What is the risk of developing tethered cord syndrome after spinal fusion surgery?

Risk of Tethered Cord Syndrome After Spinal Fusion Surgery

Spinal fusion surgery can lead to tethered cord syndrome (TCS) as a postoperative complication, with the risk being higher in patients with pre-existing spinal cord abnormalities or complex spinal deformities.

Understanding Tethered Cord Syndrome

Tethered cord syndrome occurs when the spinal cord is abnormally attached or fixed within the spinal canal, causing stretching and tension on the cord that can lead to neurological deterioration. In the context of spinal fusion surgery, several factors contribute to this risk:

Risk Factors for Post-Fusion TCS

• Pre-existing developmental abnormalities: Patients with midline fusion defects are at higher risk 1
• Complex spinal deformities: Particularly those requiring extensive fusion
• Surgical approach: Combined anterior-posterior approaches carry higher risk 2
• Inappropriate surgical techniques: Inadequate release of tethering components during initial surgery 1

Clinical Presentation of Post-Fusion TCS

Symptoms typically develop 5-10 years after the initial surgery 1 and may include:

• Pain (dull, aching, sharp, or electrical) that worsens with activity
• Progressive lower extremity weakness
• Sensory deficits
• Bowel and bladder dysfunction
• Regression in previously acquired motor skills
• Progressive musculoskeletal deformities including scoliosis 3

Diagnostic Approach

MRI is the gold standard for evaluation of suspected TCS after spinal fusion:

• Look for low-lying conus medullaris (below L1-L2 level)
• Assess anterior canal distance (ACD) and bending angle (BA)
• A preoperative BA ≥31.7° has been identified as a predictor of reoperation in pediatric patients 4
• Evaluate for cord signal changes that may indicate myelopathy 2

Management Considerations

For patients with confirmed TCS after spinal fusion:

1. Surgical untethering is the primary treatment to prevent further neurological deterioration
2. Early intervention is critical - outcomes are better when surgery is performed promptly after symptom onset 3
3. Comprehensive approach must include:
   • Removal of all tethering components
   • Reconstruction of the neural tube
   • Sectioning of tight filum terminale 1

Outcomes and Prognosis

• Approximately 48.48% of pediatric patients show improvement in symptoms after untethering procedures 4
• Complications occur in about 18.18% of pediatric cases 4
• Detethering procedures have significantly lower mortality (0.09% vs 0.33%) and procedure-related complications (7.63% vs 21.3%) compared to fusion procedures for TCS 5

Prevention Strategies

To minimize the risk of TCS after spinal fusion:

• Careful preoperative planning with high-quality MRI to identify any pre-existing tethering
• Mechanical prophylaxis with intermittent pneumatic compression devices during and after surgery 2
• Individualized surgical protocols designed to reduce stretch on the low-lying spinal cord 6
• Regular follow-up imaging to monitor for early signs of tethering

Special Considerations

For patients with pre-existing conditions like Duchenne muscular dystrophy undergoing spinal fusion:

• Assess respiratory function (FVC <30% of predicted indicates high risk for complications) 2
• Monitor for both respiratory complications and neurological deterioration postoperatively

The risk of developing TCS after spinal fusion necessitates vigilant monitoring and early intervention when symptoms develop to prevent permanent neurological damage.