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Updated: Feb 22 2024

Lumbar Disc Herniation

Images
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  • 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
      • foraminal (far lateral, extraforaminal)
        • less common (5-10%)
        • 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)
          • 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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