Is neural foraminal decompression (NFD) performed prior to artificial disc replacement (ADR)?

Neural Foraminal Decompression Timing in Artificial Disc Replacement

Neural foraminal decompression (NFD) is not routinely performed as a separate procedure prior to artificial disc replacement (ADR)—instead, the ADR procedure itself provides indirect foraminal decompression through disc height restoration, and direct foraminal decompression (when needed) is performed during the same operative session as the ADR.

Mechanism of Foraminal Decompression During ADR

Indirect decompression occurs automatically during ADR through disc height restoration:

• Increasing disc height during ACDF/ADR significantly increases foraminal height (mean +2.12 mm) and foraminal volume (mean +54 mm³), with disc height increase directly correlating with foraminal volume expansion 1
• The increase in foraminal height is the major component affecting foraminal volume increase, and this indirect decompression plays an important role in postoperative outcomes 1
• Both ACDF and ADR procedures increase neuroforaminal area through this indirect mechanism of disc height restoration 2

Direct Foraminal Decompression During ADR (When Required)

When additional direct decompression is needed for significant foraminal stenosis, it is performed during the same ADR procedure:

• The operative technique begins at the lateral edge of the ADR at the superior end plate of the inferior vertebral body, with drilling of the ipsilateral uncovertebral joint using high-speed and diamond-coated burrs 3
• The neuroforamen is entered after drilling through the posterior aspect of the uncinate process, with direct visualization of the exiting cervical nerve root 3
• A Kerrison rongeur traces along the nerve root laterally to remove any remaining uncinate osteophyte 3

Clinical Decision Algorithm

Determine the need for direct foraminal decompression based on:

1. Severity of foraminal stenosis on preoperative imaging: Moderate-to-severe or severe foraminal stenosis requires consideration of direct decompression 4, 5
2. Clinical correlation: Dermatomal sensory changes, myotomal weakness, and reflex changes corresponding to the affected nerve root 4
3. Pathology type: Hard disc (osteophyte) versus soft disc herniation—osteophytic foraminal stenosis benefits more from direct uncovertebral joint resection 2, 3

Surgical Approach Selection

The choice between indirect decompression alone versus combined indirect/direct decompression depends on:

• Indirect decompression alone (ADR without foraminotomy) is appropriate when foraminal stenosis is mild-to-moderate and primarily due to disc height loss 1
• Combined approach (ADR with anterior cervical foraminotomy) is indicated when moderate-to-severe foraminal stenosis persists despite disc height restoration, particularly with uncovertebral joint hypertrophy 3
• Foraminotomy produces the greatest increase in foraminal area and maintains this increase during neck extension better than ACDF alone (55 mm² neutral vs 40 mm² extension for ACDF alone) 2

Critical Pitfalls to Avoid

Common errors in surgical planning:

• Assuming indirect decompression is always sufficient: Partial uncovertebral joint resection (UVR) during ACDF did not significantly alter foraminal area compared with ACDF alone in biomechanical studies, suggesting that when direct decompression is needed, complete foraminotomy is superior to partial UVR 2
• Performing staged procedures unnecessarily: Direct foraminal decompression should be performed during the index ADR procedure when indicated, not as a separate prior surgery 3
• Ignoring recurrent symptoms: If radicular symptoms persist or recur after ADR, anterior cervical foraminotomy with uncovertebral joint resection can provide direct decompression without implant removal or conversion to fusion 3

Evidence Quality Considerations

The biomechanical evidence demonstrates that foraminotomy maintains foraminal area better through neck motion than anterior-only procedures 2, while clinical evidence shows that 3 of 5 patients (60%) achieved complete resolution of recurrent radicular symptoms following anterior cervical foraminotomy after ADR 3. However, these findings pertain primarily to bony stenosis and may not apply equally to soft disc herniation 2.