Degenerative lumbar stenosis is a progressive alteration of the spine affecting mainly the facet joints, the intervertebral disks and the ligamentum flavum and, in some cases, causing the compression of nerve and/or vascular structures. Such a compression typically manifests itself through symptoms such as neurogenic claudication, irradiation of pain to the extremities, lumbar pain, and even sphincter involvement [1-3]. The aim pursued by surgical management of this age-related condition [4,5] is central and foraminal decompression of the medullary canal, which should relieve the pressure on the affected nerves. The increased incidence of degenerative lumbar stenosis has resulted in the treatment of spinal stenosis becoming the most frequent surgical indication in patients over 65 years of age [1,3], with safe and effective results [2,3].

Traditional surgical approaches to the condition are associated with a series of limitations related to a potential damage to osseus and/or muscular structures, prolonged surgery times, blood loss, and a high complications rate [6]. In fact, given the instability resulting from the resection of the structures causing nerve compression and the extensiveness of the approach required [3], up to 34% of patients undergoing traditional decompression surgery without fusion must be subjected to revision surgery within 4 years of the primary procedure [7].

Spinal endoscopy has been shown to minimize postsurgical instability by reducing the risk of damaging the patients’ osseous and muscular structures [5]. Moreover, endoscopy requires smaller incisions, results in less blood loss and postoperative pain, and shortens the patients’ stay in hospital as the surgery can be performed as an outpatient procedure under awake anesthesia with conscious sedation [8-10]. Thus, studies comparing minimally invasive techniques with endoscopy have reported equivalent clinical results as well as certain benefits related to the lower invasiveness of the techniques [5,11-20]. Moreover, endoscopy has been shown to be economically efficient [21].

Nonetheless, although some authors consider that endoscopy could become a mainstay of spinal surgery [11], several aspects remain unresolved [22]. One of these has to do with the endoscopic management of multilevel stenosis, the treatment of which is controversial even with traditional approaches [23,24]. In fact, there is only 1 study (of 2 patient series) that reports on the use of biportal techniques as treatment for multilevel stenosis [25,26], and no studies whatsoever on the use of full endoscopy to treat the condition.

The purpose of this study was to analyze the results obtained in a series of patients with multilevel spinal stenosis treated by means of full endoscopy and compare them with the findings of previous studies using conventional techniques under the hypothesis that full endoscopy may be a safe and effective treatment option.

A total of 42 patients (22 male and 20 female) were included in the study. Mean age was 63.8±17.2 years and mean BMI was 27.1±4.3 kg/m². The patients’ demographic and general data is summarized in Table 1 and the surgical data is presented in Table 2.

Thirty-five patients (83.3%) presented with 2 affected levels, whereas in 7 (16.7%) the number of levels involved was 3, which adds up to a total of 91 operated levels. The L1–2 segment was affected in 2 cases (2.2%), L2–3 in 4 (4.4%), L3–4 in 20 (22%), L4–5 in 40 (44%), and L5–S1 in 25 (27.5%). In 19 cases (45.2%), stenosis was associated with a disc herniation. All the procedures were successful except one, which required a reoperation 3 months later because of a recurrent disc herniation at L5–S1. Among the 91 levels treated, 13 were identified as Schizas type B, 68 as type C, and 10 as type D, reflecting the varying degrees of spinal canal stenosis addressed in this study.

Most cases were operated under awake surgery [34] except for 6 patients (14.6%) where general anesthesia was used. Mean operative time was 83.6±39.7 minutes and mean postoperative hospital stay stood at 12.1±7.8 hours.

The statistical analysis of operative time was conducted separately for 2-level and 3-level decompressions. In the 2-level group (n=35), the mean surgical time was 77.6 minutes (standard deviation [SD], ±30.2), with a range from 25 to 160 minutes. For the 3-level group (n=7), the mean operative time was 114 minutes (SD, ±65.8), ranging from 33 to 200 minutes. When analyzing the surgical time per treated level across the entire series (n=42), the mean operative time was 38.7 minutes (SD, ±16.1), with a minimum of 11 minutes and a maximum of 80 minutes.

Considering the time patients remained in hospital before surgery and the time they spent in the postanesthesia recovery unit, the mean overall hospital stay stood at 17.6±8.9 hours. Following the procedure, 29 patients (69%) did not experience any discomfort, while 7 (16.7%) reported grade I discomfort and 6 (14.3%) grade II discomfort. Although most patients did not require preoperative analgesics (n=28, 66.7%), a few of them received paracetamol and/or dexketoprofen and 4 were administered morphine or other opioids.

