SUMMARY

• Lumbar Disc Herniation is a very common cause of low back pain and unilateral leg pain, known as radiculopathy. In rare cases a large disc herniation can lead to Cauda Equina Syndrome which requires emergent diagnosis and treatment. 

• Diagnosis is made clinically and confirmed with an MRI studies of the lumbar spine.

• Treatment for radicular leg pain is initially nonoperative with oral medications and physical therapy.  Surgical microdiscectomy is only indicated for severe pain and/or motor deficit that have failed to respond to nonoperative management. Treatment for Cauda Equina Syndrome in contrast is emergent microdiscectomy within 48 hours. 

EPIDEMIOLOGY

• Incidence

  • peak incidence is 4th and 5th decades

  • lifetime prevalence of 10%

  • only ~5% become symptomatic

• Demographics

  • 3:1 male:female ratio

• Location

  • L5/S1 most common level

  • 95% involve L4/5 or L5/S1 levels

ETIOLOGY

• Pathoanatomy

  • recurrent torsional strain leads to tears of the outer annulus which leads to herniation of nucleus pulposis

  • lateral edge of posterior longitudinal ligament weakest region

    •  common site for posterolateral/paracentral disc herniations

  • sinuvertebral nerves provide pain innervation to the posterior annulus

    • mediate vertebrogenic back pain that precedes or accompanies disc herniation 

• Pathophysiology

  • cellular senescence of fibrochondrocytes leads to loss of proteoglycan production leading to disc height loss 

    • loss of height causes increased strain on the annulus fibrosus

    • increased strain leads to fissures of the annulus fibrils 

  • annular tears compromise hoop stresses that act against the deforming forces of the nucleus pulposus 

  • nucleus pulposus herniates through tear

    • younger, well-hydrated discs more likely to herniate

      •  pediatric patients may have Salter-Harris II fracture of the ring apophysis 

    • older, desiccated discs less likely to herniate

  • sciatica symptoms result from combined mechanical compression and associated inflammation

    • not all patients with mechanical compression develop symptoms 

      • TNF-α, MMP, NO, PE2, and IL-6 are implicated in nerve irritation leading to radiculopathy

        • weak evidence to support DMARDs for treatment

ANATOMY

• Complete intervertebral disc anatomy and biomechanics 

• Disc composition

  • annulus fibrosis

    • composed of type I collagen, water, and proteoglycans

      • 15-25 sheets of lamellae

    • characterized by extensibility and tensile strength

      • high collagen / low proteoglycan ratio (low % dry weight of proteoglycans)

  • nucleus pulposus

    • composed of type II collagen, water, and proteoglycans

    • characterized by compressibility

      • low collagen / high proteoglycan ratio (high % dry weight of proteoglycans)

        • proteoglycans interact with water and resist compression

      • a hydrated gel due to high polysaccharide content and high water content (88%)

        • disc height dependent on the degree of hydration 

    • avascular structure

      • nutrients supplied by diffusion from the end plates

• Nerve root anatomy

  • key difference between cervical and lumbar spine is 

    • pedicle/nerve root mismatch

      • cervical spine C6 nerve root travels under C5 pedicle (mismatch)

      • lumbar spine L5 nerve root travels under L5 pedicle (match)

      • extra C8 nerve root (no C8 pedicle) allows transition

    • horizontal (cervical) vs. vertical (lumbar) anatomy of nerve root

      • because of vertical anatomy of lumbar nerve root a paracentral and foraminal disc will affect different nerve roots

      • because of horizontal anatomy of cervical nerve root a central and foraminal disc will affect the same nerve root

CLASSIFICATION

• Location Classification

  • central prolapse

    • often associated with back pain only

    • may present with cauda equina syndrome which is a surgical emergency

  • posterolateral (paracentral) 

    • most common (90-95%)

    • PLL is weakest here

    • affects the traversing/descending/lower nerve root 

       

      • at L4/5 affects L5 nerve root 

  • foraminal (far lateral, extraforaminal) 

      

    • less common (5-10%)

    • affects exiting/upper nerve root 

       

      • at L4/5 affects L4 nerve root 

    • herniated disc material directly compresses dorsal root ganglion

      • can manifest with more severe pain than traditional posterolateral disc herniation 

         

  • axillary

    • can affect both exiting and descending nerve roots

• Morphology classification

  • protrusion

    • eccentric bulging with an intact annulus

  • extrusion

    • disc material herniates through annulus but remains continuous with disc space

  • sequestered fragment (free)

