Posterior Approach to Lumbar Spine

Surface Landmarks and Level Identification

Iliac crest palpation - the Tuffier line:

The Tuffier line is an imaginary line connecting the highest points of the iliac crests bilaterally. In 90% of patients, this line crosses the L4-5 disc space or L4 vertebral body. This is the most reliable surface landmark for identifying L4-5 level (the most commonly operated lumbar level).

Spinous process palpation:

The L5 spinous process is the last palpable mobile spinous process before the sacrum (S1 is the first fixed spinous process, often flush with sacral surface). Counting up from L5 identifies L4, L3, etc. However, lumbosacral transitional vertebrae (sacralized L5 or lumbarized S1) occur in 10-15% of patients and cause counting errors.

CRITICAL: Always confirm level with fluoroscopy before incision (place spinal needle on skin, count from sacrum on lateral X-ray). Wrong-level surgery is a never event.

Skin and Subcutaneous Layers

Skin:

Lumbar skin is thick with robust subcutaneous fat (average 2-3cm, up to 10cm in obese patients). The skin is well-vascularized but obesity and smoking increase wound complications.

Subcutaneous tissue:

Fibrous septae connect skin to thoracolumbar fascia (tough fascial layer covering paraspinal muscles). These septae must be released to mobilize skin for retraction.

Thoracolumbar fascia:

Three-layer fascial system (posterior, middle, anterior layers) that encloses the paraspinal muscles. The posterior layer (superficial) is incised in the midline during surgery. It is thick and provides strong tissue for closure.

Paraspinal Muscles

Superficial layer:

1. Latissimus dorsi: Large muscle covering upper lumbar region (L1-3). Usually retracted laterally, occasionally divided for extensive exposure.
2. Serratus posterior inferior: Thin muscle arising from lower ribs, inserts on thoracolumbar fascia. Usually not encountered in lumbar approaches.

Deep layer (key surgical muscles):

1. Erector spinae group (lateral):

   • Iliocostalis lumborum (most lateral)
   • Longissimus thoracis (middle)
   • These muscles are innervated by dorsal rami of spinal nerves

2. Multifidus (medial to erector spinae):

   • Runs from sacrum to C2, filling the groove between spinous processes and transverse processes
   • Innervated by medial branch of dorsal rami (segmental innervation)
   • This is the PRIMARY muscle encountered during posterior lumbar approach
   • Subperiosteal dissection of multifidus off spinous processes and laminae is the key step

Wiltse internervous plane (for lateral/minimally invasive approaches):

The plane between longissimus (lateral) and multifidus (medial) at the lateral edge of the facet joint represents a true internervous plane (different branches of dorsal rami innervate these muscles). The Wiltse approach splits muscles here to access the transverse process and pars interarticularis with minimal muscle denervation.

Bony Anatomy - Lumbar Vertebra

Spinous process:

Large, rectangular, horizontal spinous processes (different from thoracic which are long and oblique). The interspinous space (gap between adjacent spinous processes) is palpable and provides window for ligamentum flavum access.

Lamina:

Flat bone connecting pedicles posteriorly. The lamina forms the roof of the spinal canal. Laminectomy = removal of lamina to decompress spinal canal.

Facet joints (zygapophyseal joints):

Superior articular process (SAP) and inferior articular process (IAP) form the facet joint. The facet joint capsule contains nociceptors (pain receptors) and is a common source of back pain (facet-mediated pain).

Critical for pedicle screw placement: The lateral facet-transverse process junction is the entry point for pedicle screws. Violation of the facet joint during screw placement increases adjacent segment disease risk.

Pedicle:

The pedicle connects the vertebral body to the posterior elements (lamina, facet, transverse process). The pedicle is a cylindrical bony tube that provides the strongest fixation point in the vertebra.

Pedicle dimensions:

• L1-4: Pedicle diameter 8-12mm (narrowest at L1, widest at L5)
• L5: Pedicle diameter 12-18mm (largest pedicle)
• Pedicle height (craniocaudal): 14-18mm
• Pedicle axis: 10-15° medial convergence, 10-15° caudal angulation

Safe zone for pedicle screw: Screw should be within the cortical boundaries of the pedicle. Medial breach (screw penetrates medial cortex) risks nerve root or cauda equina injury. Lateral breach (screw penetrates lateral cortex) is safer but provides less fixation.

Transverse process:

Lateral bony projection arising from pedicle-lamina junction. The transverse process is the insertion point for multifidus, longissimus, and iliocostalis muscles. It serves as a landmark for pedicle screw entry point (at the junction of lateral facet and transverse process base).

Pars interarticularis:

Isthmus of bone connecting superior and inferior articular processes (between facets). This is the thinnest part of the posterior arch and the site of spondylolysis (stress fracture of pars). Bilateral pars fractures allow anterior slip of vertebra (spondylolisthesis).

Neural Elements

Spinal cord termination:

The conus medullaris (distal spinal cord) terminates at the L1-2 level in adults (at birth it is at L3, ascends as spine grows). Below L1-2, the spinal canal contains the cauda equina (nerve roots of L2-S5 and coccygeal nerves).

Cauda equina:

Named for resemblance to "horse's tail." The cauda equina nerve roots float in CSF within the thecal sac. They are more mobile than the spinal cord and more tolerant of retraction (cord cannot be retracted without injury, cauda equina can be gently retracted).

Nerve root anatomy:

Each lumbar nerve root has:

1. Ventral root (motor) and dorsal root (sensory) merge to form spinal nerve
2. Dorsal root ganglion (DRG) sits in or just lateral to the intervertebral foramen
3. Spinal nerve exits below the correspondingly numbered pedicle (L4 nerve exits below L4 pedicle in L4-5 foramen)

Two nerve roots at risk at each disc level:

At L4-5 disc space:

1. Traversing root (L5): Crosses the L4-5 disc space MEDIALLY, traveling toward the L5-S1 foramen (exits below L5 pedicle)
2. Exiting root (L4): Already exited the spinal canal at L4-5 foramen (lateral to disc), traveling in neural foramen

Most disc herniations are posterolateral (lateral to midline but medial to foramen) and compress the traversing root (L5 root at L4-5 level). Far lateral herniations (lateral to foramen) compress the exiting root (L4 root at L4-5 level).

