import { OnePagerSummary, ContentSection, ExamWarning, InfoCardGrid, InfoCard, EvidenceCard, ComparisonTable, VivaScenario, MnemonicCard, ExamCheatSheet, Tab, Tabs } from '@/components/mdx' **Transforaminal lumbar interbody fusion (TLIF)** is a posterior lumbar fusion technique that accesses the disc space through a **unilateral facetectomy** and **transforaminal approach** (through the neural foramen), inserting an interbody cage from ONE side (typically right or left) while preserving the CONTRALATERAL facet. TLIF was developed by Harms and Rolinger (1982) as a modification of PLIF (posterior lumbar interbody fusion) to reduce neurological complications - the transforaminal approach avoids BILATERAL dural and nerve root retraction (required for PLIF), reducing dural tear risk from 6-12% (PLIF) to 3-8% (TLIF) and nerve root injury from 10-15% to 1-8%. The **critical anatomic concept** is **Kambin's triangle** (also called the "safe triangle") - a triangular space in the lumbar foramen bounded by: (1) **Exiting nerve root** (superior border - e.g., L4 nerve root exits L4-5 foramen superiorly), (2) **Traversing nerve root** (inferior border - e.g., L5 nerve root traverses L4-5 disc space inferiorly, descending to exit L5-S1 foramen), and (3) **Thecal sac** (medial border - dura containing cauda equina). Kambin's triangle provides a "safe zone" for transforaminal disc access, avoiding nerve root retraction (Kambin 1988). The TLIF approach offers ADVANTAGES over PLIF: (1) **Unilateral facetectomy** - preserves contralateral facet (maintains 40% of segmental stability - Oxland 1996), reduces adjacent segment degeneration (contralateral facet intact vs bilateral facetectomy in PLIF which increases adjacent level stress), (2) **Reduced dural tear risk** - dura and nerve roots retracted LATERALLY (away from midline) rather than BILATERALLY as in PLIF, dural tear 3-8% vs 6-12% PLIF (Potter 2005), (3) **Lower nerve root injury** - only exiting nerve root mobilized (vs both exiting and traversing in PLIF), nerve injury 1-8% vs 10-15% PLIF, (4) **Comparable fusion rates** - TLIF 85-92% vs PLIF 88-95% (no significant difference - Park 2011). The CRITICAL structures at risk are: (1) **Exiting nerve root** (1-8% injury risk - MOST COMMON neurological complication), nerve exits at SUPERIOR aspect of foramen 3-5mm medial to lateral pedicle wall (Panjabi 1993), injured during facetectomy (drill or rongeur injury) or aggressive disc retraction, (2) **Dura/thecal sac** (3-8% tear risk), dura is medial border of Kambin's triangle, injured during disc access or aggressive medial retraction of thecal sac, (3) **Traversing nerve root** (less than 1-3% injury risk), nerve descends through foramen inferiorly, usually SAFE if working within Kambin's triangle, but injured if disc work extends too far inferiorly or medially, (4) **Vertebral artery** (RARE complication less than 0.5%, but CATASTROPHIC), injured if pedicle screw placed too far laterally or superiorly (enters transverse foramen at L1-L4 levels - below L4 the vertebral artery is NOT at risk). **Australian Clinical Context:** TLIF is increasingly performed in Australia for single- and two-level degenerative lumbar disease (spondylolisthesis, degenerative disc disease with instability, recurrent disc herniation), with AOANJRR spine registry showing TLIF utilization growing 10-15% annually. Minimally invasive TLIF (MIS-TLIF) is rapidly expanding in Australia (15-20% annual growth) - uses tubular retractors for muscle-sparing approach, reducing blood loss (150-250mL vs 400-600mL open TLIF), hospital stay (2-3 days vs 4-6 days open), and back pain (paraspinal muscle trauma reduced). Medicare covers TLIF for degenerative disc disease with instability, spondylolisthesis, or recurrent disc herniation (MBS item numbers 50300-50330). Hospital stay typically 3-5 days for open TLIF, 2-3 days for MIS-TLIF (shorter than PLIF 5-7 days due to less soft tissue trauma). VTE prophylaxis with LMWH (enoxaparin 40mg daily) is standard for 4-6 weeks post-op (PBS-listed), with 8-12% DVT risk (lower than PLIF 12-18% but higher than anterior approaches 2-5%). ## Lumbar Facet Joint and Neural Foramen Anatomy The lumbar facet joint (also called zygapophyseal joint) is formed by the **superior articular process** (SAP) of the caudal vertebra (e.g., L5 SAP at L4-5 level) and the **inferior articular process** (IAP) of the cephalad vertebra (e.g., L4 IAP). The facet joint is a synovial joint oriented at ~45° in the sagittal plane (vertical), providing resistance to anterior translation and rotation. The ligamentum flavum attaches to the anterior surface of the superior facet (medial border) and extends medially to cover the interlaminar space. **Neural Foramen Boundaries:** The neural foramen is the exit canal for spinal nerve roots, with boundaries: - **Anterior**: Posterior vertebral body and intervertebral disc (anterior 1/3), superior endplate of inferior vertebra (middle 1/3), inferior endplate of superior vertebra (posterior 1/3) - **Posterior**: Pars interarticularis and facet joint (ligamentum flavum covers medial aspect) - **Superior**: