - ascending lumbar vein avulsion or main vein laceration), IVC 10%, aorta 8%, right common iliac 5%, other 7% (Inamasu 2005) - **Management**: - **Immediate direct pressure**: Assistant applies pressure with laparotomy pad over bleeding site for 5-10 minutes (while surgeon obtains vascular instruments - DeBakey forceps, vascular clamps, 5-0 Prolene sutures) - **Primary repair**: For VENOUS injuries (majority), use 5-0 or 6-0 vascular suture (Prolene) for simple laceration repair, or venorrhaphy for larger injuries. NEVER ligate left common iliac vein (causes venous congestion, leg swelling, DVT - must reconstruct vein). - **Arterial injury**: Requires vascular surgery consult URGENTLY - aortic or iliac artery injuries are life-threatening (mortality 10-20% - Brau 2004). Options: primary repair (if small), interposition graft (if large defect), endovascular stenting (if suitable anatomy). - **Pack and convert**: If unable to control bleeding retroperitoneally, PACK wound with laparotomy pads, convert to LAPAROTOMY (extend incision to full midline laparotomy for better exposure), obtain vascular surgery assistance - **Prevention**: Identify and ligate ascending lumbar veins BEFORE mobilization (prevents avulsion), use right-sided approach for L5-S1 (avoids left iliac vein), gentle vascular retraction with frequent release **2. Bowel Injury (Rare, less than 1%)** - **Mechanism**: Peritoneal violation during retroperitoneal dissection (wrong plane), inadvertent entry into peritoneal cavity with bowel manipulation - **Recognition**: Bowel visible in surgical field (should NOT be visible if retroperitoneal plane maintained), fecal material in wound - **Management**: If recognized intraoperatively - repair enterotomy with 3-0 absorbable suture (two-layer closure: mucosa then serosa), consider general surgery consult if large injury. If unrecognized - presents post-operatively as peritonitis (abdominal pain, fever, leukocytosis) requiring urgent laparotomy, bowel repair, washout. - **Prevention**: Maintain retroperitoneal plane (mobilize peritoneum anteriorly, stay posterior to peritoneum), if peritoneum violated, close it immediately and continue retroperitoneally **3. Ureteral Injury (Rare, less than 0.5%)** - **Mechanism**: Ureter injured during retroperitoneal mobilization if dissection extends too far anteriorly or caudally (below pelvic brim), or if prior surgery obscures anatomy - **Recognition**: May not be recognized intraoperatively (ureter injury often silent), presents post-operatively as flank pain, hydronephrosis (urine leaking into retroperitoneum), or anuria if bilateral - **Management**: Urologic consult URGENTLY, ureteral stenting (retrograde or antegrade via nephrostomy), primary repair if recognized early (within 24-48 hours), nephrectomy if delayed recognition with severe hydronephrosis - **Prevention**: Identify ureter during retroperitoneal mobilization (palpate as peristaltic cord within peritoneum), keep ureter within peritoneal sac (mobilize anteriorly with peritoneum), limit dissection to L4-5 and L5-S1 levels (avoid extending below pelvic brim where ureter crosses iliac vessels) ### Early Post-operative Complications (less than 6 weeks) **1. Ileus (10-15%)** - **Presentation**: Nausea, vomiting, abdominal distension, absent bowel sounds 2-4 days post-op - **Mechanism**: Bowel retraction during peritoneal mobilization causes transient bowel dysmotility (resolves spontaneously 2-4 days) - **Management**: Conservative - NPO (nothing by mouth), IV fluids, NG tube if persistent vomiting, ambulation (promotes bowel motility), avoid opioids (worsen ileus), usually resolves 2-4 days. If persistent >5 days, consider CT abdomen to rule out bowel obstruction or other complications. - **Prevention**: Minimize peritoneal retraction (limit anterior dissection), early ambulation post-op, multimodal analgesia (minimize opioids) **2. Retrograde Ejaculation (0.5-5% Males)** - **Presentation**: Male patient reports "dry" ejaculation after surgery - orgasm sensation preserved but no visible semen (semen flows backward into bladder) - **Timing**: Immediate (present from first sexual activity post-op), NOT delayed - **Management**: NO effective treatment (sympathetic nerve injury is permanent), counsel patient about permanence, options for fertility: sperm retrieval from bladder post-orgasm (alkalinize urine with sodium bicarbonate before collection), intrauterine insemination or IVF - **Prognosis**: PERMANENT (sympathetic nerves do NOT regenerate) - patient must accept this complication or pursue artificial reproductive techniques - **Prevention**: Use unilateral dissection for L5-S1 (right OR left, NOT bilateral - reduces from 4-5% to 0.5% - Tiusanen 1995), limit anterior dissection (stay within 2cm of disc), avoid midline dissection (stay lateral to plexus) **3. DVT/PE (2-5%)** - **Presentation**: Calf pain, leg swelling (DVT), dyspnea, chest pain (PE) - **Risk factors**: Anterior lumbar surgery has LOWER VTE risk than posterior (2-5% vs 10-15% posterior) - less muscle trauma, shorter surgery time - **Management**: Venous duplex ultrasound (DVT), CT pulmonary angiography (PE), therapeutic anticoagulation (enoxaparin 1.5mg/kg daily OR apixaban 10mg BD × 7 days then 5mg BD) for 3 months - **Prevention**: LMWH prophylaxis (enoxaparin 40mg daily) for 2-3 weeks post-op (PBS-listed in Australia), early mobilization (out of bed day 0-1), sequential compression devices intraoperatively **4. Left Common Iliac Vein Thrombosis (1-2%)** - **Presentation**: DELAYED (2-7 days post-op), left leg swelling and pain (unilateral - distinguishes from bilateral perioperative edema), positive Homan's sign - **Mechanism**: Vessel intimal injury from manipulation or retraction during surgery causes thrombus formation 2-7 days later - **Management**: Venous duplex ultrasound (confirms thrombus in left iliac vein), therapeutic anticoagulation (same as DVT above) for 3-6 months (longer than standard DVT due to vessel injury etiology), may consider IVC filter if anticoagulation contraindicated - **Prevention**: Gentle vascular manipulation (avoid excessive retraction), release retractors every 15-20 minutes, LMWH prophylaxis post-op ### Late Complications (greater than 6 weeks) **1. Subsidence (5-15% Overall, 28% if Osteoporotic)** - **Presentation**: Recurrent back pain 2-6 months post-op (after initial improvement), loss of disc height on X-ray (cage migrates into vertebral body) - **Definition**: Cage migration >2mm into vertebral body (measured on lateral X-ray or CT) - **Risk factors**: Osteoporosis (OR 4.2, p<0.001 - Malham 2017), over-aggressive endplate preparation (removes structural subchondral bone), oversized cage (>18cm² footprint - OR 2.4), L5-S1 level (higher loading than L4-5) - **Management**: - **Asymptomatic subsidence** (70% of cases - Malham 2017): Observe, no treatment needed (most patients remain pain-free despite radiographic subsidence) - **Symptomatic subsidence** (30%): Grade 1-2 (2-6mm) - conservative with PT, NSAIDs, activity modification. Grade 3 (>6mm) - often requires revision (5-10% of subsidence cases): remove cage, revise endplates, larger cage OR supplemental posterior fixation. - **Prevention**: Screen for osteoporosis pre-operatively (DEXA scan - PBS-subsidized in Australia for at-risk patients), treat osteoporosis before surgery (bisphosphonates or denosumab 3-6 months pre-op), consider supplemental posterior fixation if osteoporotic (reduces subsidence from 28% to 9% - Malham 2015), appropriate endplate preparation (remove cartilage but preserve subchondral bone) **2. Pseudarthrosis (5-10%)** - **Presentation**: Persistent back pain >6 months post-op, no improvement with conservative treatment - **Diagnosis**: CT scan at 6-12 months (gold standard) shows no bridging bone across disc space (radiolucency around cage, no trabecular bone continuity) - **Risk factors**: Smoking (OR 3.8 - impairs bone healing), diabetes (OR 2.3), NSAIDs (chronic use impairs fusion - avoid NSAIDs >3 months post-op), inadequate graft volume (small cage or insufficient bone graft), excessive motion (stand-alone ALIF without posterior fixation in unstable spine) - **Management**: Revision surgery - posterior instrumentation (if stand-alone ALIF failed - add screws/rods for stability), revision ALIF with larger cage and BMP (if posterior fixation inadequate), revision ALIF + posterior (360° fusion) - **Prevention**: Smoking cessation (Quitline 13 7848 - mandatory in Australia), avoid NSAIDs >3 months post-op (use acetaminophen for pain), adequate graft volume (pack cage completely with bone graft), posterior