Far-out syndrome:

Compression of L5 nerve root in the L5-S1 foramen (between L5 transverse process and sacral ala). This is NOT a disc herniation - it is bony compression from large L5 transverse process or high-grade spondylolisthesis. Requires foraminotomy (remove L5 transverse process or sacral ala) for decompression.

Dura and Epidural Space

Dura mater:

The dura is a tough, fibrous membrane that forms the thecal sac (CSF-containing sac surrounding cauda equina). The dura is adherent to ligamentum flavum (especially in elderly patients with stenosis), increasing dural tear risk during laminectomy.

Epidural fat:

The epidural space (between dura and spinal canal bone/ligamentum flavum) contains fat and the epidural venous plexus. The fat is yellow and soft - it is a visual landmark that you have entered the spinal canal during laminectomy.

Epidural veins:

Batson's plexus is a valveless venous system in the epidural space. These veins are fragile and bleed easily (but venous bleeding controlled with bipolar cautery and hemostatic agents). Epidural veins engorge during Valsalva maneuvers (coughing, straining) - coordinate with anesthesia to avoid high venous pressures during critical steps.

Ligamentum Flavum

The ligamentum flavum (Latin: "yellow ligament") connects adjacent laminae. It is a thick, elastic ligament that:

1. Hypertrophies with age (normal thickness 2-3mm, hypertrophic greater than 4mm)
2. Contributes to central stenosis when hypertrophic (narrows spinal canal from posterior)
3. Adheres to dura (especially in elderly and revision cases)

Surgical technique:

The ligamentum flavum is removed during laminectomy to decompress the spinal canal. It is incised laterally (at its attachment to lamina) with Kerrison rongeurs and elevated off the dura carefully (avoid dural tear).

Ligamentum flavum gap:

There is a midline gap in the ligamentum flavum (the ligamentum splits into right and left halves that meet in the midline but do not fuse). This gap is the entry point for epidural steroid injections and can be the site of disc herniation (central disc herniations extrude through this gap).

L5-S1 Unique Anatomy

Sacrum:

The sacrum is formed by fusion of S1-S5 vertebrae. The S1 vertebral body is angled (sacral slope typically 30-45°), making the L5-S1 disc space parallel to the floor when standing. This is different from L4-5 (which is angled 10-15°).

Surgical implications:

1. Trajectory: Pedicle screws at L5 and S1 have different trajectories (L5 screws angled caudally, S1 screws aimed toward sacral promontory)
2. Disc access: The L5-S1 disc is deeper (closer to anterior structures like iliac vessels) and requires different retractor angulation
3. Infection risk: L5-S1 has HIGHER infection risk (2-3x) compared to L4-5 due to proximity to rectum and longer path for hematoma drainage

Indications

1. Lumbar stenosis with neurogenic claudication (40% of cases):

Presentation: Bilateral leg pain, numbness, and weakness with walking (exacerbated by extension, relieved by sitting or flexion). Patients often report "shopping cart sign" (leaning forward on cart relieves symptoms). Neurogenic claudication is distinguished from vascular claudication by: relief with flexion (not just rest), can ride bike without symptoms (flexed posture), absent or weak pulses in vascular disease.

Pathoanatomy: Central canal stenosis (less than 10mm AP diameter is severe), lateral recess stenosis (less than 3mm), foraminal stenosis. Caused by: ligamentum flavum hypertrophy (most common), facet hypertrophy, disc bulging, spondylolisthesis.

Imaging: MRI shows canal stenosis with nerve root crowding. Cauda equina appears clumped together instead of separated (normal cauda equina has CSF around each root).

Conservative management: 6 months minimum trial of PT (flexion-based exercises), NSAIDs, epidural steroid injections. Surgery if persistent symptoms limiting function.

Surgical treatment: Laminectomy (remove lamina, ligamentum flavum, medial facet). Fusion added if: bilateral greater than 50% facetectomy (iatrogenic instability), pre-existing spondylolisthesis, pars defect.

2. Lumbar disc herniation with radiculopathy (30% of cases):

Presentation: Unilateral leg pain in dermatomal distribution (worse than back pain - leg pain greater than back pain is key for surgical candidacy). Positive straight leg raise (SLR), dermatomal sensory loss, myotomal weakness, reflex changes.

Common patterns:

• L4-5 disc → L5 radiculopathy (lateral leg, dorsum of foot, EHL weakness, no reflex loss)
• L5-S1 disc → S1 radiculopathy (posterior leg, plantar foot, gastroc-soleus weakness, absent Achilles reflex)

MRI correlation: Herniated disc compressing nerve root (extrusion or sequestration). Must correlate MRI findings with clinical symptoms (many patients have asymptomatic herniations).

Natural history: 80% of disc herniations improve with conservative treatment (6-12 weeks). Surgery indicated if: persistent pain beyond 6-12 weeks, progressive neurological deficit, cauda equina syndrome (EMERGENCY).

Cauda equina syndrome indications: Bilateral leg weakness, saddle anesthesia (perineal numbness), bladder dysfunction (retention or incontinence). Decompress within 48 hours of onset (significantly better recovery than after 48 hours); earlier surgery remains the prudent goal, and a proportion of patients have persistent bladder dysfunction despite timely decompression.

Surgical treatment: Microdiscectomy (interlaminar approach, sequestrectomy - remove loose fragment only, avoid aggressive discectomy which increases back pain).

3. Spondylolisthesis (20% of cases):

Definition: Anterior slip of one vertebra on another. Graded by Meyerding classification (percentage of vertebral body slip):

• Grade 1: 0-25% slip
• Grade 2: 25-50% slip
• Grade 3: 50-75% slip
• Grade 4: 75-100% slip
• Grade 5: Complete displacement (spondyloptosis)

Types:

1. Isthmic (type I): Pars defect (spondylolysis) allows slip. Common in athletes (gymnasts, football linemen). Occurs at L5-S1 in 80%.
2. Degenerative (type III): Facet arthropathy allows slip (no pars defect). Common in elderly females. Occurs at L4-5 in 80%.

Indications for surgery:

• Grade 2+ slip (greater than 25%)
• Mechanical back pain limiting function
• Radiculopathy or neurogenic claudication from stenosis at slip level
• Failed conservative management (6 months minimum)

Surgical treatment: Decompression (laminectomy) PLUS fusion (TLIF or PLIF with pedicle screw-rod construct). Decompression alone leads to progression of slip (30-50% progress within 2 years).

