Comparison of three different surgical techniques in cases of single-level lumbar spinal stenosis: A retrospective clinical study

INTRODUCTION

Lumbar spinal stenosis (LSS) is a pathology that may be caused by osteophytes, discal or ligamentous structures, and may lead to classic neurogenic claudication symptoms with radiculopathy secondary to compression of neural structures. The prevalence of LSS has been reported to be approximately 11% in the general population and 25–39% among clinical cohorts, with incidence increasing progressively with age.^[1] Low back pain is mostly secondary to instability or deformities.^[2,3] No correlation has been shown between the degree of stenosis observed on radiologic examinations and clinical symptoms.^[2-5] Although many different procedures have been defined for cases requiring surgical intervention, the current trend is evolving from aggressive surgery to minimally invasive surgery. Oppenheim and Krause first described the classical laminectomy technique for the surgical treatment of spinal stenosis; however, due to the potential for spinal destabilization associated with this approach, minimally invasive techniques have gained prominence in recent years.^[6] Another study reported that microendoscopic decompression provided comparable short-term outcomes to conventional open laminectomy, with significantly reduced intraoperative blood loss, shorter hospitalization, and decreased narcotic use.^[7] The expectation is that new minimally invasive procedures will minimize tissue trauma while providing adequate decompression, as in laminectomy-fusion surgery, and protect patients from the long-term negative consequences of fusion surgery. This study aimed to retrospectively compare the recently popularized full endoscopic interlaminar decompression (FEID) and microsurgical bilateral decompression through a unilateral approach (MBDU) with classical posterior segmental instrumentation-laminectomy (PSEL) surgery, and to identify the advantages and disadvantages of these techniques.

MATERIALS AND METHODS

Between 2016 and 2022, 188 patients who underwent single-level LSS surgery using three techniques at various hospitals were retrospectively analyzed, and the patients were divided into three groups. To ensure homogeneity, patients with stenosis involving the spinal transitional zone, body mass index (BMI) below 18.5 or above 24.9, motor deficits, multilevel surgery, previous spinal operations, history of trauma, infection, rheumatologic disease, tumor, osteoporosis, deformity, or instability were excluded from the study. Only patients who completed at least 12 months of follow-up were included in the final analysis.

Ultimately, 188 patients who met the inclusion criteria were analyzed: FEID (n = 61), MBDU (n = 72), and PSEL (n = 55). All patients had a BMI between 18.5 and 24.9, no motor deficits, presented with neurogenic claudication, and underwent single-level decompression between L1 and L5 performed by three different surgeons experienced in their respective techniques.

Each surgeon selected the surgical method based on their training background and clinical judgment of the most appropriate approach for the patient. In all groups, demographic and perioperative parameters, including age, sex, pre-operative symptom duration, operative time, intraoperative blood loss, and length of hospital stay, were recorded. In addition, pre-operative and post-operative radicular Visual Analog Scale (VAS) scores, Oswestry Disability Index (ODI) values (at post-operative day 10, 3^rd month, 1^st year, and final follow-up), and pre- and postoperative (3^rd month) transverse canal diameter ratios on lumbar magnetic resonance imaging (MRI) were documented. Post-operative MRI was routinely performed in all patients as part of standard follow-up, approximately 3 months after surgery. All data were subjected to statistical analysis, and inferences were drawn based on the results.

RESULTS

More than half (56.9%) of the participants were women. The mean ages of the groups were similar, all over 60. The demographic characteristics and average follow-up times of the participants are presented in Table 1. The distributions of both demographic data and follow-up times were similar, and no significant difference was found between the groups. Pre-operative radiological severity, assessed using the Schizas classification, was comparable among the three groups, with no statistically significant difference observed [Table 1].

Accordingly, a significant difference was observed between the groups in terms of operation times [Table 2] (p < 0.001). A similar situation applies to the data on blood loss volume and hospitalization duration. A significant difference was observed between the groups (p < 0.001). The source of the significant difference is that the PSEL group’s operation times are significantly higher than those of the other groups. In contrast, the source of the significant difference is that all groups differ significantly from each other in terms of blood loss. The source of the difference in the hospitalization time variable is also that all groups differ significantly from one another [Table 2].

There is no significant difference between the groups in radicular VAS values at different time points [Table 3, Graph 1a]. In the pre-operative period, ODI scores were comparable among the three groups, with no statistically significant difference observed (p = 0.158). In analyses based on ODI indices, the group data differed significantly at all times. The difference between the groups was that the PSEL group values were significantly higher than those of the others in each case [Table 3, Graph 1b].

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Graph 1:

(a) Radicular Visual Analog Scale (VAS) scores (b) Oswestry disability index (ODI) scores. MBDU: Microsurgical bilateral decompression through unilateral approach, FEID: Full endoscopic interlaminar decompression, PSEL: Posterior segmental instrumentation-laminectomy

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In the lumbar MRI taken at the pre-operative and final postoperative follow-up, the mean transverse canal diameter ratio in the stenotic segment [Figure 1] was observed as 0.51 in the FEID group, 0.46 in the MBDU group, and 0.28 in the PSEL group. When these values are considered, the decompression level in the PSEL group was significantly higher than in the other two groups. It was similar in the other two groups [Table 4] (P < 0.01).

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Figure 1:

Measurement of the transverse canal diameter at the surgically treated segment on axial lumbar MRI. (a) Preoperative image (marked as X in the figure). (b) Postoperative image (marked as Y in the figure). The red bar represents the transverse canal diameter.

