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Updated: Feb 19 2024

Lumbar Spinal Stenosis

Images
https://upload.orthobullets.com/topic/2037/images/CT - myelo - Lumbar spinal stenosis_moved.jpg
https://upload.orthobullets.com/topic/2037/images/4a_moved.jpg
https://upload.orthobullets.com/topic/2037/images/MRI - sagital - lumbar stenosis_moved.jpg
https://upload.orthobullets.com/topic/2037/images/stenosis_2.jpg
https://upload.orthobullets.com/topic/2037/images/stenosis3.jpg
https://upload.orthobullets.com/topic/2037/images/mri-sagital-t2 - shows spinal stenosis.jpg
https://upload.orthobullets.com/topic/2037/images/decompression.jpg
  • summary
    • Lumbar Spinal Stenosis is a degenerative spinal condition characterized by the narrowing of the lumbar spinal canal due to a variety of bony or soft tissues structures. 
    • Diagnosis is made with MRI studies of the lumbar spine.
    • Treatment is a trial of nonoperative management with NSAIDs and physical therapy.  Surgical laminotomy and discectomy is indicated for progressive disabling pain that has failed nonoperative management, and/or progressive neurological deficits.
  • Epidemiology
    • Incidence
      • most common reason for lumbar spine surgery in patients > 65 years old
      • seen in 20-25%
    • Demographics
      • slightly more common in males (1.5:1)
      • average age at presentation is 65 years old
    • Anatomic location
      • most commonly occurs at L4-5 (91%)
    • Risk factors
      • Caucasian race
      • increased BMI
      • congenital spine anomalies (20%)
        • failure of posterior elements to develop, leading to short pedicles and laminae
  • Etiology
    • Mechanism
      • Narrowing of the lumbar spinal canal can be due to
        • bony structures
          • facet osteophytes
          • uncinate spur (posterior vertebral body osteophyte)
          • spondylolisthesis
        • soft tissue structures
          • herniated or bulging discs
          • hypertrophy or buckling of the ligamentum flavum
          • synovial facet cysts
    • Pathophysiology
      • cell, water, and proteoglycan content in the nucleus pulposus decreases with age
      • degeneration of the intervertebral disk leads to diminished disk height and buckling/bulding of the anulus fibrosus
      • anterior spinal column begins to have decreased ability to absorb stress, leading to an abnormal transfer of force to the posterior elements
      • increased stress through the facets leads to facet joint hypertrophy, osteophyte formation, and ligamentum flavum buckling and hypertrophy
      • combined changes lead to a narrowing of the spinal canal and compression of the neural elements
    • Associated conditions
      • degenerative spondylolisthesis
      • degenerative scoliosis
      • cauda equina syndrome
        • rare
  • Anatomy
    • Osteology
      • anterior vertebral body
      • posterior arch
        • formed by
          • pedicles
            • pedicles project posteriorly from posterolateral corners of vertebral bodies
          • lamina
            • lamina project posteromedially from pedicles, join in the midline
      • spinous process
      • transverse process
      • mammillary processes
        • separate ossification centers
        • project posteriorly from superior articular facet
      • pars interarticularis
        • mass of bone between superior and inferior articular facets
        • site of spondylolysis
    • Articulations
      • intervertebral disc
        • act as an articulation above and below
      • facet joint (zygapophyseal joint)
        • formed by superior and inferior articular processes that project from junction of pedicle and lamina
        • facet orientation
          • facets become more coronal as you move inferior
    • Nerve roots
      • nerve root exits foramen under same numbered pedicle
        • central herniations affect traversing nerve root
        • far lateral herniations affect exiting nerve root
    • Blood Supply
      • segmental arteries
        • dorsal branches supply blood to the dura & posterior elements
  • Classification
    • Etiologic classification
      • acquired
        • degenerative/spondylotic changes (most common)
        • post-surgical
        • post-traumatic (vertebral fractures)
        • inflammatory (ankylosing spondylitis)
        • secondary to systemic diseases (Paget disease, acromegaly, fluorosis)
      • congenital
        • short pedicles with medially placed facets
        • can be subdivided into
          • idiopathic
          • developmental (achondroplasia)
    • Anatomic classification
      • central stenosis
        • cross sectional area <100mm2 or <10mm A-P diameter on axial CT
        • caused by ligamentum hypertrophy directly under the lamina posteriorly and the bulging disc anteriorly
        • results in thecal sac compression
        • presents with nonspecific root compression or symptoms of lower nerve root (at the L4/5 level, the root of L5 is affected)
      • lateral recess stenosis (subarticular recess)
        • caused by facet joint arthropathy and osteophyte formation
          • overgrowth of the superior articular facet is usually the primary culprit
        • results in nerve root compression
        • presents with symptoms of descending nerve root (at the L4/5 level, the root of L5 is affected)
      • foraminal stenosis
        • occurs between the medial and lateral border of the pedicle
        • caused by a substantial loss of disk height, foraminal disk protrusions or osteophytes, or angulation in the setting of degenerative scoliosis
        • results in nerve root compression by the ventral cephalad overhang of the superior facet and the bulging disc
        • presents with symptoms of exiting nerve root (at the L4/5 level, the root of L4 is affected)
      • extraforaminal stenosis
        • located lateral to the lateral edge of the pedicle
        • caused by far lateral disc herniations
        • presents with symptoms of exiting nerve root (at the L4/5 level, the root of L4 is affected)
  • Presentation
    • Symptoms
      • back pain
      • referred buttock pain
      • leg pain
        • often unilateral