Pedicle of cephalad vertebra (e.g., L4 pedicle forms superior border of L4-5 foramen) - **Inferior**: Pedicle of caudal vertebra (e.g., L5 pedicle forms inferior border of L4-5 foramen) **Foramen Dimensions:** - **Height**: 18-22mm (L1-L5, decreases caudally) - **Width**: 8-12mm (narrowest at mid-foramen where nerve root transitions from vertical to horizontal) - **Depth**: 10-15mm (anterior-posterior distance) The foramen is SMALLEST at the mid-level (where facet joint is located posterolaterally), creating a "waist" where nerve root impingement occurs in degenerative disease (facet hypertrophy, disc herniation, osteophytes reduce foraminal diameter). ## Kambin's Triangle - The "Safe Zone" for TLIF **Kambin's triangle** is a triangular anatomic space in the posterior-lateral aspect of the neural foramen, providing a "safe zone" for transforaminal disc access without nerve root retraction (Kambin 1988). The triangle's boundaries are: 1. **Superior border**: **Exiting nerve root** (e.g., L4 nerve root at L4-5 foramen) - exits ABOVE the pedicle, descends laterally 2. **Inferior border**: **Traversing nerve root** (e.g., L5 nerve root at L4-5 level) - descends THROUGH foramen, medial to exiting root, exits at NEXT level (L5-S1) 3. **Medial border**: **Thecal sac** (dura containing cauda equina) - medial boundary of foramen 4. **Anterior (base of triangle)**: Posterior vertebral body and disc 5. **Posterior (apex of triangle)**: Superior facet and ligamentum flavum **Kambin's Triangle Dimensions:** - **Height** (superior-inferior): 10-15mm (distance between exiting and traversing nerve roots) - **Width** (medial-lateral): 5-8mm (distance from thecal sac to lateral foramen) - **Depth** (anterior-posterior): 10-15mm (distance from facet to posterior vertebral body) **Clinical Significance:** Kambin's triangle provides a "safe zone" for transforaminal disc access - instruments can pass through the triangle to reach the disc space without retracting nerve roots (exiting nerve is SUPERIOR, traversing nerve is INFERIOR, thecal sac is MEDIAL - all out of the working zone). The triangle is LARGEST at the L4-5 level (10-15mm height) and SMALLEST at L5-S1 (6-10mm height - exiting L5 nerve root and traversing S1 nerve root are closer together, reducing safe zone). **CRITICAL LIMITATION:** Kambin's triangle is only "safe" if: 1. Facetectomy is adequate (medial 50-60% of superior facet removed - creates space for instruments) 2. Disc access stays within triangle boundaries (do NOT extend inferiorly beyond traversing root or medially beyond thecal sac) 3. Exiting nerve root is MOBILE (not tethered by scar tissue, osteophytes, or foraminal stenosis) ## Nerve Root Anatomy - Exiting vs Traversing Understanding the DIFFERENCE between exiting and traversing nerve roots is CRITICAL for TLIF safety: **Exiting nerve root:** - Nerve that EXITS at the level of interest (e.g., L4 nerve root exits L4-5 foramen) - Exits ABOVE the pedicle of the caudal vertebra (L4 nerve exits above L5 pedicle) - Passes beneath the pars interarticularis and superior facet, then descends laterally out of foramen - Location: SUPERIOR border of Kambin's triangle, 3-5mm medial to lateral pedicle wall at mid-foramen (Panjabi 1993) - **MOST VULNERABLE** during TLIF - injured during facetectomy (40% of nerve injuries - Kim 2006), pedicle screw placement in upper vertebra, or aggressive lateral retraction **Traversing nerve root:** - Nerve that TRAVERSES (passes through) the level of interest to exit at the NEXT level (e.g., L5 nerve root traverses L4-5 disc space, exits L5-S1 foramen) - Descends THROUGH the foramen medial to exiting nerve root, then exits at next level below - Location: INFERIOR border of Kambin's triangle, medial and caudal to exiting nerve root - **LESS VULNERABLE** during TLIF (unless disc work extends too far inferiorly or medially - then risk of compression or laceration, less than 1-3% injury rate) **Example at L4-5 level:** - **Exiting nerve**: L4 nerve root (exits L4-5 foramen, SUPERIOR border of Kambin's triangle, injured during facetectomy or upper pedicle screw) - **Traversing nerve**: L5 nerve root (traverses L4-5 disc space, exits L5-S1 foramen, INFERIOR border of Kambin's triangle, relatively safe if staying in triangle) ## Pedicle Anatomy - Screw Placement Corridor The lumbar pedicle is the "corridor" connecting the posterior elements (lamina, facets) to the vertebral body. Pedicle dimensions: - **Width**: 8-12mm at L1-L3, 12-16mm at L4-L5 (increases caudally) - **Height**: 14-18mm at L1-L3, 16-20mm at L4-L5 - **Length** (anterior-posterior): 40-50mm - **Angle** (transverse plane): 10-15° convergent at L1-L3, 0-5° at L4-L5 (less convergent caudally) **Pedicle Screw Trajectory:** For safe pedicle screw placement, the trajectory is: - **Entry point**: Lateral to pars interarticularis, at junction of transverse process and superior facet (the "eye of the Scotty dog" on lateral fluoroscopy) - **Trajectory mediolateral**: 10-15° convergent (more medial distally, toward vertebral body midline) - **Trajectory craniocaudal**: Parallel to endplates (0-5° caudal angulation) - **Depth**: 