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Isthmic Spondylolisthesis

What is Isthmic Spondylolisthesis?

Isthmic spondylolisthesis is forward slippage of a vertebra due to a pars defect (spondylolysis), most often at L5–S1. Slippage can narrow the canal or foramina, compressing nerve roots and causing back pain or sciatica.

Symptoms

Severity relates to the grade of slip and nerve involvement.

  • Low-back pain worsened by standing, extension, or prolonged activity
  • Buttock or leg pain, tingling, or weakness from nerve compression
  • Hamstring tightness, reduced endurance, and occasionally altered gait

Causes

It develops from a pars defect that compromises posterior stability.

  • Chronic pars stress injury progressing to a defect
  • Repetitive extension sports during adolescence
  • Degenerative changes exacerbating foraminal narrowing over time

Diagnosis

Evaluation confirms slip severity and nerve involvement.

  • Physical exam assessing posture, flexibility, and neurological status
  • Standing lateral X-rays to grade slip percentage and pelvic parameters
  • MRI for nerve compression and disc health; CT for detailed bony assessment

Treatment

Care is individualised based on symptoms, slip grade, and goals.

  • Activity modification, physiotherapy (core/hip strength), and analgesia
  • Sport-specific load management and gradual return-to-play protocols
  • Image-guided injections for radicular pain in selected patients
  • Surgery considered for persistent pain, progressive slip, or neurological deficit, typically involving nerve decompression with stabilisation/fusion to prevent further slippage