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Introduction
  • Reduction in dimensions of central or lateral lumbar spinal canal caused by
    • 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 
Classification
  • Etiologic classification
    • acquired
      • degenerative/spondylotic changes (most common)
      • post surgical
      • traumatic (vertebral fractures)
      • inflammatory (ankylosing spondylitis)
    • congenital
      • short pedicles with medially placed facets (e.g., 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
      • presents with nonspecific root compression or symptoms of lower nerve root (at L4/5 level the root of L5 affected)
    • lateral recess stenosis  (subarticular recess)
      • associated with facet joint arthropathy and osteophyte formation
        • overgrowth of superior articular facet usually primary culprit
      • presents with symptoms of descending nerve root (at L4/5 level the root of L5 affected)
    • foraminal stenosis
      • occurs between the medial and lateral border of the pedicle
      • exiting nerve root compressed by ventral cephalad overhang of the superior facet and the bulging disc
      • present with symptoms of exiting nerve root(at L4/5 level the root of L4 affected)
    • extraforaminal stenosis
      • located lateral to the lateral edge of the pedicle
      • lateral disc herniation causes impingement of the existing nerve root
Presentation
  • Symptoms 
    • back pain 
    • referred buttock pain
    • claudication
      • pain worse with extension (walking, standing upright) 
      • pain relieved with flexion (sitting, leaning over shopping cart, sleeping in fetal position) 
    • leg pain (often unilateral)
    • 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 extension of back
    • Straight leg raise (tension sign)
      • is 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
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
ff
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 (back extended)
Stationary bicycle (back flexed)
Relieves symptoms
Causes symptoms
Pulses
Normal
Abnormal

Imaging
  • Radiographs
    • 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
    • findings include
      • 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
      • Boden et al found that three of 14 asymptomatic patients and MRI findings of anatomic spinal stenosis
  • CT myelogram
    • more invasive than MRI
    • findings include
      • central and lateral neural element compression 
      • bony anomalies
      • bony facet hypertrophy
Treatment
  • Nonoperative
    • oral medications, physical therapy, and corticosteroid injections
      • indications
        • first line of treatment
    • modalities include
      • NSAIDS, physical therapy, weight loss and bracing
      • steroid injections (epidural and transforaminal) effective and may obviate 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 deficit (weakness or bowel/bladder)
      • 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 pedicle-to-pedicle decompression with instrumented fusion
      • indications
        • presence of 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 greater than 30% at 10 years
Surgical Techniques
  • Wide pedicle-to-pedicle decompression 
    • a single level decompression at L4/5 would include
      • resect inferior half of spinous process of L4
      • resect L4 lamina to the level of the insertion of the ligamentum flavum
      • resect 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 foramen
        • palpate L4 and L5 pedicle (pedicle-to-pedicle) and be sure nerve root is patent below it.
  • Wide decompression with posterolateral fusion
    • technique
      • 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 complication 
    • wound infection (10%) 
      • deep surgical infections are to be treated with surgical debridement and irrigation 
    • pneumonia (5%)
    • renal failure (5%)
    • neurologic deficits (2%)
  • Minor complication
    • UTI (34%)
    • anemia requiring transfusion (27%)
    • confusion (27%)
    • dural tear  
    • failure for symptoms to improve 
 

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