80-90% of vertebral body AP diameter (40-45mm typical), bicortical preferred for upper lumbar (L1-L3), unicortical acceptable for lower lumbar (L4-L5 where anterior vascular structures at risk) **Pedicle Screw Complications:** - **Medial breach**: Screw penetrates medial pedicle wall → canal encroachment, nerve root or thecal sac compression (5-10% incidence with freehand technique, less than 2% with navigation) - **Lateral breach**: Screw penetrates lateral pedicle wall → exiting nerve root injury in foramen (2-5% incidence) - **Superior breach**: Screw placed too superiorly → exiting nerve root injury at superior foramen (1-3% incidence) - **Anterior breach**: Screw penetrates anterior vertebral body → vascular injury (aorta, IVC, iliac vessels), very rare less than 0.5% but catastrophic ## Indications TLIF is indicated for lumbar conditions requiring interbody fusion with posterior instrumentation: 1. **Degenerative spondylolisthesis** (Grade I-II) - MOST COMMON indication 2. **Isthmic spondylolisthesis** (Grade I-II) with instability 3. **Degenerative disc disease** with instability or failed conservative management (>6 months PT, injections, medications) 4. **Recurrent disc herniation** after prior discectomy (unstable segment) 5. **Adjacent segment disease** after prior fusion 6. **Post-laminectomy instability** (iatrogenic instability from extensive decompression) **Contraindications:** - High-grade spondylolisthesis (Grade III-IV) - TLIF access difficult, consider ALIF or PLIF - Severe central stenosis requiring extensive bilateral laminectomy - PLIF or decompression alone - Osteoporosis with high subsidence risk - consider ALIF (better endplate contact) or supplemental anterior support - Infection or tumor - requires different approach/techniques ## Patient Positioning - **Prone position** on Jackson table or Wilson frame (hip flexion 30-45° opens interlaminar space, reduces lumbar lordosis, facilitates access) - **Chest and iliac crest support** (avoids abdominal compression - reduces epidural venous pressure, decreases bleeding) - **Arms positioned** on arm boards (flexed at shoulder 90°, elbow 90°) - **Face positioned** on horseshoe headrest or mirror (avoid eye compression, check eyes every 30-60 minutes during long cases) - **Fluoroscopy positioned** for AP and lateral lumbar spine views (confirm level before incision) **Australian Practice Note:** General anesthesia with neuromonitoring (somatosensory evoked potentials SSEPs, motor evoked potentials MEPs, electromyography EMG) is STANDARD in Australia for all lumbar fusions (monitors spinal cord and nerve root function intraoperatively, detects nerve injury in real-time). ## Skin Incision and Posterior Exposure ### Step 1: Mark Incision and Confirm Level Obtain lateral fluoroscopy image - identify target level (count from L5 - most caudal lumbar vertebra with disc space, upward to L4, L3, etc.). Mark skin incision MIDLINE over spinous processes, centered at target level, extending 2 levels above and below (e.g., for L4-5 TLIF, incision from L3 spinous process to L5 spinous process, total 6-8cm length). **Alternative:** Paramedian incision (2-3cm lateral to midline) for MIS-TLIF (not described here - this is open technique). ### Step 2: Incise Skin and Fascia Incise skin and subcutaneous tissue MIDLINE down to thoracolumbar fascia. Use electrocautery to incise fascia MIDLINE over spinous processes (bloodless plane), extending full length of incision. Elevate fascia laterally off spinous processes and lamina using electrocautery or Cobb elevator (subperiosteal dissection). ### Step 3: Paraspinal Muscle Dissection Elevate paraspinal muscles (multifidus, longissimus) OFF lamina and facets using electrocautery or Cobb elevator (SUBPERIOSTEAL - stay on bone, reduces bleeding). Dissect laterally to expose: - **Lamina** (posterior arch of vertebra) - **Spinous process** (midline) - **Facet joints** (lateral to lamina) - **Transverse processes** (lateral limit of dissection - pedicle screws placed here) Place self-retaining retractor (e.g., McCullough retractor, Caspar retractor) to hold muscles laterally and maintain exposure. Confirm level with LATERAL fluoroscopy (marker on target level spinous process). ## Pedicle Screw Insertion (Performed FIRST, Before Decompression) ### Step 4: Pedicle Screw Entry Points Identify pedicle screw entry points BILATERALLY at target level (L4 and L5 for L4-5 TLIF) and adjacent level if multi-level fusion. Entry point landmarks: - **Mamillo-accessory notch** (junction of mammillary process and accessory process on transverse process) - **OR** junction of lateral pars interarticularis and superior facet ("eye of Scotty dog" on lateral fluoroscopy) - Entry point is typically 3-5mm LATERAL to facet joint and 2-3mm INFERIOR to superior endplate of pedicle Use high-speed burr to decorticate entry point (remove cortical bone, expose cancellous pedicle). ### Step 5: Pedicle Probing and Tapping Insert pedicle probe (Lenke or Magerl probe) into entry point, directed ~10-15° CONVERGENT (medially, toward midline) in transverse plane and PARALLEL to endplates in