Effects of Vacuum Disc Phenomenon on Degenerative Spondylolisthesis versus Isthmic Spondylolisthesis on Surgical Outcomes
Introduction: Vacuum phenomenon involves one or more intervertebral discs and can be caused by an accumulation of gas with the disc(s). It usually represents advanced disc degeneration. Since discs are integral to anterior spinal support, vacuum disc is considered to be a sign of instability. In addition, vacuum disc is associated with anterior displacement of a superior vertebral body over the inferior body (spondylolisthesis, spondylolytic spondylolisthesis).
Purpose: Retrospectively study the surgical outcomes of patients with degenerative or isthmic spondylolisthesis combined with an anterior vacuum disc. Patients in the study underwent posterior decompression, posterior screw instrumentation, and posterior lumbar fusion (PLF).
Methods: This retrospective study evaluated the medical records of patients with degenerative spondylolisthesis (DS) or isthmic spondylolisthesis (IS) who underwent surgical treatment between January 2008 and December 2010.
Forty-two patients made up two groups, which depended on whether they had DS (n=22) or IS (n=20). Average age in the DS group was 65.6 years and 57.3 years in the IS group (P<0.003). All patients demonstrated vacuum signs on extension radiographs; 8 in the IS group had vacuum sign on flexion.
Inclusion criteria included single level spondylolisthesis, vacuum phenomenon of the disc space of the spondylolisthesis (demonstrated on preoperative radiographs), surgical treatment consisting of posterior decompression, posterior pedicle screw fixation, and PLF, and at least 12 months of follow-up radiographs to assess the PLF rate. Specific parameters were set for radiographic evaluation and determination of fusion, which included use of independent blinded reviewers.
Clinical assessment utilized the Oswestry Disability Index (ODI) questionnaire before and after surgery. Brodsky’s criteria were utilized to assess patient self-reported satisfaction during final follow-up.
Results: The primary surgical segment in the DS group was L4-L5 and L5-S1 in the IS group. Three patients in the DS group and 2 in the IS group developed perioperative complications. During follow-up, 3 patients in the DS group and one in the IS group developed adjacent segment disease and underwent revision surgery. In the DS group the fusion rate was 56.8% and 90% in the IS group. Patients in both groups lost some degree of lordosis and disc height.
Conclusion: This study demonstrated there was more anterior instability in the DS group, higher fusion rate, but less satisfaction with the clinical outcome.
Lin TY, Liao JC, Tsai TT, Lu ML, Niu CC, et al. The Effects of Anterior Vacuum Disc on Surgical Outcomes of Degenerative versus Spondylolytic Spondylolisthesis: At a Minimum Two-year Follow-up. BMC Musculoskeletal Disorders. 2014;15:329.
The authors of this retrospective study reviewed vacuum disc findings on radiographs to determine if those findings could be used as an indicator of segmental instability and PLF outcomes in patients with DS or IS.
Given the higher nonfusion rate in the DS group, the authors hypothesized that since the DS group showed more instability on preoperative flexion and extension, presence of vacuum disc is a rough indicator of instability. They concluded that, in these patients, perhaps interbody fusion would help to increase stability as well as the rate of fusion.