CC BY
1
a.g. aganesov et al. , 2024
spinal canal stenosis: comparative analysis of minimally invasive
bilateral decompression through a unilateral approach and laminectomy
A.G. Aganesov, M.M. Aleksanyan, E.G. Gemdzhian
Petrovsky National Research Centre of Surgery, Moscow, Russia
Objective. To analyze and compare the results of treatment of lumbar spinal stenosis using minimally invasive unilateral decompression and classical laminectomy.
Material and Methods. The retrospective comparative monocentric study included 68 patients (2 groups of 34 patients each) operated on in 2018—2021 for spinal stenosis in the lumbar spine who met certain eligibility criteria. Patients of one group were operated on using minimally invasive bilateral decompression through a unilateral approach, while patients in the other group were operated on using classical laminectomy. The results of surgical treatment were compared during 24 months by assessing pre- and postoperative indicators of the intensity of pain in the back and lower extremities using a 10-point VAS, and the patient's functional activity — using the Oswestry index. Results. A statistically significant clinical effect of surgical treatment was noticed in both groups. At the end of the follow-up period, the results of back pain relief in the minimally invasive surgery group were significantly better (0.3 vs 0.9, respectively), and the improvement in functional activity was comparable to the laminectomy group (8.8 vs 9.8, respectively). A clinical effect of pain relief in the lower extremities was obtained in both groups (up to 1.2 and 1.4, respectively). The length of hospital stay, time to activation, and volume of blood loss were significantly lower in minimally invasive decompression group.
Conclusion. Minimally invasive unilateral decompression of the spinal canal for lumbar spinal stenosis demonstrates a better effect in relieving back pain than classical laminectomy, with no significant difference in relieving pain in the lower extremities. The minimally invasive technique allows patients to rehabilitate as quickly as possible and return to everyday life and work. It has socio-economic advantages compared to classical laminectomy — a shorter period of activation and hospital treatment, and less blood loss. Key Words: spinal stenosis, laminectomy, minimally invasive treatment, spinal decompression.
Please cite this paper as: Aganesov AG, Aleksanyan MM, Gemdzhian EG. Spinal canal stenosis: comparative analysis of minimally invasive bilateral decompression through a unilateral approach and laminectomy. Russian Journal of Spine Surgery (Khirurgiya Pozvonochnika). 2024;21(1):35—43. In Russian. DOI: http://dx.doi.org/10.14531/ss2024.L35-43.
Degenerative lumbar stenosis is the most common indication for surgical treatment in elderly and senile patients (over 60 years of age), who are often comor-bid [1, 2]. Degenerative changes include herniation of spinal discs, hypertrophy or ossification of yellow ligaments, often in combination with hypertrophy of facet joints. These changes result in compression of nerve roots in the spinal canal, lateral canals and intervertebral foramen, causing pain and neurological disorders that significantly reduce the quality of life [2, 3]. In the absence of therapeutic effect, surgery is the only option, but the optimal surgical approach, especially in comorbid elderly patients, remains a matter of debate among spine surgeons today [4-6]. Classical procedures include laminectomy,
resection of the medial facet joints, and foraminotomy. These procedures require an extensive surgical approach that can lead to injury to paravertebral muscles and a highly radical resection of posterior supporting complex of the spine [7, 8]. Massively resecting bone tissue or injuring muscle tissue can cause instability, muscle dysfunction, atrophy, or failed back surgery syndrome [6, 9]. If stenosis and instability are combined in a spinal motion segment, decompression alone is not enough to produce a clinical outcome, and surgery should be supplemented with stabilization, usually using a transpedicular system [10, 11]. If lumbar spine deformities are detected, decompressions can be performed if there are no risk factors for instability development [12]. It is important to
consider the area of decompression. It is recommended to perform the procedure on the convexital side of the deformity for ease of approach and maximum preservation of the stability of the spinal motion segment [13, 14].
Given the fact that central stenosis mainly develops in the interlaminar space, surgical techniques slowly shift towards minimally invasive procedures [15]. Previously used in microdiscecto-mies, microendoscopic tubular retractors began to be used to treat stenosis, making this technique a viable alternative to classical laminectomies (Fig. 1). Minimally invasive decompression aims to maximally reduce the amount of bone resection and intraoperative injury to paravertebral tissue, as well as the risk of postoperative instability [8]. With
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a.g. aganesov et al spinal canal stenosis: minimally invasive bilateral decompression through a unilateral approach and laminectomy
minimally invasive approaches, paravertebral muscles are bluntly separated while maintaining the integrity of median structures of muscle fixation point and the ligamentous apparatus, reducing intraoperative blood loss and postoperative pain syndrome [16]. A technique similar to the described one is minimally invasive bilateral decompression through a unilateral approach. This technique can also be applied to multisegmental lesions. [17-19].