sagittal plane. Advance probe through pedicle into vertebral body (40-45mm depth typical), palpating walls of pedicle with probe (feel bone on all four sides - superior, inferior, medial, lateral - confirms intra-pedicle trajectory). **CRITICAL:** If probe BREACHES pedicle wall (no resistance on one side), REMOVE probe, redirect entry point or trajectory, reprobe. DO NOT advance probe or screw if medial breach (canal encroachment) or lateral breach (exiting nerve root injury). After successful probing, use pedicle tap (same diameter as intended screw) to create threaded pathway for screw. Confirm trajectory with LATERAL and AP fluoroscopy: - **Lateral view**: Probe/tap parallel to endplates, extending into anterior 80-90% of vertebral body - **AP view**: Probe/tap 10-15° convergent, within pedicle borders (no medial or lateral breach) ### Step 6: Pedicle Screw Insertion Insert pedicle screws (typically 5.5-6.5mm diameter, 40-50mm length) along probed trajectory. Use fluoroscopy to confirm screw position (AP and lateral views). Perform triggered EMG on each screw: - **Threshold greater than 8-10mA**: SAFE (screw in bone, not touching nerve) - **Threshold less than 8mA**: CONCERN for nerve proximity (screw may be breaching medial pedicle wall or laterally into foramen), consider screw removal and replacement Leave screw heads TALL (do NOT fully seat screws) - allows rod connection later without compressing decompression site. ## Unilateral Facetectomy and Decompression ### Step 7: Choose Side for TLIF TLIF is performed UNILATERALLY (one side only, typically RIGHT or LEFT). Choose side based on: - **Pathology side**: If lateral recess stenosis or foraminal stenosis predominant on one side, choose THAT side for TLIF (combines decompression + fusion) - **Surgeon preference**: Most surgeons have a preferred side (right-handed surgeons often prefer RIGHT side for ergonomics) - **Contralateral facet preservation**: The NON-TLIF side preserves facet (maintains 40% stability, reduces adjacent segment disease) For this description, assume RIGHT-SIDED TLIF (access disc from right side). ### Step 8: Laminotomy (Partial Laminectomy) On the RIGHT side, use Kerrison rongeurs to remove the INFERIOR portion of the lamina (cephalad vertebra, e.g., L4 lamina for L4-5 TLIF). Remove lamina medial to facet joint, exposing underlying ligamentum flavum. Extend laminotomy superiorly to expose superior edge of facet joint. **Goal:** Create space for facetectomy and access to neural foramen (laminotomy exposes ligamentum flavum and superior facet medially). ### Step 9: Facetectomy (Remove Medial 50-60% of Superior Facet) Use high-speed burr or Kerrison rongeurs to remove the MEDIAL 50-60% of the SUPERIOR facet (e.g., right L5 superior facet for right L4-5 TLIF). This is the CRITICAL step for exposing Kambin's triangle and exiting nerve root. **Facetectomy Technique:** 1. **Identify facet joint capsule**: Incise capsule with scalpel or cautery (exposes cartilage of facet joint) 2. **Drill medial facet**: Using high-speed burr (5mm diamond burr), thin medial 50-60% of superior facet in INCREMENTS (do NOT drill through full thickness aggressively - risk of nerve laceration). Keep irrigation on burr (bone dust obscures nerve, heat damages nerve). 3. **Identify exiting nerve root**: As medial facet is thinned, the exiting nerve root becomes visible DEEP to facet (use micro-Kerrison rongeurs to remove final layer of bone over nerve). The nerve is a soft, white, pulsatile structure at the SUPERIOR aspect of foramen, 3-5mm medial to lateral pedicle wall. 4. **Palpate nerve**: Use ball-tip probe or angled nerve hook to GENTLY palpate exiting nerve root - confirm nerve is mobile, not tethered, and out of working zone for disc access. 5. **Preserve lateral 40-50% of facet**: Do NOT remove entire facet - lateral facet protects exiting nerve and maintains some stability. **CRITICAL:** Inadequate facetectomy (less than 50% removed) is the #1 cause of exiting nerve root injury - surgeon cannot SEE nerve during disc access, leading to blind instrumentation and nerve laceration. Adequate facetectomy (greater than 50%) allows nerve visualization and safe disc access. ### Step 10: Ligamentum Flavum Removal After facetectomy, remove ligamentum flavum from interlaminar space using Kerrison rongeurs. Start laterally (at facet) and work medially toward midline. Ligamentum flavum is THICK (3-5mm) and YELLOW (hence "flavum" = yellow). **Goal:** Expose epidural space, thecal sac medially, and exiting nerve root laterally (completes decompression of central and lateral recess stenosis). ## Discectomy and Endplate Preparation Through Kambin's Triangle ### Step 11: Identify Kambin's Triangle With facetectomy complete and ligamentum flavum removed, identify Kambin's triangle: - **Superior border**: Exiting nerve root (e.g., RIGHT L4 nerve root for right L4-5 TLIF) - visible at superior foramen, beneath pars and superior facet (already mobilized during facetectomy) - **Inferior border**: Traversing nerve root (e.g., L5 nerve root) - visible in canal, descending medial to exiting nerve, covered by epidural