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

  • Epidemiology
  1. Uncommon cause of back pain in general population
  2. Common cause of back pain in athletes
    1. Gymnastics, ballet or dance
    2. Football (e.g. blocking)
    3. Volleyball (e.g. serving the ball)
    4. Soccer
    5. Weightlifting
  • Pathophysiology
  1. Repetitive back hyperextension
  2. Causes Fracture at pars interarticularis resulting in Pars Interarticularis Defect
  3. Most commonly occurs at L4 or L5
  • Symptoms
  1. Back pain exacerbated by Lumbar Spine hyperextension
  • Signs
  1. Hyperlordotic curvature of the Lumbar Spine
  2. Decreased Lumbar Spine range of motion
  3. Hamstring tightness
  4. Stork 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
  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. Single photon emission computed tomography (SPECT)
    1. Most sensitive for Spondylolysis
    2. Consider for nondiagnostic XRay
  2. 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. Relative rest period with no sports activity
    1. Chronic Spondylolysis: Rest until no pain
    2. Acute Spondylolysis: Rest minimum of 3 months
  2. Adjunctive measures
    1. Bracing could be considered at 3 weeks of rest
    2. Consider repeat CT to survey acute injury for healing
  3. Rehabilitation program
    1. Spine stabilization (flexion, hamstring, core muscle)
    2. Low-impact aerobics
    3. Progress to sport-specific activity
  • Management
  • Orthopedics or spine surgery referral indications
  1. Spondylolysis refractory to above management
  • Complications