    • disc material herniates through annulus and is no longer continuous with disc space

    • prone to proximal or distal migration

• Containment classification

  • contained 

    • disc material is contained beneath the posterior longitudinal ligament

  • uncontained

    • disc material passes dorsal to the posterior longitudinal ligament

• Timing classification

  • acute

    • herniations present < 3-6 months

      • important consideration given surgical outcomes are associated with chronicity 

  • chronic

    • herniations present >6 months

PRESENTATION

• History

  • sudden onset of pain after lifting a heavy object

  • occupational exposure

    • prolonged sitting with lateral bending and rotation in the presence of vibrational energy

  • symptomatic improvement lying supine with knees and hips flexed

    • especially with lower lumbar disc herniations

• Symptoms 

  • can present with symptoms of

    • axial back pain (low back pain)

      • this may be discogenic or mechanical in nature

      • can precede herniation 

    • radicular pain (buttock and leg pain)

      • often worse with sitting, improves with standing

      • symptoms worsened by coughing, valsalva, sneezing

      • pain not worsened with ambulation 

    • cauda equina syndrome (present in 1-10%)

      • bilateral leg pain

      • LE weakness

      • saddle anesthesia

      • bowel/bladder symptoms

• Physical exam 

   

  • inspection

    • limited lumbar range of motion

      • often the pain is the limiting factor

    • patient leaning away from side of radiculopathy

      • effort to increase the size of the neuroforamen

  • palpation

    • spasms of the paraspinal musculature

      • nonspecific

    • associated tenderness in the paraspinal musculature

      •  nonspecific 

  • motor exam & reflexes

    • see lower extremity neuro exam 

      • L3 radiculopathy

        • hip adduction weakness 

           

        • knee extension weakness

        • dermatomal pain in the anteromedial thigh

      • L4 radiculopathy

        • ankle dorsiflexion weakness (L4 > L5)

        • decreased patellar reflex

        • dermatomal pain in the lateral thigh, crossing the knee, to medial foot

      • L5 radiculopathy

        • EHL weakness (L5)

          • manual testing

        • ankle dorsiflexion weakness (L4 > L5 contribution)

          • test by having patient walk on heels

        • ankle inversion weakness 

           

        • hip abduction weakness (L5) 

           

          • have patient lie on side on exam table and abduct leg against resistance

        • dermatomal pain in anterolateral leg and dorsum of foot 

      • S1 radiculopathy

        • ankle plantar flexion weakness (S1)

          • have patient do 10 single leg toes stands

        • decreased Achilles tendon reflex

        • dermatomal pain in posterior calf and lateral foot

  • provocative tests

    • straight leg raise (Lasegue's sign)

      • a tension sign for L4, L5 and S1 nerve root

      • technique

        • can be done sitting or supine

        • reproduces pain and paresthesia in leg at 30-70 degrees hip flexion

      • sensitivity/specificity

        • most important and predictive physical finding for identifying who is a good candidate for surgery

    • contralateral SLR

      • crossed straight leg raise is less sensitive but more specific

    • femoral nerve stretch test (Wasserman sign)

      • tension sign for L2 and L3

      • performed in prone position

        • knee flexed and hip exteneded

        • reproduction of pain in anterior thigh is considered positive

    • Braggard's sign

      • perform SLR to the point of exacerbation

      • lower leg just to the point where pain recedes

        • ankle dorsiflexion causes exacerbated pain

    • Bowstring sign

      • SLR aggravated by compression on popliteal fossa

    • Kernig test

      • pain reproduced with neck flexion, hip flexion, and leg extension

    • Naffziger test

      • pain reproduced by coughing, which is instigated by lying patient supine and applying pressure on the neck veins

    • Milgram test

      • pain reproduced with straight leg elevation for 30 seconds in the supine position

  • gait analysis

    • Trendelenburg gait

      • due to gluteus medius weakness which is innervated by L5

IMAGING

• Radiographs

  • recommended views

    • AP and lateral radiographs

      • helpful for surgical localization 

        • identify anomalous vertebrae (sacralized L5 or lumbarized S1)

  • optional views

    • flexion-extension

      • identifies instability

        • if present can changes surgical plan to involve fusion

  • findings

    • most often normal 

    • abnormal findings

      • loss of lordosis (spasm) 

      • loss of disc height 

        • especially at the involved level

      • lumbar spondylosis (degenerative changes)

