Management of Adjacent Segment Disease Following ACDF Surgery
For patients with adjacent segment disease (ASD) following anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (CDA) is the preferred surgical approach as it maintains motion at the affected segment while addressing neural compression.
Understanding Adjacent Segment Disease
Adjacent segment disease is a common complication following ACDF, with radiographic evidence occurring at a rate of approximately 2-4% per year 1. While many patients with radiographic changes remain asymptomatic, those who develop persistent neck pain, radiculopathy, or myelopathy due to adjacent segment degeneration may require intervention.
Diagnostic Evaluation
- Initial imaging: Cervical spine radiographs, including anteroposterior and lateral views, are useful to assess hardware integrity and detect adjacent segment disease 2
- Advanced imaging: MRI of the cervical spine without contrast is the most sensitive test for detecting soft-tissue abnormalities associated with neck pain and is recommended to evaluate neural compression 2
- Flexion/extension radiographs: May supplement conventional views to detect vertebral body nonunion or pseudoarthrosis 2
Treatment Options
1. Cervical Disc Arthroplasty (CDA)
CDA is the preferred surgical approach for ASD following ACDF for several reasons:
- Preserves motion: Maintains range of motion at the affected segment, potentially reducing stress on other adjacent levels 3, 4
- Clinical efficacy: Studies show significant improvements in pain (VAS scores), function (JOA scores), and disability (NDI scores) following CDA for ASD 4
- Long-term outcomes: Follow-up studies demonstrate that CDA can effectively maintain the range of motion of both the replaced segment and adjacent unfused segments 4
2. Revision ACDF
While revision ACDF with extension of fusion is an alternative approach, it has several disadvantages:
- Biomechanical concerns: Additional fusion may further increase stress on remaining mobile segments, potentially leading to new ASD 5
- Loss of motion: Results in further reduction of cervical spine mobility 5
- Higher reoperation rates: Younger patients (<40 years) have 4.56 times higher reoperation rates compared to older patients (>70 years) following ACDF 1
Surgical Decision-Making Algorithm
Confirm symptomatic ASD:
- Correlate imaging findings with clinical symptoms
- Rule out other causes of neck/arm pain
Evaluate patient factors:
- Age: Younger patients may benefit more from motion-preserving procedures
- Location of ASD: Above or below previous fusion
- Number of previously fused levels
Assess adjacent segment pathology:
- Degree of degeneration
- Presence of instability
- Extent of neural compression
Choose appropriate intervention:
First choice: Cervical disc arthroplasty if patient has:
- Preserved motion at the affected level
- No significant facet arthropathy
- No significant osteoporosis
Consider revision ACDF if:
- Significant facet degeneration present
- Instability at the affected level
- Multiple level disease requiring treatment
Post-Surgical Management
- Regular clinical and radiographic follow-up to monitor implant position and function
- Physical therapy to maintain range of motion and strengthen neck muscles
- Monitor for development of heterotopic ossification, which can occur in CDA patients (reported in approximately 6% of cases) 4
Outcomes and Expectations
- Most patients experience significant improvement in pain and function following CDA for ASD 3, 4
- Range of motion at the operated level is typically maintained 4
- The risk of developing new ASD at other levels remains, but may be lower than with revision fusion
Potential Complications
- Heterotopic ossification
- Device migration or subsidence
- Persistent or recurrent symptoms
- Development of ASD at other levels
CDA represents the most effective approach for managing ASD following ACDF as it addresses the neural compression while preserving motion and potentially reducing the risk of further adjacent segment degeneration.