fixation for high-risk patients (osteoporosis, instability) **3. Adjacent Segment Disease (ASD, 10-20% at 10 Years)** - **Presentation**: New back pain or radiculopathy 5-10 years after fusion (pain above or below fusion level) - **Mechanism**: Fusion eliminates motion at L4-5 or L5-S1, transferring stress to adjacent levels (L3-4 above or L5-S1 below L4-5 fusion), accelerating degenerative changes at adjacent levels - **Diagnosis**: MRI shows new disc degeneration, stenosis, or instability at adjacent level (NOT present pre-operatively) - **Management**: Conservative first (PT, NSAIDs, epidural steroid injection), revision surgery if conservative fails (extend fusion to adjacent level - but this increases ASD risk at next level), disc replacement at adjacent level (motion-preserving alternative - controversial) - **Prevention**: Controversial - some evidence that motion-preserving techniques (disc replacement instead of fusion) reduce ASD, but long-term data lacking. Maintain lumbar lordosis at index fusion (reduces adjacent level stress). 2-3cm anterior where plexus lies. Use right-sided approach if possible - theoretically avoids plexus on left/midline.)", "Was informed consent adequate in this case? (MUST review consent form - if patient was NOT counseled about retrograde ejaculation risk pre-operatively, this represents INADEQUATE consent (medicolegal issue in Australia). All male patients undergoing L5-S1 ALIF MUST have documented discussion of sexual function and fertility risks. If consent inadequate, this is a patient safety/quality issue requiring disclosure and potential institutional review.)", "Patient asks: can I still father children? (YES, but NOT naturally - requires assisted reproductive techniques: sperm retrieval from bladder post-orgasm (alkalinize urine with sodium bicarbonate first to protect sperm from acidic pH), then IUI or IVF using retrieved sperm. Refer to reproductive endocrinology or urology for fertility planning. For future patients, consider sperm banking PRE-operatively for young males desiring fertility.)" ]} /> 6mm migration requires surgery." ]} followUpQuestions={[ "What if this patient had normal bone density (T-score >-1.0) - would you still do posterior fixation? (Less clear indication - stand-alone ALIF is appropriate for non-osteoporotic patients with 12% subsidence rate. For symptomatic subsidence in normal bone, try conservative FIRST (PT, NSAIDs, brace) for 3-6 months. If conservative fails, then consider posterior fixation. In osteoporotic patients, posterior fixation is more clearly indicated due to 28% subsidence rate.)", "How do you screen for osteoporosis and when should you treat it? (DEXA scan for all females >50 years and males >60 years undergoing fusion surgery - PBS-subsidized in Australia. T-score interpretation: >-1.0 normal, -1.0 to -2.5 osteopenia, less than -2.5 osteoporosis. Treat osteoporosis BEFORE elective fusion: bisphosphonates - alendronate 70mg weekly OR denosumab 60mg SC every 6 months for 3-6 months pre-op - PBS-listed. This improves bone quality and reduces subsidence risk.)", "What if patient refuses revision surgery despite intolerable pain? (Conservative management: long-term PT, pain management (NSAIDs, neuropathic pain medications if radicular component), activity modification, LSO brace indefinitely. Pain may persist but many patients adapt over 6-12 months. Consider pain clinic referral if refractory. Document discussion about revision surgery and patient refusal (medicolegal).)" ]} /> 50, males >60 - PBS-subsidized in Australia)" } ]} clinicalPearl="Retrograde ejaculation is a PERMANENT complication of L5-S1 ALIF (0% recovery - Tiusanen 1995) occurring in 0.5-5% of males depending on technique. CRITICAL PREVENTION: (1) UNILATERAL dissection - stay on ONE side of disc (right OR left, NOT both), reduces retrograde ejaculation from 4-5% (bilateral) to 0.5% (unilateral, p=0.02 - Tiusanen 1995), (2) Limit anterior dissection - stay within 2cm of disc space (plexus 2-5cm anterior), (3) Avoid midline violation (plexus is midline). MANDATORY consent for all male patients (medicolegal in Australia)." /> 50, males >60 (PBS-subsidized), treat BEFORE surgery" }, { letter: "N", text: "NSAIDs limited - avoid chronic use >3 months post-op (impairs fusion), use acetaminophen for pain