        • facet hypertrophy

        • disc space collapse

        • peridiscal osteophytes

      • sciatic scoliosis

        • convex or concave list to the ipsilateral side of herniation

  • sensitivity 

    • poor sensitivity for identifying disc herniation

    • more often used as a screening tool for other pathology prior to proceeding with MRI

• CT myelogram 

  • indications

    • patients unable to obtain MRI 

      • pacemaker

  • views

    • sagittal and coronal reconstructions demonstrate compression of the thecal sac

  • findings

    • myelography filling defect at the level of herniation

    • a calcified disc may be visible

  • sensitivity

    • 93% accurate at detecting associated surgical pathology

    • unable to detect foraminal or extraforaminal herniations

• MRI without gadolinium

  • indications for obtaining an MRI

    • pain lasting > one month and not responding to nonoperative management or

    • red flags are present

      • infection (IV drug user, h/o of fever and chills)

      • tumor (h/o or cancer)

      • trauma (h/o car accident or fall)

      • cauda equina syndrome (bowel/bladder changes)

  • modality of choice for diagnosis of lumbar disc herniations

    • highly sensitive and specific

    • helpful for preoperative planning

    • useful to differentiate from synovial facet cysts

  • however high rate of abnormal findings on MRI in normal people

    • need to correlate MRI findings with symptoms and physical exam findings

  • views

    • sagittal and coronal T2 reconstructions

      • localize the level and side of the herniation

      • location anatomic location (central vs paracentral vs foraminal vs extraforaminal)

• MRI with gadolinium

  • indications

    • useful for revision surgery

  • findings

    • allows to distinguish between post-surgical fibrosus (enhances with gadolinium) vs. recurrent herniated disc (does not enhance with gadolinium)

TREATMENT

• Nonoperative

  • rest and physical therapy, anti-inflammatory medications, and limited narcotics  

     

    • indications

      • first line of treatment for most patients with disc herniation

        • new-onset radicular pain

        • no significant motor weakness

        • absence of cauda equina syndrome

        • no bowel/bladder incontinence

    • outcomes

      • 90% improve without surgery

      • positive predictors of good outcomes with nonoperative treatment

        •  higher level of education

  • selective nerve root corticosteroid injections 

     

    • indications

      • second line of treatment if therapy and medications fail

        • usually after 6 weeks

    • outcomes

      • leads to long lasting improvement in ~ 50% (compared to ~90% with surgery)

      • results best in patients with extruded discs as opposed to contained discs

      • no difference in pain relief using lidocaine with and without steroids

• Operative

  • laminotomy and discectomy (microdiscectomy) 

    • indications 

       

      • persistent disabling pain lasting more than 6 weeks that have failed nonoperative options (and epidural injections) 

        • timing of appropriate nonoperative treatment varies

        • better surgical outcomes if addressed within 2 months

      • progressive and significant weakness 

         

      • cauda equina syndrome

    • rehabilitation

      • patients may return to medium to high-intensity activity at 4 to 6 weeks 

         

    • outcomes

      • outcomes with surgery compared to nonoperative

        • improvement in pain and function greater with surgery 

           

        • early and sustained pain relief out to 2 years 

        • equal likelihood of receiving disability at 5 years 

      • positive predictors for good outcome with surgery

        • leg pain is chief complaint

        • positive straight leg raise

        • weakness that correlates with nerve root impingement seen on MRI

        • married status

        • progressively worsening symptoms prior to surgery  

           

        • professional athletes 

           

          • younger age, greater number of games played prior to injury

        • paracentral and foraminal herniations

          • central and extraforaminal associated with worse outcomes 

        • herniation at caudal levels

          • L5-S1 results in better outcomes than L2-3

      • negative predictors for good outcome with surgery

        • worker's compensation 

           

          • WC patients have less relief from symptoms and less improvement in quality of life with surgical treatment 

        • smokers

        • chronic headaches

        • depression

  • far lateral microdiskectomy 

    • indications

      • for far-lateral disc herniations

TECHNIQUES

• Rest and physical therapy, anti-inflammatory medications, and limited narcotics 

  • bedrest followed by progressive activity as tolerated

    • historical treatment

      • most modern protocols involve immediate activity with modification to avoid pain exacerbation 

  • medications

    • NSAIDS

    • muscle relaxants (more effective than placebo but have side effects)

    • oral steroid taper

      • modest but significant improvement in function, no significant improvement in pain

