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Degenerative Spondylolisthesis: Does Fusion Method Influence Outcome? Four-Year Results of the Spine Patient Outcomes Research Trial

Abdu, William A. MD, MS*; Lurie, Jon D. MD, MS†‡; Spratt, Kevin F. PhD*‡; Tosteson, Anna N. A. ScD†‡; Zhao, Wenyan MS*; Tosteson, Tor D. ScD; Herkowitz, Harry MD§; Longely, Michael MD; Boden, Scott D. MD; Emery, Sanford MD**; Weinstein, James N. DO, MS*‡§

doi: 10.1097/BRS.0b013e3181b8a829
Health Services Research

Study Design. Clinical trial subgroup analysis.

Objective. To compare outcomes of different fusion techniques treating degenerative spondylolisthesis (DS).

Summary of Background Data. Surgery has been shown to be more effective than nonoperative treatment out to 4 years. Questions remain regarding the differential effect of fusion technique.

Methods. Surgical candidates from 13 centers in 11 states with at least 12 weeks of symptoms and confirmatory imaging showing stenosis and DS were studied. In addition to standard decompressive laminectomy, 1 of 3 fusion techniques was employed at the surgeon’s discretion: posterolateral in situ fusion (PLF); posterolateral instrumented fusion with pedicle screws (PPS); or PPS plus interbody fusion (360°). Main outcome measures were the SF-36 bodily pain (BP) and physical function (PF) scales and the modified Oswestry Disability Index (ODI) assessed at 6 weeks, 3 months, 6 months, and yearly to 4 years. The as-treated analysis combined the randomized and observational cohorts using mixed longitudinal models adjusting for potential confounders.

Results. Of 380 surgical patients, 21% (N = 80) received a PLF; 56% (N = 213) received a PPS; 17% (N = 63) received a 360°; and 6% (N = 23) had decompression only without fusion. Early outcomes varied, favoring PLF compared to PPS at 6 weeks (PF: 12.73 vs. 6.22, P < 0.020) and 3 months (PF: 25.24 vs.18.95, P < 0.025) and PPS compared to 360° at 6 weeks (ODI: −14.46 vs. −9.30, P < 0.03) and 3 months (ODI: −22.30 vs. −16.78, P < 0.02). At 2 years, 360° had better outcomes: BP: 39.08 versus 29.17 PLF, P < 0.011; and versus 29.13 PPS, P < 0.002; PF: 31.93 versus 23.27 PLF, P < 0.021; and versus 25.29 PPS, P < 0.036. However, these differences were not maintained at 3- and 4-year follow-up, when there were no statistically significant differences between the 3 fusion groups.

Conclusion. In patients with DS and associated spinal stenosis, no consistent differences in clinical outcomes were seen among fusion groups over 4 years.

The Spine Patient Outcomes Research Trial prospectively investigated the effectiveness of surgical versus nonsurgical treatment of degenerative spondylolisthesis, using health-related quality of life outcomes. From this cohort, 356 patients underwent 1 of 3 fusion methods: posterolateral in situ fusion, posterolateral fusion with pedicle screws, or circumferential fusion, in association with their decompression, and completed at least 1 follow-up survey. With early follow-up, there was variation favoring one fusion method over another. However, at 3 and 4 years, there were no significant differences in outcomes among any of the 3 fusion methods.

From the Departments of *Orthopaedics and †Medicine, Dartmouth Medical School, Dartmouth College, Hanover, NH; ‡The Dartmouth Institute for Health Policy and Clinical Practice, Dartmouth College, Hanover, NH; §William Beaumont Hospital, Royal Oak, MI; ¶The Nebraska Spine Research Foundation, Omaha, NE; ∥Emory Spine Center, Atlanta, GA; and **Case-Western Reserve University, Cleveland, OH.

Acknowledgment date: October 21, 2008. Revision date: July 15, 2009. Acceptance date: July 21, 2009.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Federal funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (U01-AR45444), the Office of Research on Women’s Health, the National Institutes of Health, and the National Institute of Occupational Safety and Health, the Centers for Disease Control and Prevention.

Spine Patient Outcomes Research Trial (SPORT): Degenerative Spondylolisthesis with Spinal Stenosis; NCT00000409; Available at:

Address correspondence and reprint requests to James N. Weinstein, DO, MS, The Dartmouth Institute for Health Policy and Clinical Practice, One Medical Center Dr., Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756; E-mail:

© 2009 Lippincott Williams & Wilkins, Inc.