Spondylolysis, Pars Interarticularis Fracture, Pars Interarticularis Defect, Pars Defect, Scotty Dog Sign

  • Definitions
  1. Spondylolysis
    1. Vertebral defect at pars interarticularis (one or two defects)
    2. When two, bilateral Pars Defects occur, Spondylolisthesis (Vertebral slippage) occurs
  • Epidemiology
  1. Uncommon cause of back pain in general population, non-athletes
  2. Incidence in age <40 years old: 6%
    1. Spondylolisthesis is much less common, and typically at L5-S1
  3. Pars Interarticularis Defect is twice as common in men
    1. However women have higher risk of high grade Spondylolisthesis
  4. Common cause of back pain in athletes (esp. repeated spine extension)
    1. Gymnastics, ballet or dance
    2. Football (e.g. blocking, lineman)
    3. Volleyball (e.g. serving the ball)
    4. Soccer
    5. Weightlifting
    6. Diving
    7. Baseball Players
  • Pathophysiology
  1. Repetitive back hyperextension
  2. Most commonly occurs at L4 or, especially L5
  3. Results in Fracture at pars interarticularis resulting in Pars Interarticularis Defect
    1. One Pars Defect: Spondylolysis
    2. Two Pars Defects: Spondylolisthesis
  • Symptoms
  1. History should include Cauda Equina Syndrome symptoms and other cord compression symptoms
  2. Back pain exacerbated by Lumbar Spine hyperextension
  3. Radiation into posterior legs
  • Signs
  1. Perform complete Neurologic Exam of lower extremity
  2. Hyperlordotic curvature of the Lumbar Spine
  3. Decreased Lumbar Spine range of motion
  4. Hamstring tightness
  5. Quadriceps tightness
  6. Altered gait (crouched position)
  7. One Legged Hyperextension (Stork Standing Test)
    1. Examiner stands behind patient for support
    2. Patient balances on one leg and hyperextends back
    3. Positive if pain at affected lumbar Vertebrae
  • Imaging
  • XRay
  1. Indicated for back pain lasting >3 weeks (esp. athletes)
  2. Views: AP, lateral and oblique views
  3. Findings: Scotty Dog Sign on oblique view
    1. Identify landmarks corresponding to Scotty Dog
      1. Head of Scotty Dog: Superior articular process
      2. Neck of Scotty Dog: Pars interarticularis
      3. Front leg of Scotty Dog: Inferior articular process
      4. Body and back leg of Dog: Transverse process
    2. Findings consistent with Spondylolysis
      1. Collar on Scotty Dog neck: Fracture through pars
  4. Pitfalls
    1. Pars Fracture often not seen in early Spondylolysis
  • Imaging
  • Advanced Imaging
  1. MRI L-Spine
    1. Preferred imaging for non-diagnostic XRay
    2. MRI sequenced for pedicle and pars region Bone Marrow edema
  2. Single photon emission computed tomography (SPECT)
    1. Most sensitive for Spondylolysis
    2. Consider for nondiagnostic XRay
  3. CT L-S Spine (thin cut, reverse gantry CT)
    1. Highly specific for Spondylolysis
    2. Consider for positive SPECT scan
    3. Differentiates acute versus chronic Spondylolysis
  • Management
  1. Consider 6 weeks of conservative therapy if XRay negative, but suspect Spondylolysis
  2. NSAIDs
  3. Relative rest period with no sports activity
    1. Chronic Spondylolysis: Rest until no pain
    2. Acute Spondylolysis: Rest minimum of 3 months
  4. Adjunctive measures
    1. Low Thoracolumbar Orthosis bracing could be considered at 3 weeks of rest
      1. Taper the Orthosis to pain free status (regardless of imaging)
    2. Transcutaneous electrical nerve stimulation (TENS)
    3. Consider repeat imaging to survey acute injury for healing
  5. Rehabilitation program
    1. Quadriceps and Hamstring flexibility
    2. Spine stabilization (flexion, core Muscle)
    3. Low-impact aerobics
    4. Progress to sport-specific activity
    5. Gradual return to activity over a 5 month period
  6. Orthopedics or Spine Surgery referral indications
    1. Spondylolysis refractory to above management (<10% of cases)
  • Complications