Orthopaedic Surgery - Lumbar Disc Herniation

Basics

Lumbar disc herniation is a common cause of acute and chronic low back pain and may also produce radicular symptoms in the lower extremity.

Low back pain affects a large proportion of the population at some point during life.

When disc material compresses or irritates a lumbar nerve root, patients may develop:

Leg pain, numbness, paresthesia, weakness, or reflex changes, commonly referred to as sciatica.

Synonyms

Lumbar disc herniation may also be called:

Herniated nucleus pulposus, slipped disc, ruptured disc, or lumbar radiculopathy with sciatica.

Classification by Location

Disc herniations may be classified according to their location within the spinal canal.

Posterolateral Herniation

Posterolateral herniations are the most common.

The posterior annulus is relatively vulnerable, and disc material usually compresses the traversing ipsilateral nerve root.

For example:

An L4–L5 posterolateral herniation usually affects the L5 nerve root.

Far-Lateral Herniation

Far-lateral or foraminal herniations lie outside or within the neural foramen.

They usually compress the exiting nerve root at that level.

For example:

A far-lateral L4–L5 disc herniation may compress the L4 nerve root.

Central Herniation

Central disc herniations may produce:

Predominantly axial back pain or bilateral neurologic symptoms.

A large central herniation can compress multiple nerve roots and cause cauda equina syndrome.

Classification by Morphology

Disc Protrusion

A protrusion is a localized displacement of disc material in which the herniated portion remains broadly connected to the parent disc.

The annulus may be stretched or partially disrupted.

Disc Extrusion

In an extrusion, disc material extends through a defect in the annulus and has a narrower connection with the parent disc.

Sequestered Disc

A sequestered disc occurs when a fragment becomes completely separated from the parent disc and lies freely within the spinal canal.

Epidemiology

Lumbar disc herniation most commonly affects adults between approximately 30 and 50 years of age.

It is unusual before the age of 20.

Men are affected somewhat more frequently than women in many series.

Common Levels

The lumbar spine is the most frequently affected region of the spine.

The most common levels are:

L4–L5, followed by L5–S1.

Risk Factors

Important risk factors include:

Tobacco smoking, obesity, repetitive heavy lifting, occupational spinal loading, and repeated bending or twisting.

Genetics

A genetic contribution to disc degeneration and herniation has been proposed.

However, disc herniation is multifactorial, and the relative importance of genetic susceptibility varies among individuals.

Anatomy and Pathophysiology

The intervertebral disc consists of:

An inner nucleus pulposus and an outer annulus fibrosus.

Nucleus Pulposus

The nucleus pulposus is rich in water and proteoglycans and helps distribute compressive forces.

Annulus Fibrosus

The annulus fibrosus consists of concentric collagenous layers that contain the nucleus.

Blood vessels and sensory nerves are largely limited to the outer peripheral annulus.

Disc Nutrition

The adult intervertebral disc has very limited direct blood supply.

Nutrients reach the disc primarily by diffusion through the cartilaginous vertebral endplates.

Age-Related Degeneration

Disc degeneration can begin relatively early in adulthood.

With increasing age, the nucleus gradually:

Loses water, proteoglycan content, height, and viscoelastic properties.

The disc becomes less capable of distributing load, and annular fissures may develop.

Etiology

Lumbar disc herniation usually results from a combination of:

Age-related degeneration and mechanical stress.

Trauma

A specific traumatic event may precipitate symptoms when a degenerating disc is already vulnerable.

Repetitive Loading

Repeated:

Heavy lifting, bending, twisting, and occupational spinal loading

may accelerate annular degeneration or provoke herniation.

Diagnosis

Signs and Symptoms

Pain is the most common presenting symptom.

Patients may have:

Low back pain alone, leg pain alone, or a combination of both.

Radicular Pain

Radicular pain typically follows the distribution of an affected nerve root.

