Study design: Retrospective subgroup analysis of prospectively collected data according to treatment received.
Objective: The purpose of this study is to determine whether the duration of symptoms affects outcomes after the treatment of spinal stenosis (SS) or degenerative spondylolisthesis (DS).
Summary of background data: The Spine Outcomes Research Trial (SPORT) study was designed to provide scientific evidence on the effectiveness of spinal surgery versus a variety of nonoperative treatments.
Methods: An as-treated analysis was performed on the patients enrolled in SPORT for the treatment of SS or DS. A comparison was made between patients with SS with 12 or fewer months' (n = 405) and those with more than 12 months' (n = 227) duration of symptoms. A comparison was also made between patients with DS with 12 or fewer months' (n = 397) and those with more than 12 months' (n = 204) duration of symptoms. Baseline patient characteristics were documented. Primary and secondary outcomes were measured at baseline and at regular follow-up time intervals up to 4 years. The difference in improvement among patients whose surgical or nonsurgical treatment began less than or greater than 12 months after the onset of symptoms was measured. In addition, the difference in improvement with surgical versus nonsurgical treatment (treatment effect) was determined at each follow-up period for each group.
Results: At final follow-up, there was significantly less improvement in primary outcome measures in SS patients with more than 12 months' symptom duration. Primary and secondary outcome measures within the DS group did not differ according to symptom duration. There were no statistically significant differences in the treatment effect of surgery in SS or DS patients.
Conclusion: Patients with SS with fewer than 12 months of symptoms experienced significantly better outcomes with surgical and nonsurgical treatment relative to those with symptom duration greater than 12 months. There was no difference in the outcome of patients with degenerative spondylolisthesis according to symptom duration.