Microdiscectomy for Sciatica, and What the SPORT Trial Actually Showed

What does a microdiscectomy actually remove?

A microdiscectomy removes the fragment of disc material that has pushed out through its casing and is pressing on a nerve root. It does not take out the whole disc, replace it, or fuse anything. The surgeon removes the piece causing the compression, through a small incision, and leaves the rest of the joint where it is. The operation is decompression of one nerve.

That narrow purpose explains the narrow benefit. Sciatica is what a compressed lumbar nerve root feels like: pain travelling from the low back through the buttock and down the leg, often past the knee, sometimes with numbness or with weakness in the muscles that nerve supplies. A herniated disk in the lower back is one common way that compression happens, and most people who have one improve within weeks to months without an operation; only a small share end up needing microdiscectomy 1Ref 1American Academy of Orthopaedic Surgeons (OrthoInfo) (2024).Herniated Disk in the Lower Back.That a lumbar herniated disk can compress a nerve root and cause sciatica, that most people improve within weeks to months without surgery, and that only a small percentage require microdiscectomy..

So the surgery is aimed at leg pain. Back pain is a different problem with different causes, and someone whose main complaint is a sore back rather than a burning leg is generally not the person the procedure was designed for. The operation is for the leg, not the back. That mismatch — hoping the operation will quiet the back and finding that it quieted the leg — is the most common disappointment after an otherwise technically perfect microdiscectomy, and it is worth settling in clinic before a date is booked rather than after.

What did the SPORT trial actually show?

The Spine Patient Outcomes Research Trial randomly assigned people with a lumbar disc herniation and radiculopathy either to discectomy or to nonoperative care. Both groups improved substantially. But the intent-to-treat comparison — the analysis randomization exists to support — came out inconclusive, because a large number of participants crossed from the arm they were assigned into the other one 2Ref 2Weinstein JN, Tosteson TD, Lurie JD, et al. (SPORT) (2006).Surgical vs Nonoperative Treatment for Lumbar Disk Herniation: The Spine Patient Outcomes Research Trial (SPORT): A Randomized Trial.That in the SPORT randomized trial of lumbar disc herniation with radiculopathy, both surgery and nonoperative care produced substantial improvement, and that the intent-to-treat comparison was inconclusive because of high crossover between the assigned arms..

The crossover is the whole story, and it is almost always told wrong. People assigned to surgery who did not want it declined it. People assigned to conservative care who could not tolerate the pain any longer went and had the operation. That is what human beings do with their own spines, and it is what a randomized trial of an elective operation struggles to survive intact. The crossover is less a flaw in the trial than a fact about the decision.

What survives. Two things. First, both strategies produced substantial improvement, which means this was never a choice between a treatment and nothing 2Ref 2Weinstein JN, Tosteson TD, Lurie JD, et al. (SPORT) (2006).Surgical vs Nonoperative Treatment for Lumbar Disk Herniation: The Spine Patient Outcomes Research Trial (SPORT): A Randomized Trial.That in the SPORT randomized trial of lumbar disc herniation with radiculopathy, both surgery and nonoperative care produced substantial improvement, and that the intent-to-treat comparison was inconclusive because of high crossover between the assigned arms.. Second, the trial could not demonstrate that being assigned to surgery beat being assigned to nonoperative care. So when a headline says SPORT proved surgery works, or that SPORT proved it does not, the headline is describing a trial that did not happen. What SPORT delivered instead is a large, careful record of people getting better along both routes — which turns out to be more useful than a winner would have been, because it moves the question from which treatment is better to which trade do I want.

Does waiting cost you anything?

A Dutch trial answered the question SPORT could not. It compared early surgery against prolonged conservative treatment for sciatica caused by a lumbar disc herniation. Early surgery relieved leg pain faster. At one year, the two strategies had arrived at the same place 3Ref 3Peul WC, van Houwelingen HC, van den Hout WB, et al. (2007).Surgery versus Prolonged Conservative Treatment for Sciatica.That early surgery for sciatica from lumbar disc herniation gave faster relief of leg pain than prolonged conservative treatment, while outcomes at one year were similar between the two strategies.. That is the finding that matters most to a person actually holding this decision.

