Posterior Lumbar Element Enforcement by Decompression Alone with Interspinous Fixation without Interbody Fusion for the Surgical Management of Lumbar Spondylolisthesis

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J Korean Neurosurg Soc. 2025;68(2):150-158

Publication date (electronic) : 2024 November 21

doi : https://doi.org/10.3340/jkns.2024.0172

Hyun-Woong Park¹, Moon-Soo Han², Ji-Ho Jung², Jong-Hwan Hong², Shin-Seok Lee³, Jung-Kil Lee^,2

¹Department of Neurosurgery, Gwangju Heemang Hospital, Gwangju, Korea

²Department of Neurosurgery, Chonnam National University Medical School & Research Institute of Medical Sciences, Gwangju, Korea

³Division of Rheumatology, Department of Internal Medicine, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea

Address for reprints : Jung-Kil Lee Department of Neurosurgery, Chonnam National University Hospital, 42 Jebong-ro, Dong-gu, Gwangju 61469, Korea Tel : +82-62-220-6602, Fax : +82-62-224-9865, E-mail : jkl@chonnam.ac.kr

Received 2024 September 24; Revised 2024 October 28; Accepted 2024 November 18.

Abstract

INTRODUCTION

In degenerative lumbar spondylolisthesis, interbody fusion surgery (IFS) such as posterior lumbar interbody fusion (PLIF) has long been recommended as the gold standard of surgical management [12]. However, IFS is less recommended for high-risk patients such as the elderly because it involves extensive surgery, with a long operation time and high volumes of blood loss, which lead to marked perioperative morbidity [8,9]. Meanwhile, several studies have reported a surgical technique called interspinous fixation (ISF) for the surgical management of increased perioperative morbidity in lumbar spondylolisthesis. ISF was proposed on the premise that posterior element reinforcement could serve as an alternative to pedicle screws in IFS, while potentially providing similar efficacy with reduced morbidity [6,13,14]. Moreover, a recent study recommended decompression alone instead of IFS as a result of their finding that decompression alone was non-inferior to IFS [1]. However, the use of decompression alone without interbody fusion in lumbar spondylolisthesis remains controversial because it does not prevent aggravation of the disease course and is unable to correct spinal alignment, including the dynamic instability at the level of spondylolisthesis.

In this study, we report an alternative primary and salvage treatment technique for lumbar spondylolisthesis followed by posterior lumbar element reinforcement using ISF and decompression alone without interbody fusion.

MATERIALS AND METHODS

Patient population and study design

This study was approved by the Institutional Review Board of Chonnam National University Medical School Research Institute (approval number CNUH-2021-456). This study included 16 patients treated at our institution who underwent bilateral decompression alone and posterior ISF (SPIRETM; Medtronic Sofamor Danek, Memphis, TN, USA) performed by a single neurosurgeon from January 2013 to July 2017. The inclusion criteria were as follows : 1) single-level degenerative lumbar spondylolisthesis (less than Meyerding spondylolisthesis classification grade I) [7] and 2) patients with a clinical and radiological follow-up of ≥12 months after surgery. The exclusion criteria were as follows : 1) history of lumbar spine surgery; 2) patients with non-degenerative types of spondylolisthesis (e.g., isthmic defect type); and 3) patients with a clinical or radiological follow-up of <12 months after surgery. Patients’ baseline characteristics were recorded, including age, sex, vertebral level of spondylolisthesis, bone mineral density (BMD), local segmental motion angle (SMA), disc height (DH), and body slippage (BS). Additionally, patient charts were reviewed to collect data regarding past history, underlying diseases, level of operation, operative time, estimated blood loss, and surgical or medical related complications.

Anteroposterior, lateral, flexion, and extension plain radiographs were taken preoperatively, immediately postoperatively, 3 and 6 months after surgery, and once a year thereafter. Computed tomography (CT) and magnetic resonance imaging of the spine were also performed preoperatively in all patients. The SMA was measured as the difference in Cobb’s angle (CA) between flexion and extension lateral radiographs. The CA refers to the angle formed between the superior endplate of the upper vertebra and the inferior endplate of the lower vertebra in the sagittal view, with a positive value indicating the presence of lordosis (Fig. 1A). The DH was measured as the average distance between the anterior and posterior endplates of the two spondylolisthetic vertebral bodies. BS was defined as the distance between the lines drawn posterior to the two spondylolisthetic vertebral bodies in the plane sagittal view (Fig. 1B). Serial dynamic and static radiographs were evaluated and reviewed by two independent surgeons who evaluated all radiographs and CT images.

