Grade 1 Anterolisthesis at L4 and L5
Grade 1 anterolisthesis at L4 and L5 refers to a forward slippage of the fourth lumbar vertebra (L4) over the fifth lumbar vertebra (L5), where the vertebral body has shifted forward by less than 25% of the vertebral body width. This represents the mildest degree of vertebral slippage on the Meyerding classification scale.
Definition and Classification
Grade 1 anterolisthesis specifically indicates 0-25% forward displacement of the superior vertebra relative to the inferior vertebra, distinguishing it from higher grades (Grade 2: 26-50%, Grade 3: 51-75%, Grade 4: 76-100%) 1.
The L4-L5 level is one of the most common sites for spondylolisthesis in the lumbar spine, second only to L5-S1 2.
Anterolisthesis (forward slippage) accounts for approximately 38.49% of all vertebral slippages, with Grade 1 representing 95.71% of all anterolisthesis cases 2.
Clinical Significance
Grade 1 anterolisthesis at L4-L5 is clinically significant when combined with symptoms, failed conservative management, and documented instability, as it represents a risk factor for progressive deformity and clinical failure after decompression procedures 3.
Preoperative spondylolisthesis (including Grade 1) is identified as the main risk factor for 5-year clinical and radiographic failure in patients undergoing lumbar decompression, with progression rates ranging from 9% to 73% depending on baseline stability 3.
The presence of any degree of spondylolisthesis, even Grade 1, constitutes documented spinal instability that warrants consideration of fusion in addition to decompression when surgical intervention is indicated 1.
Diagnostic Considerations
Dynamic lateral flexion-extension radiographs are essential to identify subtle forms of preoperative spinal hypermobility or instability that may not be apparent on static imaging 3.
Grade 1 slippage may be associated with foraminal stenosis, disc degeneration, or facet joint pathology that contributes to clinical symptoms 1.
The mechanical nature of symptoms (pain worse with standing/walking, relieved by sitting/bending forward) indicates dynamic instability at the affected level 1.
Treatment Implications
Surgical fusion is specifically recommended when Grade 1 anterolisthesis is present with symptomatic stenosis requiring decompression, as decompression alone carries higher rates of progressive slippage and clinical failure 3, 1.
Conservative management should include comprehensive physical therapy for at least 6 weeks, anti-inflammatory medications, and potentially epidural steroid injections before considering surgical intervention 1.
When fusion is indicated for Grade 1 anterolisthesis at L4-L5, instrumented fusion with pedicle screws provides optimal biomechanical stability with fusion rates up to 95% 1.
Common Pitfalls
Failing to recognize Grade 1 anterolisthesis as a significant risk factor for postoperative instability can lead to inadequate surgical planning and higher failure rates 3.
Performing wide decompression or extensive facetectomy without fusion in the presence of Grade 1 anterolisthesis may result in iatrogenic destabilization and progressive deformity 3.
Static imaging alone may underestimate the degree of instability; dynamic studies are necessary to fully assess segmental motion 3.