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Pars Fracture | Pars Stress Reaction | Pars Defect (Spondylolysis)

What is Pars Fracture | Pars Stress Reaction | Pars Defect (Spondylolysis)?

A pars defect is a stress injury or fracture of the pars interarticularis, most commonly at L5, seen in young athletes and active adults. It can be a stress reaction (pre-fracture), an incomplete fracture, or a chronic non-healed defect, and may lead to isthmic spondylolisthesis if instability develops.

Symptoms

Symptoms are typically activity-related and localised.

  • Localised low-back pain that worsens with extension, rotation, or sport
  • Hamstring tightness and lumbar stiffness after activity
  • Occasionally radiating pain if nerve irritation occurs

Causes

Repetitive extension and rotation create cumulative stress on the pars.

  • Sports with hyperextension/rotation (cricket fast bowling, gymnastics, AFL, tennis)
  • Rapid growth periods and training load spikes
  • Structural predisposition such as lumbar hyperlordosis

Diagnosis

Early identification improves healing rates.

  • Clinical exam including extension-based pain provocation tests
  • Standing X-rays; oblique views may show a defect, but early stress reactions can be missed
  • MRI detects bone stress before a visible fracture; CT defines chronic defects or non-union

Treatment

  • Relative rest from extension sports, graded return-to-play plan
  • Physiotherapy focusing on core/hip stability and hamstring flexibility
  • Activity modification, taping/bracing in selected cases
  • Image-guided injections for pain control where needed
  • Surgical options (direct pars repair) considered for persistent pain with a discrete defect and preserved disc health; fusion is reserved for instability or slippage