Spondylolysis & Spondylolisthesis

Spondylolysis

  • Traumatic Pars defect - unilateral
  • Common cause of pain in children & adolescents
  • Fatigue fracture from repeated hyperextension

Associated with

  • Ballet dancers
  • Tight hamstrings
  • Boys

Diagnosis

  • Lateral XR picks up 85%
  • Oblique picks up 10% more
  • 5% require CT, bone scan, or SPECT (best)

Management

  • Symptomatic relief & activity modification
  • Bracing
  • Non-union common but asymptomatic
  • Surgery rarely indicated

Spondylolisthesis

Classification

Type (Wiltse) – Dad Is Down The Pub & Iatrogenic

  • Type 1: Dysplastic
  • Type 2: Isthmic
    • 2a: Pars stress fracture
    • 2b: Elongated pars
    • 2c: Acute pars fracture
  • Type 3: Degenerative
  • Type 4: Traumatic
  • Type 5: Pathologic
  • Type 6: Iatrogenic

Grade (Myerding)

  • Grade 1: 0-25% slip
  • Grade 2: 25-50% slip
  • Grade 3: 50-75% slip
  • Grade 4: 75-100% slip
  • Grade 5: >100% slip (spondyloptosis)

Radiographic Assessment of SL

  • Slip angle – normal = <0
  • Sacral inclination – normal = >30°
    • Alteration in both indicates kyphosis – poor prognostic factor
  • Pelvic incidence – increase is related to increased progression

General Presenting Features

  • Pelvic waddle
  • Heart-shaped bottom
  • Palpable step
  • Mechanical pain
  • Neurologic symptoms

Dysplastic Spondylolisthesis

  • Not strictly congenital – develops by age 5
  • Girls > Boys
  • Eskimos

Radiographic Features

  • L5/S1 level
  • No pars defect – intact neural arch
  • Dome-shaped S1
  • Incompetent facet joint
    • L5 inferior facet poorly formed, S1 superior facet absent
  • Trapezoidal L5
  • >30% slip is uncommon

Clinical Features

  • Patient presents during growth spurt most commonly
  • Slip usually <30%
  • High rate of neurologic compromise (cauda equina) with >30% slip
    • Intact neural arch

Isthmic Spondylolisthesis

  • Most common type (type 2a is most common, then 2b, then 2c)

Pathology

  • Pars interarticularis stress fracture – repeated hyperextension
  • Boys > Girls
  • Eskimos
  • Hyperextension sports

Associations

  • Spina bifida
  • Scheuermann’s

Radiographic Presentation

  • L5/S1
  • Sagittally orientated facets but not dysplastic
  • Pars defect
  • Usually <25% slip

Clinical Features

  • Uncommon for slip to progress especially after skeletal maturity
  • Mechanical back pain
  • Tight hamstrings
  • Rare to get neurologic deficit
    • High-grade slips
  • L5 exiting root rather than traversing S1 is affected

Risk Factors for Progression

  • Girls
  • Younger age at presentation
  • High-grade slip
  • L4/5 or L3/4 slip
    • Iliolumbar ligament stabilises L5/S1

Adult Isthmic Spondylolisthesis

  • Present in 30’s usually
  • When an adolescent isthmic SL becomes symptomatic
  • Due to degenerative process beginning with ageing
  • Mechanical pain usually
  • Sometimes radicular or stenotic pain
  • Pars defect apparent on imaging

Degenerative Spondylolisthesis

  • Older adults
  • L4/5 most common level

Risk Factors

  • Diabetes
  • Blacks
  • Women > Men
  • Sacralised (transitional) L5

Pathology

  • DDD with segmental instability
  • Facet arthrosis
  • Abnormal loading and mechanics

Management of Spondylolisthesis

Low Grade (<50%)

  • Try non-operative treatment whatever the case
    • Activity modification
    • Analgesia
    • Flexion exercises
    • Bracing in adolescents/children
  • Indication for surgery:
    • Intractable pain
    • Neurologic deficit
    • Progression of slip

High Grade (>50%)

  • In adolescents/children:
    • Prophylactic surgery in children – high risk of progression
    • High risk of neurologic compromise, especially dysplastic
  • Adults with high-grade slips tend to be symptomatic
    • Surgery is warranted as chance of progression higher
    • Results of surgery better than non-operative for high grade

Surgical Treatment

  • Gold standard in all groups:
    • In situ posterolateral instrumented fusion
      • Through a midline approach or Wiltse para-transverse approach
      • Favoured – less disruption to posterior structures
      • Low risk of neurologic compromise
      • Instrumentation increases fusion rate
        • Solid fusion associated with better outcome

Controversies

Slip Reduction

  • Not for low-grade slips – risk outweighs benefit
  • Indications:
    • Significant L5/S1 kyphosis with hyperlordosis above
    • High slip angle (>45°)
    • Badly altered sagittal balance
  • Increases chance of neurologic injury – 10% (most transient)
  • May decrease long-term chance of stenosis
  • Reduction opens up and re-orientates foramina

Anterior Supplementation

  • Should be considered for high-grade slips
  • Less stress on posterior instrumentation
  • Higher chance of fusion
  • Anterior fusion alone does not work as well

ORIF of Pars Defect

  • Tension band wiring or compression screw
  • 90% rate of union and good outcome
  • Best results in:
    • No DDD
    • Single-level slip
    • Low-grade slip
    • No neurologic deficit

Management of Spondyloptosis

  • Extremely challenging surgery
  • Usually done in a 2-stage procedure:
    • 1st stage: Removes L5
    • 2nd stage: Fuses L4 to sacrum circumferentially
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