Dynamic Stabilization Surgery in Patients With Spinal Stenosis

Long-Term Outcomes and the Future

Jong-myung Jung, MD; Seung-Jae Hyun, MD, PhD; Ki-Jeong Kim, MD, PhD; Tae-Ahn Jahng, MD, PhD


Spine. 2021;46(16):E893-E900. 

In This Article

Materials and Methods

Between April 2005 and August 2017, 120 consecutive patients underwent decompression and DS by a single surgeon (T.A.J.) at a single institution (Figure 1). Patients who underwent DS surgery for LSS with herniated intervertebral disc, LSS with degenerative lumbar scoliosis exceed 30° and failed back surgery syndrome were excluded. Given the lack of consensus about whether LSS and LSS with spondylolisthesis patients differ clinically, the patients were divided into an LSS group and a spondylolisthesis group according to the presence of degenerative spondylolisthesis. Patients who underwent hybrid surgery combined with fusion and had <5 years of follow-up were also excluded from this study. Ultimately, 65 patients were included in the present study.

Figure 1.

Flow chart of the study participants. HIVD indicates herniated intervertebral disc.

Demographic characteristics, radiographic parameters, and surgical factors were reviewed, including age, sex, body mass index (BMI), bone mineral density (BMD), Modic type, Pfirrmann grade, and follow-up period. The follow-up period was calculated as extending from the date of DS surgery to the date of the last follow-up radiograph.

All patients underwent preoperative standing lumbar spine x-rays and magnetic resonance imaging (MRI) examinations. Plain radiographs (anteroposterior and lateral) and dynamic radiographs (lateral flexion and extension views) were taken preoperatively and at every postoperative follow-up visit. The radiographic analysis included disc height at index level and the proximal adjacent level, segmental lordosis at the index level and the proximal adjacent level, global lordosis, segmental range of motion (ROM) at the index level and the proximal adjacent level, and global ROM. The disc height was defined as the mean of the anterior and posterior disc heights on lateral radiographs. Global lordosis was defined as the intersection of the line extending from the superior endplate of L1 and the superior endplate of S1. Segmental ROM was defined as the difference between the segmental angle in flexion and extension. Global ROM was calculated as the difference between the global lordotic angle in flexion and extension.

Clinical outcomes were evaluated using visual analog scales (VAS) for back and leg pain and the Oswestry Disability Index (ODI) preoperatively, at 2 years postoperatively, and the final follow-up.

Postoperative complications, such as screw loosening and ASD, were also noted. The occurrence of radiographic and symptomatic ASD was also evaluated, as described in a previous study.[16] Radiographic ASD was defined by the presence of one or more of the following three radiographic criteria at the level immediately above the fusion, comparing immediate postoperative and 1-year follow-up radiographs: ≥3 mm anteroposterior translation, ≥50% loss of disc height, and the onset of ≥10° segmental kyphosis.

The review of radiologic assessments did not involve the operating surgeons. All the radiological assessments were evaluated by two independent spine surgeons blinded to the study information. One spine surgeon measured all of the parameters twice with a 7-day interval. Another spine surgeon measured all of the parameters independently again. The intra- and interobserver reliability were assessed based on an interrater correlation coefficient.[17] The interrater correlation coefficient values were 0.98 within the observer and 0.94 between observers. The average of the three measured values was used for the analysis. Informed consent was waived due to the retrospective design and minimal risk of the study, which received approval from the institutional ethics review board of the hospital.

Statistical Analysis

The paired t test was used to assess differences in radiologic and clinical status from the preoperative (baseline) examination to the final follow-up. The differences in proportions for postoperative complications between the groups were evaluated using the Fisher exact test. Logistic regression analysis was performed to assess for independent demographic, radiographic, and surgical factors associated with radiographic ASD. The linear assumption for continuous confounders in the logistic regression was checked by restricted cubic splines. Odds ratios were reported as (odds ratio [OR] [95% confidence interval {CI}]), with significance set at P < 0.05. SPSS version 25 (IBM Corp., Armonk, NY) was used for all data analyses.