What is Grade I Spondylolisthesis?
Grade I spondylolisthesis is defined as forward displacement of one vertebra over the adjacent vertebra by 0-25% of the vertebral body width, representing the mildest degree of slippage on the Meyerding classification system. 1
Classification and Grading
The Meyerding classification grades spondylolisthesis based on the percentage of vertebral body slippage seen on lateral standing radiographs: Grade I (0-25%), Grade II (25-50%), Grade III (50-75%), Grade IV (75-100%), and Grade V (>100%, also called spondyloptosis). 1
Grades I and II are considered "low-grade" spondylolisthesis, while Grades III-V are considered "high-grade." 1
The forward slippage occurs when anatomical structures that normally resist anterior displacement are compromised, including the posterior facets, neural arch, pedicle, and intervertebral disc. 2
Common Types and Locations
Isthmic spondylolisthesis is the most commonly seen type clinically, involving a defect in the pars interarticularis of L5 with resultant slippage of L5 on S1. 2
Degenerative spondylolisthesis arises from remodeling of the facet joints and most commonly occurs at the L4-5 level in women over age 40. 2, 3
Degenerative spondylolisthesis is defined as displacement of one vertebra over the subjacent vertebra associated with degenerative changes, without an associated disruption or defect in the vertebral ring. 3
Clinical Significance
Grade I spondylolisthesis is a common cause of low back pain, radiculopathy, and neurogenic claudication in adults. 3, 4
Plain radiographs can reveal the structural change, though they are not helpful for diagnosing most other causes of low back pain. 2
The degree of slippage does not always correlate with symptom severity, and many patients with Grade I spondylolisthesis may be asymptomatic. 2