Lumbar discectomy

Discectomy is the most common operation performed in the United States for patients who are experiencing lumbar-related symptoms. Nonetheless, despite the wide acceptance of discectomy as a treatment option for symptomatic lumbar disc herniation, there has been a paucity of level I evidence supporting the effectiveness of this surgery compared with nonoperative care. Significant regional variation in discectomy rates in the United States and lower international rates have also raised questions about when these surgeries should be performed.

Several studies have compared surgical and nonoperative treatment, but small sample sizes, study design limitations, and failure to plan for high crossover rates limit the strength of these studies. Between the years of 1983 and 2007 there were 4 randomized controlled trials (RCTs) comparing operative care with more conservative management, not including the well-publicized Spine Patient Outcomes Research Trial (SPORT).

Weber performed a controlled, prospective study with 10 years of follow-up. Of the 280 patients enrolled in this study, 126 were randomized to either surgery or physical therapy. The others were not randomized and had surgery or nonoperative treatment. The group randomized to surgery had statistically better outcomes after 1 year. After 4 years, however, although the surgery outcomes were still better, this difference was no longer statistically significant.

Buttermann conducted a prospective, randomized study comparing epidural steroid injection (ESI) with discectomy for treatment of lumbar disc herniation. One hundred patients who had failed noninvasive therapy for 6 weeks were randomly assigned to receive ESI or discectomy. This study found that discectomy patients had more rapid improvement in their symptoms. The investigators stated that ESI was not as effective as surgery in reducing symptoms in those with large herniations.

Osterman and colleagues conducted a prospective, randomized study comparing physical therapy with discectomy for treatment of lumber disc herniation. Fifty-six patients who had radiating back pain below the knee for 6 to 12 weeks were randomized to receive either isometric physical therapy or discectomy. Patients were followed for 2 years and at final follow-up the study found no clinically significant difference between the groups in terms of leg pain intensity and other secondary outcomes. These investigators proposed discectomy provided only some short-term benefit.

Another study by Peul and colleagues was a prospective, randomized study comparing nonsurgical treatment with discectomy for the treatment of lumbar disc herniation. Two hundred and eighty subjects were followed for a year and the investigators found that the 2 groups had similar outcomes at 1 year, but those who underwent surgery had faster rates of recovery and self-perceived pain.

These studies together contribute significant information about the outcomes that can be expected from lumbar discectomy. For an outcome measure, Weber used a patient-described 4-tier descriptive scale (poor, fair, good, excellent). The 3 other more recently published studies by Osterman and colleagues, Peul and colleagues, and Butterman used more common general and disease-specific health quality surveys, and clinical examination. Each of these studies had 1 year follow-up, except for Weber’s, in which long-term follow-up to 10 years after surgery was included.

Crossover rates were an issue for each of these RCTs. The crossover from nonsurgical treatment group to the surgical treatment group ranged from 34.7% to 54%, with the average being 42.6%. In each of these studies, a smaller number of patients crossed over from the surgical treatment group to the nonsurgical treatment group, with an average of 21.4%.

Two of the 4 studies used an intent-to-treat (ITT) analysis. Weber used an ITT analysis but also used tables to show the treatment assigned and the treatment received. However, in the primary analysis these investigators left out the 34.7% of patients who crossed over to the surgical group. Osterman and colleagues used an ITT and an as-treated analysis but the as-treated analysis was not reported in detail.

The results of these lumbar disc herniation RCTs were variable when compared with each other. The general observed trend was that early outcomes were improved with surgical intervention, but longer-term outcomes were more similar when comparing nonoperative and surgical management.

SPORT trial

The SPORT trial was a federally funded, multicenter, prospective, randomized, controlled study assessing the efficacy of surgery versus nonsurgical treatment of lumbar intervertebral disc herniation. This large undertaking took more than 7 years to complete and was published in the Journal of the American Medical Association in 2006. Despite the tremendous amount of work and resources that were put into this research study, the primary investigators were unable to make a definitive statement about the advantage of any 1 treatment type, largely because of issues with study group crossover.

The main goal of this trial was to evaluate the efficacy of surgery versus nonoperative treatment of lumbar disc herniation. Patients were enrolled over a 4-year period from 13 multidisciplinary spine clinics in 11 US states. Investigators screened 2720 patients and 1991 were found eligible. Of these 1991 patients, 1244 enrolled in the trial, 501 agreeing to be randomized, and 743 enrolled in an observational arm of the study. The primary outcomes measures used in this study were changes in the Medical Outcomes Study Health Survey bodily pain and physical function scales and the modified Oswestry Disability Index for a 2-year period.