Fig. 1.

A : Radiological measurements in the sagittal view of the CA and lumbar disk height. Disc height was measured by (Ant-DH + Post-DH) / 2. B : Body slippage (BS) of the segmental vertebral bodies. BS was defined as the distance between the line drawn on the posterior of the two spondylolisthetic vertebral bodies in the plane sagittal view. CA : Cobb angle, Ant-DH : disc height anterior, Post-DH : disc height posterior.

The clinical outcome was evaluated using the Visual analogue scale (VAS) of back and leg pain and Oswestry disability index (ODI), which was compared preoperatively and at the last follow-up.

Surgical technique

Under general anesthesia, the patients were positioned prone on a radiolucent spine surgery table. A classic midline skin incision was made minimally extending from the upper spinous process of the upper vertebra to the lower spinous process level of the lower vertebra to be targeted. After dividing the lumbodorsal fascia, electrocautery was employed to perform a subperiosteal dissection to elevate the erector spinae muscles bilaterally off the rostral and caudal spinous processes down to the spinolaminar junction. Subsequently, a laminotomy, flavectomy, and partial medial inferior facetectomy were performed on both sides to gain access to the central canal, followed by superior facetectomy up to the pedicle, and superior undercutting to clear the lateral recess and foramina under surgical microscopy. Subsequently, the thecal sac was decompressed by removing the adhesive ligament flavum, and then the roots were decompressed by removing the lateral recess and widening the neural foramen without touching the intervertebral disc using Kerrison punch forceps.

Next, for ISF, the interspinous ligament at the target level was made a small hole using right angle-Kelly forceps (Fig. 2A). The spinous process construct was fixed to the insertion instrument and inserted. One half of the construct was placed on each side of the spinous processes, with the sliding post lying in the space between the spinous processes (Fig. 2B). Once the two plates were optimally situated, with one plate on either side of the spinous processes and the stem in the interspinous space, handheld compression instruments were used to clamp the plates toward each other, driving the spikes into the bone (Fig. 2C). Maintaining compression, a locking screw was inserted and tightened to a predetermined torque (Fig. 2D). ISF device (SPIRE; Medtronic, Dublin, Ireland; Fig. 3) made up of two titanium plates with spikes. Rigid fixation is achieved when the top of the locking plug is broken off. After copious irrigation, the incision was closed meticulously. Finally, we conducted fluoroscopy to confirm that the posterior ISF device appeared in the anteroposterior view in the lateral view. Postoperatively, none of the patients braced a thoraco-lumbar sacral orthosis or lumbar brace.

Fig. 2.

Intraoperative photographs. A : A small hole was mad into the interspinous ligament at the target level using right angle-Kelly forceps. B : The spinous process construct is fixed to the insertion instrument and inserted. One half of the construct is placed on each side of the spinous processes, with the sliding post lying in the space between the spinous processes. C : Hand-held compression instruments are used to clamp the plates toward each other, driving the spikes into the bone. D : A locking screw is inserted and tightened to a predetermined torque.

Fig. 3.

Interspinous fixation device (SPIRE; Medtronic, Dublin, Ireland) made up of two titanium plates with spikes.

RESULTS

The mean age of the patients at the time of surgery was 68.2 years (range, 48–76); seven patients (44%) were men and nine (56%) were women. The baseline study data and patient characteristics are provided in Tables 1-3. At the level of operation, two patients were L 2/3 (12%), five patients were L 3/4 (31%), and nine patients were L 4/5 (56%). Regarding the preoperative BMD T-score, 10 patients (62%) had a score of >–1, four patients (25%) had a score of –2.5≤ and ≤–1, and two patients (12%) had a score of <–2.5. The mean operation time was 149 minutes (range, 95–245), the mean blood loss was 117.5 mL (range, 20–300), and the mean hospital day was 11.2 days (range, 5–36). None of the patients reported surgical-related complications, such as neural injury, cerebrospinal fluid leakage, and surgical site infection, and only one patient suffered a medical complication (Table 3). The mean follow-up duration after the operation was 15.1 months (range, 12.0–39.3).

Table 1.

Demographic and clinical data of all patients

Table 2.

Operative data and radiological features of all patients

Table 3.

