Abstract:

BACKGROUND: Lumbar spondylolisthesis directly reduces contact areas between dislocated vertebral body and subjacent vertebral body, which is an important factor that decides intervertebral stress and lumbar degeneration. The cross section of lumbar is irregular reniform shaped and there is no mathematical formula to calculate changing regularity of intervertebral contact areas of lumbar spondylolisthesis directly.
OBJECTIVE: To study changing regularity of intervertebral contact areas during lumbar spondylolisthesis and to analyze its clinical significance. 
METHODS: Super-surface of L5 vertebra and sub-surface of L4 from 25 cases were taken by a digital camera and computer simulation spondylolisthesis process and every intervertebral contact areas (Sn) were measured by Image-Pro Plus software. The mean value was obtained and converted into percentage area according to Sn%=Sn/S×100%. The change rules of vertebral bodies were observed from 0 to 100% spondylolisthesis. Based on this regularity, a new clinical stage of lumbar spondylolisthesis was proposed and guided for treatment of 56 cases with lumbar spondylolisthesis.
RESULTS AND CONCLUSION: During lumbar spondylolisthesis process, Sn% changes like a hyperbola. Sn% lost slowly during spondylolisthesis rate at 0-23% and quickly during 23%-44%, and then it become slowly once again after spondylolisthesis rate at 44%-100%, the inflection points appeared at (23±2)% and (44±2)%. Totally 48 patients were followed up, according to Staufee standard rate, the clinical curative effect reached approximately 90%. It suggests that the intervertebral contact areas present with a non-linear change, which is helpful to judge the stability of lumbar spine and guide the treatment of lumbar spondylolisthesis.