The results of the series are summarized in Table 3 and Figure 1. Radicular pain, as measured by means of the VAS, decreased significantly going from 7.5±1.8 points preoperatively to 0.4±0.9 points at 24 hours postoperatively (p<0.001). Similarly, the intensity of axial pain decreased from 3.4±2.5 to 0.4±1 points (p<0.001). The ODI went down from 49.6% preoperatively to 19.7% at 6-month follow-up (p<0.001). As regards patient satisfaction with the procedure, 37 (88.1%) rated their experience as excellent, and all of them mentioned that they would undergo the procedure again if required.

As far as the consumption of opioids is concerned, the proportion of patients who used them preoperatively experienced a statistically significant reduction at 6 months from the procedure, going from 30.8% (n=12) to 9.8% (n=4) (p<0.001).

We do not place drains in any patients, and we have not observed any postoperative epidural hematomas. However, it is important to note that we do not routinely perform postoperative MRI, which could potentially lead to overdiagnosis. In this type of patient, meticulous hemostasis and blood pressure control by the anesthesiologist are essential to optimize visualization. Surgical time is often impacted by intraoperative bleeding due to the hypervascularity of the capillary membrane. To minimize bleeding, we rely on a combination of precise hemostatic techniques, including the use of a diamond burr to reduce thermal injury, intermittent irrigation, and, when necessary, hemostatic agents. Proper patient positioning can also help reduce venous congestion, further improving the surgical field.

The most significant finding of this study was that full endoscopy is a safe and effective treatment option for patients with multilevel vertebral stenosis, which confirmed the initial hypothesis put forward.

Although laminectomy is considered an effective technique for the treatment of single-level spinal stenosis, a significant amount of controversy exists as to what technique should be used to address multiple-level stenosis [26,35]. This is, on the one hand, due to the fact that not all spinal levels diagnosed with stenosis result in neurological symptoms and, on the other, to the fact that the literature has not yet sufficiently determined whether arthrodesis ought to be an integral part of the procedure [24]. As regards the first point, some authors have observed better results when only one of the affected levels is treated in cases of multilevel stenosis [23,24]. As to the second, while some studies have reported better results when fusion surgery is added to the decompression [36,37], others have found that arthrodesis leads to higher revision rates, and to a higher risk of morbidity or disease in the adjacent segment [38-40]. A large-scale study using data from the Swedish register [41] did not, over a 2-year period, find differences in the ODI or the VAS scores between patients subjected to decompression with and without an added fusion procedure.

Studies comparing single- versus multiple-level open laminectomies without fusion performed through open or mini-open approaches in patients with multilevel lumbar stenosis have reported contradictory results. While Adilay and Guclu [24] found that patients with multiple levels affected presented poorer ODI and VAS scores than patients where only one level was involved, Gunzburg et al. [42] found no association between the number of levels affected and patient-reported outcomes. Similarly, Nolte et al. [35] found no statistically significant differences between patients treated for one single level and those where 3 or more levels were involved. Park et al. [43], for their part, claimed that the number of levels treated should not be used as a predictor of the final outcome. Amundsen et al. [44] suggested that the results of multilevel patients treated surgically are not worse than those of single-level subjects. There is even a third way, represented by a study which, in spite of finding similar ODI and VAS scores in single- and multilevel patients, found widely varying degrees of patient satisfaction between the 2 groups, with only 56% of multilevel patients versus 80% of single-level patients declaring that they would undergo the procedure again [42].

At any event, there seems to be little doubt that the number of stenotic lesions to be decompressed depends on the patients’ symptoms [26]. Moreover, it would appear logical to avoid fusion surgery whenever possible to avert the problems it can cause. To achieve this goal, it is necessary to avoid damaging the structures responsible for the stability of the spine as such damage would make it advisable to add fusion surgery to the decompression [35]. That is precisely where the role of endoscopic surgery becomes crucial.

Full endoscopy has already demonstrated its effectiveness and safety in the management of lumbar stenosis, allowing surgeons to perform an effective bilateral decompression with one single point of entry [28,45-49]. In addition, there are 2 articles [25,26] plus a case report [50] where multilevel stenosis was successfully treated by biportal techniques. Nevertheless, although some of the full endoscopy series do include some multilevel cases [28,45,46], until the publication of the present analysis no studies were available that analyzed the results of a complete series where unilateral full endoscopy was used in the context of stenosis at multiple spinal levels.