It may be described as:

Sharp, burning, electric, or shooting pain radiating from the back or buttock into the leg.

Effect of Lumbar Motion

Symptoms often worsen with:

Lumbar flexion, prolonged sitting, coughing, sneezing, or straining.

Extension may relieve symptoms in some patients, although response varies according to the location and mechanics of the herniation.

Sensory Symptoms

Numbness or paresthesia may develop in the dermatome of the compressed nerve root.

Motor Symptoms

Weakness may occur in muscles supplied by the affected root.

A careful motor examination is therefore essential.

L3–L4 Disc Herniation

An L3–L4 disc herniation commonly compresses the L4 nerve root.

Findings may include:

Weakness of knee extension or ankle dorsiflexion, diminished patellar reflex, and sensory disturbance over the medial leg.

L4–L5 Disc Herniation

An L4–L5 herniation usually affects the L5 nerve root.

Typical findings include:

Weakness of great-toe extension, possible ankle dorsiflexion weakness, and altered sensation over the lateral leg and dorsum of the foot, including the first dorsal web space.

Extensor hallucis longus weakness is particularly useful clinically.

L5–S1 Disc Herniation

An L5–S1 herniation usually compresses the S1 nerve root.

Typical findings include:

Weak plantarflexion, reduced Achilles reflex, and diminished sensation along the lateral foot.

The patient may have difficulty performing repeated single-leg heel raises.

Cauda Equina Syndrome

A large central disc herniation may compress multiple lumbosacral nerve roots and produce cauda equina syndrome.

Warning signs include:

Saddle anesthesia

Urinary retention or overflow incontinence

Loss of bowel control

Bilateral leg weakness or numbness

Progressive neurologic deficits

This is a surgical emergency requiring urgent imaging and decompression.

History

A thorough history should establish:

Time of symptom onset, progression, pain distribution, occupational demands, smoking history, trauma, previous episodes, and neurologic symptoms.

Bowel and Bladder Function

Ask specifically about:

Urinary retention, difficulty initiating urination, incontinence, bowel dysfunction, and saddle numbness.

These symptoms may indicate cauda equina compression.

Constitutional Symptoms

Ask about:

Fever, night sweats, unexplained weight loss, cancer history, immunosuppression, or recent infection.

These findings may suggest an alternative diagnosis such as infection or malignancy.

Physical Examination

A detailed neurologic examination is the most important component.

Sensory Examination

Assess sensation throughout the major lower-extremity dermatomes.

Motor Examination

Document strength of the major muscle groups, including:

Hip flexion

Knee extension

Ankle dorsiflexion

Great-toe extension

Ankle plantarflexion

Reflexes

Evaluate:

Patellar and Achilles reflexes, comparing both sides.

Gait

Observe for:

Antalgic gait, foot drop, inability to heel walk, or inability to toe walk.

These findings may reflect motor root compression.

Straight-Leg Raise Test

The straight-leg raise test is used to assess lower lumbar nerve-root irritation.

Technique

With the patient supine, gradually elevate the straight leg while keeping the knee extended.

Reproduction of radicular pain radiating below the knee suggests nerve-root tension.

Ankle Dorsiflexion

Dorsiflexing the ankle during the test may further increase nerve tension and reproduce symptoms.

Crossed Straight-Leg Raise

In the crossed straight-leg raise, elevation of the asymptomatic leg reproduces radicular pain in the symptomatic leg.

Although less sensitive, a positive test is relatively specific for a substantial lumbar disc herniation.

Sacral Examination

When cauda equina syndrome is suspected, evaluate:

Perianal sensation, anal sphincter tone, and sacral neurologic function.

Urgent MRI should not be delayed in a patient with convincing clinical signs.

Imaging

Plain Radiographs

Routine radiographs are usually unnecessary during the first several weeks of uncomplicated acute radicular symptoms.