    • narcotic medications

      • typically avoided due to complication profile

        • dependence

        • difficult post-op pain control

        • worse outcomes following surgical treatment

      • if used, usually for a short period (2-3 days) in the acute setting

  • physical therapy

    • typically initiated three weeks after symptom onset

    • extension exercises are extremely beneficial

    • traction

    • chiropractic manipulation

      • should be performed with care

• Selective nerve root corticosteroid injections 

  • epidural

  • selective nerve block

    • can be therapeutic and diagnostic 

      • useful in case of diagnostic dilemmas 

• Laminotomy and discectomy (microdiscectomy)

  • various techniques available

    • most techniques can be performed in a "minimally invasive" fashion

      • can be done with small incision or through "tube" access

      • open technique using a crank (McCulloh) retractor

    • discectomy performed through microscope or loupe magnification

      • no difference in outcomes between the two

    • endoscopic techniques available

      • provide smaller incisions

    • similar outcomes between all techniques surgical techniques

    • fragment excision vs extended disc space curettage (subtotal discectomy) 

      • lower long term back pain with fragment excision

      • higher reherniation rates with fragment excision at 2-years follow-up

• Far lateral microdiskectomy 

  • utilizes a paraspinal approach of Wiltse

    • can also be done with tubular or crank retractors 

       

COMPLICATIONS 

• Dural tear

  • occurs in 0-4% of cases

  • treatment

    • if have tear at time of surgery then perform water-tight repair

      • has not been shown to adversely affect long term outcomes

• Recurrent HNP 

   

  • defined as recurrent sciatica at the same operated level

    •  pain-free interval of 6 months prior to recurrence of symptoms

    • pathology can be ipsilateral to contralateral to the index presentation 

  • recurrence rate 5-15%

    • revision rate at 8-year follow-up is 15% according to the SPORT trial

    • risk factors protective against recurrent herniation

      • discrete herniations

      • small annular defects (<6 mm)

  • treatment

    • can treat nonoperatively initially

    • revision microdiscectomy in patients with persistent symptoms 

      • outcomes for revision discectomy have been shown to be as good as for primary discectomy 

         

• Wound infections

  • occurs in up to 3% of cases

    • epidural abscess in 0.3% of cases

  • risk factors

    • microscope usage proposed as a source of infection

      • some date refutes this claim

  • treatment

    • superficial infections

      • treat with local wound care and antibiotics

    • deep infections

      • surgical I&D

• Epidural fibrosis

  • scarring the compresses the dura leading to radicular symptoms

    • associated with poor outcomes following revision surgery

      • persistent back pain

      • patients 3.2 times more likely to suffer from recurrent radiculopathy

  • MRI may demonstrate retraction of the dura on the side of the lesion

• Pyogenic discitis 

  • occurs in 2.3% of cases

  • treatment

    • IV antibiotics +/- surgical I&D

• Chronic low back pain

  • not completely understood but central sensitization may be a factor 

     

    • amplification of neural signaling within the central nervous system (CNS) that elicits pain hypersensitivity.

  • Modic changes on MRI imaging are associated with post-operative back pain  

  • Pain diagrams may be useful in identifying patients with an increased likelihood of pain sensitization, psychosocial load, and utilizing pain management resources 

     

• Vascular catastrophe

  • exceedingly rare

  • caused by breaking through anterior annulus and injuring vena cava/aorta

  • treatment

    • immediate recognition of complication followed by coordinated repair by vascular service

• Instability

  • due to over resection of lamina and pars interarticularis

  • not all patients are symptomatic

  • treatment

    • instrumentation and fusion of the affected segment

PROGNOSIS

• Natural history

  • 90% of patients will have improvement of symptoms within 3 months without substantial medical treatment

    • patients less likely to improve if still symptomatic after 6 weeks

  • factors associated with good outcomes with nonoperative treatment

    • lack of radiculopathy

  • factors associated with worse outcomes with nonoperative treatment

    •  obese patients (BMI >30)

    • symptoms present >6 months prior to starting treatment

• Size of herniation decreases over time (reabsorbed) 

   

  • sequestered disc herniations show the greatest degree of spontaneous reabsorption

  • macrophage phagocytosis and enzymatic degradation is the mechanism of reabsorption

• Factors associated with favorable surgical outcomes

  • severe preoperative leg pain

  • shorter symptom duration

  • younger age

  • increased preoperative physical activity

• Surgical treatment is equivalent to nonsurgical treatment in the long term

  • surgery provides faster pain relief