Unfortunately, the world literature still contains very few studies clearly describing the advantages of this minimally invasive technique compared to classical laminectomy [20-24].
The objective is to analyse and compare the results of treatment of lumbar spinal canal stenosis using minimally invasive unilateral decompression and classical laminectomy.
The level of evidence is 3b.
Material and Methods
A total of 637 patients with degenerative and dystrophic conditions of the lumbar spine underwent surgery at the Spine Surgery Unit of the B.V. Petrovsky National Research Centre of Surgery (Moscow) in 218-2021.
All surgeries were performed by one surgical team in the same operating room. All patients gave voluntary consent to surgery. The study was approved by the local ethics committee of the hospital.
Inclusion criteria:
1) symptomatic lumbar spinal stenosis causing radiculopathy (pain syndrome, weakness and numbness in the lower extremities), neurogenic claudication or pelvic organ dysfunction;
2) visually confirmed (MRI or CT) combined lumbar stenosis associated with hypertrophy of facet joints, hypertrophy/ossification of the yellow ligament and broad-based disc protrusion [25];
3) spinal canal stenosis at no more than two levels;
4) lack of a therapeutic effect for more than 3 months;
5) follow-up period of 24 months;
Exclusion criteria:
1) spinal motion segment instability, lumbar spine deformity, confirmed by standard and functional radiological imaging;
2) surgical procedures on the lumbar spine in the case history;
3) anterior compression of neural structures (herniated disc);
4) severe pathology of other organs and systems (according to the examinations of subject matter experts and anaesthesiologists);
5) focuses of purulent inflammation.
Sixty eight (11 %) patients met the
specified criteria and were divided into two groups of 34 patients, depending on the surgery performed. The severity of spinal stenosis was evaluated according to the Lee classification [26] that distinguishes 3 grades: mild (Grade 1), moderate (Grade 2) and severe (Grade 3).
The main demographic, clinical, physical, radiological and functional features of patients are shown in Table 1.
The surgical outcomes were evaluated by comparing pre- and postoperative parameters, including functional activity (intensity of pain in the back and lower extremities using the 10-point VAS, level of functional activity using the Oswestry Disability Index). Patients were surveyed before surgery, 5 days after surgery, 6 weeks, 12 months and 24 months later. The follow-up periods in both groups were the same; 61 patients attended follow-up appointments, and 7 completed online surveys. In addition, the length of hospital stay, time to patient activation after surgery and surgical blood loss were analysed.
In both groups, surgeries were performed under general anaesthesia on an operating table with a Wilson frame, with the patient in the knee-elbow position to straighten the lumbar lordosis. Before suturing the wound, ropivacaine was injected into the paravertebral muscles to reduce postoperative pain.
Standard Laminectomy Technique. An incision of the skin was made in the projection of the central line, followed by dissection of the thoracodorsal fascia and subperiosteal separation of the paravertebral muscles from the spinous
processes and vertebral arches. After that, retractors were placed on both sides. Decompression was performed by removal of the spinous process, vertebral arches, yellow ligament, medial resection of the facet joints, superior articular process to the inner wall of the pedicle of the caudal vertebral arch to visualise the lateral canal, and was completed with radiculolysis. Haemostasis was achieved using bipolar coagulation and, if necessary, haemostatic materials (Surgicel).
The technique of minimally invasive bilateral decompression through a unilateral approach. The incision of the skin up to 3 cm was performed 1.5 cm laterally from the median line, after intraoperative marking of the required level using a radiological image intensifier. Next, the thoracodorsal fascia was dissected sequentially in an arc wise manner, and a minimally invasive tubular wound retractor was placed to expose the inter-spinous space, vertebral arch and yellow ligament. Muscles and soft tissues in the approach area were subperiosteally skeletonized. Decompression was performed with a high-speed microsurgical spine drill using a surgical microscope. To facilitate visualisation of the contralateral side, the base of the spinous process, the medial section of the hypertrophic facet joint (its medial third) and the inferior edge of the superjacent vertebral arch were removed. At this point, the deep layer of the yellow ligament remained intact, acting as an excellent barrier to protect the dura mater. Next, the anterior part of the contralateral arches and the hypertrophied joints were resected. After visualising the lateral canal on the opposite side, the yellow ligaments were elevated from the cranial side using a hooked probe or a curved curette, and then resected to perform central decompression. Lateral canals and intervertebral foramina were visualised on both sides, providing an option for full-fledged root revision to verify the relevance of the decompression (Fig. 2). Haemostasis was achieved through bipolar coagulation and, if necessary, haemostatic materials (Surgicel).