Reduction of slip: Controversial. Some surgeons reduce high-grade slips (Grade 3-4), others fuse in situ (without reduction) to avoid nerve stretch injury.

4. Degenerative disc disease with instability (10% of cases):

Definition: Painful disc with evidence of instability on flexion-extension X-rays (greater than 3mm translation or greater than 10° angulation).

Presentation: Mechanical back pain (worse with activity, better with rest), pain with transitions (sit-to-stand), no consistent radiculopathy.

Imaging: MRI shows disc degeneration (Modic changes Type I or II, loss of disc height greater than 50%, HIZ - high intensity zone in posterior annulus). Flexion-extension X-rays show instability.

Conservative management: 6-12 months minimum. PT (core strengthening), activity modification, NSAIDs. Surgery is LAST resort (fusion has significant morbidity).

Surgical treatment: Fusion (TLIF or PLIF with pedicle screws). Decompression NOT performed unless stenosis present (pure fusion for discogenic back pain).

5. Deformity (scoliosis, kyphosis) - 5% of cases:

Adult degenerative scoliosis: Coronal curve greater than 10° in skeletally mature patient. Causes: asymmetric disc degeneration, facet arthropathy. Symptoms: back pain, neurogenic claudication (stenosis at apex of curve), coronal imbalance (trunk shift).

Kyphosis: Sagittal plane deformity (loss of lumbar lordosis or thoracic hyperkyphosis). Causes: compression fractures, degenerative disc disease, ankylosing spondylitis.

Indications: Progressive deformity, neurological deficit, severe pain limiting function, coronal or sagittal imbalance (trunk forward lean greater than 5cm from pelvis).

Surgical treatment: Multilevel fusion (often L1-S1 or T10-pelvis), osteotomies for rigid deformity, anterior-posterior combined approach for severe cases.

Contraindications

Absolute:

1. Active infection (systemic sepsis, osteomyelitis, discitis without neurological compromise) - treat infection first
2. Severe medical comorbidity unable to tolerate surgery (severe COPD, heart failure, recent MI)
3. Cauda equina syndrome with dense paraplegia greater than 48 hours (poor prognosis for recovery, relative contraindication)

Relative:

1. Obesity (BMI greater than 35): Higher infection risk (5-10%), dural tear risk, technical difficulty. Consider weight loss before elective fusion.
2. Active smoking: Increases pseudarthrosis risk from 5-10% to 20-30%. Consider cessation before fusion (decompression alone can proceed).
3. Osteoporosis (T-score less than -2.5): Poor screw purchase, higher screw pullout risk. Consider bone cement augmentation or teriparatide pretreatment.
4. Psychiatric comorbidity (untreated depression, somatization): Poor outcomes from fusion. Address psychological factors before surgery.
5. Workers' compensation or litigation: Worse outcomes in all spine surgery categories. Counsel on realistic expectations.
6. Multilevel disease (4+ levels): Higher morbidity with long fusion. Consider staged procedures or motion-preserving alternatives.

Guidelines, Registries and Global Practice

Named-society indications (side by side):

• NASS (North America): Decompression for symptomatic stenosis or radiculopathy failing structured non-operative care; fusion added for instability or spondylolisthesis, not for isolated stenosis without instability.
• NICE / BOA (UK): Spinal decompression offered for stenosis or sciatica with persistent radicular symptoms after non-surgical management; routine fusion not recommended for non-specific low back pain.
• AOSpine / EFORT (Europe): Decompression alone favoured for degenerative stenosis; instrumented fusion reserved for demonstrable instability, deformity, or high-grade slip.

Return to work (general guidance, not jurisdiction-specific):

• Discectomy: 2-4 weeks sedentary, 6-12 weeks manual labour
• Laminectomy: 4-6 weeks sedentary, 3-4 months manual labour
• Fusion: 6-12 weeks sedentary, 6-9 months manual labour (await radiographic fusion before heavy loading)

Smoking cessation:

Document cessation counselling and consider deferring elective fusion until cessation is established (commonly 6-8 weeks), as smoking is the strongest modifiable risk factor for pseudarthrosis. Some surgeons use nicotine/cotinine testing before instrumented fusion.

Standard Prone Positioning

Jackson table or Wilson frame:

Most common positioning systems for posterior lumbar surgery. Both provide:

1. Abdomen free (reduces epidural venous engorgement, decreases blood loss)
2. Hips and knees flexed (reduces lumbar lordosis, opens interlaminar spaces)
3. Pressure relief for chest and pelvis (gel pads, foam supports)

Jackson table advantage: Adjustable (can increase or decrease lumbar flexion intraoperatively). Can "break" table for lateral X-ray without moving patient.

Wilson frame advantage: Simpler, radiolucent (easier fluoroscopy), lower cost.

Positioning Steps

1. Anesthesia induction:

Induce anesthesia supine on transport bed. Place large-bore IV access (14-16 gauge) and arterial line for fusion cases (blood loss monitoring).

2. Log-roll to prone:

Requires 4 people minimum (anesthesiologist at head, 3 to turn patient). Protect ETT (ensure secure, avoid extubation), protect IV lines and arterial line, support head and neck in neutral alignment. Roll patient onto positioning frame in one coordinated movement.

3. Head positioning:

Use ProneView headrest or horseshoe headrest to support forehead and allow eyes to be visible (check for pressure). Mirror placed below face to allow anesthesia to monitor eyes during case (check every 30 minutes for periorbital edema or pressure).

Alternative: Mayfield 3-pin skull fixation (used for long cases, allows perfect neutral head position, eliminates facial pressure risk).

4. Chest support:

Longitudinal gel rolls or chest supports under chest from shoulders to costal margins. Verify abdomen is free (palpate - should not feel abdominal wall against table). Allowing abdomen to rest on table compresses IVC, increases epidural venous pressure, and increases blood loss.

5. Pelvic support:

Gel pads or supports under iliac crests. Avoid direct pressure on abdomen.

6. Upper extremity positioning:

Arms positioned above head (swimmer's position) or at sides (arms tucked). Swimmer's position provides more access for anesthesia but risks brachial plexus stretch injury (keep shoulders abducted less than 90°, elbows flexed).

