Application of standing flexion X-ray and supine MRI to evaluate degenerative lumbar spondylolisthesis segmental instability

English Keywords:Degenerative lumbar spondylolisthesis  Lumbar instability  Flexion -extension X-ray  Supine position MRI

English Abstract:

  【Abstract】 Objectives: To investigate the reliability and feasibility in evaluating degenerative lumbar vertebral instability through combined standing flexion X-ray with supine MRI. Methods: Retrospectively reviewed the 87 patients with degenerative lumbar spondylolisthesis treated in the spinal surgery department of Qilu Hospital of Shandong University(Qingdao) from January 2016 to June 2018. Among them, 67 cases were female and 20 cases were male, with an average age of 65.9±9.0 years(ranged from 47-87). Spondylolisthesis segment distribution: 10 cases at L3 segements, 66 cases at L4, and 11 cases at L5 segement. According to Meyerding classification, 82 cases were of degree Ⅰ, and 5 cases were of degree Ⅱ has. All the patients underwent flexion-extension X-ray in standing position and MRI in supine position. Image data were retrospectively analyzed through Picture Archiving and Communication System(PACS), including data of standing flexion position X-ray(F), extension position X-ray(E) and supine MRI(S). For the MRI image, T1 weighted and mid-sagittal were selected. The percentage of slip distance to the width of vertebral body was defined as slip percentage for analysis. The difference of slip percentage between F and E position, F and S position was defined as slip rate. Slip rate≥8% was defined as segmental instability. Results: The average slip percentage was the highest at F position(16.97±5.93)%, followed by E position(14.04±6.38)% and S position(9.89±5.34)%. There were significant statistical differences between the three positions (F-E: P<0.01; F-S, P=0.00; E-S: P=0.00). The average slip rate of F-S and F-E was (7.08±4.60)%(-0.49%-24.32%) and (2.93±3.29)%(-3.46%-11.24%) respectively, with significant statistical differences(P=0.00). Defining slip rate≥8% as the standard, 40 cases were diagnosed as segmental instability. Among them, F-S has 37 cases(92.5%), F-E has 7 cases(17.5%). Of the 7 cases shown segmental instability in F-E, 4 cases also showed instability in F-S, while the other 3 cases(7.5%) didn′t show instability in F-S. Conclusions: For the evaluation of segmental stability of degenerative lumbar spondylolisthesis, the application of standing flexion lateral X-ray combined with MRI in the supine position can better show segmental instability of the sliding segment than the X-ray of standing flexion-extension. The combination of standing flexion position X-ray and supine position MRI significantly improved the diagnostic sensitivity and reduced the rate of missed diagnosis.