Spondylolisthesis

In one minute

Spondylolisthesis is a vertebra that has slid forward on the one below it. The degenerative type appears in older adults, most often in women and at L4-L5; the isthmic type starts with a stress fracture at the back of the vertebra in youth, usually at L5-S1. It feels like low back pain with leg pain or heaviness that builds with standing and walking and eases when you sit. A standing X-ray shows the slip; an MRI (magnetic resonance imaging) shows what it does to the nerves. Most low-grade slips are managed without surgery. When leg symptoms persist, the operation is a decompression, alone or with fusion, and both can be done endoscopically.

What it is

One vertebra moves forward relative to the one below, so the canal and the side openings (foramina) at that level become narrower. Reports call it a slipped vertebra, listhesis or instability.

Two types matter in adults. Degenerative spondylolisthesis comes from wear of the disc and facet joints, with the ring of bone intact. Isthmic spondylolisthesis comes from a defect in the pars interarticularis, the small bridge of bone joining the front and back of a vertebra; the defect on its own is called spondylolysis. Rarer types follow trauma, tumour, infection or a congenital malformation.

The slip is graded on the Meyerding scale by how far the upper vertebra has moved, as a fraction of the width of the one below: grade I is 1% to 25%, grade II 26% to 50%, grade III 51% to 75%, and grade IV more than 75%, up to the full width. A vertebra that has slipped off the one below entirely is called spondyloptosis. In our experience the degenerative slip is nearly always grade I, and the SLIP trial described below, a randomised comparison of decompression with and without fusion, enrolled only that grade.

Causes and risk factors

Spondylolysis is found in about 5% to 11.5% of the population and isthmic spondylolisthesis in roughly 4% to 8%, more often in men. The pars defect usually develops in adolescence as a fatigue fracture, and most people who have one never know.

Degenerative spondylolisthesis is reported in 2.7% of men and 8.4% of women, rising with age and after the menopause. Wear of the disc and facet joints, female sex, age and the L4-L5 level itself are the recognised associations.

How it develops

In the degenerative type the disc loses height and the two facet joints behind it wear, loosen and grow. With the disc no longer holding the segment, the upper vertebra creeps forward a millimetre at a time. The slipped vertebra, the overgrown joints and the thickened ligamentum flavum together narrow the canal, which is why the condition so often presents as spinal stenosis (narrowing of the canal the nerves run through).

In the isthmic type the pars defect separates the body of the vertebra from its posterior arch. The body slides forward while the arch stays behind, and the foramen at that level, most often for the L5 nerve, becomes narrower.

Symptoms

The classic picture is back pain with a positional pattern in the legs: aching, heaviness or pins and needles in the buttocks and thighs that build with standing and walking and fade within minutes of sitting or bending forward (neurogenic claudication). Some people have a single-root pattern instead, pain running down one leg to the foot, because the slip narrows a foramen. Young people with an isthmic slip may have back pain and tight hamstrings and little else.

A disc herniation usually hurts most on sitting and bending forward; a slip tends to hurt on standing straight or arching backward.

Diagnosis

History and examination come first: where the pain goes, what brings it on, and whether any nerve has lost strength, sensation or a reflex.

The NASS (North American Spine Society) guideline names the lateral X-ray as the most appropriate non-invasive test for detecting the slip and advises taking it standing whenever possible, because a slip seen lying down on MRI can be smaller than it is under load. Bending-forward and bending-backward views show whether the vertebra moves. MRI is the test for the stenosis that accompanies the slip. CT (computed tomography) shows the pars defect and is the alternative when MRI is not possible.

For an opinion, send the standing lateral X-ray, the sagittal (side-on) and axial (cross-section) MRI slices at the affected level, and the written report.

Treatment without surgery

The NASS guideline found insufficient evidence for or against medication, physiotherapy, manipulation, bracing, traction or injections in degenerative spondylolisthesis, and advises treating the leg symptoms the way stenosis is treated. In practice that means staying active, an exercise programme, weight control and short courses of anti-inflammatory medication when needed; NICE (the UK National Institute for Health and Care Excellence) supports exercise and advises against belts, corsets and traction. NICE supports an epidural injection of local anaesthetic and steroid for acute, severe sciatica, but not for claudication caused by central canal stenosis.

