Definition of Spondylolisthesis
Spondylolisthesis is defined as the displacement or misalignment of one vertebral body relative to an adjacent vertebra, most commonly involving forward slippage (anterolisthesis) of the upper vertebra on the lower one 1.
Key Anatomical and Clinical Features
The term derives from Greek: "spondylos" (vertebra) and "olisthesis" (sliding on a slope) 1. This spinal condition is characterized by:
- Forward or backward displacement of a vertebral body, predominantly affecting the lower lumbar spine 2
- Most common locations: L4/5 for degenerative type and L5/S1 for isthmic/nondegenerative type 3
- High prevalence: Found in approximately 20% of the adult population 3
Classification Components
A complete description of spondylolisthesis includes 1:
- Vertebral segment involved (which vertebrae)
- Degree of slippage (percentage of one vertebral body displaced over another)
- Direction of displacement (anterolisthesis vs. retrolisthesis)
- Etiology (degenerative, isthmic, dysplastic, traumatic, or pathologic)
Specific Subtypes
Degenerative Spondylolisthesis
Develops in adulthood, most commonly at L4/5 3
Isthmic Spondylolisthesis
Associated with spondylolysis (a defect or elongation in the pars interarticularis), which can be unilateral or bilateral 4. In children with bilateral spondylolysis, forward slipping may develop over time 4.
Clinical Significance
Patients with stenosis associated with spondylolisthesis typically present with neurogenic claudication, radiculopathy, and/or low-back pain 5. The condition creates inherent spinal instability that may progress after decompression, potentially leading to further misalignment and recurrent symptoms 5.