During statistical analysis, a parametric method (two-tailed unpaired Stu-
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a.g. aganesov et al. spinal canal stenosis: minimally invasive bilateral decompression through a unilateral approach and laminectomy
dent's t-test) was used to assess the difference in measurement results since the normality assumption of the compared distributions was not rejected by verification (the Shapiro - Wilk test). Pain intensity (according to the VAS) and functional activity (according to the Oswestry Disability Index) are presented as mean values (in points). The calculations were performed using Statistica 10.
Results
There was no significant difference in the indicators of pain intensity according to the VAS and functional activity according to the Oswestry Disability Index in the compared groups before treatment (Table 1). As a result of surgery, a significant clinical and statistical (p = 0.01) reduce (relief) of the pain syndrome and an improvement in functional activity were observed in both groups (Figs. 3, 4).
In the early postoperative phase (the fifth day after surgery), the mean intensity of back pain in patients following minimally invasive surgery was lower than in patients after laminectomy (2.0 vs 2.7). This difference remained in the long-term postoperative period: 1.1 vs 1.6 after 12 months and 0.3 vs 0.9 at the end of follow-up (Fig. 3). Thus, the effectiveness of reducing back pain after minimally invasive surgery was consistently better than after laminectomy. Radicular pain in the lower limbs was stopped in all patients, and there was no significant difference in the effectiveness of pain relief between minimally invasive surgery and laminectomy (Tables 2, 3).
In the postoperative period, the mean value of the Oswestry Disability Index in patients after minimally invasive surgery was higher than in patients after laminec-tomy: 11.7 vs 12.5 after 12 months and 8.8 vs 9.8 after 24 months (Fig. 4). This suggests that functional activity improvement with minimally invasive techniques is not worse than with laminectomy.
In one of the patients, a hematoma developed after extensive decompression and required ultrasonography-guid-ed puncture. There were 3 cases of injury to the dura mater with the development
of intraoperative cerebrospinal fluid leakage (2 of them in the group of minimally invasive surgery). In two cases, primary suture of the dura was performed; in the third one, cerebrospinal fluid was stopped during surgery, suturing the wound was not necessary. There was suture line disruption after laminectomy in one case, requiring surgical debride-ment. No lethal outcomes occurred in both groups. A lower back pain syndrome returned in one patient following minimally invasive decompression after 8 months, and was stopped by radiofre-quency denervation of facet joints. No revision surgeries were needed at that time of follow-up.
Statistical analysis indicates that minimally invasive surgery has several advantages, and corresponding parameters dif-
fer significantly or approach statistical significance.
Discussion
With a stable spinal motion segment, classical laminectomy results in good and excellent treatment outcomes for spinal stenosis in 64-82 % of cases. Nevertheless, massive intraoperative injury to soft tissues and a large amount of bone resection can result in the formation of instability and cicatricial changes in the paravertebral muscles [9, 27]. According to the literature [28], the mean incidence of instability after spinal decompression surgery is 5.06.0 %, with 13.0 % after laminectomy and 3.2 % after minimally invasive surgery. The frequency of revision
Fig. 1
Schematic illustration of a normal spinal canal (a), spinal canal stenosis (b), classical laminectomy (c) and minimally invasive unilateral decompression (d): minimal damage to soft tissues and minimal amount of bone resection can be noted, but at the same time there is excellent visualisation and possibility for decompression (drawing by O.A. Spirin)
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degenerative diseases of the spine
a.g. aganesov et al. spinal canal stenosis: minimally invasive bilateral decompression through a unilateral approach and laminectomy
Table 1 Features of patients in the study groups
Parameter Minimally invasive unilateral decompression (n= 34) Classical laminectomy (n = 34)
Age median, years 69 66
Gender, n (%)
Male 18 (52.9) 20 (58.8)
Female 16 (47.1) 14 (41.2)
Follow-up median, months 12 12
Stenosis severity according to Lee classification, n (%)
Grade 1 4 (11.8) 5 (14.7)
Grade 2 15 (44.1) 16 (47.0)
Grade 3 15 (44.1) 13 (38.3)
Initial symptoms, n (%)
Back pain 20 (57.7) 23 (68.3)
Radiculopathy 22 (65.7) 25 (74.8)
Neurogenic claudication 23 (67.1) 20 (58.4)
Pelvic organ dysfunction 2 (4.2) 3 (10.3)
Concomitant factors and comorbidity, n (%)
Smoking 7 (20.5) 6 (18.6)
Obesity 10 (29.6) 9 (25.4)
Hypertension 19 (56.7) 20 (58.1)
Cardiovascular diseases 10 (29.1) 11 (31.7)
Respiratory diseases 6 (18.5) 8 (23.3)
Diabetes mellitus type 2 2 (4.5) 4 (11.3)
Pain syndrome and functional activity before surgery
VAS (back), points 7.4 7.1
VAS (extremities), points 6.5 5.4
Oswestry Disability Index 39.8 42.2
Operated segments, n (%)
|L2-L3 4 (11.8) 2 (5.9)
L3—L4 8 (23.5) 6 (17.6)
L4—L5 22 (64.7) 24 (70.6)
L5—S1 5 (14.7) 3 (8.8)
Checking with Fisher's exact test showed that significantly in terms of the given features (p > the compared groups did not differ statistically 0.05).
