To evaluate the grade of lumbosacral stability, shape analysis was conducted on plain radiographs of the lumbar spine.
One hundred twenty-six patients were classified into 2 groups: those with a single-segment disc space narrowing at L5–S1 or at L4–5. Stability was evaluated using the discriminant function (z score) derived from the analysis of radiographic parameters—that is, relative thickness of transverse process of L-5 and the sacral table angle.
In patients with a space narrowing at L5–S1, the author observed a significantly slender L-5 transverse process and acute obliquity of the sacral endplate; accordingly, the z score was negative. In patients with a broad transverse process and a positive z score, the segment associated with disc height loss was L4–5. Thus, a close correlation was found between the site of the disc height loss and the bony characteristics of L-5 and S-1. Furthermore, it could be expected with a high degree reliability that when young adult patients had a z score less than −2 or −3, their L-5 vertebra would develop degenerative spondylolisthesis after middle age and the L5–S1 segment could be saved from age-related alterations as long as the z score was greater than 2.5.
The constitutional characteristics of the lumbosacral junction may exert a major influence on the site of disc degeneration.
Stability at the lumbosacral junction was thought to be quantitatively represented by the z score, with z being designated the lumbosacral stability score.
Abbreviations used in this paper: LDF = linear discriminant function; RT = relative thickness; STA = sacral table angle.
RiihimäkiHMattssonTZittingAWickströmGHänninenKWarisP: Radiographically detectable degenerative changes of the lumbar spine among concrete reinforcement workers and house painters. Spine15:114–1191990
RiihimäkiH, MattssonT, ZittingA, WickströmG, HänninenK, WarisP: Radiographically detectable degenerative changes of the lumbar spine among concrete reinforcement workers and house painters. 15:114–119, 1990)| false