instead" } ]} clinicalPearl="ALIF has SUPERIOR fusion biology compared to posterior approaches (PLIF/TLIF): 94% fusion vs 82% (p=0.008 - Christensen 2018) due to (1) larger interbody graft surface area (30-40% bigger anteriorly), (2) compression loading (anterior column under compression - optimal for bone healing), (3) preserved posterior structures (facets, PLL, musculature intact). OPTIMIZATION: smoking cessation (OR 3.8 for pseudarthrosis), adequate bone graft volume (pack cage completely), osteoporosis treatment pre-op (bisphosphonates or denosumab 3-6 months), posterior fixation if osteoporotic (reduces subsidence)." /> 50, males >60), treatment (alendronate 70mg weekly OR denosumab 60mg SC Q6 months) PBS-listed, treat 3-6 months pre-op before elective fusion. **VTE prophylaxis**: LMWH (enoxaparin 40mg daily) for 2-3 weeks post-op is STANDARD (PBS-listed), lower VTE risk than posterior fusion (2-5% vs 10-15%). **Hospital stay**: Typically 2-3 days ALIF (shorter than posterior fusion 4-6 days). **Return to work**: WorkCover coverage for occupational injuries, typical 6-12 weeks sedentary work, 3-6 months manual labor. **Smoking cessation**: Quitline 13 7848 referral MANDATORY (smoking OR 3.8 for pseudarthrosis)." }, { title: "Viva Traps - Don't Get Caught", content: "**TRAP**: Examiner says 'Why not use left-sided approach for L5-S1?' **RESPONSE**: Left-sided L5-S1 has 4× HIGHER vascular injury rate (8.2% vs 2.1% right-sided, p=0.003 - Faciszewski 1995) because left-sided requires mobilizing left common iliac VEIN from right to left across disc space, risking avulsion of ascending lumbar vein tributaries (accounts for 70% of vascular injuries). RIGHT-SIDED approach avoids crossing left vein entirely - safer. **TRAP**: 'Can you ligate the left common iliac vein if injured?' **RESPONSE**: NEVER ligate main left common iliac vein (causes venous congestion, left leg swelling, DVT risk) - MUST reconstruct vein with primary repair using 5-0 Prolene. Only small TRIBUTARY veins (ascending lumbar veins) can be safely ligated. **TRAP**: 'Will retrograde ejaculation recover?' **RESPONSE**: NO - retrograde ejaculation from superior hypogastric plexus injury is PERMANENT (sympathetic nerves do NOT regenerate). Tiusanen 1995: NONE of 4 patients recovered at 24-month follow-up. Patient can achieve orgasm (sensation preserved) but no visible ejaculate (semen in bladder). **TRAP**: 'What is subsidence risk in this osteoporotic patient with stand-alone ALIF?' **RESPONSE**: 28% (Malham 2017) - stand-alone ALIF is CONTRAINDICATED in osteoporosis (T-score less than -2.5). Should have had supplemental posterior fixation (reduces subsidence from 28% to 9% - Malham 2015)." }, { title: "Safe Answers When Unsure", content: "If asked about an unfamiliar vascular injury: 'The MOST COMMON vascular injury during anterior lumbar surgery is left common iliac vein injury (70% of injuries - Inamasu 2005), specifically ascending lumbar vein avulsion during mobilization. Management is: (1) direct pressure first (5-10 minutes), (2) primary repair with 5-0 Prolene if main vein injured, (3) ligation acceptable for small tributaries but NEVER main vein, (4) call vascular surgery if unable to control or arterial injury. Prevention: RIGHT-SIDED approach for L5-S1 (reduces injury 8% to 2%), ligate ascending lumbar veins BEFORE mobilization.' If asked about approach selection: 'Approach selection depends on LEVEL: LEFT-SIDED for L4-5 (aorta mobilizes easily, IVC stays right), RIGHT-SIDED for L5-S1 (avoids left iliac vein crossing, 4× lower vascular injury - Faciszewski 1995). Use UNILATERAL dissection (right OR left, NOT both) to protect superior hypogastric plexus (reduces retrograde ejaculation from 4-5% to 0.5% - Tiusanen 1995).' If asked about fusion optimization: 'ALIF has SUPERIOR fusion biology (94% vs 82% posterior - Christensen 2018) due to larger graft surface, compression loading, preserved posterior structures. Optimization: smoking cessation (OR 3.8 pseudarthrosis - Quitline 13 7848), osteoporosis treatment pre-op (DEXA scan PBS-subsidized, treat 3-6 months before surgery), adequate bone graft volume, posterior fixation if osteoporotic (reduces subsidence 28% to 9%).'" } ]} />

Anterior Retroperitoneal Approach to Lumbar Spine

Anterior Retroperitoneal Approach to Lumbar Spine