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DISCUSSION

Although laminectomy or extensive resection has been defined as the preferred technique in degenerative lumbar stenosis surgery,^[8-11] granulation tissue formation in the epidural space may cause problems in cases requiring revision,^[12,13] and, in some patients, it may lead to tethering of the cauda equina due to adhesions between the epidural space and the paravertebral muscle group.^[14,15] Since resection of structures that provide stability for wide decompression may result in segmental instability, posterior segmental instrumentation is often performed after aggressive bone resection. This approach, however, negatively affects operative duration, intraoperative blood loss, and post-operative back pain.^[7,16] In addition, because the disease predominantly affects the elderly population, instrumentation in osteoporotic or osteopenic patients may lead to loosening over time.^[17-20]

Today, full-endoscopic or microscopic procedures are widely used in such cases.^[21-28] These techniques provide adequate decompression while minimizing tissue trauma.^{[22,23,25-27,29]} In our study, the favorable clinical outcomes obtained in patients who underwent PSEL for neurogenic claudication and radiculopathy during approximately 3 years of follow-up were found to be similar to those in patients treated with FEID and MBDU.

There was no significant difference between FEID and MBDU in operative time; however, operative time was higher in the PSEL group than in the other two groups [Table 2], consistent with the more extensive nature of the procedure.

When evaluated for intraoperative blood loss, FEID appeared significantly more advantageous than the other two techniques, whereas MBDU also demonstrated an advantage over PSEL [Table 2]. The greater blood loss observed in PSEL may be attributed to the more invasive nature of the procedure and its longer duration; however, other factors, such as surgeon-related variables and patient-specific coagulation status, may also contribute. No massive bleeding requiring blood transfusion was noted.

Regarding hospital stay duration, the shortest duration was observed in the FEID group, followed by MBDU, which was shorter than in PSEL. Because FEID and MBDU caused less tissue trauma compared to PSEL, patients were able to ambulate on the same day and were discharged earlier. In contrast, this period was considerably longer in the PSEL group (p < 0.001) [Table 2]. The shorter hospitalization in the FEID group compared with the MBDU group may be related to reduced soft-tissue disruption and earlier post-operative mobilization.

In terms of radicular pain, no significant difference was observed between the three groups based on post-operative VAS evaluations [Table 3, Graph 1a and 1b]. When ODI indices were assessed, the values were markedly lower in the FEID and MBDU groups than in the PSEL group. Based on these findings, it can be inferred that post-operative lumbar back pain (LBP) severity decreases as the extent of resection decreases. Similar results have been reported in the literature.^[21,24-31] The ODI values were consistently lower in the FEID group compared to PSEL at all follow-ups and lower in the MBDU group during the first 10 post-operative days, after which they became comparable [Table 3]. The shorter skin incision in FEID and MBDU, reduced tissue trauma, absence of biomechanical stress secondary to fixation, and the elimination of pseudoarthrosis or hardware loosening may have contributed to the lower incidence of LBP. After the early post-operative period (first 10 days), ODI indices in the MBDU group approached those of patients who underwent FEID.

In accordance with previously described radiological morphometric measurements of the lumbar spinal canal,^[32,33] the mean transverse canal diameter ratio of the stenotic segment measured on pre-operative and 3^rd-month control lumbar MRI [Figure 1] was 0.51 in the FEID group, 0.46 in the MBDU group, and 0.28 in the PSEL group [Table 4]. These findings indicate that decompression was greatest in the PSEL group and similar between FEID and MBDU (p < 0.01). Although aggressive facet resection can be achieved in PSEL, the need to preserve the facet joints to prevent instability in minimally invasive approaches may explain the broader decompression in PSEL. However, no clinical findings secondary to inadequate decompression were observed during a mean follow-up of 33 months. In addition, no statistically significant differences were found among the groups in terms of overall complication or reoperation rates. Furthermore, the lack of significant differences in radicular VAS scores among the groups was taken as evidence that neural decompression was adequate across all three techniques, despite variations in decompression rates.^[22,29]

Although the question of “In which cases should fusion be added to decompression?” remains controversial, it may be advantageous in selected patients to prefer minimally invasive approaches – particularly in those without predominant LBP, segmental instability, or deformity –to shorten operative time, reduce blood loss, minimize post-operative LBP, and avoid potential complications such as fracture, slippage, or loosening secondary to instrumentation.

In cases of single-level lumbar stenosis without axis deviation or instability, FEID or MBDU appears to be more advantageous than PSEL. In the 3-year follow-up, FEID and MBDU showed similar results, except for hospitalization time and the early ODI index. No significant superiority was observed between the two minimally invasive techniques, which is consistent with previous reports in the literature.^[34]

As a result of our study, the significant advantages and disadvantages of each technique can be summarized as follows:

• PSEL was found to be disadvantageous compared to the other two techniques in terms of operative time, intraoperative bleeding, hospitalization duration, anatomical trauma, early and late post-operative LBP, and late complications secondary to instrumentation.

• MBDU was found to be disadvantageous compared with FEID in terms of hospitalization duration and early post-operative LBP (first 10 days).

CONCLUSION

In cases of single-level lumbar stenosis, FEID or MBDU appears to be more advantageous than PSEL when there is no predominant complaint of low back pain, axis deviation, or instability, and when the stenotic level does not involve the spinal transitional zone. Although PSEL – performed with concomitant fusion in our cohort – resulted in greater post-operative canal expansion, it did not translate into meaningful improvements in functional outcomes.