Lumbar Retrolisthesis in Aging Spine What are the Associated Factors?

Study Design: A retrospective radiographic study. Objective: The aim of this study is to demonstrate that lumbar retrolisthesis serves as an important compensatory mechanism and to identify the possible factor related to lumbar retrolisthesis. Summary of Background Data: Lumbar instability is one of the common degenerative changes, which presents as 2 radiologic features: anterolisthesis and retrolisthesis. Compared with the extensive studies on anterolisthesis, limit data are available on the characteristics and clinical relevance of lumbar retrolisthesis. Materials and Methods: In this study, 105 adult patients with low back pain were prospectively recruited, of which 60 patients had retrolisthesis (group 1) and 45 patients had anterolisthesis (group 2). Another 40 healthy age-matched adults (group 3) were also included to serve as the control group. Sagittal spinopelvic parameters were measured from the standing lateral radiograph, including thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), sacrum slope (SS), pelvic tilt (PT), sagittal vertical axis (SVA), spinosacral angle (SSA), and C7 tilt (C7T). In addition, disk degeneration was quantitatively evaluated by Pfirrmann score on T2-weighted magnetic resonance images in patients with retrolisthesis. Results: For all the sagittal parameters, SVA, PI, SS, and LL in retrolisthesis group were found to be significantly lower than those in the anterolisthesis group and in the control group, respectively (P< 0.05), whereas TLK in retrolisthesis group was significantly larger than other 2 groups (P< 0.01). In addition, the average Pfirrmann disk score was 2.11 at levels with retrolisthesis indicating that the disks were not severely degenerated. Conclusions: Lumbar retrolisthesis, together with thoracolumbar kyphosis, appears to be associated with mechanisms associated with regulation of sagittal balance. Low PI and disk instability due to degeneration may contribute to the development and progression of retrolisthesis.