Surgery buys time, not a better destination. It converts an unanswerable question — will this help me? — into an answerable one: what are the next few months worth? Those are different questions, and only the second has an answer that turns on your life rather than on the biology.

For someone who cannot sit through a workday, who has burned through their leave, who is a single parent carrying a child up stairs, months are expensive and the trade reads one way. For someone who can work standing, whose pain is trending down week over week, and who has watched the leg pain retreat up from the calf toward the buttock, months are cheaper and the trade reads the other way. Neither person is being braver than the other. They are paying different prices for the same commodity.

The reason waiting works at all is the sciatica natural history. Most people with a lumbar herniated disk improve within weeks to months without an operation, and only a small share need a microdiscectomy 1Ref 1American Academy of Orthopaedic Surgeons (OrthoInfo) (2024).Herniated Disk in the Lower Back.That a lumbar herniated disk can compress a nerve root and cause sciatica, that most people improve within weeks to months without surgery, and that only a small percentage require microdiscectomy.. The mechanism usually offered for that recovery is disc reabsorption — the herniated fragment shrinking over months — which carries its own evidence and its own arguments. The microdiscectomy recovery arc belongs on the same ledger: the operation is not a switch, it has its own weeks of restriction and rebuilding, and those weeks are part of what is being bought.

Where does an epidural steroid injection fit?

An epidural corticosteroid injection places anti-inflammatory medication near the irritated nerve root. A systematic review and meta-analysis of these injections in sciatica found small, short-term relief of leg pain and disability — real but modest, and measured in weeks. It found no meaningful long-term benefit, and no reduction in the rate of subsequent surgery 4Ref 4Pinto RZ, Maher CG, Ferreira ML, et al. (2012).Epidural Corticosteroid Injections in the Management of Sciatica: A Systematic Review and Meta-analysis.That epidural corticosteroid injections provide small, short-term relief of leg pain and disability in sciatica, with no meaningful long-term benefit and no reduction in the rate of subsequent surgery..

That last clause is the one that gets left out. The injection is often framed as a way to stay out of the operating room, a step that might make surgery unnecessary. The pooled evidence does not support that framing: people who had the injection went on to have surgery at about the same rate as people who did not 4Ref 4Pinto RZ, Maher CG, Ferreira ML, et al. (2012).Epidural Corticosteroid Injections in the Management of Sciatica: A Systematic Review and Meta-analysis.That epidural corticosteroid injections provide small, short-term relief of leg pain and disability in sciatica, with no meaningful long-term benefit and no reduction in the rate of subsequent surgery.. The injection is a bridge across the worst weeks, not a fork in the road.

This does not make it worthless. A few weeks of meaningful relief is not nothing when the alternative is a few weeks of not sleeping, and if what is needed is passage through a bad stretch while the natural history does its work, a bridge is exactly the right object. It is worth going in with the accurate expectation, though. The disappointment of an injection that "did not work" is often really the disappointment of an injection that did what injections do and no more.

When is waiting the wrong call?

Three situations take the choice off the table. Cauda equina syndrome — a large herniation compressing the bundle of nerves at the base of the spine — is a surgical emergency, and its signs are new trouble starting or stopping urination, loss of bowel control, and numbness across the saddle area that would touch a bicycle seat. That combination is an emergency-department visit the same day, not a clinic appointment next week.

Progressive motor weakness. Not the leg that feels weak because it hurts to push against — the leg that is measurably losing strength over days. A foot that slaps the floor when walking, an ankle that cannot lift the toes, a knee that buckles on stairs. Weakness deepening on a timescale of days is a different animal from pain that is severe, and it is why surgeons ask about strength rather than about the pain score.

Pain that has not yielded to an honest conservative trial. This one is a judgment rather than a threshold, and it is where the sequence of care actually lives. Weeks of severe leg pain that has not begun to move, in a person whose imaging matches their symptoms and whose nerve findings match both, is the classic and entirely appropriate indication. The trials do not argue against operating on that person. They observe that a great many people who look like that person at week two no longer look like them at week ten, which is the entire reason sequencing exists.

