What is the management approach for adjacent segment disease following Anterior Cervical Discectomy and Fusion (ACDF) surgery?

Management of Adjacent Segment Disease Following ACDF Surgery

The management of adjacent segment disease (ASD) following Anterior Cervical Discectomy and Fusion (ACDF) should prioritize cervical arthroplasty (artificial disc replacement) at the affected adjacent level when clinically appropriate, as it preserves motion and may prevent further degeneration while addressing neurological symptoms.

Diagnostic Approach

Initial Evaluation

• MRI of the cervical spine is the preferred imaging modality to evaluate adjacent segment disease due to superior soft tissue contrast for assessing nerve root impingement 1
• CT scan may be beneficial for evaluating bony elements and can help detect adjacent segment degeneration 1
• CT myelography can be considered when MRI is limited by hardware artifact 1

Clinical Correlation

• Imaging findings must correlate with clinical symptoms as MRI alone has high false-positive/negative rates 2
• Diagnostic selective nerve root blocks may help identify the symptomatic level when MRI shows multilevel degeneration 2

Management Algorithm

1. Conservative Management (First-line approach)

• Physical therapy focusing on:
  • Range of motion exercises
  • Strengthening of cervical and upper back muscles
  • Postural training 2
• Medications:
  • NSAIDs for inflammatory pain
  • Muscle relaxants for associated muscle spasm
  • Avoid long-term opioid use 2
• Activity modification:
  • Short-term use of soft cervical collar
  • Avoidance of activities that exacerbate symptoms 2
• Epidural steroid injections or selective nerve root blocks for persistent radicular pain 2

2. Surgical Intervention

Indicated when:

• Persistent symptoms despite conservative management
• Progressive neurological deficits
• Significant functional limitations that correlate with imaging findings 2

Surgical Options:

A. Cervical Arthroplasty (Preferred for ASD)

• Artificial disc replacement at the affected adjacent segment preserves motion and may prevent further degeneration 3
• Provides encouraging clinical results in patients who previously underwent cervical fusion 3
• Statistically significant improvements in VAS scores for neck/arm pain and NDI scores have been demonstrated 3
• Increases overall lordosis and range of motion at the treated level 3

B. Extension of Fusion (Alternative)

• Consider when:
  • Advanced degeneration makes arthroplasty unsuitable
  • Significant instability is present
  • Patient has contraindications to arthroplasty

C. Hybrid Constructs

• Combination of ACDF at one level and TDR at an adjacent level
• Can be performed for both contiguous and non-contiguous segments 4
• Shown to reduce rates of further ASD in contiguous hybrid constructs 4

Risk Factors for ASD Development

Understanding risk factors helps in prevention and patient counseling:

• Advanced age (OR 1.271,95% CI 1.005-1.607) 5
• Low preoperative overall lordosis (OR 0.858,95% CI 0.786-0.936) 5
• Low preoperative segmental lordosis (OR 1.185,95% CI 1.086-1.193) 5
• Plate-to-disc distances <5 mm (both cephalad and caudal) 6
• Developmental canal stenosis 6
• Preoperative radiographic ASD 6
• Unfused C5-C6 or C6-C7 adjacent segments 6

Location Patterns of ASD

• ASD is more likely to develop above the index level of fusion 7
• This pattern persists even for patients undergoing revision surgery due to recurrent ASD 7
• The highest rates of cervical spinal degenerative disease requiring surgery occur at C5/C6, followed by C6/C7 7

Monitoring and Follow-up

• Regular clinical and radiographic follow-up is essential to detect early signs of ASD
• CT is the most sensitive and specific modality to assess spinal fusion and can aid in detecting adjacent segment degeneration 1
• For patients with isolated degenerative changes at adjacent segments without symptoms, imaging surveillance is recommended:
  • Every 12 months for segments <4.0 cm in diameter
  • Every 6 months for segments ≥4.0 cm in diameter 1

Pitfalls and Caveats

• Metal artifact may limit assessment of cervical hardware and complications on MRI 1
• Degenerative findings on MRI are commonly observed in asymptomatic patients 1
• Approximately 65% of asymptomatic patients 50-59 years old will have radiographic evidence of significant cervical spine degeneration 1
• Adjacent segment degeneration rates are high regardless of surgical approach (48.72% in ACDF vs. 44.83% in CDA groups) 5

By following this structured approach to managing adjacent segment disease after ACDF, clinicians can optimize outcomes while minimizing the risk of further degeneration and need for additional surgeries.