Distribution of patients’ clinical characteristics

On radiological follow-up examination, the mean DH was 8.41±2.48 mm at the last follow-up compared to 8.61±2.88 mm preoperatively, representing a decrease of 0.20±2.46 mm, with no statistical significance (p=0.074). The mean BS was 3.49±4.29 mm preoperatively and 3.41±4.91 mm at the last follow-up, representing a decrease of 0.07±3.10 mm, with no statistical significance (p=0.092). The mean SMA was 10.61°±3.42° preoperatively and 7.15°±3.70° at the last follow-up, representing a significant decrease of 3.46°±3.07° (p<0.001).

The mean VAS of back was 6.78±1.89 points preoperatively and 3.0±1.87 points at the last follow-up, with a decrease of 3.78±2.54 points (p<0.001), while the mean VAS of leg was 5.32±0.94 points preoperatively and 2.68±0.74 points at the last follow-up, with a decreased of 2.63±1.06 points (p<0.001). The mean ODI was 34±4.95 points preoperatively and 14.5±2.96 points at the last follow-up, with a decrease of 15.66±7.36 points (p<0.001). None of the patients reported worsening pain or an increased ODI after surgery, and there were no surgery-related complications (Table 4).

Table 4.

The mean values for radiological parameters, VAS scores, and ODI measured at the pre operation and at the last follow-up

Case illustration

A 61-year-old woman was admitted to our hospital with severe back and leg pain, corresponding to a VAS score of 6 for each. The ODI was 37 points preoperatively. Neurological examination revealed no abnormal findings other than pain. The patient’s BMD was measured as –2.8 at the femur neck. Radiological findings of the lumbar spine showed an L 4/5 spondylolisthesis grade I (Fig. 4A and B). The DH and BS were measured as 11.2 mm and 6.3 mm, respectively, and the SMA was measured as 10.4° (Fig. 4C and D). The patient underwent L 4/5 decompression alone with ISF (Fig. 4E). The operation time was 145 minutes, and the blood loss was measured as 40 mL. The length of hospital stay was 6 days. At the last follow-up, the DH and BS were measured as 9.0 and 6.2 mm, respectively, while the SMA was measured as 8.5° (Fig. 4F and G). The VAS score of the back and leg was 2 and 4, respectively. The ODI was 13 points at the last follow-up. The patient’s clinical and radiological data are shown as number 12 in Tables 1 and 2.

Fig. 4.

Case illustration. A and B : Radiological findings of the lumbar spine show an L 4/5 spondylolisthesis grade I. C and D : The disc height (DH) and body slippage (BS) were measured as 11.2 mm and 6.3 mm, respectively, and the segmental motion angle (SMA) was measured as 10.4°. E : Postoperative lateral whole-spine lateral radiography. F and G : At the last follow-up, DH and BS were measured as 9.0 mm and 6.2 mm, respectively, and the SMA was measured as 8.5°.

DISCUSSION

IFS with placement of interbody cage and screw fixation followed by laminectomy and discectomy, such as PLIF, anterior lumbar interbody fusion, and transforaminal lumbar interbody fusion, is the established gold standard surgical technique for the treatment of degenerative lumbar spondylolisthesis [2,15]. However, for high-risk grade I spondylolisthesis patients, such as the elderly, patients with cardiopulmonary disease, and those who are hemodynamically unstable, IFS may be contraindicated due to its prolonged operation time and increased blood loss resulting in increased perioperative morbidity [11].

Several clinical and biomechanical studies have reported the surgical technique called ISF for the surgical management of lumbar spondylolisthesis. ISF was developed to achieve lumbar spinal fixation at the index level with minimal invasiveness. Wang et al. [13,14] suggested that ISF can provide comparable lumbar stability to pedicle screw instrumentation while offering certain advantages over pedicle screw fixation. In these studies, ISF effectively limited the range of motion in flexion and extension, which was comparable to the restriction achieved with bilateral pedicle screw fixation. Furthermore, other biomechanical studies investigating different ISF devices also reported significant restriction of motion, especially during flexion and extension, and to a lesser extent during lateral bending and axial rotation [4,5]. However, previous studied have only evaluated the potential of the ISF plate as an alternative instrument for pedicle screws, excluding the issues such as cage insertion.