fat - **Medial border**: Thecal sac (dura) - visible medially in canal after ligamentum flavum removal The triangle is the SPACE between these three structures - this is the "safe zone" for disc access (instruments pass through triangle without retracting nerves). ### Step 12: Annulotomy and Discectomy Using a #15 scalpel blade on a long handle, make an annulotomy (incise annulus fibrosus) over the RIGHT lateral disc space (within Kambin's triangle, between exiting and traversing nerve roots). Typical annulotomy size 10-12mm (vertical incision). **Discectomy Technique:** 1. **Remove nucleus pulposus**: Use pituitary rongeurs and angled curettes to remove soft nucleus centrally (bulk of disc) 2. **Remove annulus**: Extend discectomy circumferentially, removing annular fibers from anterior, contralateral (left), and posterior disc space. Goal: 360° discectomy (remove ALL disc material down to vertebral endplates). 3. **Preserve posterior longitudinal ligament (PLL)**: Do NOT violate PLL (posterior boundary of disc space, separates disc from thecal sac anteriorly). PLL violation causes CSF leak if dura torn. 4. **Contralateral disc access**: Use angled curettes and reverse-angle rongeurs to reach LEFT (contralateral) side of disc space through RIGHT-sided annulotomy (work around thecal sac anteriorly - PLL separates instruments from dura). **CRITICAL:** Complete discectomy (remove ALL disc material, 360° circumferential) is ESSENTIAL for fusion - residual disc material blocks bone graft incorporation and causes pseudarthrosis. ### Step 13: Endplate Preparation After discectomy, prepare vertebral endplates (superior L5 endplate and inferior L4 endplate) for fusion: 1. **Remove cartilaginous endplate**: Use curettes or endplate scrapers to remove thin cartilaginous layer (0.5-1mm) from both endplates - exposes bleeding cancellous bone (necessary for fusion) 2. **Preserve subchondral bone**: Do NOT violate thick subchondral bone (dense bone beneath cartilage) - provides structural support, prevents cage subsidence 3. **Create bleeding bone bed**: Endplates should be actively bleeding (confirms viable bone for fusion) **Balance:** Remove cartilage (non-vascular, blocks fusion) but preserve subchondral bone (structural support). Over-aggressive endplate preparation causes subsidence (cage migrates into soft cancellous bone - 8-15% incidence). ## Interbody Cage Insertion and Bone Graft ### Step 14: Measure and Size Cage Measure disc space height and depth using trial spacers or calipers. Select appropriate cage: - **Height**: Restore disc height to pre-degenerative state (typically 10-12mm at L4-5, 8-10mm at L5-S1) - **Depth**: 25-30mm typical (fits within anterior 60-70% of disc space - avoid oversizing anteriorly, risk of cage migration into retroperitoneum or vascular injury) - **Width**: 10-12mm (fits through Kambin's triangle annulotomy) - **Lordosis**: 6-10° lordotic angle built into cage (restores lumbar lordosis) **Cage types:** - **PEEK cages**: Most common, radiolucent (allows fusion assessment), filled with bone graft or BMP - **Titanium cages**: Radiopaque (obscures fusion on X-ray), higher subsidence risk - **Expandable cages**: Inserted collapsed, expanded in situ (less endplate preparation needed, but higher cost) ### Step 15: Pack Cage with Bone Graft Fill cage central cavity with bone graft: - **Autograft**: Local bone (laminectomy bone, facet bone) morselized - GOLD STANDARD (best osteogenic potential) - **Allograft**: Freeze-dried or fresh-frozen cancellous chips (if inadequate autograft) - **Bone graft substitute**: BMP (bone morphogenetic protein, e.g., Infuse), demineralized bone matrix (DBM), synthetic graft (calcium phosphate, hydroxyapatite) Compress graft into cage (maximize graft volume). Pack graft around edges of cage as well (additional graft in disc space, outside cage). ### Step 16: Insert Cage Under Fluoroscopy Using cage holder/inserter, advance cage through annulotomy into disc space under continuous LATERAL fluoroscopy (ensures cage positioned centrally in disc space, not posteriorly). Insert cage from RIGHT side, angled slightly LEFT (toward contralateral side) to center cage in disc space. **Fluoroscopy Confirmation:** - **Lateral view**: Cage at midline of disc space (anteroposterior), parallel to endplates, within anterior 60-70% of vertebral body (NOT too anterior - risk of vascular injury or retroperitoneal migration) - **AP view**: Cage centered mediolaterally, symmetric positioning (NOT too far right or left) **CRITICAL:** Avoid oversizing cage height (causes subsidence or endplate fracture), under-sizing (inadequate disc height restoration, foraminal stenosis persists), or excessive anterior placement (cage migrates anteriorly into retroperitoneum or injures great vessels - RARE less than 0.5% but catastrophic). ### Step 17: Place Additional Bone Graft Posterolaterally After cage inserted, pack additional bone graft posterolaterally (in gutter between transverse processes, over pedicle screws, along lateral fusion bed). This supplements interbody fusion with posterolateral fusion (360° fusion - interbody PLUS