Prolapsed intervertebral disc
Authors: Jeremy Fairbank
Journal: BMJ (2008)

Prolapsed intervertebral disc is common—it is seen in up to a quarter of magnetic resonance scans and can be detected even in asymptomatic adults.1 Disc prolapse is genetically driven—twin studies indicate that at least 60% of the variance can be explained on genetic grounds and not by the commonly assumed environmental factors (work, trauma, exposure to excessive driving, smoking, and so on).2 In the linked randomised controlled trial, Peul and colleagues compare the effects of early surgery with conservative management at two years in 283 patients who have had sciatica for six to 12 weeks.3 A second study by van den Hout and colleagues compares the costs of each approach.4

Current guidelines indicate that radicular pain should improve within six to eight weeks with conservative management.5 Surgery should be performed before eight weeks only in patients with progressive neurological deficit, which can be detected by magnetic resonance imaging. Some people will have radicular pain and no prolapse. Epidural local anaesthetic and steroids may benefit these patients, although the evidence base is weak.6

Management problems arise if severe pain lasts for longer than eight weeks. A few trials and many guidelines indicate that even at this stage many people will recover. Patients are more likely to have surgery if they have had one or more previous attack of pain.

Commonly used non-operative measures such as manipulation, epidurals, physiotherapy, and analgesics have little effect on the course of sciatica.6 No features have been identified that can predict the time scale of recovery, except perhaps psychosocial factors. This is important because most people with radicular pain are of working age or are supporting young families. The risks of conservative treatment (as opposed to surgery) are low, although a few people will develop progressive neurology or cauda equina problems and 10% will have attacks in the future at the same site or another one. Again, we cannot predict who will have these complications.

Surgery is effective and alleviates at least 90% of radicular leg pain. It is less successful for back pain, and around 70% of people will continue to have long term back pain after surgery. Up to 10% of people will report more serious back pain and in some of these it will be disabling. 

Surgery has no effect on recurrence, so the benefit of surgery is only short to medium term. Surgery is potentially dangerous. Up to 5% of people may have more pain and up to 1% may have neurological damage and will regret the decision to operate.6 Psychological factors are important both for persisting pain and the failure to meet the expectation of a good outcome, which surgeons should be aware of when advising treatment.

Peul and colleagues found no significant overall difference in disability scores during the first two years between early surgery and six months of conservative management. Leg pain improved significantly faster in patients who had early surgery. The relative short term global benefit of early surgery was no longer statistically significant by six months and continued to narrow between six months and two years. 

The trial has some limitations. The non-operative arm is not evidence based—the evidence for all forms of non-operative treatment is poor, and many people get better spontaneously. The rate of transfer to the surgery arm from the conservative treatment arm was high (44% switched to surgery compared with 30% in a previous trial7). This high rate of transfer reflects the large impact that this condition has on patients’ quality of life and the difficulty of designing surgical versus non-surgical trials. The surgical technique used reflects current practice, but the aggressive curretage of the disc space used in the trial may be less effective than simply removing the herniated material.8 9

The design of the trial was ideal for coping with a potentially risky treatment for a largely benign but unpredictably malign condition. In the United States, the SPORT trial allowed patients to join a trial comparing surgery with non-operative care or to make their own choice about treatment.7 This study should be examined carefully by people designing randomised controlled trials because many would object to this type of “patient choice” protocol, which was designed to accommodate patients’ reluctance to be randomised. The results supported the use of surgery.

Peul and colleagues’ trial is similar in design to another trial done in the United Kingdom, which has never been fully published, but which had similar findings.10 Weber reported the first randomised controlled trial of surgical treatment versus non-operative care, although it was poorly designed.6 11 This trial found that surgery was better than non-operative care. It has informed decision making during the past 30 years,6 11 and it is still helpful despite its well recognised flaws.12

The economic evaluation of Peul and colleagues’ trial found that because early surgery was associated with quicker recovery from sciatica it is likely to be more cost effective than prolonged conservative care. The estimated difference in healthcare costs of€40 000 (£32 000; $62 000) or more per quality adjusted life year was considered acceptable and was compensated for by the difference in absenteeism.

The focus of Peul and colleagues’ study is on health economics based on the intelligent system of bottom-up procedure pricing used in Holland. Early surgery is a viable economic option and should be applied in the UK.

What research questions remain? Major gaps exist in our knowledge of the underlying mechanisms of disc degeneration and prolapse. Of the trials that are available, few have shown non-operative treatments can improve the course of sciatica.6 Further trials of the risks of curretage and of minimally invasive versus open techniques would also be helpful. Finally, injections of chymopapain may be effective for young people with disc prolapse, but it has been rejected for reasons that are not backed by science.13

This trial adds to the body of evidence supporting surgery eight weeks after onset of sciatica if symptoms persist. Patients should understand the arguments for and against surgery and their perceived pain should be severe enough to justify the risks.