The efficacy and safety of decompression with interspinous fixation for lumbar spondylolisthesis when compared with posterior lumbar interbody A pilot study

Authors: Seong-Chan Jung, Ji-Ho Jung, Jong-Hwan Hong, Moon-Soo Han, Shin-Seok Lee, Jung-Kil Lee

Abstract

Posterior lumbar interbody fusion (PLIF) is widely used to treat degenerative spondylolisthesis because it provides definitive decompression and fixation. Although it has several advantages, it has some disadvantages and risks, such as paraspinal muscle injury, potential intraoperative bleeding, postoperative pain, hardware failure, subsidence, and medical comorbidity. Lumbar decompressive bilateral laminectomy with interspinous fixation (DLISF) is less invasive and can be used on some patients with PLIF, but this has not been reported. To compare the efficacy and safety of DLISF in the treatment of low-grade lumbar spondylolisthesis with that of PLIF. We retrospectively analyzed the medical records of 81 patients with grade I spondylolisthesis, who had undergone PLIF or DLISF and were followed up for more than 1 year. Surgical outcomes, visual analog scale, radiologic outcomes, including Cobb angle and difference in body translation, and postoperative complications were assessed. Forty-one patients underwent PLIF, whereas 40 underwent DLISF. The operative times were 271.0 ± 57.2 and 150.6 ± 29.3 minutes for the PLIF and DLISF groups, respectively. The estimated blood loss was significantly higher in the PLIF group versus the DLISF group (290.7 ± 232.6 vs 122.2 ± 82.7 mL, P < .001). Body translation did not differ significantly between the 2 groups. Overall pain improved during the 1-year follow-up when compared with baseline data. Medical complications were significantly lower in the DLISF group, whereas perioperative complications and hardware issues were higher in the PLIF group. The outcomes of DLISF, which is less invasive, were comparable to PLIF outcomes in patients with low-grade spondylolisthesis. As a salvage technique, DLISF may be a good option when compared with PLIF.

1. Introduction

Posterior lumbar interbody fusion (PLIF) is widely used to treat degenerative spondylolisthesis because it provides definitive decompression and fixation. Its advantages include excellent nerve root visualization and the possibility for direct decompression, immediate postoperative stability, maintenance of intervertebral height, and 360-degree fusion through a single incision. However, it also has several disadvantages, such as paraspinal muscle injury, potential intraoperative bleeding, delayed postoperative recovery, postoperative pain, long hospital stay, hardware failure, subsidence, dural injury, cerebrospinal fluid leakage, direct root injury, infection, and medical comorbidity. From a less invasive point of view, some studies have reported favorable outcomes when decompression surgery is used alone for lumbar spondylolisthesis, but there is controversy over the possibility of spondylolisthesis progression and the risk of reoperation. Interspinous fixation (ISF) devices were proposed 30 years ago as a way of restricting posterior movement by fixing 2 adjacent spinous processes with a fixation device. Although the replacement of posterior screw fixation with ISF devices during vertebral fusion surgery has exhibited positive results, it is not widely used. In particular, lumbar decompressive bilateral laminectomy with interspinous fixation (DLISF) has not been reported. This pilot study compared the therapeutic effects of DLISF with those of PLIF in lumbar spondylolisthesis treatment.

2. Materials and methods

2.1. Study design and population

This study was approved by the Institutional Review Board of Chonnam National University Medical School Research Institute (Approval No. CNUH-2021-456). This retrospective study involved 81 patients who underwent DLISF or PLIF from November 2015 to September 2022. Included cases met the following diagnosis with single-level grade I degenerative lumbar spondylolisthesis; and persistent back pain and leg-radiating pain with suspicious traversing radiculopathy and/or neurogenic claudication despite conservative treatment for more than 6 weeks. Patients with non-degenerative types of spondylolistheses, such as trauma, and those with a follow-up period of less than 6 months, were excluded. Digital medical records were reviewed to obtain data on demographics, medical history, operation level, complications, operative time, and estimated blood loss. Preoperative lumbar computed tomography and magnetic resonance imaging data were assessed. Dynamic and static radiographs taken before surgery and 12 months after surgery were also evaluated. Clinical outcomes were assessed based on preoperative, postoperative, and 12-month post-surgery visual analog scale (VAS) data for the back and legs.

2.2. Surgical technique

All surgical procedures were performed at our institution by 2 surgeons and the chosen surgical procedure depended on the surgeon’s preference. PLIF was carried out using the usual method. Briefly, a midline incision was made, followed by subperiosteal dissection from the spinous process and the bilateral facet. Decompressive laminectomy, bilateral facetectomy, and additional decompression were then performed for both roots. This was followed by discectomy and endplate preparation followed by an interbody cage insertion and transpedicular screw fixation.