Interbody fusion cages have several disadvantages or limitations. DiPaola and Molinari [3] reported a dural tear rate ranging from 5.4% to 10% and a neurologic injury rate ranging from 9% to 16% in PLIF surgery. Moreover, cage-related complications, such as subsidence, migration, and failure, can lead to a loss of correction achieved during surgery and compromise fusion stability. Fusion with cages can also increase stress on adjacent spinal segments, potentially contributing to degenerative changes. Additionally, there is a growing need for less invasive treatment methods in medical practice owing to the increasing number of elderly individuals in the population. In a study evaluating the surgical outcomes of PLIF in elderly patients (average age, 74 years), Okuda et al. [10] reported that 10% of patients had medical complications of brain infarction and delirium, and 23% had difficulty achieving fusion. Moreover, Wang et al. [13,14] reported an operation time of 164 mintues (median) and estimated blood loss of 75 mL (median) in IFS with ISF. Likewise, IFS, with or without pedicle screw fixation and ISF, is associated with a relatively longer surgical time and significant blood loss, which does not dramatically reduce the risk of postoperative morbidity.

Another recent noteworthy study recommended decompression alone instead of IFS because decompression alone was found to be non-inferior to IFS. Austevoll et al. [1] compared the outcomes between the decompression alone and fusion groups in single-level degenerative spondylolisthesis. The authors assessed the overall changes following surgery using the ODI, EuroQol Group 5-Dimension, and NRS for pain, and found no significant difference between the two groups. However, the authors reported that approximately 20% of the patients experienced slippage or angulation in the decompression alone group, as evaluated by dynamic standing radiographs, indicating that the deterioration of disease could not be prevented.

Therefore, we conducted an analysis by gathering the advantages of the aforementioned studies and implementing them in our approach for high-risk patients such as the elderly or medically complicated. In this study, we observed clinical improvement in both back and leg pain, although we could not evaluate values of the quality of life. Moreover, our technique was also found to reduce blood loss and surgical time compared to previous studies on IFS. Although one case of postoperative medical complication occurred in a patient with a history of coronary artery bypass, the incidence rate was not high (6%, 1 of 16).

The significant issue associated with decompression alone with ISF is that unlike with IFS, disease progression cannot be prevented, which eliminates motion at the spinal segment, restores spinal alignment, and helps prevent spondylolisthesis deterioration. In other words, spondylolisthesis cannot be completely cured if the motion of the spinal segment is completely removed. In our study, the SMA significantly decreased by 3.46°±3.07°, from 10.61°±3.42° preoperatively to 7.15°±3.70° at the last follow-up (p<0.001, Fig. 5). Consistent with the findings of biomechanical research by Wang et al. [13,14], we confirmed a significant restriction of segmental motion, indicating posterior element reinforcement by ISF. Consequently, these findings suggests that the deterioration of spondylolisthesis can be prevented or delayed by reducing SMA, which indicates dynamic instability.

Fig. 5.

Changes in the segmental motion angle recorded preoperatively, immediately after surgery, at 1 year post-operatively, and at the last follow-up.

This retrospective study has some limitations. First, the number of patients included was relatively low, and there was no control group, such as an IFS and decompression alone group, for comparison of the radiological and clinical outcomes. Second, as the enrolled patients in this study were not randomized, the data are affected by bias. Third, we did not identify factors that predicting the deterioration of spondylolisthesis. Fourth, because of the small number of patients and short follow-up period, surgical complications related to the IFS device, such as fixation loosening and spinous process fracture, may not have occurred. Further randomized prospective studies are required to determine the efficacy and toxicity of decompression alone with ISF.

Despite these limitations, we believe that both clinicians and patients should participate in decision-making discussions of all relevant treatment options to achieve the ideal of today’s patient-centered care demands. To avoid bias toward one specific treatment modality, patients should be counseled on all available treatment options based on objective data and experience, without showing preference for one treatment modality over others. Additionally, treatments should be individualized according to the patient’s characteristics, preference, and priority. In our study, decompression alone with SPIRE fixation was found to be suitable for patients with less than grade I spondylolisthesis, who are elderly, have poor physical status, and are medically complicated.

CONCLUSION

Although we do not claim that ISF produces superior outcomes compared to standard surgical techniques such as IFS, our findings highlight that posterior lumbar element reinforcement by decompression alone with ISF is an alternative primary and salvage treatment option in patients with spondylolisthesis less than grade I, which is considered reliable and less invasive for selected cases.

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