Arm-tuck technique: Tuck arms at sides with gel pads under elbows (ulnar nerve protection). Secure arms with tape or arm slings.

7. Lower extremity positioning:

Hips flexed 45-60°, knees flexed 30-45° (supported by leg rests or pillows). This position decreases lumbar lordosis and opens interlaminar spaces for easier laminectomy.

Calf compression devices: Sequential compression devices (SCDs) applied to calves for DVT prophylaxis (mechanical compression during long cases).

8. Fluoroscopy positioning:

C-arm positioned on patient's right side (surgeon stands on left). Ensure ability to obtain true lateral and AP images before prepping and draping. For L5-S1 imaging, may need to bring C-arm between patient's legs.

Pressure Point Checks

Critical areas to check:

1. Eyes: No direct pressure on globes (check with mirror every 30 minutes)
2. Elbows: Ulnar nerve padding
3. Knees: Padding at contact points
4. Breasts (in females): Position laterally, no compression
5. Genitals (in males): Ensure not compressed
6. Toes: Ensure no pressure from footrest (avoid compartment syndrome)

Recheck after surgical prep and draping - drapes can shift patient position.

Neurophysiological Monitoring

Somatosensory evoked potentials (SSEPs):

Monitor dorsal column (sensory) function. Electrodes placed on scalp (recording) and peripheral nerves (stimulation). Change in SSEP amplitude (greater than 50% decrease) or latency (greater than 10% increase) suggests spinal cord ischemia or injury.

Motor evoked potentials (MEPs):

Monitor ventral cord (motor) function. More sensitive than SSEPs for detecting cord injury. Transcranial electrical stimulation → motor response in limbs recorded.

EMG (electromyography):

Monitors individual nerve roots. Spontaneous EMG activity (triggered EMG) during pedicle screw placement suggests nerve root irritation (screw too close to root). Stimulation threshold less than 10mA suggests medial pedicle breach (screw in contact with nerve).

Use for fusion cases (pedicle screws) and decompression in presence of myelopathy or severe stenosis.

Step 1: Skin Incision and Superficial Dissection

Mark the incision:

Palpate spinous processes. Mark the midline over spinous processes corresponding to operative levels. Use fluoroscopy to confirm (place spinal needle on skin, obtain lateral X-ray, count from sacrum or L5).

Incision length:

• Single-level discectomy: 3-4cm incision centered over disc space
• Single or two-level laminectomy: 5-7cm incision
• Multilevel fusion: Incision from one level above to one level below instrumented levels (e.g., L2 to S1 skin incision for L3-S1 fusion)

Incise skin and subcutaneous tissue:

Use scalpel (No. 10 blade) to incise skin sharply. Electrocautery through subcutaneous fat to thoracolumbar fascia. Maintain strict midline (visible as relatively avascular plane - midline has less bleeding than paramedian).

Inject local anesthetic with epinephrine:

0.25% marcaine with 1:200,000 epinephrine injected into subcutaneous tissue and planned muscle dissection planes (reduces bleeding, postoperative pain).

Step 2: Incise Thoracolumbar Fascia

Identify midline:

The thoracolumbar fascia has a midline raphe (where right and left fascia meet). This is identified as a white line in the fascia.

Incise fascia:

Use electrocautery to incise fascia in midline from superior to inferior extent of incision. Deepen the incision through fascia to expose spinous processes (bone visible in midline).

Step 3: Subperiosteal Dissection of Paraspinal Muscles

Cobb elevator or periosteal elevator:

Place elevator on lateral side of spinous process (starting at base) and sweep laterally in subperiosteal plane. The multifidus muscle is elevated off bone (spinous process, lamina, facet, transverse process).

Key principle: Subperiosteal dissection preserves muscle blood supply (periosteum contains blood vessels) and innervation (medial branch dorsal rami enters muscle from deep surface). This minimizes muscle ischemia and denervation atrophy.

Extent of dissection:

• Laminectomy: Dissect to lateral edge of facet joints bilaterally
• Fusion with pedicle screws: Dissect to transverse process tips bilaterally (expose pedicle entry point at transverse process-facet junction)

Bipolar cautery for hemostasis:

Muscle bleeding is controlled with bipolar electrocautery (not monopolar, which causes more tissue damage). Maintain meticulous hemostasis - pooled blood obscures anatomy and increases infection risk.

Step 4: Place Self-Retaining Retractors

Taylor or Wiltse retractor system:

Self-retaining retractors with toothed blades that grip bone (spinous process, lamina, facet). The teeth prevent retractor migration.

Blade placement:

Place retractor blades under the multifidus muscle (subperiosteally) bilaterally. The blades sit on lamina and facet laterally. Gradually open retractor to desired width (exposes bilateral laminae, facets, transverse processes).

Avoid over-retraction: Excessive retraction pressure causes muscle ischemia (increased postoperative pain and muscle atrophy). Use the minimum retraction necessary for exposure.

Check fluoroscopy: Obtain lateral X-ray to confirm you are at the correct level (place marker on spinous process, count from sacrum).

Step 5A: Laminectomy Technique

Goal: Remove lamina and ligamentum flavum to decompress spinal canal.

5A-1: Remove spinous process:

Use rongeur or high-speed burr to remove spinous process at base (creates working room). Some surgeons preserve spinous process for morselized bone graft.

5A-2: Thin lamina with burr:

Use high-speed burr (matchstick or cutting burr) to thin the lamina bilaterally. Burr from lateral (facet) toward midline, removing outer cortex and cancellous bone. Leave thin inner cortex intact (protects dura from burr).

Visual cue: As you approach dura, the bone changes from white/pink (cancellous bone) to blue-purple (dura visible through thin cortex).

5A-3: Remove inner cortex with Kerrison rongeurs:

Use Kerrison rongeurs (2mm or 3mm) to carefully remove the remaining inner cortex. Start at the superior edge of lamina (L4 lamina for L4-5 stenosis). "Walk" the Kerrison under the lamina, staying in the epidural space.

"Yellow fat" landmark: Once you enter the epidural space, you see yellow epidural fat (confirms you are in correct plane).

5A-4: Remove ligamentum flavum:

Identify the ligamentum flavum (yellow, rubbery ligament connecting adjacent laminae). It is often adherent to dura (especially in elderly with stenosis).

