Long-Term Follow Up Suggests Spinal Fusion is Associated With Increased Adjacent Segment Disc Degeneration but Without Influence on Clinical Outcome: Results of a Combined...

Mannion, Anne F; Leivseth, Gunnar; Brox, Jens-Ivar; Fritzell, Peter; Hägg, Olle; Fairbank, Jeremy CT Less

Spine., Post Acceptance: May 22, 2014

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Study Design. Cross-sectional analysis of long term follow-up (LTFU) data from four randomized controlled trials of operative versus non-operative treatment for chronic low back pain.

Objective. To examine the influence of spinal fusion on adjacent segment disc space height as an indicator of disc degeneration at LTFU.

Summary of Background Data. There is ongoing debate as to whether adjacent segment disc degeneration results from the increased mechanical stress of fusion.

Methods. Plain standing lateral radiographs were taken at LTFU (mean 13+/-4 years post-randomization) in 229/464 (49%) patients randomized to surgery and 140/303 (46%), to non-operative care. Disc space height and posteroanterior displacement were measured for each lumbar segment using a validated computer-assisted distortion compensated roentgen analysis (DCRA) technique. Values were reported in units of standard deviations (SDs) above or below age and gender-adjusted normal values. Patient-rated outcomes included the Oswestry Disability Index and pain scales.

Results. Radiographs were usable in 355/369 (96%) patients (259 fusion and 96 non-operative treatment). Both treatment groups showed significantly lower values for disc space height of the adjacent segment compared with norm values. There was a significant difference between treatment groups for the disc space height of the cranial adjacent segment (in both as-treated and intention-to-treat analyses). The mean treatment effect of fusion on adjacent segment disc space height was -0.44 SDs (95% CI, -0.77 to -0.11; p = 0.01; as-treated analysis); there was no group difference for posteroanterior displacement (0.18 SDs (95% CI, -0.28 to 0.64, p = 0.45)). Adjacent level disc space height and posteroanterior displacement were not correlated with Oswestry or pain scores at LTFU (r = 0.010-0.05; p>0.33).

Conclusions. Fusion was associated with lower disc space height at the adjacent segment after an average of 13 years follow-up. The reduced disc space height had no influence on patient self-rated outcomes (pain or disability).

(C) 2014 by Lippincott Williams & Wilkins