Spondylolisthesis: When Is Surgery Necessary?

Spondylolisthesis is the forward slippage of one vertebra over the vertebra below it. It can be of degenerative origin (wear of the posterior facet joints, common after age 50) or isthmic (stress fracture of the vertebral isthmus, often discovered in young adults). The slip is classified into 4 grades according to its severity. The majority of grade 1 and 2 spondylolisthesis cases are treated without surgery.

Spondylolisthesis is a common pathology of the lumbar spine, characterized by the forward slippage of one vertebra over the one below it. This condition raises many questions among patients: is it serious? Is surgery always necessary? When does surgery become essential? As a neurosurgeon specializing in spine surgery, I regularly see patients concerned after discovering spondylolisthesis on their X-rays. This article aims to clarify this condition and explain the situations in which surgery is truly indicated.

What Is Spondylolisthesis?

Spondylolisthesis refers to the anterior (forward) slippage of a vertebra relative to the vertebra below it. This pathology primarily affects the lumbar spine, particularly the L4-L5 (fourth and fifth lumbar vertebrae) and L5-S1 (fifth lumbar vertebra and first sacral vertebra) levels.

There are several types of spondylolisthesis, classified according to their origin:

Degenerative Spondylolisthesis

This is the most common form, generally occurring after age 50. It results from the progressive wear of the posterior facet joints that normally stabilize the spine. This arthritic degeneration leads to vertebral instability and allows the progressive slippage of the vertebra. Women are more frequently affected than men, with a ratio of approximately 3 to 1. The L4-L5 level is most frequently involved in this degenerative form.

Isthmic Spondylolisthesis

This form is due to a stress fracture of the vertebral isthmus, the posterior part of the vertebra that connects the superior and inferior facets. This isthmic lysis (or spondylolysis) generally occurs during childhood or adolescence, often in young athletes practicing activities that heavily stress the spine in hyperextension (gymnastics, dance, diving, weightlifting). However, isthmic spondylolisthesis is often asymptomatic for years and discovered incidentally in adulthood. The L5-S1 level is most frequently affected in this form.

Dysplastic Spondylolisthesis

Much rarer, this congenital form results from a malformation of the posterior facets from birth. It can lead to severe slips (grades 3 and 4) often requiring early surgical management.

Meyerding Classification: Understanding the Grades

The Meyerding classification allows quantification of the importance of vertebral slip as a percentage. This classification is essential for assessing the severity of spondylolisthesis and guiding therapeutic decisions.

It is important to note that the grade of slip does not always correspond to the intensity of symptoms. Some patients with grade 2 may be very symptomatic, while others with grade 3 may have little pain. This is why the surgical decision is not based solely on radiological grade, but on a comprehensive evaluation including clinical symptoms, functional impact, and evolution over time.

Symptoms According to Spondylolisthesis Grade

Grade 1 Spondylolisthesis

Grade 1 spondylolisthesis is frequently asymptomatic and discovered incidentally during imaging examinations performed for other reasons. When symptoms are present, they manifest primarily as mechanical low back pain, meaning lumbar pain aggravated by physical activity, prolonged standing, or certain movements (flexion, extension), and relieved by rest. These pains may radiate to the buttocks but generally remain localized to the lumbar spine.

Grade 2 Spondylolisthesis

At this stage, symptoms are more frequent and more pronounced. Chronic low back pain becomes more disabling and more resistant to simple analgesic treatments. Radiculopathy may appear, corresponding to irritation or compression of lumbo-sacral nerve roots, manifesting as sciatica (pain descending into the leg) or cruralgia (pain in the anterior thigh). Neurogenic claudication may also occur, characterized by pain and weakness in the lower limbs triggered by walking and relieved by sitting or flexed position.

Grade 3 and 4 Spondylolisthesis

These severe grades are generally accompanied by more pronounced neurological symptoms. Compression of nerve roots can lead to motor deficits (muscle weakness), sensory disorders (numbness, tingling), or chronic neuropathic pain. Postural deformity becomes visible, with compensatory lumbar hyperlordosis (excessive arch), apparent trunk shortening, and sometimes flexed gait. The functional impact is significant, with limitation of daily activities and substantial alteration of quality of life.

Conservative Treatment: The First-Line Therapy

For the vast majority of grade 1 and 2 spondylolisthesis cases, conservative treatment constitutes the first-line option. This non-surgical approach allows significant symptom improvement in 70 to 80% of patients.

Physiotherapy and Muscle Strengthening

Functional rehabilitation is the cornerstone of conservative treatment. It aims to strengthen the paraspinal and abdominal musculature (core muscles) to stabilize the unstable vertebral segment. Core strengthening exercises, proprioception, and lumbar stabilization are particularly effective. A personalized program of several months is generally necessary to obtain lasting results.

Lifestyle Modifications

Certain adaptations can significantly reduce symptoms: avoiding activities heavily stressing the spine in hyperextension, favoring low-impact sports (swimming, cycling, aquagym), maintaining a healthy weight to reduce stress on the lumbar spine, and adopting good ergonomics at work and in daily activities.

Medical Treatment

Analgesics (paracetamol, non-steroidal anti-inflammatory drugs) can be used during acute painful phases. Level 2 or 3 analgesics are reserved for more intense pain and for limited periods.