      • neurogenic claudication
        • pain worse with extension (walking, standing upright)
        • pain relieved with flexion (sitting, leaning over shopping cart, sleeping in fetal position)
      • weakness
      • bladder disturbances
        • recurrent UTI present in up to 10% due to autonomic sphincter dysfunction
      • cauda equina syndrome (rare)
    • Physical exam
      • Kemp sign
        • unilateral radicular pain from foraminal stenosis made worse by back extension
      • straight leg raise (tension sign)
        • usually negative
      • Valsalva test
        • radicular pain not worsened by Valsalva as is the case with a herniated disc
      • normal neurologic exam
        • patients may have no focal deficits, as exam often takes place with patient seated and symptoms may be reproducible or exacerbated only with lumbar extension or ambulation
  • Imaging
    • Radiographs
      • findings do not always correlate with clinical symptomatology
      • standing AP and lateral may show
        • nonspecific degenerative findings (disk space narrowing, osteophyte formation)
        • degenerative scoliosis
        • degenerative spondylolisthesis
      • flexion/extension radiographs may show
        • segmental instability and subtle degenerative spondylolisthesis
      • myelogram
        • plain film myelography provides dynamic information such as degree of cut off when a patient goes into extension
        • an invasive procedure
    • MRI
      • imaging modality of choice
      • findings
        • central stenosis with a thecal sac <100mm2
        • obliteration of perineural fat and compression of lateral recess or foramen
        • facet and ligamentum hypertrophy
      • MRI findings of spinal stenosis may found in asymptomatic patients
    • CT myelogram
      • more invasive than MRI
      • findings
        • central and lateral neural element compression
        • bony anomalies
        • bony facet hypertrophy
  • Differential
    • Important to differentiate symptoms of neurogenic claudication from vascular claudication
      • flexion improves symptoms in neurogenic claudication because this posture increases the limited area available for the neural elements in the spinal canal and foramen
      • Neurogenic Claudication vs. Vascular Claudication
      • Neurogenic Claudication
      • Vascular Claudication
      • Postural changes
      • Yes
      • No
      • Walking upright
      • Causes symptoms
      • Causes symptoms
      • Standing stationary
      • Causes symptoms
      • Relieves symptoms
      • Sitting
      • Relieves symptoms
      • Relieves symptoms
      • Stair climbing
      • Up easier (back flexed)
      • Down easier
      • Stationary bicycle (back flexed)
      • Relieves symptoms
      • Causes symptoms
      • Pulses
      • Normal
      • Abnormal
    • Hip-spine syndrome
      • presence of coexisting hip and spine pathology
      • must determine primary pain generatory prior to surgical treatment
      • may require diagnostic injections to aid in diagnosis
  • Treatment
    • Nonoperative
      • oral medications, physical therapy, and corticosteroid injections
        • indications
          • first line of treatment
      • modalities include
        • NSAIDS, physical therapy, weight loss and bracing
          • preoperative opioid use associated with prolonged hospital stays and increased postoperative pain
        • steroid injections (epidural and transforaminal)
          • found to be effective and may obviate the need for surgery
    • Operative
      • wide pedicle-to-pedicle decompression
        • indications
          • persistent pain for 3-6 months that has failed to improve with nonoperative management
          • progressive neurologic deficits (weakness or bowel/bladder)
        • outcomes
          • results in better improvement in pain and function than nonsurgical treatment
      • wide pedicle-to-pedicle decompression with instrumented fusion
        • indications
          • segmental instability (isthmic spondylolisthesis, degenerative spondylolisthesis, degenerative scoliosis)
          • surgical instability
            • created by complete laminectomy and/or removal of > 50% of facets
          • risk of adjacent segment degeneration >30% at 10 years
  • Techniques
    • Wide pedicle-to-pedicle decompression
      • technique
        • a single level decompression at L4/5 would include
          • resection of the inferior half of spinous process of L4
          • resection of the L4 lamina to the level of the insertion of the ligamentum flavum
          • resection of the ligamentum flavum
          • medial facetectomy and lateral recess decompression
            • undercutting of facets and removal of ligamentum flavum from lateral recess
          • exploration and decompression of the L4/5 and L5/S1 foramina
            • palpate L4 and L5 pedicle (pedicle-to-pedicle) and be sure the nerve root is patent below it
      • complications specific to this treatment
        • infection
        • dural tear
        • epidural hematoma
        • instability
      • outcomes
        • improved pain, function, and satisfaction with surgical treatment
        • most common cause of failed surgery is recurrence of disease above or below decompressed level
        • comorbid conditions are strongest predictor of clinical outcomes after decompression for lumbar spinal stenosis
    • Wide decompression with posterolateral fusion
      • instrumentation is controversial
      • circumferential fusion (with PLIF or TLIF) is accepted but no studies showing its superiority
  • Complications
    • Complications increase with age, blood loss, and levels fused
    • Major complications
      • wound infection (10%)
        • deep surgical infections are to be treated with surgical debridement and irrigation
      • pneumonia (5%)
      • renal failure (5%)
      • persistent neurologic deficits (4%)
    • Minor complications
      • transient neurologic deficits (36%) 
      • UTI (34%)
      • anemia requiring transfusion (27%)
      • confusion (27%)
      • failure for symptoms to improve
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