DLISF was performed using decompressive laminotomy and ISF using a fixation device (SPIRE, Medtronic, Dublin, Ireland, Fig. 1) made up of 2 titanium plates with spikes. After midline incision and bilateral subperiosteal dissection from the spinous process and lower lamina, decompressive laminotomy was performed using the usual method. Briefly, the hypertrophic ligamentum flavum and medical facet were removed on both sides. After confirming decompression on both traversing roots, 2 plates of the ISF device were used to longitudinally compress the upper and lower spinous processes together (Fig. 2).

2.3. Radiologic assessments

Preoperative and 1-month and 12-month postoperative lumbar spine radiographs were acquired. To evaluate segmental motion, the Cobb angle difference (CAd), body translation (BT), body translation difference (BTd), and disc height were measured.

The Cobb angle is the angle between 2 tangents drawn along the upper and lower endplates of the upper and lower end vertebrae. CAd is the difference in Cobb angle during flexion and extension of the surgical segment (Fig. 3).

BT is the distance between the point where the line extending the posterior margin of the upper vertebral body touches the upper endplate of the lower vertebral body, and the posterior end of the upper endplate of the lower vertebral body at the surgical segment. The difference in BT between flexion and extension is known as the BTd (Fig. 3).

Disc height refers to the distance between the upper and lower endplate midpoints.

All parameters were measured at 1.5× magnification. The mean of the values obtained by 2 researchers was used to reduce inter-observer variability.

2.4. Statistical analyses

Data were analyzed on SPSS version 18.0 (IBM Corp., Armonk, New York, USA). Differences in nominal variables were compared using the chi-square test. For continuous variables, eg, and radiologic differences, between-group differences were compared using the Student t test. P < .05 indicated statistically significant differences.

3. Results

This study involved 81 patients. Of these, 41 underwent PLIF (mean 71.7 years), whereas 40 underwent DLISF (mean 70.7 years). Baseline data (age, sex, follow-up duration, bone mineral density, and underlying disease) did not differ significantly between the 2 groups. The patients’ demographic data are presented in Table 1.

The mean operative time in the DLISF group was significantly lower than in the extended PLIF group (150.6 ± 29.3 vs 271.0 ± 57.2 minutes, *P < *.001). Intraoperative blood loss was also significantly lower in the DLISF group than in the extended PLIF group (122.2 ± 82.7 vs 290.7 ± 232.6 mL, P < .001). The operative data are summarized in Table 2. Three complications (1 case of non-ST-elevation myocardial infarction and 2 cases of surgical site infection) occurred in the DLISF group (7.5%). For only 1 case, symptomatic progression of spondylolisthesis followed revision and PLIF in postoperative 6 months. Seven complications (17.0%) were reported in the PLIF group. Two cases of surgical complication involved screw pullout and revision was performed. Six medical complications, including 1 mortality, involved urinary tract infection, electrolyte imbalance, acute asthma exacerbation, and small bowel perforation. The overall complication rate was higher in the PLIF group than in the DLISF group, although the difference was not statistically significant (P > .193).

Clinical outcomes improved significantly in both groups (P < .001). In the DLISF and PLIF groups, the preoperative mean back VAS scores were 5.4 ± 0.4 and 6.6 ± 0.4, respectively, the 1-month postoperative mean back VAS scores were 3.0 ± 0.5 and 3.6 ± 0.5, respectively, and the 12-month mean back VAS scores were 3.1 ± 0.5 and 3.5 ± 0.5, respectively. In the DLISF and PLIF groups, the preoperative mean leg VAS scores were 7.8 ± 0.4 and 7.4 ± 0.4, respectively, the 1-month postoperative mean leg VAS scores were 3.0 ± 0.5 and 3.6 ± 0.5, respectively, and the 12-month mean leg VAS scores were 3.1 ± 0.5 and 3.5 ± 0.5, respectively. After surgery, the VAS scores improved in both groups and clinical outcomes did not differ significantly between the 2 groups (Table 3).

The CAd values were significantly improved in both groups (P < .001). In the DLISF and PLIF groups, the preoperative CAd values were 8 ± 0.6° and 8.3 ± 0.5°, respectively, the 1-month postoperative Cad values were 4.9 ± 0.6° and 2.4 ± 0.5°, respectively, and the 12-month postoperative CAd values were 2.6 ± 0.6° and 1.5 ± 0.5°, respectively. In the DLISF and PLIF groups, the preoperative BTd values were 2 ± 0.2 mm and 1.4 ± 0.2 mm, respectively, the 1-month postoperative BTd values were 1.1 ± 0.2 mm and 1.2 ± 0.2 mm, respectively, and the 12-month BTd values were 0.8 ± 0.2 mm and 1.0 ± 0.2 mm, respectively. The BTd improved in both groups after surgery (P < .014). The radiologic outcomes in the 2 groups were not significantly different 12 months after surgery (Table 3).

