In people with slipped lumbar disks, comparisons of surgery and nonoperative therapy show that both have beneficial outcomes; however, surgery may be slightly superior, if the patient chooses this approach.
Introduction
Should you have surgery for your back problem? That's a common question asked around the world, as slipped disk (herniated lumbar disk) continues to be a common cause of low back pain. There are several causes of low back pain: muscle strain or spasm, sprains of ligaments (which attach bone to bone), joint problems, or a slipped disk. The most common cause is using your back muscles in activities you're not used to, like heavy lifting or yard work. But some patients have, indeed, a slipped disk, and the obvious question is whether surgery can help.
Lumbar diskectomy (removal of the disk) is one of the most common surgical procedures done in the USA for patients with back and leg symptoms, even though herniated disks are known to improve without surgery. The need for surgery has been assessed in patients in the so-called SPORT study (the Spine Patient Outcomes Research Trial). The results have been published in the Journal of the American Medical Association, and are summarized here.
What was done
The SPORT study enrolled patients between 2000 and 2004 at 13 spine clinics in 11 US states. They had to have an intervertebral disk herniation with persistent symptoms despite 6 months' continuous nonoperative treatment. Herniation was demonstrated by nerve-root pain, irritation, or loss of sensation, together with visualization on MRI. Patients who had had prior lumbar surgery were excluded, as were those with severe scoliosis, cauda equina syndrome (loss of bladder or bowel control), vertebral fractures, spine infection or tumors, and so on.
A total of 501 patients were randomized to one of two groups: surgical intervention, or nonoperative treatment. There were 743 patients who refused randomization, preferring to be able to chose surgery if they wanted to; these patients went onto form a separate part of the study - the Observational Cohort - which was reported separately1.
Surgery was standard open diskectomy under general or local anesthesia. Nonoperative treatment received 'usual care', which consisted of active physical therapy, counseling with home exercise instruction, and non-steroidal and opioid analgesics, as required.
Determination of successful treatment was based on improvements in pain and bodily function scores, and the American Academy of Orthopedic Surgeons' version of the Oswestry Disability Index (ODI). These were measured at baseline, 6 weeks, 3, 6, 12, and 24 months from enrollment.
What was found
There were 232 patients randomized to surgery, and 240 to nonoperative treatment. Their average age was 42, and 58% of them were men. Half of those assigned to receive surgery were operated on within 3 months of enrollment, while 30% of those assigned to nonoperative treatment also had surgery within the first 3 months.
The results were assessed using an 'intent-to-treat' analysis, thus making allowance for the relatively high percentage of crossover patients (50% from the surgical to the non-operative group, and 30% from the nonoperative to surgical group).
In an intent-to-treat analysis patients are analyzed for results according to the groups for which they were originally assigned. Why is this necessary? Patients who change groups are not typical of the patient population, and allowing them to change groups may counteract the intent behind the randomization process.) This was the case in the present study; there were statistically significant differences between the crossover patients and the rest of the patients.) The intent-to-treat analysis estimates so-called "use-effectiveness," the causal effect of selecting a treatment, rather than the "method-effectiveness", the causal effect of actually taking the treatment.
Both treatment groups showed considerable improvements in their pain and disability scores, their Oswestry index, and the other measurements made. Although all the differences between the groups favored the surgical patients, the differences were small and not statistically significant. Moreover, the differences between the two groups got smaller with time.
The analyses made on all the participants, according to their actual treatment (rather than the treatment they were randomly allocated) showed strong, statistically significant advantages for surgery at all times through two years.
The Observation Cohort findings
In this group of patients, 528 decided on surgery, while 191 elected nonoperative therapy. After 3 months, those who chose surgery had statistically-significant greater improvements in all scores over those on nonoperative therapy; the differences had narrowed somewhat by 2 years, but remained significant. In particular, self-reported changes in symptoms were greater for surgery. Both groups reported high levels of satisfaction for 'patient care'.
How to interpret these findings
The results of this study (or rather the two parts of this study) are not conclusive. In the randomized trial the number of patients who crossed over between treatments suggests that an intent-to-treat analysis was not really informative about comparative effectiveness of the two forms of treatment (surgery or nonoperative therapy). Both forms of treatment showed considerable improvement over 2 years, with surgery probably superior, but not significantly so. It may be tempting to take the 'as-treated' analysis of this study as showing the superiority of surgery, but this is less helpful than the 'intent-to-treat' in deciding which treatment the physician should recommend. In particular, it's unclear whether similar results would have been obtained if the patients had been restricted to their originally assigned treatments.
Again, the Observation Cohort result might appear to demonstrate that surgery offers the greatest benefits. However, the self-selection process invalidated proper comparison of the two treatments, as the patients in each group differed regarding age, work status, pay, pain perception, and self-assessment of their condition.
The only way a true comparison of surgery and nonoperative therapy for slipped lumbar disk can really be resolved is for a dummy-placebo study; in other words, patients would have to receive a sham surgical operation, a condition that would be unacceptable.
The best solution, therefore, according to the investigators and editorialists, is to allow the patient to select their therapy - surgery or nonoperative - according to their circumstances and their informed knowledge that both treatments offer a good chance of relief in the long term.
