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

Disclosures

Spine. 2021;46(16):E893-E900. 

In This Article

Results

LSS Group

The demographic data of the LSS group are shown in Table 1. Their mean age at the time of surgery was 64.9 years, and 63.0% (17/27) were women. Preoperative MRI demonstrated Modic I changes in 11 patients (40.7%), Modic II changes in 14 patients (51.9%), and Modic III changes in two patients (7.4%) at the uppermost disc within fixed vertebrae. According to the Pfirrmann classification, we had six patients with grade III, 16 patients with grade IV, and five patients with grade V at the uppermost disc within fixed vertebrae. Two-level surgery was performed in 13 patients, one-level surgery in eight patients, three-level surgery in five patients, and four-level surgery in one patient at index levels. The mean follow-up period was 110.2 ± 41.7 months (range, 60–152 months).

Radiographic parameters are shown in Table 2. The disc height at index level increased after DS surgery and was maintained well until the last follow-up, without a significant change (P = 0.312). Segmental lordosis at the index level also increased and was maintained well until the last follow-up, with no significant change (P = 0.387). Segmental ROM at the index level decreased after DS surgery (P < 0.001). The disc height at the proximal adjacent level decreased continuously from the preoperative examination to the last follow-up, but with no significant change (P = 0.168). The segmental lordosis at the proximal adjacent level likewise decreased steadily from the preoperative examination to the last follow-up, but without a significant change (P = 0.142). Segmental ROM at the proximal adjacent level increased from 9.9° ± 2.9° preoperatively to 10.3° ± 2.5° at the postoperative 2-year follow-up and was maintained well at the last follow-up, with no significant change (P = 0.337). Global lordosis decreased continuously from 38.4° ± 5.5° preoperatively to 35.9° ± 5.8° at the last follow-up, without a significant change (P = 0.159). Global ROM also decreased steadily from 23.2° ± 3.0° preoperatively to 21.1° ± 4.0° at the last follow-up, with no significant change (P = 0.135).

Spondylolisthesis Group

The spondylolisthesis group showed slightly more degenerative changes than the LSS group (Table 3). At the uppermost disc within fixed vertebrae, Modic II changes were most common (52.6%) on preoperative MRI, followed by Modic I (39.5%) and Modic III (7.9%). According to the Pfirrmann classification, we had three, 26, and nine patients with grades III, IV, and V, respectively. One-level surgery was performed in 23 patients, two-level surgery in 10 patients, three-level surgery in four patients, and four-level surgery in one patient (2.6%). The mean follow-up duration was 89.0 ± 27.6 months (range, 60–148 months).

Radiographic parameters except for segmental ROM at the index level were maintained well over five years postoperatively (Table 4). Global lordosis slightly decreased from 36.5° ± 8.2° preoperatively to 36.0° ± 9.3° at the postoperative 2-year follow-up and further decreased to 32.6° ± 6.0° at the last follow-up (P = 0.039). Global ROM decreased continuously from 22.1° ± 6.9° preoperatively to 18.8° ± 7.1° at last follow-up (P = 0.012).

Clinical Outcome

Clinical outcomes, including back pain, leg pain, and ODI, significantly improved and were maintained well until the last follow-up in both groups without significant difference (Figure 2A–C). In LSS group, back pain decreased from 6.5 ± 1.9 preoperatively to 3.2 ± 1.6 at the postoperative 2-year follow-up and was maintained well at the last follow-up. Leg pain decreased from 7.0 ± 1.6 preoperatively to 3.5 ± 1.4 at the postoperative 2-year follow-up and was maintained well at the last follow-up. The ODI also decreased from 41.9 ± 5.5 preoperatively to 18.8 ± 6.7 at the postoperative 2-year follow-up and was maintained well at the last follow-up. In spondylolisthesis group, back pain, leg pain, and ODI significantly improved at the postoperative 2-year follow-up and were maintained well until the last follow-up. The radiographs of a typical patient are shown in Supplement Figure 1, http://links.lww.com/BRS/B763.

Figure 2.

Clinical outcomes, including back pain (A), leg pain (B), and ODI (C), significantly improved and were maintained well until the last follow-up in the lumbar spinal stenosis and spinal stenosis with spondylolisthesis group. There were no significant differences between the two groups during the study period. ODI indicates Oswestry Disability Index; VAS, visual analog scale.

Complications

There were no significant differences in the occurrence of postoperative complications between the LSS group and the spondylolisthesis group. Screw loosening without clinical symptoms occurred in three patients (11.1%) in the LSS group and five patients (13.2%) in the spondylolisthesis group. Among them, four patients had a normal bone density, three had osteopenia, and one had osteoporosis on the BMD test. Radiographic and symptomatic ASD occurred in four patients (14.8%) and two patients (7.4%) in the LSS group, and five patients (13.2%) and three patients (7.9%) in the spondylolisthesis group, respectively. There was one reoperation in the spondylolisthesis group due to symptomatic ASD (Supplement Figure 2, http://links.lww.com/BRS/B763).

Multivariable analysis revealed that Pfirrmann grade > III at proximal adjacent level (adjusted odds ratio = 2.815; 95% confidence interval, 1.491–7.329; P = 0.021), Pfirrmann grade > III at uppermost disc within fixed vertebrae (adjusted OR = 2.391; 95% CI, 1.429–5.265; P = 0.011), and BMI ≥25 kg/m2 (adjusted OR = 1.197; 95% CI, 1.186–6.444; P = 0.043) could significantly increase the occurrence of radiographic ASD after DS surgery (Table 5).

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