The sheer variety of spinal surgery techniques introduced in the last few years (open, mini-open, Minimal Invasive Surgery, full endoscopy, biportal endoscopy, etc.), compounded by the wide range of options available for managing multilevel stenosis (associated or otherwise to fusion surgery and/or instrumentation) and the varying characteristics of individual patients, makes it difficult to find a valid benchmark to compare our results with those published in the existing literature. The various methods used to evaluate patient outcomes and even the way they are reported (some of them not disclosing preoperative VAS or ODI values) add to the difficulty of the task at hand.

Tables 4–6 contain a list of studies similar to this one found in the literature. In the case of comparison studies, only the information on the multilevel group has been included.

The improvement in the ODI score obtained in the present multilevel full endoscopy series was of 29.9 points, i.e., within the range obtained by the series reviewed (13.5–58.6 points). In fact, the improvement experienced by our patients was considerably higher than that reported in other studies. In any event, the U.S. Food and Drug Administration requires an ODI improvement of 15 points for results to be considered good or excellent, a condition that was met comfortably by our series.

As far as complications are concerned, our patients experienced a 7.1% (N=3) complications rate (2 patients with postoperative pain in the foot, which resolved without complications, and one recurring herniated disc), a percentage in the lower end of the range reported in the literature (6.4%–18.8%).

As regards radicular pain, although the results of previous studies vary widely (range, 0.3–4.9), the 0.4-point pain score resulting from multilevel full endoscopy places the procedure in the lower end of the ranges obtained by the various techniques reported in the literature. The same thing can be said for axial VAS, where the present series obtained a more favorable score (0.4) than the other publications analyzed (range, 0.7–3.2). Moreover, considering that one of the main advantages of endoscopic techniques is fast pain relief, the fact that our patients experienced considerable pain relief within 24 hours from the procedure and that such pain relief was maintained over time is certainly encouraging. However, a comparison with the other series considered is not possible because none of them analyze the evolution of pain within such a short term.

One of the advantages of endoscopic procedures is the short operative time required, which in our case was shorter than that associated with conventional techniques (range, 90.6–135.3 minutes), and the fact that the surgery is typically performed in the outpatient setting. Mean hospital stay in the present series was under 24 hours, far below the one reported in the literature (range, 3–6.9 days). In fact, only 11 of the patients in the sample stayed in hospital overnight, most of them because they presented with an elevated ASA physical status classification grade or obesity, or because they had required general anesthesia, all of which advised the exercise of caution. None of the patients required placement of a catheter. Against this background, even if the data from our study do not warrant any hard-and-fast conclusions in this regard, we believe that comparative cost-effectiveness studies should be carried out in the future given the significant role played by the patients’ length of hospital stay in the total cost of their treatment.

It was mentioned above that, despite satisfactory clinical results, patient satisfaction with the multilevel procedure was the weak link in some of the previously published series [42]. However, 88.1% of patients in our series rated the procedure as excellent and all of them stated that they would undergo the same procedure in the future, if required.

The natural evolution of symptoms following decompressive surgery for lumbar stenosis follows a characteristic pattern. Most patients experience a significant initial improvement in neurological symptoms during the first postoperative days. However, between 2 to 3 weeks postoperatively, a subset of patients may report a temporary worsening of symptoms, including dysesthesias and paresthesias, sometimes more intense than preoperative levels. This phase typically resolves spontaneously, leading to progressive clinical improvement over the following weeks.

It is crucial to inform patients preoperatively about this expected symptom evolution to prevent unnecessary concern and to ensure adherence to rehabilitation protocols. Early initiation of physiotherapy and rehabilitation at 2 weeks postoperatively is highly recommended to enhance recovery, prevent muscle atrophy, and optimize functional outcomes. Proper counseling regarding this process helps improve patient satisfaction and confidence in the procedure's long-term benefits.

This study is not without limitations, one of the most obvious ones being its retrospective observational design. Although this prevented us from making head-to-head comparisons with alternative techniques used on similar patient populations, we believe that this design is the most appropriate one to address the question regarding the effectiveness and safety of full endoscopy for managing lumbar canal stenosis in patients with multiple spinal level involvement. Another limitation is related to the evaluation of results, given the heterogeneity of the treatments reported in the existing literature. Nonetheless, the improvement reflected by clinical scores, together with the low revision and complications rate obtained, provides in our view sufficient grounds to draw solid conclusions. Clearly, however, comparative clinical trials will be needed to define the role of each technique and determine whether some patient or pathological profiles may benefit more from some techniques than from others. Finally, it must be underscored that ours was the first study in the medical literature to analyze multilevel full endoscopy in a separate and independent way and to do so through a more-than-acceptable sample size, considering how novel these techniques are.

Full endoscopy is a safe and reliable technique for the treatment of central and foraminal multilevel lumbar stenosis, with fewer complications and a shorter hospital stay compared to traditional approaches.