Study Design. Cross-sectional analysis of long-term follow-up (LTFU) data from 4 randomized controlled trials of operative versus nonoperative 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 obtained at LTFU (mean, 13 ± 4 yr postrandomization) in 229 of 464 (49%) patients randomized to surgery and 140 of 303 (46%), to nonoperative care. Disc space height and posteroanterior displacement were measured for each lumbar segment using a validated computer-assisted distortion compensated roentgen analysis technique. Values were reported in units of standard deviations above or below age and sex-adjusted normal values. Patient-rated outcomes included the Oswestry Disability Index and pain scales.
Results. Radiographs were usable in 355 of 369 (96%) patients (259 fusion and 96 nonoperative treatment). Both treatment groups showed significantly lower values for disc space height of the adjacent segment than 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% confidence interval, −0.28 to 0.64, P = 0.45). Adjacent level disc space height and posteroanterior displacement were not correlated with Oswestry Disability Index or pain scores at LTFU (r = 0.010–0.05; P > 0.33).
Conclusion. Fusion was associated with lower disc space height at the adjacent segment after an average of 13 years of FU. The reduced disc space height had no influence on patient self-rated outcomes (pain or disability).
Level of Evidence: 2
Cross-sectional analysis of the radiographical data at long-term (average, 13 yr) follow-up of 355 patients with chronic low back pain who had been randomized to fusion or nonoperative treatment revealed significantly greater adjacent segment disc degeneration in the fusion group that was nonetheless unrelated to clinical outcome.
*Spine Center, Schulthess Klinik, Zurich, Switzerland
†Department of Clinical Medicine, Neuromuscular Diseases Research Group, University of Tromso, Norway
‡Departments of Physical Medicine and Rehabilitation and Orthopedics, Oslo University Hospital and Oslo University, Norway
§Neuroortopediskt Centrum, Länssjukhuset Ryhov, Jönköping, Sweden
¶Spine Center Göteborg, Gruvgatan, Vä Frölunda, Sweden; and
‖Nuffield Orthopaedic Centre, Oxford University Hospitals, Oxford, United Kingdom.
Address correspondence and reprint requests to Anne F. Mannion, PhD, Schulthess Klinik, Lengghalde 2, 8008 Zurich, Switzerland; E-mail: firstname.lastname@example.org
Acknowledgment date: October 19, 2013. Revision date: January 18, 2014. Acceptance date: January 20, 2014.
The manuscript submitted does not contain information about medical device(s)/drug(s).
AO Spine funds were received via the Hansjorg Wyss Research Award. In the United Kingdom, the study was also supported by Thames Valley Comprehensive Local Research Network for National Institutes for Health Research. In Norway, the Norwegian Research Council grant funds were received to support this work.
Relevant financial activities outside the submitted work: royalties.