Clinical application of a novel assessment for lumbosacral stability.
OBJECTIVE
To evaluate the grade of lumbosacral stability, shape analysis was conducted on plain radiographs of the lumbar spine.


METHODS
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.


RESULTS
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.


CONCLUSIONS
Stability at the lumbosacral junction was thought to be quantitatively represented by the z score, with z being designated the lumbosacral stability score.
Ohmori
Kazuo
K
Department of Orthopedic and Spinal Surgery, Nagoya, Daini Red Cross Hospital, Nagoya, Japan. caz-fb27@hotmail.co.jp
D000328:Adult; D000368:Aged; D001175:Arthrography / Q000379:methods* / Q000592:standards*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging*; D007593:Joint Instability / Q000000981:diagnostic imaging*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011446:Prospective Studies; D015203:Reproducibility of Results; D012447:Sacrum / Q000000981:diagnostic imaging*; D012727:Sex Characteristics; D013168:Spondylolisthesis / Q000000981:diagnostic imaging; D055815:Young Adult