Causes / typical injury mechanism: Spondylolisthesis is the translation of a superior vertebral body relative to the inferior vertebra. This translation is most commonly anterior, referred to as anterolisthesis. It can result from congenital abnormalities (dysplastic), defects of the pars interarticularis (isthmic) due to spondylolysis, facet joint arthrosis (degenerative), trauma, neoplastic processes, or spinal surgery. It is most common in the lumbar spine.

Classic history and presentation: History and presentation vary by type, but the most common presenting symptom is long-standing, insidious mechanical back pain that is relieved with rest and sitting. Pain is often worse with walking (neurogenic claudication), and patients may describe numbness and/or tingling down the leg (radiculopathy). In the isthmic type, the classic history element is repetitive, forceful hyperextension of the low back (as seen in volleyball, gymnastics, and football). Other history elements include trauma, metastatic cancer, prior spine surgery, and osteoporosis. Many cases of spondylolisthesis are found asymptomatically. Cervical and thoracic spondylolisthesis are rare.

Prevalence: Depending on the type of spondylolisthesis, approximately 5% of the population is affected. Isthmic spondylolisthesis is the most common subtype, followed by the degenerative and dysplastic types, respectively.

• Age –
  • Isthmic spondylolisthesis is seen in all age groups and is the most common type in children and adolescents (bimodal distribution, ages 5-7 years and then during teenaged years). In pediatric patients, 85% of cases are of the isthmic subtype.
  • Degenerative spondylolisthesis is most common in adults (age older than 40 years).
  • The dysplastic type is seen in children.
  • Traumatic, neoplastic, and postsurgical spondylolisthesis are seen in all age groups.
• Sex / gender –
  • Isthmic and dysplastic spondylolisthesis are approximately twice as common in males.
  • Degenerative spondylolisthesis is 4-5 times more common in women.
  • There are no sex differences in the other types.

Risk factors: Risk factors include spondylolysis, family history of spondylolisthesis, elevated body mass index (BMI), increased pelvic incidence, spina bifida occulta, activities involving hyperextension and persistent lordosis (eg, gymnastics, weight lifting, diving, football, volleyball), osteoporosis, and slip angle over 50 degrees. Risk factors for the degenerative type include African descent, diabetes mellitus, and the presence of transitional L5 vertebrae.

Pathophysiology: Pathophysiology varies by type. In isthmic spondylolisthesis, a bilateral defect in the pars interarticularis (from stress fracture, remodeling, or trauma), known as spondylolysis, causes discontinuity between the anterior and posterior vertebral columns. Over time (or acutely in trauma), the vertebral body displaces ventrally once other supporting structures (ie, intervertebral disk, soft tissues) are no longer able to maintain normal structural integrity. In the degenerative subtype, disk degeneration leads to narrowing of the disk space and microinstability, which can progress to forward (anterolisthesis) or backward (retrolisthesis) slippage. In degenerative spondylolisthesis, the neural arch, and therefore the pars interarticularis, is intact.

Grade / classification systems:
Wiltse-Newman classification of spondylolisthesis (etiology).

• Type I: Dysplastic / congenital
• Type II: Isthmic
  • IIa – Stress fracture of pars interarticularis
  • IIb – Elongation of pars interarticularis (from repeated stress and bony remodeling)
  • IIc – Acute / traumatic fracture of pars interarticularis
• Type III: Degenerative
• Type IV: Post-traumatic (defects in posterior elements besides pars interarticularis fractures)
• Type V: Neoplastic
• Type VI: Iatrogenic / postsurgical

Myerding classification for severity of slip (percentage of slip compared to caudal vertebrae).

• Grade 1: 0%-25% (low grade)
• Grade 2: 25%-50% (low grade)
• Grade 3: 50%-75% (high grade)
• Grade 4: 75%-100% (high grade)
• Grade 5: > 100% (spondyloptosis)