surgeries also varies: 11.0 % after open surgery, 0.7 % after minimally invasive surgery, and the presence of spondylolisthesis before surgery increases the risk of instability by 4-l0 times. The extensive blind spaces that form as an outcome of surgery are an environment for the development of bacteria and the formation of scar tissue. Such complications result in the development of chronic pain syndrome and failed back surgery syndrome.
The newly developed minimally invasive techniques allow for the limitation of amount of bone resection and relevant decompression of neural structures [4, 21, 22, 29]. Tubular or endoscopic decompression of the spinal canal are used in practice, with the amount and efficiency of decompression not statistically differing. However, blood loss is lower and rehabilitation is earlier with the endoscopic technique [30]. Preservation of the contra-
lateral facet joint and preserving resection of the ipsilateral joint are crucial in maintaining the stability of the spinal motion segment [9, 31]. Minimally invasive decompression is a safe and efficient technique for treating spinal stenosis that minimizes intraoperative soft tissue injury, blood loss, and reduces the length of hospital stay [32, 33]. According to the literature [22, 23, 34-36], unilateral decompression falls within the reasonable timelines, results in small blood loss and a lower intake of analgesics compared to the classical laminectomy technique. Minimally invasive surgical techniques result in a reduction in the incidence of intraoperative complications [37]. All these advantages make it possible to perform such surgeries under local anaesthesia in comorbid patients with contraindications for general anaesthesia [38].
Meanwhile, the researchers found no difference in efficacy between minimally invasive decompression and traditional laminectomy, when comparing these two techniques. However, the second approach has a greater number of complications and repeat procedures (although patients differed due to the presence of obesity) [39]. During a comparison of standard open bilateral decompression with bilateral unilateral decompression after 3 years, no difference was found. In this respect, the complexity of minimally invasive treatment is not justified [40].
There is ongoing debate in the world literature about the influence of a patient's age on the outcome of surgery [1]. Elder age implies worse outcomes due to changes in bone and soft tissue structures: smoothing of the lumbar lordosis, fatty degeneration of the paraverte-bral muscles and weakness of the extensor muscles of the back.
Some advantages of minimally invasive techniques were observed during the postoperative period. Since most patients with degenerative disc disease belong to the elderly and senile age groups (over 60 years old), reducing back pain, the time to activation, length of inpatient treatment, and recovery are of particular importance [31, 42].
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ag. aganesov et al. spinal canal stenosis: minimally invasive bilateral decompression through a unilateral approach and laminectomy
Fig. 2
Preoperative MRI (a): L3-L4 spinal canal stenosis associated with hypertrophied facet joints, yellow ligaments and intervertebral disc protrusion (Grade 3 according to Lee); MRI 6 weeks after surgery (b): relevant decompression of neural structures with minimal injury to soft tissues (moderate edema); postoperative CT scan (c) shows preserving resection of bone tissue - medial resection of the facet joint on the left, marginal resection of the base of the spinous process, lower arcotomy
The only disadvantage of minimally invasive surgical treatment for stenosis is the long learning curve for surgeons [44], during which the complication rate is higher (especially injury to the dura mater and cerebrospinal fluid leakage), as well as the need for repeated surgeries due to recurrence.