Technique:

Place Woodson elevator or Penfield dissector between ligamentum flavum and dura to create a plane. Carefully dissect the ligament off dura (gentle sweeping motions). Use Kerrison rongeurs to remove ligamentum flavum from lateral to medial (both sides).

Midline dural exposure: The dura should be visible centrally. You should see pulsations of dura with patient breathing (if dura not pulsating, residual compression may be present or dura may be tethered by epidural scarring).

5A-5: Medial facetectomy (if needed for lateral recess stenosis):

Use Kerrison rongeurs or burr to remove the medial 50% of facet joint. This decompresses the lateral recess (where nerve root exits spinal canal).

CRITICAL: Preserve lateral 50% of facet to maintain stability. Bilateral greater than 50% facetectomy creates iatrogenic instability (requires fusion).

5A-6: Foraminotomy (if foraminal stenosis):

Remove bone from lateral recess and foramen to decompress exiting nerve root. This is an undercutting facetectomy - removing medial and inferior facet to open foramen without destabilizing joint.

5A-7: Confirm decompression:

Pass ball-tip probe under nerve roots to ensure complete decompression (probe should pass freely from medial to lateral under root). Dura should pulsate freely.

Step 5B: Discectomy Technique

Goal: Remove herniated disc fragment compressing nerve root (sequestrectomy, NOT aggressive discectomy).

5B-1: Identify interlaminar window:

The disc space is located between adjacent laminae (L4 and L5 laminae for L4-5 disc). If window is too small, perform minimal laminotomy (remove inferior edge of superior lamina and superior edge of inferior lamina with Kerrison rongeurs).

5B-2: Remove ligamentum flavum:

Same as laminectomy - carefully remove ligamentum flavum from lamina and off dura.

5B-3: Identify nerve root:

The traversing nerve root (L5 root at L4-5 level) is visible crossing the disc space toward the foramen. It appears as a white band (nerve) coursing over the disc.

Fat plane: There is a fat plane between the nerve root and dura (medial) and between the nerve root and disc (lateral). This fat is your safe dissection plane.

5B-4: Retract nerve root:

Use nerve root retractor (blunt, angled retractor) to gently retract the nerve root medially (toward midline). This exposes the disc herniation (which is lateral to the nerve root).

CRITICAL: Use gentle, sustained retraction (not aggressive pulling). Excessive retraction causes nerve injury (postoperative dysesthesia or motor deficit).

5B-5: Incise annulus and remove disc fragment:

Identify the herniated disc fragment (soft, white or yellow tissue protruding from disc space). Use scalpel or pituitary rongeurs to grasp the fragment and remove it.

Sequestrectomy technique: Remove only the extruded or sequestered fragment (loose piece). Do NOT perform aggressive discectomy (removing normal nucleus pulposus from disc space) - this increases postoperative back pain and instability.

Disc space exploration: After removing visible fragment, use pituitary rongeurs to carefully explore the disc space through the annular defect. Remove any additional loose fragments. Avoid forcing instruments deep into disc (risks anterior annulus perforation and vascular injury).

5B-6: Confirm decompression:

The nerve root should be relaxed and mobile after removing disc fragment. There should be no tension on the root. Pass ball-tip probe under root to confirm free passage.

Step 6: Fusion Technique (If Indicated)

Indications to add fusion to decompression:

1. Pre-existing instability (spondylolisthesis, greater than 3mm translation, greater than 10° angulation on flexion-extension)
2. Iatrogenic instability from decompression (bilateral greater than 50% facetectomy, complete facetectomy, pars resection)
3. Degenerative disc disease with instability (not common - fusion alone for discogenic pain controversial)

6-1: Complete facetectomy:

Use Leksell rongeurs, Kerrison rongeurs, or osteotomes to remove facet joints bilaterally. This exposes the disc space for interbody fusion (TLIF or PLIF).

6-2: Discectomy:

Perform complete discectomy (remove annulus, nucleus, cartilaginous endplates) using pituitary rongeurs, curettes, and shavers. Goal is to create parallel endplates with exposed bleeding subchondral bone (optimal for fusion).

6-3: Interbody cage placement:

TLIF (transforaminal lumbar interbody fusion): Place cage from one side (unilateral approach through neural foramen). Preserves contralateral facet and ligamentous structures.

PLIF (posterior lumbar interbody fusion): Place two cages (one on each side) via bilateral approach. Requires more neural retraction.

Cage packing: Fill cage with bone graft (local bone from decompression, autograft from iliac crest, allograft, or bone graft substitute with BMP).

6-4: Pedicle screw placement:

Entry point: Junction of lateral facet (mid-facet) and transverse process base (mamillary process). This is the "safe zone" for pedicle entry.

Trajectory:

• Sagittal plane (lateral view): 10-15° caudal angulation (aim toward endplate of vertebra below)
• Axial plane (AP view): 10-15° medial convergence (aim toward midline/sacral promontory)

Technique:

1. Mark entry point with burr or awl
2. Create pilot hole with pedicle awl or drill (gentle tapping, feel for cortical boundaries of pedicle)
3. Palpate pedicle walls with ball-tip probe (all 4 walls - medial, lateral, superior, inferior - should be intact cortical bone)
4. Tap threads (if using tapered screws) or use self-tapping screws
5. Insert screw under fluoroscopic guidance (confirm position on AP and lateral X-ray)
6. EMG stimulation (if neuromonitoring used): Threshold greater than 10mA confirms screw NOT in contact with nerve (greater than 10mA = safe, less than 6mA = likely medial breach)

6-5: Rod placement and compression:

Insert rods into screw heads bilaterally. Apply compression across disc space (brings vertebrae together, loads interbody cage in compression for optimal fusion environment).

6-6: Decortication and posterolateral fusion:

Decorticate (roughen) the transverse processes bilaterally with burr. Place morselized bone graft over decorticated transverse processes (creates posterolateral fusion mass in addition to interbody fusion).

Dual fusion (interbody + posterolateral) has highest fusion rate (95-98%) but higher morbidity than interbody alone.

Dural Tear Recognition and Repair

Incidence: 10-17% overall (higher in revision 20-30%, stenosis 15-20%, elderly 15%, lower in primary discectomy 5-10%).