They may be considered when:

Symptoms persist beyond approximately 6 weeks, significant trauma has occurred, deformity is suspected, or another structural diagnosis is being considered.

Radiographs do not directly visualize disc herniation.

MRI

MRI is the preferred imaging study for suspected lumbar disc herniation when advanced imaging is indicated.

It demonstrates:

Disc morphology, nerve-root compression, spinal stenosis, and other soft-tissue abnormalities.

Indications

MRI is particularly appropriate when:

Surgery is being considered

Symptoms persist despite appropriate nonoperative treatment

A significant or progressive neurologic deficit is present

Cauda equina syndrome is suspected

Infection or tumor is a concern

Incidental MRI Findings

Disc bulges and herniations are common in asymptomatic individuals.

Therefore, MRI abnormalities must be correlated with:

The patient’s symptoms, neurologic examination, and affected nerve-root distribution.

CT Myelography

CT myelography may be useful when MRI cannot be performed or is nondiagnostic.

However, it is more invasive and involves:

Ionizing radiation and intrathecal contrast.

MRI has largely replaced it for routine evaluation.

Discography

Provocative discography has occasionally been used to investigate suspected discogenic back pain.

Its clinical role remains controversial and it is not routinely used for uncomplicated lumbar disc herniation.

Pathological Findings

Herniated nucleus pulposus material extends through defects in the annulus fibrosus.

Symptoms result from a combination of:

Mechanical nerve-root compression and local inflammatory irritation.

Inflammatory Component

Chemical mediators released from degenerating disc tissue may produce:

Nerve-root inflammation and radicular pain, even when mechanical compression is modest.

Differential Diagnosis

Important alternatives include:

Lumbar spinal stenosis

Peripheral sciatic nerve entrapment

Spondylolysis or spondylolisthesis

Mechanical muscular back pain

Degenerative disc disease

Hip pathology

Tumor

Spinal infection

Treatment

Initial Stabilization

Short-term relative rest may be appropriate during the most painful acute period.

Prolonged bed rest should be avoided.

If bed rest is needed, it should generally be limited to approximately 1–2 days, followed by gradual resumption of activity as tolerated.

General Principles

Most lumbar disc herniations are initially treated nonoperatively.

A substantial proportion improve spontaneously as:

Inflammation settles and the herniated fragment shrinks or resorbs.

Early Activity

Early return to tolerable daily activity is encouraged.

Patients should avoid:

Prolonged inactivity and movements that clearly exacerbate radicular symptoms.

Analgesia

Common first-line options include:

Acetaminophen and NSAIDs, when not contraindicated.

Muscle Relaxants

Muscle relaxants may have a limited short-term role when substantial paraspinal spasm accompanies the acute episode.

They do not treat the underlying disc herniation.

Opioids

Opioid medication should generally be reserved for:

Severe acute pain that cannot be controlled with safer alternatives, and should be used for the shortest practical duration.

Epidural Steroid Injection

An epidural corticosteroid injection may reduce radicular pain in selected patients.

Its principal role is to:

Provide temporary symptom relief and facilitate activity and rehabilitation while natural recovery occurs.

It does not remove the disc herniation itself.

Manipulation and Traction

Manual therapy or traction may provide short-term symptomatic relief in selected patients.

They should be used cautiously and are not substitutes for appropriate neurologic evaluation.

Manipulation should be avoided when:

Progressive neurologic deficit, fracture, infection, malignancy, or cauda equina syndrome is suspected.

Physical Therapy

Physical therapy is useful for many patients once acute pain permits participation.

Goals

Therapy focuses on:

Restoring motion, maintaining activity, improving trunk control, and preventing recurrence.

Strengthening

Programs commonly emphasize:

Abdominal muscles, spinal extensors, hip musculature, and overall core stabilization.

Lower-Extremity Flexibility

Stretching and strengthening of the lower extremities may help improve:

Movement mechanics and tolerance for daily activity.