Therefore, it is recommended that the first 30 procedures be performed under the supervision of experienced doctors [32, 45]. All procedures in our research were performed by a qualified surgeon with experience in both open and minimally invasive spine surgery techniques.
Conclusion
An analysis of the treatment outcomes based on the VAS and Oswestry Disability Index data revealed a statistically significant clinical benefit of surgical treatment for spinal canal stenosis using minimally invasive bilateral decompression through a unilateral approach compared to classical laminectomy. This benefit persisted for 24 months after surgery. Using minimally invasive surgery, the results in relieving back pain, especially in the early postoperative period, were found to be better than those achieved with laminectomy. The results of improving functional activity in the groups are comparable; the clinical effect on relieving radicular pain syndrome in the lower extremities with minimally invasive decompression and laminectomy was almost the same.
In the group of patients who underwent minimally invasive bilateral decompression through a unilateral approach, the time to activation, the length of inpatient stay, and the amount of blood loss were all significantly lower compared to those who had undergone laminectomy.
The study had no sponsors. The authors declare that they have no conflict of interest. The study was approved by the local ethics committee of the institution. All authors contributed significantly to the research and preparation of the article, read and approved the final version before publication.
39
Points
9 1 m
8 " — •
7 "
6 - —M—\—
VAS 5 " 4 -3 - • \ p = 0.01 vS. m •
2 -1 - ■ **•* -----mm m • •
• ' •M»
• ------
0 - • ————
I Before surgery 1 the fifth day 12 months 1 24 months
Fig. 3
Changes of pain intensity according to the VAS in the back in patients with minimally invasive unilateral laminotomy (red line) and classic laminectomy (blue line)
Points
50 -| 9 • • •T' •m»
40 30- • if^v. • Vv
•
VAS 20 - \\ <w •
p = 0.01 •
10 - mm m m — • • • • ----- ■ ••• •
0 -
1 Before surgery 12 months l 24 months
Fig. 4
Changes of the Oswestry Disability Index in patients with minimally invasive unilateral decompression (red line) and classic laminectomy (blue line), indicating a positive result
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a.g. aganesov et al. spinal canal stenosis: minimally invasive bilateral decompression through a unilateral approach and laminectomy
Table 2
Changes of the pain intensity reduction in the lower extremities of patients in the study groups after surgical treatment
Period Pain intensity according to the VAS, points
Laminotomy* Laminectomy*
Before surgery 6.5 (1.7)** 5.4 (2.0)
The fifth day 1.4 (1.6) 1.6 (1.8)
12 months after 1.6 (0.8) 1.5 (0.6)
24 months after 1.2 (0.8) 1. 4 (0.8)
* Values are not statistically significantly different; ** mean (standard deviation).
Table 3
Blood loss and treatment duration in patients of the study groups
Parameter Minimally invasive unilateral Classical
decompression laminectomy
Mean blood loss, ml 200* 800*
Time to activation, hours 15** 26**
Length of hospital stay, days 4 6
* p = 0.05;
** p = 0.01.
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Address correspondence to:
Aleksanyan Mark Mikaelovich Petrovsky National Research Centre of Surgery, 2 Abrikosovskiy pereulok, Moscow, 119991, Russia, Alexanyanmm@gmail.com
scopic unilateral laminectomy for bilateral decompression surgery using the cumulative summation test for learning curve. Medicine (Baltimore). 2022;101:E31069. DOI: 10.1097/MD.0000000000031069.
Received 07.07.2022 Review completed29.01.2024 Passed for printing 18.02.2024
Alexandr Georgyevich Aganesov, DMSc, Prof., Chief of Spine Surgery Department, Petrovsky National Research Centre of Surgery, 2 Abrikosovskiy pereulok, Moscow, 119991, Russia, ORCID: 0000-0001-8823-5004, aaganesov@gmail.com;
Mark Mikaelovich Aleksanyan, MD, PhD, senior researcher, Spine Surgery Department, Petrovsky National Research Centre of Surgery, 2 Abrikosovskiy pereulok, Moscow, 119991, Russia, ORCID: 0000-0003-1321-086X, Atexanyanmm@gmail.com;
Eduard Georgyevich Gemdzhian, biostatistician, Petrovsky National Research Centre of Surgery, 2 Abrikosovskiy pereulok, Moscow, 119991, Russia, ORCID: 0000-0002-8357-977X edstat@mail.com.
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