• Adam M Pearson, Jon D Lurie, Tor D Tosteson, Wenyan Zhao, William A Abdu, and James N Weinstein.
• *Geisel School of Medicine at Dartmouth, Hanover, NH †Dartmouth-Hitchcock Medical Center, Lebanon, NH; and ‡The Dartmouth Institute for Health Policy and Clinical Practice, Lebanon, NH.
• Spine. 2013 Oct 1;38(21):1799-811.

Study DesignCombined prospective randomized controlled trial and observational cohort study of degenerative spondylolisthesis (DS) with an as-treated analysis.ObjectiveTo determine modifiers of the treatment effect (TE) of surgery (the difference between surgical and nonoperative outcomes) for DS using subgroup analysis.Summary Of Background DataSpine Patient Outcomes Research Trial demonstrated a positive surgical TE for DS at the group level. However, individual characteristics may affect TE.MethodsPatients with DS were treated with either surgery (n = 395) or nonoperative care (n = 210) and were analyzed according to treatment received. Fifty-five baseline variables were used to define subgroups for calculating the time-weighted average TE for the Oswestry Disability Index during 4 years (TE = [INCREMENT] Oswestry Disability Index(surgery)- [INCREMENT] Oswestry Disability Index(nonoperative)). Variables with significant subgroup-by-treatment interactions (P< 0.05) were simultaneously entered into a multivariate model to select independent TE predictors.ResultsAll analyzed subgroups that included at least 50 patients improved significantly more with surgery than with nonoperative treatment (P< 0.05). Multivariate analyses demonstrated that age 67 years or less (TE -15.7 vs.-11.8 for age >67, P= 0.014); female sex (TE -15.6 vs.-11.2 for males, P= 0.01); the absence of stomach problems (TE -15.2 vs.-11.3 for those with stomach problems, P= 0.035); neurogenic claudication (TE -15.3 vs.-9.0 for those without claudication, P= 0.004); reflex asymmetry (TE -17.3 vs.-13.0 for those without asymmetry, P= 0.016); opioid use (TE -18.4 vs.-11.7 for those not using opioids, P< 0.001); not taking antidepressants (TE -14.5 vs.-5.4 for those on antidepressants, P= 0.014); dissatisfaction with symptoms (TE -14.5 vs.-8.3 for those satisfied or neutral, P= 0.039); and anticipating a high likelihood of improvement with surgery (TE -14.8 vs.-5.1 for anticipating a low likelihood of improvement with surgery, P= 0.019) were independently associated with greater TE.ConclusionPatients 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.Level Of Evidence3.

16 keywords...

hide…