Lumbar Microdiscectomy

Lumbar microdiscectomy is the most commonly performed spinal surgery worldwide, involving removal of herniated disc material compressing a nerve root through a minimally invasive approach. It remains the gold standard surgical treatment for symptomatic lumbar disc herniation unresponsive to conservative management.

Historical Development

Open discectomy was first described by Mixter and Barr in 1934. Caspar and Yasargil introduced the operating microscope for spine surgery in the 1970s. Modern microdiscectomy achieves decompression through incisions of 2-3 cm with minimal tissue disruption.

Epidemiology

Lumbar disc herniation affects 1-3% of the population. Peak incidence occurs in the 30-50 age group. L4-5 and L5-S1 account for 95% of herniations. Approximately 10% of symptomatic patients ultimately require surgery.

Spinal Canal Anatomy

Key Structures:

• Dural sac containing cauda equina
• Traversing nerve root (descending to exit one level below)
• Exiting nerve root (leaving at current foramen)
• Epidural fat and veins
• Ligamentum flavum posteriorly

Nerve Root Anatomy - Critical for Exams

Pathophysiology of Radiculopathy

Mechanical Compression:

• Direct pressure on nerve root
• Venous congestion
• Ischemia

Chemical Irritation:

• Nucleus pulposus is inflammatory
• Phospholipase A2, TNF-alpha release
• May cause symptoms without mechanical compression

Disc Herniation Classification

By Location:

• Central: May cause bilateral symptoms or CES
• Posterolateral: Most common, affects traversing root
• Foraminal: Affects exiting root
• Far lateral/extraforaminal: Also affects exiting root

By Morphology:

• Protrusion: Base wider than dome, contained
• Extrusion: Dome wider than base, through annulus
• Sequestration: Free fragment separated from disc

Patient Selection

Physical Examination

Neurological Assessment:

Tension Signs:

• Straight leg raise (SLR): Positive 30-70°, worse with dorsiflexion
• Crossed SLR: Raising unaffected leg causes affected side pain (highly specific)
• Femoral stretch test: For L2-L4 radiculopathy
• Bowstring sign: Popliteal pressure during SLR reproduces pain

Red Flags - Require Urgent Evaluation

Cauda Equina Syndrome:

• Urinary retention or incontinence
• Fecal incontinence
• Saddle anesthesia
• Bilateral progressive weakness

Other Red Flags:

• Progressive motor deficit
• Fever, infection signs
• History of malignancy
• Unexplained weight loss

Differential Diagnosis of Lumbar Radiculopathy

A herniated disc should only be implicated when the clinical syndrome, dermatomal distribution and imaging level are concordant; otherwise these mimics must be actively excluded before any operation is offered.

Additional Investigations

Plain Radiographs:

• Limited role for disc herniation
• Assess alignment, instability, degenerative changes
• Flexion-extension views for instability

Diagnostic Injections:

• Selective nerve root block (SNRB)
• Helpful when imaging shows multi-level disease
• Confirms symptomatic level before surgery
• Therapeutic and diagnostic

Preoperative Planning

Positioning: Prone on Wilson frame or Jackson table

• Hip flexed to flatten lumbar lordosis
• Abdomen free to reduce venous pressure
• Eyes protected, arms positioned

Level Confirmation:

• Fluoroscopy mandatory
• Mark incision preoperatively
• Verify with intraoperative imaging

Surgical Steps

Intraoperative Considerations

Dural Tear Management:

• Primary repair with 4-0 or 5-0 suture if possible
• Dural sealant (fibrin glue, DuraSeal)
• Fat graft or muscle patch
• Bed rest 24-48 hours postoperatively
• May need lumbar drain for persistent leak

Hemostasis:

• Bipolar cautery for epidural veins
• Avoid monopolar near neural structures
• Hemostatic agents (Gelfoam, Surgicel)
• Ensure dry field before closure

Intraoperative Complications

Postoperative Complications

Early Complications:

• Wound infection (1-2%)
• CSF leak (if dural tear)
• Recurrent herniation (5-10%)
• Persistent radiculopathy

Late Complications:

• Recurrent disc herniation
• Adjacent segment disease
• Chronic pain
• Instability (rare with limited laminotomy)

Recurrent Disc Herniation

Incidence: 5-10% at same level, 5% at different level

Risk Factors:

• Obesity (BMI above 25)
• Smoking
• Larger annular defect
• Occupational factors
• Diabetes

Management:

• Conservative treatment trial again
• Repeat imaging (MRI with gadolinium)
• Revision microdiscectomy vs fusion
• Consider fusion if significant instability

Immediate Postoperative

Day of Surgery:

• Mobilize same day (most patients)
• Neurological assessment
• Pain management (multimodal)
• Encourage ambulation

Day 1:

• Discharge if stable (day surgery or overnight stay)
• Wound care instructions
• Activity guidelines

Activity Guidelines

Rehabilitation

Physical Therapy:

• Core strengthening (delayed 2-4 weeks)
• Flexibility exercises
• Posture education
• Ergonomic training

Lifestyle Modifications:

• Weight optimization
• Smoking cessation
• Proper lifting technique
• Activity modification

Follow-up Schedule

• 2 weeks: Wound check, early progress
• 6 weeks: Clinical assessment, activity progression
• 3 months: Outcome assessment
• 12 months: Final follow-up (if needed)

Success Rates

Leg Pain Relief: 90-95% of patients Back Pain Improvement: 70-80% Return to Work: 80-90% Patient Satisfaction: 80-85%

SPORT Trial Findings

Key Results:

• Surgery provides faster improvement in first 3 months
• By 4 years, outcomes similar between surgical and conservative
• Both groups showed substantial improvement
• Cross-over rates were high (affects interpretation)

Clinical Implications:

• Surgery accelerates recovery but doesn't change ultimate outcome
• Patient preference important in decision-making
• Conservative treatment remains reasonable option

Prognostic Factors

Favorable:

• Leg pain more than back pain
• Short duration of symptoms
• Clear imaging correlation
• No previous surgery
• Extruded/sequestered disc
• Good psychosocial status

Unfavorable:

• Predominant back pain
• Long symptom duration
• Previous failed surgery
• Workers compensation
• Depression/anxiety
• Obesity, smoking

Revision Microdiscectomy

Indications:

• Recurrent disc herniation (not scar tissue)
• New symptoms at same level
• Failed to improve or worsening after initial surgery

Technical Considerations:

• MRI with gadolinium to distinguish recurrence from scar
• Epidural fibrosis increases dural tear risk (5-10%)
• Consider fusion if significant instability or multiple recurrences

Microdiscectomy vs Fusion

When to Consider Fusion:

• Significant instability
• Multiple recurrent herniations
• Concomitant spondylolisthesis
• Large annular defect with disc space collapse
• Significant back pain component

Endoscopic vs Open Microdiscectomy

Endoscopic Advantages:

• Smaller incision
• Less muscle damage
• Faster recovery
• Day surgery

Open Advantages:

• Better visualization
• Shorter learning curve
• Lower complication rate early in experience
• More versatile

Workers Compensation Cases

Considerations:

• Outcomes generally inferior
• Higher recurrence rates reported
• Multidisciplinary approach recommended
• Clear documentation essential
• Manage expectations carefully

Management Pathway

Step 1: Clinical Assessment

• Confirm radiculopathy (dermatomal, tension signs)
• Rule out red flags (CES, progressive weakness, infection, malignancy)
• Assess symptom duration and severity

Step 2: Imaging

• MRI lumbar spine
• Confirm imaging-clinical correlation
• Assess herniation type and location

Step 3: Conservative Trial (6-12 weeks)

• Activity modification, NSAIDs
• Physical therapy
• Consider ESI if symptoms severe