Recognition:

1. CSF leak: Clear fluid pooling in wound (check: is it CSF or irrigation fluid? CSF continues to accumulate after suction)
2. Visualization: Tear in dura visible (white dural membrane interrupted)
3. Beta-2 transferrin test: Send fluid for lab analysis if uncertain (CSF has beta-2 transferrin, irrigation fluid does not)

Management - DO NOT IGNORE:

Small tear (less than 5mm):

1. Extend laminectomy to visualize tear edges (you need to SEE the tear to repair it - blind repair fails)
2. Primary repair with 4-0 Nurolon (silk or nylon, NOT absorbable suture like Vicryl which absorbs before dura heals)
3. Interrupted or running suture to re-approximate dura edges
4. Fibrin glue or DuraSeal over repair (sealant layer)
5. Valsalva test: Ask anesthesia to increase airway pressure to 30-40 cm H2O (checks for leak - if CSF visible, repair is inadequate)

Large tear (greater than 5mm) or tear in difficult location:

1. Attempt primary repair if possible (extend laminectomy for exposure)
2. If primary repair not possible: dural patch (collagen matrix, AlloDerm, or autologous fascia) sutured over defect
3. Fibrin glue or DuraSeal over patch
4. Paraspinal muscle flap over repair (additional layer)
5. Closed suction drain AVOIDED (drain creates negative pressure gradient pulling CSF through repair - if drain must be used, place it superficial to fascia, NOT deep)

Nerve root through tear:

If nerve root is extruded through dural tear, attempt to reduce root back into thecal sac before repair. If root cannot be reduced (tethered by scar in revision cases), repair dura around root (leave root outside dura, close dura around it as best as possible).

Postoperative management after dural tear:

1. Flat bed rest 24-48 hours (minimizes CSF pressure gradient across repair)
2. No wound drain or remove drain early (6-12 hours instead of 24-48 hours)
3. Observe for CSF leak: Wound drainage (clear fluid soaking dressing), pseudomeningocele (fluctuant subcutaneous collection on exam), meningitis (fever, headache, neck stiffness - rare)
4. If CSF leak persists: Consider lumbar drain (temporary spinal catheter draining CSF at 10-20 cc/hour for 3-5 days to decrease CSF pressure and allow dural repair to seal)
5. If pseudomeningocele develops: Observation if asymptomatic (many reabsorb over weeks-months). Revision surgery if symptomatic (nerve compression from CSF collection) or persistent leak

Routine Closure (No Dural Tear)

1. Irrigate:

Copious irrigation with normal saline (1-2 liters) or antibiotic solution (bacitracin 50,000 units in 1 liter saline). Removes bone dust, blood clot, and debris.

2. Hemostasis:

Bipolar electrocautery for muscle and epidural bleeding. Bone wax for bleeding bone (use sparingly - foreign body). Hemostatic agents (Gelfoam soaked with thrombin, FloSeal, Surgicel) for epidural venous bleeding.

Verify hemostasis before closing: Suction all blood, ensure dry field. Residual bleeding causes hematoma (can compress cauda equina - reoperation needed).

3. Drain placement:

Controversial. Many surgeons place closed suction drain (10mm flat Blake drain) to prevent hematoma. Others avoid drains (no proven benefit, may increase infection risk via bacterial seeding along drain track).

Indications for drain:

• Multilevel fusion (large dead space)
• Extensive epidural bleeding despite hemostasis
• Revision surgery (more bleeding)
• Anticoagulation planned postoperatively

Drain removal: 24-48 hours or when output less than 50cc/8 hours.

NO drain if dural tear (drain creates negative pressure pulling CSF through repair).

4. Fascial closure:

Close thoracolumbar fascia with #1 Vicryl or #1 PDS (absorbable, strong suture). Use interrupted or running technique. The fascia provides primary strength to closure (critical to prevent incisional hernia and fluid collection).

Watertight closure if dural tear (prevents CSF leak through fascia).

5. Subcutaneous closure:

Close subcutaneous layer with 2-0 or 3-0 Vicryl to obliterate dead space (reduces seroma/hematoma risk).

6. Skin closure:

Options:

• Skin staples (most common in spine surgery - fast, strong, easy removal)
• Subcuticular 3-0 or 4-0 Monocryl (absorbable, better cosmesis)
• Nylon or Prolene interrupted sutures (non-absorbable, good for revision cases or obese patients)

Dressing: Sterile gauze, Tegaderm. Some surgeons use negative pressure wound therapy (NPWT, e.g., PICO dressing) for high-risk wounds (obesity, revision, diabetes) - reduces infection and seroma.

Immediate Postoperative Care

Neurological assessment:

Check motor and sensory function in bilateral lower extremities in recovery room. Compare to preoperative baseline. New deficit suggests:

1. Hematoma compressing cauda equina (progressive bilateral weakness, bladder dysfunction)
2. Nerve root injury from retraction or screw malposition (unilateral weakness)
3. Pedicle screw medial breach contacting an exiting or traversing root (focal radicular motor/sensory loss)

If new deficit: Obtain urgent CT or MRI (MRI better for soft tissue/hematoma, CT faster and shows hardware). Consider reoperation for decompression if hematoma present.

Pain management:

Multimodal analgesia:

1. Acetaminophen 1000mg IV or PO every 6 hours (baseline)
2. Ketorolac 30mg IV every 6 hours x 48 hours (NSAID - controversial in fusion due to possible delayed fusion, but short-term use likely safe)
3. Gabapentin or pregabalin (300mg PO TID) for radicular pain
4. Opioids for breakthrough pain: oxycodone 5-10mg PO every 4 hours PRN or hydromorphone 0.5-1mg IV every 3 hours PRN
5. Muscle relaxants (diazepam 5mg PO TID or cyclobenzaprine 10mg PO TID) if muscle spasm

Avoid over-reliance on opioids - leads to chronic use. Wean opioids by 2 weeks postoperatively (transition to non-opioid pain management).

Mobilization:

Early mobilization improves outcomes and reduces DVT/PE risk.