posterolateral). ## Rod Placement and Compression ### Step 18: Connect Rods to Pedicle Screws Bend rods (5.5mm diameter cobalt-chromium or titanium rods) to match lumbar lordosis (typically 40-60° lordosis from L1-S1, with most lordosis at L4-5 and L5-S1 levels). Insert rods into screw heads (pass rod through open screw heads from caudal to cephalad). Provisionally tighten set screws (setscrews secure rod to screw head). ### Step 19: Apply Compression Across Disc Space Using rod persuader or compression instrument, apply compression force across disc space (brings vertebral endplates together, compresses bone graft in cage, promotes fusion). Compression is applied by tightening setscrews while maintaining compression force. **Compression Goals:** - Restore disc height (not over-distract) - Compress graft (but not excessively - graft should be under compression loading, not crushed) - Maintain lumbar lordosis (rods should match pre-operative lordosis) ### Step 20: Final Fluoroscopy and Closure Obtain AP and lateral fluoroscopy to confirm: - **Pedicle screws**: All screws within pedicles, no breaches, appropriate depth - **Cage**: Centered in disc space, parallel to endplates, appropriate height - **Rods**: Secure to all screws, lordotic contour If satisfactory, perform FINAL wound irrigation with antibiotic solution (bacitracin 50,000 units in 1L saline), place deep drain (if desired - reduces hematoma), close fascia with #1 absorbable suture (Vicryl), close subcutaneous tissue with 2-0 absorbable, close skin with 3-0 non-absorbable (nylon) or staples. **Post-operative immobilization:** LSO brace for 6-12 weeks if single-level TLIF (supports fusion during early healing), NOT required if solid instrumentation and patient has good bone quality. 7 days despite conservative treatment - revision surgery required (re-explore, repair tear, muscle/fascia graft). UNRECOGNIZED TEAR (presents post-operatively): Patient develops positional headache, nausea, photophobia (classic CSF leak symptoms) or wound drainage (clear fluid, positive beta-2 transferrin confirms CSF). Management: (1) Conservative FIRST - bed rest, IV fluids, analgesics (caffeine, NSAIDs for headache), 80% heal spontaneously with conservative treatment, (2) Blood patch (inject autologous blood epidurally - seals leak, effective in 60-80%), (3) Lumbar drain (reduces CSF pressure, 3-5 days), (4) Surgical repair if conservative fails (re-explore wound, identify tear, repair primarily or with graft). PREVENTION: Gentle thecal sac retraction (avoid forceful medial retraction), blunt dissection (avoid sharp instruments near dura), adequate bone removal (smooth bone edges before dural manipulation - sharp edges tear dura), careful PLL preservation during discectomy (PLL is barrier between disc and dura - do NOT violate posteriorly)." /> ## Post-operative Protocols **Phase 1 (Days 0-2): Immediate Post-op** - **ICU/HDU monitoring**: Not routinely required (unlike complex multi-level fusions or patients with comorbidities) - **Pain control**: Multimodal analgesia (acetaminophen 1g Q6h, NSAIDs cautiously - concern for fusion impairment, opioids PRN via PCA, consider epidural for first 24-48 hours) - **Early mobilization**: Out of bed to chair post-op day 1 (early mobilization reduces VTE risk, ileus, pulmonary complications), walking with assistance day 1-2 - **Neuromonitoring**: Continue EMG/SSEP monitoring for first 2-4 hours post-op (detect delayed neurological deficit from hematoma or retraction injury) - **Drain management**: Remove deep drain when output less than 50mL per 8-hour shift (typically 24-48 hours post-op) - **Urinary catheter**: Remove day 1 (prolonged catheterization increases UTI risk) - **Discharge**: Typically post-op day 3-5 for open TLIF, day 2-3 for MIS-TLIF **Phase 2 (Weeks 0-6): Brace and Activity Modification** - **LSO brace**: If single-level TLIF - wear brace during upright activities for 6-12 weeks (supports fusion, reduces motion). NOT required if solid instrumentation and multi-level fusion (instrumentation provides adequate stability). - **Activity**: NO bending, lifting greater than 10 pounds, twisting for 6-12 weeks (until fusion progressing) - **Walking**: Unlimited walking encouraged (promotes healing, cardiovascular fitness, does NOT harm fusion) - **Driving**: Resume at 4-6 weeks if no opioids and adequate mobility (twisting to check blind spots may strain fusion site - delay until 6 weeks) - **Return to sedentary work**: 6-8 weeks (desk work, no lifting) - **X-rays**: AP and lateral lumbar spine at 2 weeks, 6 weeks, 3 months (assess hardware position, disc height, 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 6 months if fusion questionable on X-ray (CT is gold standard - shows trabecular bone bridging through cage) - **Physical therapy**: Core strengthening, lumbar stabilization exercises (once fusion solid - typically 3-6 months) - **Return to manual labor**: 6-9 months (based on fusion status and functional recovery) - **Return to high-impact activities**: 9-12 months (running, contact sports - only after confirmed solid fusion on CT) **Phase 4 (12+ Months): Long-term Surveillance** - **Annual X-rays**: Monitor for adjacent segment disease (disc degeneration above or below fusion level) - **Assess function**: ODI (Oswestry Disability Index), VAS pain scores (track long-term outcomes) - **Address complications**: Hardware failure (screw breakage, rod fracture - rare less than 2% if solid fusion), pseudarthrosis (persistent pain >12 months, no bridging bone on CT - requires revision) **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 6-12 weeks for sedentary work, 6-9 months for manual labor. Inpatient rehabilitation (2-4 weeks) is occasionally needed for complex multi-level fusions or elderly patients with limited mobility, but NOT routine for single-level TLIF. ## Complications ### Intraoperative Complications **1. Exiting Nerve Root Injury (1-8% - MOST COMMON Neurological Complication)** - **Presentation**: Intraoperative EMG activity (spontaneous or triggered less than 8mA threshold during facetectomy or pedicle screw placement), patient reports radicular pain in distribution of exiting nerve post-operatively (e.g., L4 nerve injury causes anterior thigh pain and quadriceps weakness) - **Mechanism**: Facetectomy (64% of injuries - Kim 2006, overzealous drilling or rongeur laceration), upper pedicle screw malposition (18% - screw too lateral or superior), aggressive lateral retraction (18% - nerve stretched over pedicle) - **Management**: - **Intraoperative detection (EMG fires)**: STOP, identify cause (facet drilling, screw placement, retraction), address cause (reposition screw, release retraction, stop drilling and use Kerrison rongeurs), confirm nerve intact (visualize nerve, palpate with nerve hook - should be soft, not transected), continue if nerve intact - **Post-operative deficit (motor or sensory)**: Obtain URGENT MRI or CT myelogram (rule out hematoma compression - if present, requires emergent re-exploration and evacuation), if imaging shows no compressive lesion (hematoma, cage malposition), likely neuropraxia or stretch injury - manage conservatively - **Prognosis**: Neuropraxia (most common - 70-80% of injuries) recovers over 3-6 months (64% full recovery - Kim 2006), axonotmesis (nerve intact but axons damaged) recovers slower (12-18 months, 30-40% full recovery), neurotmesis (nerve transected) does NOT recover (requires nerve exploration and repair or grafting - poor outcomes) - **Prevention**: Adequate facetectomy (greater than 50% medial facet removed allows nerve visualization), micro-Kerrison rongeurs for final bone removal over nerve (NOT high-speed burr), neuromonitoring with EMG (threshold greater than 8mA confirms safe screw position), gentle retraction with frequent release **2. Dural Tear (3-8%)** [Covered comprehensively in SafetyAlert above] **3. Cage Malposition (2-5%)** - **Presentation**: Post-operative X-ray shows cage too posterior (canal encroachment, nerve root compression), too anterior (risk of vascular injury or retroperitoneal migration), or too lateral (foraminal stenosis, exiting nerve compression) - **Management**: If cage causing neural compression (radiculopathy, cauda equina), requires URGENT revision (remove cage, reposition correctly). If asymptomatic malposition, observe. - **Prevention**: Continuous fluoroscopy during cage insertion (lateral and AP views), confirm cage position before wound closure ### Early Post-operative Complications (less than 6 weeks) **1. Hematoma with Neurological Deficit (2-5%)** - **Presentation**: New or progressive neurological deficit 6-24 hours post-op (foot drop, cauda equina syndrome), back pain, wound swelling - **Diagnosis**: URGENT MRI or CT (shows epidural hematoma compressing thecal sac or nerve roots) - **Management**: URGENT re-exploration and evacuation (decompress neural elements, achieve hemostasis, close over drain). Delay >24 hours reduces chance of neurological recovery. - **Prevention**: Meticulous hemostasis during closure, deep drain placement (evacuates blood, reduces hematoma formation), monitor neurological status closely first 24 hours (neuro checks every 2-4 hours) **2. Wound Infection (2-5%)** - **Superficial infection** (1-2%): Erythema, purulent drainage, cellulitis within 2-4 weeks. Management: Oral antibiotics (eTG: cephalexin 500mg QID or clindamycin 300mg TDS, 7-10 days), wound care, close monitoring. - **Deep infection** (1-3%): Persistent drainage, wound dehiscence, exposed hardware, fever, elevated CRP/ESR. Management: IV antibiotics (eTG: vancomycin 25-30mg/kg IV loading, then 15-20mg/kg IV Q8-12h based on levels + ceftriaxone 2g IV daily, adjust per cultures), surgical debridement (remove necrotic tissue, irrigate, RETAIN hardware if fixation stable - removal causes instability), negative pressure wound therapy (NPWT), prolonged antibiotics (6-12 weeks IV + PO). - **Prevention**: Pre-operative antibiotics (cefazolin 2g IV within 1 hour of incision), re-dose Q4 hours if surgery >4 hours, meticulous sterile technique, minimize operative time, blood glucose control if diabetic (target less than 180mg/dL perioperatively) **3. DVT/PE (8-12%)** - **Risk factors**: Posterior lumbar surgery