What is the step-by-step procedure for managing Prolapsed Intervertebral Disc (PIVD) at L4-L5 via spinal fusion?

Spinal Fusion Procedure for PIVD L4-L5

Spinal fusion at L4-L5 for prolapsed intervertebral disc involves a systematic surgical approach that includes decompression of neural elements followed by fusion with instrumentation to stabilize the segment and prevent recurrence of symptoms.

Preoperative Assessment

• Confirm diagnosis with appropriate imaging (MRI is preferred for evaluating patients with persistent symptoms after 6 weeks of conservative therapy) 1
• Evaluate spinopelvic parameters as they correlate with health-related quality-of-life outcomes 2
• Assess for any contraindications to surgery
• Optimize patient's medical status for surgery

Surgical Approaches

1. Posterior Approach (PLIF - Posterior Lumbar Interbody Fusion)

This is the most common approach for L4-L5 PIVD with fusion:

• Patient positioning: Prone position on a radiolucent operating table

• Incision: Midline incision centered over L4-L5 level

• Muscle dissection: Paraspinal muscles are dissected subperiosteally from spinous processes and laminae

• Decompression:

  • Laminectomy or laminotomy of L4 and/or L5 to expose the dural sac and nerve roots
  • Medial facetectomy to access the disc space
  • Foraminotomy to decompress the exiting nerve roots 1
  • Complete removal of disc material, including any herniated fragments

• Preparation of disc space:

  • Thorough discectomy with removal of cartilaginous endplates
  • Preservation of bony endplates
  • Sizing of the intervertebral space for appropriate cage selection

• Interbody fusion:

  • Insertion of cage(s) filled with bone graft material
  • Restoration of disc height and foraminal dimensions 1

• Instrumentation:

  • Placement of pedicle screws in L4 and L5 vertebrae under fluoroscopic guidance
  • Connection with rods to provide immediate stabilization 1
  • Final tightening after confirmation of proper alignment

• Bone grafting:

  • Application of additional bone graft material in the posterolateral gutters
  • Options include autologous bone (iliac crest), allograft, or bone substitutes 3

2. Alternative Approach: TLIF (Transforaminal Lumbar Interbody Fusion)

• Similar to PLIF but with a more lateral approach to the disc space
• Requires less retraction of neural elements
• Allows access to both the disc space and vertebral body 1
• Enables adequate decompression with less muscle manipulation 1

3. Alternative Approach: LLIF (Lateral Lumbar Interbody Fusion)

• Patient positioned in lateral decubitus position
• Retroperitoneal approach through the psoas muscle
• Lower complication rates when using standardized techniques 4
• Potential complications include femoral neuropraxia (1.2%), non-femoral neuropraxia (1.8%), and thigh pain (6.2%) 4

4. Alternative Approach: ALIF (Anterior Lumbar Interbody Fusion)

• Transperitoneal or retroperitoneal approach
• For L4-L5, requires careful mobilization of great vessels
• May access disc space above, below, or between the great vessel bifurcation 5
• Provides excellent exposure for complete discectomy and large cage placement

Intraoperative Considerations

• Aggressive surgical debridement is essential for optimal outcomes 3
• Titanium constructs are preferred for hardware instrumentation 3
• Cadaveric allograft is an acceptable substitute for autologous graft 3
• Intraoperative fluoroscopy to confirm proper placement of implants
• Careful hemostasis throughout the procedure

Postoperative Management

• Early mobilization as tolerated
• Optimize postoperative pain control to facilitate early mobilization 3
• Consider neuraxial techniques (epidural catheters) for pain management with minimal respiratory side effects 3
• Monitor for potential complications:
  • Wound infection
  • Neurological deficit
  • Hardware failure
  • Adjacent segment disease 1

Expected Outcomes

• Improvement in L4-L5 local lordosis (from approximately 6.4° to 11.3° at 2 years) 2
• Correlation between change in L4-L5 local lordosis and change in overall lumbar lordosis 2
• Long-term fusion rates of 65-67.5% with sustained symptom relief 6
• Patients with L5 sacralization may have lower fusion rates after L4-L5 PLIF surgery 7

Potential Complications and Management

• Respiratory complications: Consider non-invasive positive pressure ventilation (NPPV) for patients at high risk 3
• GI dysfunction: Use bowel regimens to avoid constipation; consider prokinetic medications 3
• Cardiovascular issues: Careful attention to fluid balance and intensive monitoring 3
• Neurological deficits: Immediate evaluation and potential revision surgery

Special Considerations

• Minimally invasive approaches are associated with less blood loss and shorter hospital stays compared to open procedures 3
• Total disc replacement may be an alternative to fusion in selected cases, with potential benefits including improved pain scores, reduced reoperation rates, and decreased post-surgical complications 3
• Avoid spinal manipulation with high-velocity thrusts in patients with spinal fusion or advanced spinal osteoporosis 3

Spinal fusion for L4-L5 PIVD requires meticulous surgical technique and appropriate patient selection to achieve optimal outcomes. The procedure aims to decompress neural elements, restore normal spinal alignment, and provide stability to prevent recurrence of symptoms.