• Discectomy: Walking within 4-6 hours (same day as surgery)
• Laminectomy: Walking postoperative day 1
• Fusion: Walking postoperative day 1-2 (cautious ambulation with walker or PT assistance)

Brace:

• Discectomy and laminectomy: NO brace (not needed)
• Fusion: Lumbosacral orthosis (LSO) for comfort during mobilization (first 6 weeks). Some surgeons avoid brace entirely (instrumentation provides stability, brace not needed). No evidence that brace improves fusion rates.

If dural tear repaired: Flat bed rest 24-48 hours (head of bed less than 30°), then mobilize slowly. Watch for CSF leak (clear wound drainage), headache (positional headache worse with sitting/standing), pseudomeningocele (subcutaneous fluid collection on exam).

DVT Prophylaxis

Lumbar spine surgery is HIGH RISK for DVT (prolonged prone positioning, venous stasis, pelvic surgery).

Mechanical prophylaxis:

1. Sequential compression devices (SCDs) intraoperatively and postoperatively until ambulatory
2. Early mobilization (walking day 1-2)
3. Adequate hydration (IVF to maintain urine output)

Chemical prophylaxis (controversial):

Low molecular weight heparin (LMWH, e.g., enoxaparin 40mg SC daily) or unfractionated heparin (5000 units SC TID).

Risk: Epidural hematoma from anticoagulation (0.1-0.2% risk, but catastrophic - causes cauda equina compression).

Timing: Many surgeons avoid chemical prophylaxis for 24 hours after surgery (allow hemostasis), then start if patient not ambulatory. Some avoid entirely if drain in place (remove drain first, then start anticoagulation).

Balance risk-benefit: High-risk patients (prior DVT/PE, obesity, cancer) may benefit from early chemical prophylaxis. Low-risk patients can use mechanical prophylaxis alone.

Activity Restrictions

Discectomy:

• No lifting greater than 5kg for 6 weeks (allow annulus to heal)
• No bending, lifting, twisting (BLT) for 6 weeks
• Walking encouraged (no distance limit)
• Driving when off opioids and can comfortably turn (2-4 weeks)
• Return to sedentary work 2-4 weeks, manual labor 6-12 weeks

Laminectomy:

• No lifting greater than 5kg for 6 weeks
• Walking encouraged (builds endurance)
• Driving when comfortable (3-4 weeks)
• Return to sedentary work 4-6 weeks, manual labor 3-4 months

Fusion:

• No lifting greater than 5kg for 3 months (wait for early fusion healing)
• No BLT for 3 months
• Walking encouraged (start with short distances, gradually increase)
• LSO brace for 6 weeks if used (wean after 6 weeks)
• Driving when off opioids and comfortable (4-6 weeks)
• Return to sedentary work 6-12 weeks, manual labor 6-9 months (wait for fusion evidence on imaging)
• Smoking cessation CRITICAL (smoking increases pseudarthrosis risk from 5-10% to 20-30%)

Radiographic Follow-Up

Discectomy:

• No routine imaging unless symptomatic (new pain or deficit)
• If recurrent symptoms: MRI to assess for recurrent herniation (5-10% risk) or epidural scarring

Laminectomy:

• 6 weeks: AP and lateral X-rays to assess alignment (check for instability from decompression)
• Flexion-extension lateral X-rays at 3-6 months if concern for instability (greater than 3mm translation or greater than 10° angulation suggests need for fusion)

Fusion:

• Immediate postop: AP and lateral X-rays to document hardware position, alignment
• 6 weeks: AP and lateral X-rays to check for early subsidence, hardware loosening
• 3 months: AP, lateral, and flexion-extension lateral X-rays to assess fusion (bridging bone, less than 2mm motion)
• 6 months and 1 year: Repeat imaging if fusion uncertain or patient symptomatic
• CT scan if fusion uncertain on X-ray (better visualization of bone bridging through cage and posterolaterally)

Fusion criteria:

1. Bridging bone across disc space (visible trabeculation through cage on CT)
2. Posterolateral fusion mass connecting transverse processes (on CT)
3. Less than 2mm motion on flexion-extension X-rays
4. No hardware failure (no screw loosening, breakage, or rod fracture)
5. No lucency around screws (lucency suggests loosening from pseudarthrosis)

Pseudarthrosis (non-union): 5-10% single-level, 10-20% multilevel. Risk factors: smoking (strongest), multilevel, obesity, diabetes, NSAIDs. Management: observation if asymptomatic, revision fusion if symptomatic (persistent back pain, hardware failure).

Intraoperative Complications

1. Dural tear (10-17% overall, see SafetyAlert above):

Already covered extensively. Key points: Repair primarily with 4-0 Nurolon, fibrin glue seal, flat bed rest 24-48 hours postop, observe for CSF leak or pseudomeningocele.

2. Nerve root injury (1-2%):

Mechanism: Retractor pressure (most common), pulling nerve during discectomy, pedicle screw medial breach, aggressive foraminotomy.

Presentation: Immediate postop weakness in specific myotome (foot drop if L5 injured, plantar flexion weakness if S1 injured), sensory loss in dermatomal distribution.

Management: Immediate recognition (neuromonitoring helps - MEP changes during retraction). If due to retractor: release retractor pressure. If due to screw: remove screw, redirect. Most injuries are neuropraxia (recovers over 3-6 months). Document injury and discuss with patient postoperatively. Consider EMG/NCS at 3 weeks if no improvement (distinguishes neuropraxia from axonotmesis/neurotmesis).

3. Vascular injury (less than 0.1% but potentially fatal):

Great vessels (aorta, IVC, iliac vessels) can be injured by:

1. Anterior disc space perforation during aggressive discectomy (instruments exit anterior annulus)
2. Anterior screw penetration (screw too long, exits anterior vertebral body)
3. L4-5 level has iliac vessels immediately anterior to disc (1-2cm anterior to anterior annulus)

Presentation: Sudden hypotension, massive blood loss (not visible in wound - bleeding into retroperitoneum). Cardiac arrest possible.

Management: This is a SURGICAL EMERGENCY:

1. Pack abdomen (place laparotomy pads in disc space to tamponade bleeding)
2. Call for vascular surgery or general surgery immediately
3. Fluid resuscitation (activate massive transfusion protocol)
4. Prepare for laparotomy (vascular repair from anterior approach)

Prevention: Use appropriate instrument depth (disc space is 4-6cm deep at L4-5 in average patient, measure on preop MRI), avoid excessive anterior instrumentation, use blunt-tipped instruments for disc removal.