The evidence supports sequencing surgery, not avoiding it. A microdiscectomy done for a clear indication in a person who has not improved is good medicine, and the same body of evidence that counsels patience in the early weeks is what makes the operation defensible later. Nothing in SPORT or in the Dutch trial says the operation fails. Both say it works — and that many people reach the same place without it 2Ref 2Weinstein JN, Tosteson TD, Lurie JD, et al. (SPORT) (2006).Surgical vs Nonoperative Treatment for Lumbar Disk Herniation: The Spine Patient Outcomes Research Trial (SPORT): A Randomized Trial.That in the SPORT randomized trial of lumbar disc herniation with radiculopathy, both surgery and nonoperative care produced substantial improvement, and that the intent-to-treat comparison was inconclusive because of high crossover between the assigned arms.3Ref 3Peul WC, van Houwelingen HC, van den Hout WB, et al. (2007).Surgery versus Prolonged Conservative Treatment for Sciatica.That early surgery for sciatica from lumbar disc herniation gave faster relief of leg pain than prolonged conservative treatment, while outcomes at one year were similar between the two strategies..

Why the MRI does not settle it

An MRI showing a herniated disc does not by itself explain the pain, because those findings are extremely common in people who have no pain at all. A systematic review of imaging in people without symptoms found disc degeneration in 37% of 20-year-olds and 96% of 80-year-olds, with bulges and protrusions climbing along the same curve 5Ref 5Brinjikji W, Luetmer PH, Comstock B, et al. (2015).Systematic Literature Review of Imaging Features of Spinal Degeneration in Asymptomatic Populations.That degenerative spine findings including disc degeneration, bulges, and protrusions are highly prevalent on imaging in pain-free people and rise with age (disc degeneration in 37% at age 20 to 96% at age 80), so such findings often do not by themselves explain symptoms..

Disc degeneration appears in 37% of pain-free 20-year-olds and 96% of pain-free 80-year-olds 5Ref 5Brinjikji W, Luetmer PH, Comstock B, et al. (2015).Systematic Literature Review of Imaging Features of Spinal Degeneration in Asymptomatic Populations.That degenerative spine findings including disc degeneration, bulges, and protrusions are highly prevalent on imaging in pain-free people and rise with age (disc degeneration in 37% at age 20 to 96% at age 80), so such findings often do not by themselves explain symptoms.. That is a fact about aging more than a fact about injury. Scan a corridor of people who have never had back pain and most of the images come back abnormal.

What makes an MRI useful is not the herniation itself. It is whether the herniation sits at the level that would produce the symptoms this person actually has, on the side they actually have them, compressing the root that supplies the muscles that are actually weak. A scan that corroborates the story is worth a great deal. A scan read in isolation is a list of findings most of the room would also have.

This is why a surgeon who spends ten minutes examining your leg before glancing at your images is doing the job correctly, and why "the MRI looked terrible" is not, on its own, a reason to operate. The same logic drives the rotator cuff repair decision, the cervical radiculopathy decision, and most of the rest of orthopedics: the picture and the person have to agree before the picture means anything.

Microdiscectomy is not fusion, and the difference matters

When people hear "back surgery" they usually picture a fusion: hardware, bone graft, two vertebrae joined permanently into one. A microdiscectomy is not that. It removes a fragment and leaves the anatomy mobile. Conflating the two is why some people refuse a small decompression out of fear of a large reconstruction nobody was offering them.

The distinction is not cosmetic, and the evidence treats the two operations differently. In a randomized trial of stenosis decompression surgery, adding instrumented fusion to the decompression did not improve clinical outcomes at two years or at five, while it did increase cost and operative burden 6Ref 6Försth P, Ólafsson G, Carlsson T, et al. (2016).A Randomized, Controlled Trial of Fusion Surgery for Lumbar Spinal Stenosis.That adding instrumented fusion to decompression for lumbar spinal stenosis did not improve clinical outcomes at 2 or 5 years compared with decompression alone, while increasing cost and operative burden.. More metal did not buy more relief.

Lumbar spinal stenosis is a different condition from a herniated disc — a narrowing that crowds the nerves rather than a fragment pressing on one — and the surgical conversation there runs on its own evidence. But the structural lesson carries across: in spine surgery the bigger operation is not automatically the better one, and "while we are in there" is a phrase that has earned a follow-up question.

Ask which operation, not only whether to operate. The scale of the procedure being proposed, what it removes, what it leaves mobile, and what the recovery costs are separate questions from whether surgery is reasonable at all. They are also the questions where a second opinion tends to earn its keep.