The purpose of our study is to assess the degenerative changes in the motion segments above a L5S1 spondylolytic spondylolisthesis, and to analyse the factors that contribute towards a retro-listhesis in the segment immediately above the slip.

Prospective radiographic case series

38 patients with a symptomatic L5S1 spondylolytic spondylolisthesis, with a mean age of 52.8 yrs (95% CI 47.2 – 58.4). 55.3% (n = 21) were females and 44.7% (n = 17) males. 58% (22) had grade 1 and 42% (16) grade 2 slips.

Plain radiographs: Lumbar lordosis, slip angle, sacral slope, grade of the slip, and retro-listhesis at L45. MRI scans: facet angles at L34 and L45, facet degenerative score at L34 and L45 (cartilage and sclerosis), disc degenerative score at L45 and L5S1 (Pfirrmann).

The Pfirmann disc score for L45 was 2.75 and L5S1 4.4 (p < 0.0001); the mean facet angle at L34 50.9° and L45 57.9° (p = 0.001) and the facet score at L34 was 8 and at L45 was 10.5 (p = 0.0001). 29% (11) demonstrated a retrolithesis at L45. Analysing the effect of these factors on the causation of retro-listhesis at L45 (table) the slip angle and L45 disc degenerative score were the only factors that predicted a retro-listhesis.

There is a cascade of degenerative changes involving both the disc and the facet joints at the levels above a spondylolytic spondylolisthesis. The degenerative changes at the L45 disc and a higher slip angle predict a retro-listhesis at the level above the slip.