The isthmic type in young people is usually managed with rest from the provoking sport and rehabilitation; StatPearls describes non-operative care as the first-line treatment, with surgery reserved for those who do not settle or who develop a neurological deficit or a progressing slip.

When surgery is considered

Surgery is discussed when leg pain or claudication persists after a fair trial of conservative care, when a nerve is losing strength, or, rarely and urgently, when bladder and bowel control are affected (cauda equina syndrome). Back pain on its own is a weaker reason: NICE advises against fusion for low back pain outside a trial.

The AANS/CNS (American Association of Neurological Surgeons and Congress of Neurological Surgeons) fusion guideline notes that the trials comparing surgery with continued non-surgical care for stenosis with spondylolisthesis, including SPORT (the Spine Patient Outcomes Research Trial), consistently showed better outcomes with surgery. None of the trials listed here compared early with delayed surgery, so a period of conservative care is reasonable as long as the nerves are not deteriorating.

Surgical options

Decompression alone removes the bone and ligament pressing on the nerves and leaves the slip as it is. The NASS guideline rates it as an option for stenosis with a low-grade slip, and states that for a single-level slip under 20% without foraminal narrowing, decompression alone with the midline structures preserved gives outcomes equivalent to decompression with fusion.

Decompression with fusion adds screws, usually with an interbody cage, so the segment can no longer move. The NASS guideline suggests it improves outcomes compared with decompression alone in the general case, and notes that instrumentation raises the fusion rate without changing the clinical result. In general practice surgeons choose fusion more readily when the slip moves on bending films or when there is a pars defect; for slips at two or more levels the NASS guideline found insufficient evidence to recommend for or against fusion, and the decision is made case by case.

The two trials that tested the question disagree. SLIP (66 patients, grade I) found a modest advantage for fusion in physical quality of life at two to four years and reoperation in 14% of the fusion group against 34% after decompression alone, at the cost of longer stays and more blood loss. The Swedish Spinal Stenosis Study (247 patients, 135 with a slip) found no difference in disability at two or five years, a stay of 4.1 days without fusion against 7.4 with it, and further surgery in 21% and 22% over 6.5 years. A carefully selected stable slip does well with decompression alone; fusion is for the slips that do not meet those conditions.

Endoscopic fusion is one of the fusion options. A 2026 meta-analysis of 18 studies with 1,200 spondylolisthesis patients found no difference in pain, disability, fusion rate or complications between endoscopic and conventional surgery, with about 130 mL less blood loss and a stay shorter by nearly three days in the endoscopic group; the certainty is very low because most studies were retrospective.

How we treat it at spine.uz

Send the MRI, the standing X-ray if you have one, and the report; a doctor from the team replies by voice within 48 hours, free of charge.

When decompression alone is the right operation, it is done endoscopically through a 7 mm incision, with no screws or implants. Most endoscopic decompressions are done without general anaesthesia, under local anaesthesia with sedation; the anaesthetist and surgeon decide per patient. When the segment needs fusion, the team performs it fully endoscopically, with an interbody cage and percutaneous screws. Most patients walk on the day of surgery and go home within 24 hours. Every patient receives a written conclusion from the team. Across 27,600+ endoscopic and spine operations, the team's complication rate is well below 1%.

Recovery and outcomes

After decompression alone, walking starts the same day and the stay is short. After fusion the bone needs months to join, so heavy lifting and twisting are limited for longer. In our experience leg symptoms improve faster than back pain.

Both trials show that some patients need a second operation over the years: 14% to 34% at four years in SLIP, about one in five over 6.5 years in the Swedish study, whichever operation was done first. The AANS/CNS guideline describes the first reason: after decompression alone the slip can progress and symptoms return. The second, in our experience, is wear of the level next to a fusion.

Living with it and prevention

Keep walking and keep the trunk muscles working; exercise is the measure NICE supports for the back pain that goes with this condition. Keep weight down and do not smoke. A repeat standing X-ray, when symptoms change, shows whether a slip has moved. Corsets and traction do not help, and forcing the back into backward bends provokes the pain.