A total of 654 SPORT participants were enrolled out of 1,091 eligible for enrollment (289 in the RC and 365 in the OC) (). In the RC, 138 were assigned to surgical treatment and 151 to non-operative treatment. Of those randomized to surgery, 67% received surgery by 2 years, 68% by 4 years. In the group randomized to non-operative care, 43% received surgery by two years, 49% by 4 years (). In the OC group, 219 patients initially chose surgery and 146 patients initially chose non-operative care. Of those initially choosing surgery, 96% received surgery by two years and 97% by 4 years. Of those choosing non-operative treatment, 22% had surgery by two years, 26% by 4 years (). In both cohorts combined, 419 patients received surgery at some point during the first 4 years; 235 remained non-operative. The proportion of enrollees who supplied data at each follow-up visit interval ranged from 67% to 89% with losses due to dropouts, missed visits, or deaths.
shows the baseline characteristics and clinical findings of participants in the randomized and the observational cohorts. The cohorts were remarkably similar except for their preferences for surgery (p < 0.001), with more RC patients unsure of their preference (34% vs. 7%), and fewer RC patients definitely preferring either surgery (12% vs. 46%) or non-operative treatment (13% vs. 24%).
Patient baseline demographic characteristics, comorbidities, and health status measures according to study cohort and treatment received.
Summary statistics for the combined cohorts are also shown in according to treatment received. At baseline, patients in the group undergoing surgery within 4 years from the combined randomized and observational cohorts were younger than those receiving non-operative treatment. They had worse pain, function, disability, and symptoms than patients in the non-operative group. Patients in the surgery group were more dissatisfied with their symptoms and at enrollment more often rated their symptoms as worsening and definitely preferred surgery. These observations highlight the need to control for baseline differences in the adjusted models. Based on the selection procedure for variables associated with treatment, missing data and outcomes, the final as-treated models controlled for the following covariate: center; age; gender; baseline score (for SF-36, ODI); income; treatment preference; current duration of symptoms; compensation; smoking status; BMI; baseline sciatica bothersomeness; joint; stomach; and bowel ().
Primary analysis results for years 3 and 4. Intent-to-treat for the randomized cohort and adjusted* analyses according to treatment received for the randomized and observational cohorts combined. ‡‡
Non-operative treatments used during SPORT included physical therapy (44%); visits to a surgeon (46%); nonsteroidal anti-inflammatory drugs (49%); and opioids (37%); More patients in the randomized cohort reported receiving injections (54% vs. 41%, p=0.02) while more observational patients reported receiving other medications (74% vs. 62%, p=0.02). Pre-enrollment there were no significant differences in non-operative treatments received between the RCT and OBS cohorts.
Surgical Treatment and Complications
The mean surgical time was 129 minutes, with a mean blood loss of 311 ml (). There was no significant difference between the cohorts in rates of intraoperative blood replacement, or postoperative transfusion rates. The most common surgical complication was dural tear (9%). The 4-year reoperation rate was 13%.
Operative treatments, complications and events.
Over four years, there were 12 deaths in the non-operative group within 4 years of enrollment compared to 23 expected based on age-gender specific mortality rates, and 15 deaths in the surgery group within 4 years of surgery, compared to 29 expected. The hazard ratio based on a proportional hazards model adjusted for age was 0.7 (95% CI: 0.32, 1.6); p=0.43. All 27 deaths were independently reviewed and 23 were judged not to be treatment-related. Four deaths were of unknown cause and unknown treatment relation but occurred 1203, 1192, 855, 501 days post-surgery/enrollment. Three of these deaths were in patients who had had surgery and one was in a patient who had not had surgery.
Non-adherence to treatment assignment affected both arms: patients chose to delay or decline surgery in the surgical arm and crossed over to surgery in the non-operative arm (). The characteristics of cross over patients that were statistically different from patients who did not cross over are shown in . Patients who crossed over to non-operative care were: less likely to be white; less bothered by their symptoms; more likely to judge their symptoms as improving at baseline; and had stronger baseline treatment preferences for non-operative care. Patients crossing over to surgery: had lower mental component summary scores, were more disabled and bothered by their symptoms, were less satisfied by their symptoms, and had stronger baseline preference for surgery.
Statistically significant predictors of adherence to treatment among RCT patients.
Main Treatment effects
The intent-to-treat analysis of the randomized cohort showed no statistical differences between surgery and non-operative care based on overall global hypothesis tests for differences in mean changes from baseline (). The randomized and observational cohorts’ as-treated treatment effects were similar at 4 years ():
- Bodily Pain: RC 11.4 (95% CI, 5.1 to 17.6) vs. OC 14.9 (95% CI, 9.3 to 20.5);
- Physical Function: RC 8.0 (95% CI, 1.7 to 14.3) vs. OC 10.1 (95% CI, 4.7 to 15.5); and
- Oswestry Disability Index: RC −7.8 (-12.9, −2.6) vs. OC −11.5 (-15.8, −7.3).
The global hypothesis test comparing the as-treated RC and OC treatment effects over all time periods showed no difference between the cohorts (p = 0.27 for BP; p = 0.56 for PF; and p= 0.25 for ODI).
Results from the intent-to-treat and as-treated analyses of the two cohorts are compared in . The as-treated treatment effects significantly favored surgery in both cohorts. In the combined analysis, treatment effects were statistically significant in favor of surgery for all primary and secondary outcome measures at each time point out to four years (). At 4 years the treatment effect for bodily pain was 12.6 (95%CI, 8.5 to 16.7) for physical function was 8.6 (95%CI, 4.6 to 12.6) and for Oswestry Disability Index was −9.4 (95%CI, −12.6 to −6.2).
shows the proportion of patients in the as-treated comparison of surgery versus non-operative care who achieved at least a 15-point improvement in the ODI at 1 and 4 years respectively. 23
These proportions at 4 years (61% in surgery group, 32% in non-operative group) are quite similar to the proportions rating themselves as being very/somewhat satisfied with their symptoms (63% in the surgery group, 32% in the non-operative group) and having had a major improvement (53% in surgery group, 23% in non-operative group).
Proportion of patients who had a change of ≥ 15 on the ODI at 1-year and 4-years from baseline. Based on the adjusted as-treated analysis for the randomized and observational cohorts combined, according to treatment received.