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Lumbar Disc Herniation

  • 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

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