Study Design. Combined prospective randomized controlled trial and observational cohort study of spinal stenosis (SpS) with an as-treated analysis.
Objective. To determine modifiers of the treatment effect (TE) of surgery (the difference between surgical and nonoperative outcomes) for SpS using subgroup analysis.
Summary of Background Data. The Spine Patient Outcomes Research Trial demonstrated a positive surgical TE for SpS at the group level. However, individual characteristics may affect TE. No previous studies have evaluated TE modifiers in SpS.
Methods. SpS patients were treated with either surgery (n = 419) or nonoperative care (n = 235) and were analyzed according to treatment received. Fifty-three baseline variables were used to define subgroups for calculating the time-weighted average TE for the Oswestry Disability Index (ODI) over 4 years (TE = ΔODIsurgery – ΔODInonoperative). Variables with significant subgroup × treatment interactions (P < 0.05) were simultaneously entered into a multivariate model to select independent TE predictors.
Results. Other than smokers, all analyzed subgroups including at least 50 patients improved significantly more with surgery than with nonoperative treatment (P < 0.05). Multivariate analysis demonstrated: baseline ODI ≤ 56 (TE −15.0 vs. −4.4, ODI > 56, P < 0.001), not smoking (TE −11.7 vs. −1.6 smokers, P < 0.001), neuroforaminal stenosis (TE −14.2 vs. −8.7 no neuroforaminal stenosis, P = 0.002), predominant leg pain (TE −11.5 vs. −7.3 predominant back pain, P = 0.035), not lifting at work (TE −12.5 vs. −0.5 lifting at work, P = 0.017), and the presence of a neurological deficit (TE −13.3 vs. −7.2 no neurological deficit, P < 0.001) were associated with greater TE.
Conclusion. With the exception of smokers, patients who met strict inclusion criteria improved more with surgery than with nonoperative treatment, regardless of other specific characteristics. However, TE varied significantly across certain subgroups, and these data can be used to individualize shared decision making discussions about likely outcomes. Smoking cessation should be considered before surgery for SpS.
Surgical treatment effect modifiers were evaluated in the Spine Patient Outcomes Research Trial spinal stenosis cohort. Other than smokers, all subgroups improved more with surgery than with nonoperative treatment. Baseline Oswestry Disability Index score less than 56, not smoking, neuroforaminal stenosis, predominant leg pain, not lifting at work, and baseline neurological deficit predicted greater treatment effect.
*Department of Orthopaedics
†Department of Medicine and Orthopaedics
‡Department of Community and Family Medicine, Dartmouth Medical School and the Dartmouth Institute for Health Policy and Clinical Practice, Hanover, NH.
Address correspondence and reprint requests to Adam Pearson, MD, MS, Department of Orthopaedics, Dartmouth-Hitchcock Medical Center, 1 Medical Center Dr, Lebanon, NH 03756; E-mail: firstname.lastname@example.org
Acknowledgment date: October 21, 2011. First revision date: April 3, 2012. Acceptance date: April 20, 2012.
The manuscript submitted does not contain information about medical device(s)/drug(s).
The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) (U01-AR45444) and 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. The Multidisciplinary Clinical Research Center in Musculoskeletal Diseases is funded by NIAMS (P60-AR048094).
One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: for example, honoraria, gifts, consultancies.