Injections

Epidural corticosteroid injections can provide temporary relief in cases of associated radiculopathy. They are performed under radiological control (CT or fluoroscopy) and can be repeated if necessary, with a maximum of three injections per year.

Lumbar Brace

Wearing a support brace can be offered temporarily during acute painful phases, but should not be systematic as prolonged wear can lead to muscle atrophy.

The duration of conservative treatment before considering surgery is generally 3 to 6 months. This period allows evaluation of response to different therapies and identification of patients who will truly benefit from surgical intervention.

When Is Surgery Necessary?

Surgery for spondylolisthesis is not systematic and should be considered after failure of well-conducted conservative treatment. Several situations may lead to a surgical indication:

Chronic Disabling Pain

When chronic low back pain persists despite 3 to 6 months of well-conducted medical and rehabilitation treatment, with significant impact on quality of life and daily activities, surgery may be considered. The objective is then to stabilize the unstable vertebral segment responsible for mechanical pain.

Progressive Neurological Deficit

The occurrence or worsening of a motor (muscle weakness) or sensory (sensory disturbances) deficit constitutes a more urgent surgical indication. Nerve compression must be relieved quickly to avoid permanent sequelae.

Refractory Radiculopathy

Sciatica or cruralgia resistant to well-conducted medical treatment (analgesics, injections) for several months may require surgical decompression of nerve roots, with or without fusion depending on the degree of instability.

Severe Neurogenic Claudication

When walking distance becomes very limited (less than 100 meters) and symptoms significantly affect autonomy and daily activities, surgery may be offered.

High-Grade Spondylolisthesis

Symptomatic grade 3 and 4 spondylolisthesis often require surgical management, particularly in young patients. The objective is to prevent progression of the slip and correct postural deformity.

Progression of the Slip

A slip that progresses significantly on follow-up X-rays, particularly in a young patient with isthmic spondylolisthesis, may justify preventive surgical stabilization, even in the absence of major symptoms.

Surgical Techniques: Lumbar Fusion

The reference surgery for symptomatic spondylolisthesis is lumbar fusion, which involves fusing vertebrae together to eliminate segmental instability. Several techniques can be used depending on the case:

TLIF Fusion (Transforaminal Lumbar Interbody Fusion)

This is the technique I use most frequently. It involves approaching the intervertebral disc through a unilateral posterior approach, allowing decompression of nerve roots, removal of the degenerated disc, and placement of an intervertebral cage filled with bone graft. Fixation is ensured by pedicle screws and rods. This technique offers a good balance between fusion effectiveness and respect for anatomical structures.

PLIF Fusion (Posterior Lumbar Interbody Fusion)

This technique uses a bilateral posterior approach to insert two intervertebral cages. It offers excellent stability but requires greater retraction of nerve roots.

Slip Reduction

In certain cases of isthmic spondylolisthesis in young patients, partial or complete reduction of the slip can be performed. This maneuver remains delicate and is not systematic, as it carries increased neurological risk. The main objective of surgery remains above all nerve decompression and stabilization, rather than perfect anatomical reduction.

Isthmic Repair

In certain young patients with low-grade isthmic spondylolisthesis and good disc quality, direct repair of the vertebral isthmus (isthmic osteosynthesis) can be offered as an alternative to fusion. This technique preserves vertebral segment mobility but is only possible in very select indications.

Procedure Details

The operation generally lasts between 2 and 4 hours depending on case complexity. It is performed under general anesthesia, with intraoperative neurophysiological monitoring (recording of nerve electrical activity) to secure the surgical procedure. The average hospital stay is 3 to 5 days.

Results and Prognosis of Surgery

The results of fusion surgery for spondylolisthesis are generally very satisfactory when the surgical indication is well-established.

Success Rate

Scientific studies report a satisfaction rate of 85 to 90% after fusion for symptomatic spondylolisthesis. Improvement primarily concerns radicular pain (sciatica), which disappears or markedly improves in more than 90% of patients. Mechanical low back pain improves in 70 to 80% of patients, with however more variable results than for radicular pain.

Vertebral Fusion

The bone fusion rate (arthrodesis consolidation) exceeds 90% with modern techniques using intervertebral cages and pedicle screw fixation. This fusion is generally achieved within 6 to 12 months postoperatively.

Postoperative Recovery

Recovery progresses gradually over several months. Walking resumes immediately the day after surgery. Discharge home is possible after 3 to 5 days of hospitalization. Return to sedentary work is possible after 6 to 8 weeks, while physical work requires a break of 3 to 6 months. Sports activities can be resumed progressively after 3 to 6 months, initially favoring low-impact sports (swimming, cycling).

Possible Complications

Like any surgery, lumbar fusion carries risks that should be known: surgical site infection (2-3%), nerve injury (1-2%), thromboembolic complications (phlebitis, pulmonary embolism), dural tear sometimes requiring repair, pseudarthrosis (absence of bone fusion) rarely requiring surgical revision. Adherence to enhanced recovery after surgery (ERAS) protocols helps minimize these risks.

Frequently Asked Questions About Spondylolisthesis

Sources: HAS (Haute Autorité de Santé), SFCR (French Spine Surgery Society), AOSpine — Classification and treatment of spondylolisthesis, NASS (North American Spine Society) — Evidence-based clinical guidelines.