A 38-year-old construction worker has a grade II isthmic spondylolisthesis at L5–S1 confirmed on lateral X-ray. The Meyerding classification is used. Which measurement defines each grade and what does 'isthmic' type specifically refer to?

• A Meyerding grade = degree of slip in millimetres; isthmic type involves facet joint arthropathy
• B Meyerding grade = total vertebral rotation in degrees; isthmic type is degenerative disc collapse
• C Meyerding grade = Cobb angle on standing X-ray; isthmic type is congenital posterior element hypoplasia
• D Meyerding grade = degree of slip expressed as percentage of vertebral body width; isthmic type involves a defect (lysis) in the pars interarticularis (spondylolysis) ✓

Explanation

Meyerding grading divides the superior surface of the inferior vertebral body into four equal quarters: Grade I = <25% slip, Grade II = 25–50%, Grade III = 50–75%, Grade IV = 75–100%, and spondyloptosis = >100% (complete dislocation). Isthmic spondylolisthesis (Wiltse type II) involves a stress fracture or elongation of the pars interarticularis (isthmus between superior and inferior facets), allowing forward translation without facet constraint. Degenerative type (Wiltse type III) involves intact pars with facet arthropathy.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.