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Updated: Jul 14 2024

Adult Isthmic Spondylolisthesis

Images isthmic3.jpg I_moved.jpg isthmic2.jpg isthmic.jpg
  • summary
    • Adult Isthmic Spondylolisthesis is a common adult spinal condition characterized by subluxation of one vertebral body anterior to the adjacent inferior vertebral body, caused by a defect in the pars interarticularis.
    • Diagnosis is made with lateral radiographs. Flexion and extension lateral lumbar radiographs can identify the degree of instability. MRI studies can be helpful for central or foraminal stenosis.
    • Treatment is a trial of nonoperative management with NSAIDs and physical therapy.  Surgical management is indicated for progressive disabling pain that has failed nonoperative management, and/or progressive neurological deficits.
  • Epidemiology
    • Incidence
      • spondylolysis is seen in 4-6% of population
      • increased prevalence in sports that involve repetitive hyperextension (gymnasts, weightlifters, football linemen)
    • Anatomic location
      • 82% occur at L5/S1
      • 11% occurs L4/5 (11%)
      • due to forces in the lumbar spine being greatest at these levels and the facet being more coronal
  • Etiology
    • Pathophysiology
      • foraminal stenosis
        • adult isthmic spondylolisthesis at L5/S1 often leads to radicular symptoms caused by compression of the exiting L5 nerve root in the L5-S1 foramen
        • compression can be caused by
          • hypertrophic fibrous repair tissue of the pars defect
          • uncinate spur formation of the posterior L5 body
          • bulging of the L5/S1 disc
        • lateral recess stenosis
          • caused by facet arthrosis and hypertrophic ligamentum flavum
        • central stenosis
          • rare due to fact that these slips are usually only Grade I or II
  • Classification
      • Wiltse-Newman Classification
      • Type I
      • Dysplastic: a congenital defect in pars
      • Type II-A
      •  Isthmic - pars fatigue fx
      • Type II-B
      •  Isthmic - pars elongation due to multiple healed stress fx
      • Type II-C
      •  Isthmic - pars acute fx
      • Type III
      • Degenerative: facet instability without a pars fx
      • Type IV
      • Traumatic: acute posterior arch fx other than pars
      • Type V
      • Neoplastic: pathologic destruction of pars
      • Myerding Classification
      • Grade I
      • < 25%
      • Grade II
      • 25-50%
      • Grade III
      • 50-75%
      • Grade IV
      •  75-100%
      • Grade V
      • Spondyloptosis
  • Physical Exam
    • Symptoms
      • axial back pain
        • most common presentation
        • pain usually has a long history with periodic episodes that vary in intensity and duration
      • leg pain
        • usually a L5 radiculopathy usually caused by foraminal stenosis at the L5-S1 level
      • neurogenic claudication
        • caused by spinal stenosis
        • characterized by buttock and leg pain worse with walking
        • symptoms of neurogenic claudication rare because these slips rarely progress beyond Grade II
      • cauda equina syndrome
        • rare because these slips rarely progress beyond Grade II
    • Physical exam
      • L5 radiculopathy
        • ankle dorsiflexion and EHL weakness
  • Imaging
    • Radiographs
      • recommended views
        • obtain AP, lateral, obliques, and flexion-extension views
      • findings
        • AP
          • deformity in coronal plane
        • lateral
          • will see spondylolisthesis and pars defect
        • flexion-extension
          • instability defined as 4 mm of translation or 10° of angulation of motion compared to adjacent motion segment
      • measurements
        • pelvic incidence
          • pelvic incidence = pelvic tilt + sacral slope
          • a line is drawn from the center of the S1 endplate to the center of the femoral head
          • a second line is drawn perpendicular to a line drawn along the S1 endplate, intersecting the point in the center of the S1 endplate
          • the angle between these two lines is the pelvic incidence (see angle X in figure above)
          • correlates with severity of disease
          • pelvic incidence has direct correlation with the Meyerding–Newman grade
        • pelvic tilt
          • sacral slope = pelvic incidence - pelvic tilt
          • a line is drawn from the center of the S1 endplate to the center of the femoral head
          • a second vertical line (parallel with side margin of radiograph) line is drawn intersecting the center of the femoral head
          • the angle between these two lines is the pelvic tilt (see angle Z in figure above)
        • sacral slope
          • pelvic tilt = pelvic incidence - sacral slope
          • a line is drawn parallel to the S1 endplate
          • a second horizontal line (parallel to the inferior margin of the radiograph) is drawn
          • the angle between these two lines is the sacral slope (see angle Y in the figure above)
    • MRI
      • views
        • T2 parasagittal images are best study to evaluate for foraminal stenosis and compression of neural elements
  • Treatment
    • Nonoperative
      • oral medications, lifestyle modifications, therapy
        • indications
          • most patients can be treated nonoperatively
        • techniques
          • activity restriction
          • NSAID
          • role of injections unclear
          • bracing may be beneficial especially in the acute phase
    • Operative
      • L5-S1 decompression and instrumented fusion +/- reduction
        • indications
          • L5-S1 low-grade spondylolisthesis with persistent and incapacitating pain that has failed 6 months of nonoperative management (most common)
          • progressive neurologic deficit
          • slip progression
          • cauda equina syndrome
        • reduction
          • improved sagittal balance with reduction
          • risk of stretch injury to L5 nerve root with reduction
      • L4-S1 decompression and instrumented fusion +/- reduction
        • indications
          • L5-S1 high-grade spondylolithesis with persistent and incapacitating pain that has failed 6 months of nonoperative management
      • ALIF
        • indications
          • can be used successfully to treat low-grade isthmic spondylolisthesis even when radicular symptoms are present
          • cannot be used to treat high grade isthmic spondylolisthesis due to translational and angular deformity
        • outcomes
          • studies have shown good to excellent results in 87-94% at 2 years
  • Techniques
    • L5/S1 wide decompression and instrumented fusion
      • approach
        • posterior midline
      • decompression
        • indicated in adult with leg pain below knee
        • usually involves Gill laminectomy and foraminal decompression
          • removal of loose lamina and scared pars defect allows decompression of nerve root
          • a Gill decompression is destabilizing and should be combined with fusion
      • fusion
        • posterolateral fusion is standard
        • interbody fusion (PLIF/TLIF) commonly performed
          • posterior lumbar interbody fusion (PLIF) involves insertion of device medial to facets
          • transforaminal lumbar interbody fusion (TLIF) requires facetectomy and more lateralized and transforaminal approach to the disc space
      • cons
        • interbody fusion has increased operative time with greater blood loss and longer hospitalizations
    • Anterior Lumbar Interbody Fusion (ALIF)
      • approach
        • usually done through trans-retroperitoneal approach
      • decompression
        • decompression of nerve root done indirectly by foraminal distraction via restoration of disc height
      • fusion
        • grafts used include autologous iliac crest, structural allograft, and cages of various materials
      • pros
        • may increase chance of union by more complete discectomy and endplate preparation
        • allows improved restoration of disc height
      • cons
        • retrograde ejaculation and sexual dysfunction
        • persistent radiculopathy due to inadequate indirect foraminal decompression
        • persistent low back pain may be caused by nociceptive pain fibers in pars defect that are not removed in an anterior procedure alone
    • preferred treatment is surgeon dependent with each technique having similar outcomes
  • Complications
    • Psuedoarthrosis
    • Dural Tear
  • Prognosis
    • Relatively few patients (5%) with spondylolysis with develop spondylolisthesis
    • Slip progression more common in females
    • Slip progression usually occurs in adolescence and rare after skeletal maturity
    • Slip angle is the most predictive factor of slip progression and overall outcomes 
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