Medication

First-Line Therapy

Common initial medications include:

Acetaminophen and NSAIDs.

A short course of opioid medication may occasionally be used for severe acute symptoms.

Second-Line Options

Selected patients may receive:

Short courses of oral corticosteroids

Muscle relaxants

Neuropathic pain medications in selected situations

Epidural corticosteroid injections

The benefit of drugs such as gabapentin for true sciatica is variable and should be weighed against adverse effects.

Surgery

The decision to proceed with surgery should be individualized and based on:

Symptoms, neurologic findings, duration, imaging correlation, functional impairment, and patient preferences.

Indications for Elective Surgery

Surgery may be considered when:

Persistent radicular pain remains disabling despite appropriate nonoperative care

Imaging demonstrates a corresponding compressive lesion

Neurologic weakness persists or progresses

The patient’s quality of life remains substantially impaired

Emergency Surgical Indications

Urgent surgery is indicated for:

Cauda equina syndrome or severe progressive neurologic deficit.

Surgical Benefit

Disc surgery generally provides more reliable relief of:

Leg-dominant radicular pain

than of nonspecific axial low back pain.

Surgical Options

Open Discectomy

The herniated disc fragment is removed through an open posterior approach.

Laminotomy

A small portion of lamina may be removed to provide access to the compressed nerve root and disc.

Laminectomy

More extensive removal of the lamina may be necessary when significant spinal stenosis accompanies the herniation.

Microdiscectomy

Microdiscectomy uses magnification and a smaller surgical exposure to remove the offending disc fragment.

It is a common surgical technique for symptomatic lumbar disc herniation.

Endoscopic Discectomy

Selected disc herniations may be treated through an endoscopic approach using very small incisions.

Patient selection and surgeon experience are important.

Obsolete or Rarely Used Techniques

Chemonucleolysis and similar invasive nonsurgical disc-decompression methods have largely fallen out of favor because of:

Variable effectiveness and potential complications.

Postoperative Care

Patients should be monitored for:

New neurologic deficits, wound infection, recurrent radicular pain, hematoma, and cerebrospinal fluid leak.

Activity After Surgery

Older protocols routinely imposed strict activity restrictions for approximately 6 weeks.

Modern postoperative recommendations vary according to:

Procedure, surgeon preference, symptoms, and patient occupation.

Heavy lifting, repetitive bending, and twisting are generally limited during early healing.

Follow-Up

Patients treated nonoperatively should be reassessed if symptoms persist or worsen.

Historical follow-up schedules used visits approximately every 6 weeks for 12–18 weeks, followed by review as needed.

Prognosis

The overall prognosis is excellent for most patients.

Many improve substantially with nonoperative treatment.

Even large disc herniations may decrease in size over time.

Persistent Symptoms

Some patients continue to experience:

Intermittent low back pain, residual numbness, weakness, or recurrent radiculopathy.

Recurrent Herniation

Disc herniation may recur at:

The same spinal level or a different level.

Recurrent symptoms should be reassessed clinically and with imaging when appropriate.

Postoperative Back Pain

Some patients develop persistent or recurrent low back pain after discectomy even when leg symptoms improve.

Potential causes include:

Progressive disc degeneration, facet disease, recurrent herniation, scar formation, or another pain generator.

Complications

Potential complications include:

Persistent pain

Degenerative disc disease

Recurrent disc herniation

Neurologic deficit

Wound infection

Disc-space infection

Dural tear or cerebrospinal fluid leak

Scar-related nerve irritation

Rarely, adhesive arachnoiditis may occur.

Patient Monitoring

Clinical progress is primarily monitored through:

Pain severity, neurologic function, walking ability, sensory changes, strength, reflexes, and return of daily function.

Serial imaging is not routinely necessary when symptoms are improving.

New or worsening:

Weakness, saddle anesthesia, urinary retention, bowel dysfunction, fever, or severe unremitting pain

should prompt urgent reassessment.