Step 4: Surgical Decision

• If failed conservative: Offer surgery
• If CES: Emergency surgery
• If progressive weakness: Urgent surgery

Step 5: Surgical Planning

• Standard approach for posterolateral herniation
• Wiltse approach for far lateral
• Consider tubular or endoscopic based on expertise

High-Yield MCQ Topics

Global Epidemiology and Burden

Lumbar disc herniation affects an estimated 1-3% of the population, with a lifetime prevalence of sciatica of 13-40%. Peak incidence is in the fourth and fifth decades, and L4-5 and L5-S1 together account for around 95% of symptomatic herniations. Discectomy is consistently the most commonly performed spinal operation in high-income health systems. The natural history is favourable: roughly 90% of symptomatic patients improve without surgery, and the central message of the SPORT randomised trial (Weinstein, JAMA 2006) and the Leiden sciatica trial (Peul, NEJM 2007) is that surgery accelerates recovery rather than changing the eventual outcome for most patients.

Side-by-Side Guideline Comparison

All four bodies converge on the same principles: a time-limited conservative trial for uncomplicated radiculopathy, imaging-clinical concordance before surgery, and emergency decompression for cauda equina syndrome. Differences are largely in emphasis and the structure of referral pathways rather than in the indication itself.

Registry and Practice-Variation Evidence

Large national spine registries (for example the Swedish Swespine register, the British Spine Registry and the Norwegian NORspine register) collect patient-reported outcomes after discectomy and consistently report leg-pain relief and satisfaction in the region of 80-90% at 1 year, mirroring the trial literature. Registry data also document substantial geographic variation in discectomy rates that is not explained by disease prevalence, underscoring the influence of local practice and patient preference highlighted by SPORT. A Dutch surveillance survey (Arts, J Neurosurg Spine 2008) found unilateral transflaval discectomy to be the dominant technique, with surgeons expecting minimally invasive approaches to carry higher recurrence and percutaneous laser decompression to be least effective.

Current Practice in Australia

Lumbar microdiscectomy is one of the most commonly performed spinal operations in Australia, undertaken by both neurosurgeons and orthopaedic spine surgeons across public and private hospitals. Practice follows international guidance, with emphasis on appropriate patient selection and an adequate conservative trial before elective surgery, and day-case or overnight pathways are increasingly used for uncomplicated cases. Smoking cessation support (Quitline 13 7848) is relevant given the association between smoking and reherniation.

Medicolegal Considerations

Key documentation points for medicolegal protection include recording of red-flag assessment, documentation of concordance between symptoms and imaging, the consent discussion (including recurrence risk and the possibility of dural tear), and the level-confirmation process (pre-operative marking and intra-operative fluoroscopy). Cauda equina syndrome cases require meticulous documentation of timing: when symptoms began, when the patient presented, when imaging was obtained and when surgery was performed.

Key Takeaways

1. Nerve Root Anatomy is Essential: Posterolateral herniations affect the traversing root (L4-5 = L5), while far lateral herniations affect the exiting root (L4-5 = L4). This is the most commonly tested topic.

2. Cauda Equina Syndrome is a Surgical Emergency: Recognize the triad of urinary retention, saddle anesthesia, and bilateral leg symptoms. Decompress within 24-48 hours for best outcomes.

3. SPORT Trial Shapes Practice: Surgery accelerates recovery but 4-year outcomes are similar to conservative treatment. Patient preference matters in surgical decision-making.

4. Patient Selection is Critical: Best outcomes when leg pain predominates over back pain, imaging correlates with symptoms, and adequate conservative trial has failed.

5. Limited Discectomy Preferred: Remove only loose fragments rather than aggressive curettage. This may reduce recurrence while achieving adequate decompression.

6. Dural Tear is a Recognized Complication: 1-2% in primary surgery, higher in revisions. Know repair techniques and postoperative management.

7. Recurrence Requires MRI with Gadolinium: Distinguishes recurrent disc (no enhancement) from scar tissue (enhances). Scar tissue does not benefit from surgery.