A radiographic analysis of degenerative spondylolisthesis at the L4-5 level

Lumbar degenerative spondylolisthesis (LDS) is common and has generally been characterized as a homogeneous disease entity in the literature and in clinical practice. Because disease variability has not been carefully characterized, stratification of treatment recommendations based on scientific evidence is currently lacking. In this study, the authors analyzed radiographic parameters of patients with LDS at the L4-5 level to better characterize this entity.

Demographic data were collected from 304 patients (200 women and 104 men) with LDS at the L4-5 level. Plain radiographs including anteroposterior, lateral, and flexion-extension lateral radiographs were analyzed for disc height, segmental angulation, segmental translation, and osteophyte formation. Correlations were sought between the variables of age, sex, disc height, segmental angulation, segmental translation, and osteophyte formation.

The mean patient age was 63.8 years (range 40-86 years). The mean mid-disc height was 7 mm (range 0-14 mm) on the neutral lateral view. The mean angulation between the superior endplate of L-5 and the inferior endplate of L-4 was 6° of lordosis (range 13° of kyphosis to 23° lordosis) on the neutral lateral view. The mean angular change between flexion and extension lateral radiographs was 5° (range 0°-17°). The mean translation on the neutral lateral view was 6 mm (range 0-15 mm). The mean change in translational between flexion and extension was 2 mm (range 0-11 mm). Twenty patients (7%) exhibited spondylolisthesis only on the flexion view. A significant positive correlation was found between the change in angulation and the change in translation on flexion and extension views (ρ = 0.18, p = 0.001). No significant correlation was found between anterior osteophyte size and mobility with flexion-extension radiographs.

The wide range in all radiographic parameters for LDS confirms the heterogeneous nature of this condition and suggests that a grading system to subclassify LDS may be clinically useful. On flexion and extension radiographs, increased translational motion correlated with increased angular motion. Anterior osteophyte size was not found to be predictive of segmental stability. This data set should prove beneficial to those seeking to subcategorize LDS in the future.