The study reported that the ITT analysis showed significant improvement in all measured outcomes in both treatment groups. The investigators concluded by stating that because of high crossover rates from both groups, no direct comparison between surgical and nonsurgical management was warranted based on the ITT analysis. The a priori null hypothesis of no difference between surgical and nonsurgical treatments was thus unable to be ruled out.

The issues noted with this high-profile study have led to much scrutiny. Despite a clear statement by the study investigators that direct comparisons between the 2 treatments would not be valid, many have interpreted the results to suggest equivalence between surgery and nonsurgical care for patients with lumbar disc herniations. The error in these statements was most likely caused by the reader interpreting the treatment groups in the SPORT trial as the treatment received. However, because of the ITT analysis and a high crossover rate, the nonoperative group contained many patients who did have surgery. The surgical benefits for those patients who crossed over into the surgery treatment group were allocated to nonoperative care and clearly biased the results toward the null hypothesis.

SPORT trial

The SPORT trial was a federally funded, multicenter, prospective, randomized, controlled study assessing the efficacy of surgery versus nonsurgical treatment of lumbar intervertebral disc herniation. This large undertaking took more than 7 years to complete and was published in the Journal of the American Medical Association in 2006. Despite the tremendous amount of work and resources that were put into this research study, the primary investigators were unable to make a definitive statement about the advantage of any 1 treatment type, largely because of issues with study group crossover.

The main goal of this trial was to evaluate the efficacy of surgery versus nonoperative treatment of lumbar disc herniation. Patients were enrolled over a 4-year period from 13 multidisciplinary spine clinics in 11 US states. Investigators screened 2720 patients and 1991 were found eligible. Of these 1991 patients, 1244 enrolled in the trial, 501 agreeing to be randomized, and 743 enrolled in an observational arm of the study. The primary outcomes measures used in this study were changes in the Medical Outcomes Study Health Survey bodily pain and physical function scales and the modified Oswestry Disability Index for a 2-year period.

The study reported that the ITT analysis showed significant improvement in all measured outcomes in both treatment groups. The investigators concluded by stating that because of high crossover rates from both groups, no direct comparison between surgical and nonsurgical management was warranted based on the ITT analysis. The a priori null hypothesis of no difference between surgical and nonsurgical treatments was thus unable to be ruled out.

The issues noted with this high-profile study have led to much scrutiny. Despite a clear statement by the study investigators that direct comparisons between the 2 treatments would not be valid, many have interpreted the results to suggest equivalence between surgery and nonsurgical care for patients with lumbar disc herniations. The error in these statements was most likely caused by the reader interpreting the treatment groups in the SPORT trial as the treatment received. However, because of the ITT analysis and a high crossover rate, the nonoperative group contained many patients who did have surgery. The surgical benefits for those patients who crossed over into the surgery treatment group were allocated to nonoperative care and clearly biased the results toward the null hypothesis.

SPORT study hypothesis

The formation of a reasonable and clinical relevant study hypothesis is extremely important for the success of a prospective, randomized clinical trial. The only hypothesis that can be assessed by this type of study is one that is stated before the study takes place. The stated a priori hypothesis of the SPORT study was simply to determine if there was no difference between surgical and nonsurgical management in patients with lumbar disc herniations. The dichotomous hypothesis was intended to give an answer to whether surgery was superior to nonoperative care.

This simplified hypothesis proved problematic in many ways. The stated hypothesis implied that lumbar disc herniation is a uniform condition, with surgery and nonoperative care as the competing treatments. In current practice, surgical and nonsurgical treatments for lumbar disc herniations are not thought of as competing or transposable options but rather treatments along a spectrum of care. Further, lumbar disc herniation is a heterogeneous condition with differences in pain severity, neurologic impairment, natural history, and treatment response.

The main goals in treatment of patients presenting with this heterogeneous condition are alleviating pain and returning function with as little risk as possible. Hence, almost all patients who present with painful lumbar disc herniation without acute or progressive neurologic deficit begin treatment with nonsurgical approaches. Most surgeons would be hesitant to offer surgical treatment to a patient who has pain for a short duration or who is actively improving. This situation makes it difficult to randomize patients to one of these otherwise staged treatment options.