4. Wrong-level surgery (never event):

Prevention covered earlier: Palpate iliac crest (Tuffier line), count spinous processes from L5, fluoroscopy confirmation BEFORE incision and after exposure (marker on spinous process, count from sacrum on lateral X-ray). Lumbosacral transitional vertebrae (Bertolotti syndrome) confuse counting - imaging mandatory.

Early Postoperative Complications (Less Than 6 Weeks)

1. Hematoma causing cauda equina compression (1-2%):

Presentation: Progressive bilateral leg weakness, bladder dysfunction (retention), severe back/leg pain, saddle anesthesia. Develops within first 24-48 hours postop.

Diagnosis: Urgent MRI or CT (MRI better for hematoma visualization).

Management: Immediate reoperation for hematoma evacuation and decompression. Delay worsens neurological outcome. Counsel patient: even with prompt evacuation, some deficits may be permanent.

2. Infection (2-4%, higher than other ortho sites):

Risk factors: Diabetes, obesity (BMI greater than 35), smoking, prolonged operative time (fusion cases), revision surgery, instrumentation (hardware increases infection risk).

Types:

Superficial wound infection (1-2%): Cellulitis, wound drainage, fever. Managed with antibiotics (cephalexin or clindamycin for 10-14 days). Wound opening/debridement if abscess or necrotic tissue.

Deep wound infection (1-2%): Involves fascia or deeper (epidural abscess, discitis, osteomyelitis). Presents with fever, severe back pain, elevated CRP/ESR, wound drainage. MRI shows fluid collection or enhancement.

Management of deep infection:

1. Return to OR for irrigation, debridement, culture (send tissue for culture, NOT swab)
2. Remove hardware if loose or if infection not clearing with antibiotics (hardware is a biofilm nidus)
3. Retain hardware if well-fixed and infection responds to antibiotics (removing screws destabilizes spine)
4. IV antibiotics based on culture (empiric: vancomycin + ceftriaxone or pip-tazo, then narrow based on sensitivities)
5. Duration: 6 weeks IV antibiotics for osteomyelitis/discitis, 4-6 weeks for deep soft tissue infection
6. Infectious disease consult for complex cases
7. Negative pressure wound therapy (VAC dressing) after debridement to promote granulation

Prevention: Preoperative antibiotics (cefazolin 2g IV within 60 minutes of incision), maintain normothermia intraop, minimize operative time, meticulous hemostasis (hematoma increases infection risk), tight glycemic control perioperatively (glucose less than 180mg/dL).

3. CSF leak from unrecognized or inadequately repaired dural tear (2-5% of dural tears):

Presentation: Clear fluid draining from wound, positional headache (worse when upright, better lying flat), pseudomeningocele (fluctuant subcutaneous mass on exam).

Diagnosis: Wound inspection (clear vs serous fluid), beta-2 transferrin test (CSF specific), MRI (shows CSF collection/pseudomeningocele).

Management:

• Bed rest (flat 24-48 hours, gradually elevate head of bed)
• Lumbar drain (temporary catheter draining CSF at 10-20cc/hour for 3-5 days to decrease CSF pressure and allow dural seal)
• Revision surgery if conservative measures fail (re-explore wound, repair dura, consider dural patch or muscle flap)
• Blood patch (inject 10-20cc of patient's own blood into epidural space to seal leak - used for CSF leaks after lumbar puncture, can be tried for surgical CSF leak)

Complications of CSF leak: Meningitis (if communication with skin/wound), pseudomeningocele causing nerve compression (requires revision), chronic headache.

4. Urinary retention (10-20%, especially in elderly males):

Causes: Opioid use, prolonged surgery, pre-existing BPH (benign prostatic hyperplasia), epidural anesthesia effect.

Management: Bladder scan (check postvoid residual), in-and-out catheterization if greater than 400-500cc, Foley catheter if repeated retention (remove when patient ambulatory and off opioids), alpha-blocker (tamsulosin) for BPH patients, reduce opioid dose.

Distinguish from cauda equina: Retention from cauda equina is associated with saddle anesthesia, bilateral leg weakness, absent anal tone. Retention from non-neurological causes has normal sensation, motor, reflexes.

Late Complications (Greater Than 6 Weeks)

1. Recurrent disc herniation (5-10% at 5 years after discectomy):

Presentation: Recurrent leg pain in same distribution as preoperative symptoms, usually within first 2 years.

Diagnosis: MRI shows recurrent herniation at same level (difficult to distinguish from epidural scar - contrast-enhanced MRI helps: herniation does not enhance, scar enhances).

Management: Trial of conservative treatment (PT, ESI). If persistent: revision discectomy (careful dissection through scar, higher dural tear risk 20-30%). Some surgeons add fusion at revision (controversial - increases morbidity).

2. Persistent or recurrent stenosis (10% at 10 years after laminectomy):

Causes: Inadequate decompression (missed lateral recess or foraminal stenosis), progression of degenerative disease at same level, instability from decompression (facet resection) causing recurrent stenosis.

Management: Revision decompression, consider fusion if instability present.

3. Pseudarthrosis (non-union) after fusion (5-10% single-level, 10-20% multilevel):

Already covered. Smoking is strongest risk factor. Management: observation if asymptomatic, revision fusion if symptomatic.

4. Adjacent segment disease (ASD) (10-20% at 10 years after fusion):

Definition: Degenerative changes at levels adjacent to fusion requiring surgery (new disc herniation, stenosis, or instability).

Controversy: Does fusion CAUSE ASD (altered biomechanics, stress transfer) or is ASD natural history of degenerative disease?

Management: Observation if asymptomatic. If symptomatic: extend fusion to include adjacent level OR consider motion-preserving technology (adjacent-level arthroplasty - investigational).

5. Flatback deformity / loss of lordosis (5-10% after long fusion):

Cause: Fusion in suboptimal alignment (inadequate lordosis restoration), rod contouring error, cage subsidence.

Presentation: Forward trunk lean (sagittal imbalance), inability to stand upright, compensatory hip/knee flexion, pain from muscle fatigue.

Management: Complex revision surgery with osteotomies to restore lordosis (pedicle subtraction osteotomy, vertebral column resection). High morbidity - prevention is key (restore lordosis at index fusion).