4. Discussion

Although PLIF is widely used to treat degenerative lumbar spinal diseases with segmental instability, it is associated with various complications, such as muscle traction injury, nerve injury, deep wound infection, cerebrospinal fluid leakage, and postoperative pain.^[1,2]^ Because of the complex perioperative complications associated with PLIF, various less invasive strategies for reducing comorbidity have been developed, including transforaminal lumbar interbody fusion or laminectomy alone. Although laminectomy without posterior fixation exhibits relief from radiating pain and neurogenic claudication symptoms, there are concerns about the risk of spondylolisthesis progression. A systematic review reported that the overall incidence of increased postoperative spondylolisthesis was 12.6% and that the reoperation rate for instability was 9.3%.^[3]^ In patients with spondylolisthesis, laminectomy alone does not seem to be a suitable PLIF replacement because of the risk of slip progression.

The concept of ISF has been studied for several years. As early as 2006, biomechanical tests using cadavers highlighted the efficacy of combining interbody fusion and ISF.^[4]^ To inhibit spondylolisthesis progression, ISF constrains both anterior and posterior lumbar movements, thereby augmenting the functionality of the posterior ligamentous complex. Biomechanical testing has demonstrated that ISF provides immediate rigid fixation of the destabilized lumbar motion segment.^[4]^ Long-term results indicate that using ISF only is associated with less back pain, probably because of ISF’s stabilizing effect at the target level in the lumbar spine. However, the radiating pain and function outcomes did not improve significantly and the reoperation rates were substantially higher than in the decompression group after 1 (29% vs 8%) and 2 years (33% vs 8%).^[5]^ For lumbar spondylosis, ISF alone is limited in improving lower extremity symptoms, and decompression should be considered to improve radicular symptoms. Some studies have also used ISF instead of screws as a posterior fixture in lumbar body fusion surgery. Kim et al reported that ISF had good clinical results for single-segment fusion in spondylosis, as well as better results in ASD when compared with screws.^[6]^ Over a 3-year follow-up, Bae et al^[7]^ reported that using ISF during fusion extension in ASD had good clinical results. However, a meta-analysis by Lopez et al^[8]^ compared ISF with various types of fusion and posterior fixation but the level of evidence was low, and they did not draw clear conclusions.

Our study is unique because it compares the efficacy of PLIF versus decompression without fusion and ISF for low-grade spondylolisthesis for the first time. We found that ISF application after decompression may slow down or halt the progression of spondylolisthesis in patients considered for fusion. After a 12-month follow-up, we observed good clinical outcomes without significant slippage progression of spondylolisthesis. However, the 2 groups differed significantly in vacuum disc and disc height. The choice of surgical procedure was influenced by the surgeon’s experience and preference, as well as the degree of disc viability before surgery. There was a tendency to select fusion when the disc was relatively severely degenerated and collapsed. When the disc was preserved, there was a tendency to select DLISF. The improvements in slippage, back VAS, and leg VAS were well maintained 1 year after surgery in both groups. DLISF may be a surgical option for low-grade spondylolisthesis if the disc is relatively preserved.

Despite the higher fusion rate, we found that PLIF’s overall risk of complications was approximately 17%. Complications like hardware problems, including screw violation, screw loosening, or medical problems in the PLIF group occurred. A meta-analysis found that the PLIF’s risk of perioperative complications reaches 17%.^[9]^ The complications associated with PLIF include infection, neurological injury, and implant failure. In contrast, the DLISF group had fewer complications, at an overall complication rate of 7.5% (2 cases of surgical site infection and 1 case of non-ST-elevation myocardial infarction). Recent studies suggest that ISF procedures may be associated with a lower incidence of significant complications.^[10]^ Although minor complications like fluid collection or medical problems may still occur, their incidence is generally low.

Our research results suggest that DLISF is associated with a shorter operating time, less blood loss, and a lower incidence of blood transfusion when compared with PLIF. These findings may have implications for reducing the morbidity and cost of spinal fusion surgery. For specific patient groups, such as elderly patients with multiple comorbidities and a high risk of prolonged general anesthesia, DLISF may be a less invasive option involving a shorter surgical time. Thus, it is worth considering it as an alternative salvage technique.

This pilot study is limited by its retrospective design, which has the potential for bias, the lack of long-term follow-up, and a small sample size. Nevertheless, as a pioneer study on DLISF, it has value as a potential salvage technique for groups at risk of PLIF complications. Future research, such as prospective comparative studies, may reveal the long-term outcomes and indications of DLISF.

5. Conclusion

Traditionally, degenerative spondylolisthesis is mainly treated through spinal fusion. However, DLISF, a less invasive treatment method, has been suggested as an alternative for patients with preserved discs, especially elderly patients and those with underlying medical conditions. Although PLIF is effective in providing stability and arthrodesis, DLISF may be considered a salvage surgical option for degenerative spondylolisthesis grade I patients with preserved disc and comorbidities or older patients.

Acknowledgments

This study was supported by a grant (BCRI24021) of Chonnam National University Hospital Biomedical Research Institute, Gwangju, Korea.

Author contributions

**Writing – original ** Seong-Chan Jung.

Conceptualization: Jung-Kil Lee.

**Formal ** Jong-Hwan Hong.

Methodology: Moon-Soo Han.

Investigation: Ji-Ho Jung.

**Funding ** Shin-Seok Lee.