has HIGHER VTE risk than anterior (8-12% vs 2-5%) - prolonged immobility, prone positioning, epidural venous plexus manipulation - **Presentation**: Calf pain, leg swelling (DVT), dyspnea, chest pain, hypoxia (PE) - **Management**: Venous duplex (DVT), CT pulmonary angiography (PE), therapeutic anticoagulation (enoxaparin 1.5mg/kg SC daily OR apixaban 10mg BD × 7 days then 5mg BD for 3 months) - **Prevention**: LMWH prophylaxis (enoxaparin 40mg daily) for 4-6 weeks post-op until mobilized (PBS-listed in Australia - STANDARD), early mobilization (out of bed day 1), sequential compression devices intraoperatively and post-op ### Late Complications (greater than 6 weeks) **1. Pseudarthrosis (8-15%)** - **Presentation**: Persistent back pain >6 months post-op, no improvement with conservative treatment, pain worse with activity - **Diagnosis**: CT scan at 12 months (gold standard) shows no bridging bone through cage or posterolateral fusion mass (radiolucency around cage, no trabecular continuity) - **Risk factors**: Smoking (OR 3.8 - impairs bone healing, Quitline 13 7848), diabetes (OR 2.3), NSAIDs (chronic use impairs fusion - avoid NSAIDs >3 months post-op), inadequate graft volume, excessive motion (insufficient instrumentation) - **Management**: Revision surgery - revision TLIF with larger cage and BMP (bone morphogenetic protein), OR anterior supplementation (ALIF if posterior TLIF failed), OR extension of fusion to adjacent levels if instability adjacent - **Prevention**: Smoking cessation (MANDATORY - discuss pre-op, delay elective surgery until smoke-free >4 weeks), avoid NSAIDs >3 months post-op (use acetaminophen for pain), adequate bone graft volume (pack cage and posterolateral gutters completely), brace for 6-12 weeks (reduces motion during healing) **2. Subsidence (8-15%)** - **Presentation**: Recurrent back pain or radiculopathy 2-6 months post-op (after initial improvement), loss of disc height on X-ray (cage migrates into vertebral body endplate) - **Definition**: Cage migration greater than 2mm into endplate (measured on lateral X-ray or CT) - **Risk factors**: Osteoporosis (OR 3.5 - Malham 2017), over-aggressive endplate preparation (removes structural subchondral bone), oversized cage (excessive distraction fractures endplate) - **Management**: If asymptomatic (70% of cases), observe. If symptomatic (30%), revision with anterior supplementation (ALIF) or larger cage. - **Prevention**: Screen for osteoporosis pre-op (DEXA scan for at-risk patients - females greater than 50, males greater than 60, PBS-subsidized in Australia), treat osteoporosis before surgery (bisphosphonates or denosumab 3-6 months pre-op), appropriate endplate preparation (remove cartilage but preserve subchondral bone) **3. Adjacent Segment Disease (ASD, 12-15% at 5 Years for TLIF)** - **Presentation**: New back pain or radiculopathy 2-5 years after fusion (pain above or below fusion level) - **Mechanism**: Fusion eliminates motion at fused level, transferring stress to adjacent levels (accelerates degenerative changes). TLIF has LOWER ASD than PLIF (12.8% vs 25.6% at 5 years - Park 2011) due to contralateral facet preservation. - **Management**: Conservative first (PT, NSAIDs, epidural steroid injection), revision surgery if conservative fails (extend fusion to adjacent level) - **Prevention**: Maintain lumbar lordosis at index fusion (reduces adjacent level stress), preserve contralateral facet (TLIF advantage over PLIF - 40% stability maintained reduces ASD risk) 1cm), consider nerve grafting (sural nerve graft from leg) - but outcomes poor (30-40% functional recovery). Post-operative: refer to neurosurgery for nerve exploration at 3-6 months if NO recovery - may offer neurolysis, nerve grafting, or nerve transfer. Counsel patient about PERMANENT deficit (foot drop, numbness) requiring AFO.)", "What is the prognosis for recovery if nerve was only irritated (neuropraxia)? (GOOD prognosis - Kim 2006 study: 64% of neuropraxia injuries recovered COMPLETELY by 6 months, 80% by 12 months. Mechanism: neuropraxia is conduction block without structural damage - myelin sheath damaged but axons intact, nerve recovers as myelin regenerates. Patient may have transient weakness or numbness for 3-6 months, then gradual improvement. Manage with PT, AFO if foot drop, reassurance.)", "How do you prevent this complication in future TLIF cases? (CRITICAL PREVENTION: (1) Adequate facetectomy FIRST - remove medial 50-60% of superior facet using micro-Kerrison rongeurs, identify nerve BEFORE drilling near it (Kim 2006: inadequate facetectomy OR 3.8 for injury), (2) Switch to rongeurs near nerve - do NOT use high-speed burr for final bone removal over nerve (burr provides no tactile feedback, risk of plunging through bone into nerve), (3) Drill incrementally - thin facet gradually (NOT full thickness aggressively), keep irrigation ON, (4) Neuromonitoring - EMG threshold greater than 8mA confirms safe distance from nerve during drilling and pedicle screw placement)" ]} />

Transforaminal Lumbar Interbody Fusion (TLIF) Approach

Transforaminal Lumbar Interbody Fusion (TLIF) Approach