The clinical efficacy of unilateral biportal endoscopic treatment for lumbar spinal stenosis with preservation of the ligamentum flavum

The clinical efficacy of unilateral biportal endoscopic treatment for lumbar spinal stenosis with preservation of the ligamentum flavum | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The clinical efficacy of unilateral biportal endoscopic treatment for lumbar spinal stenosis with preservation of the ligamentum flavum Kepeng Li, Bo Jiang, Ye Han This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5916963/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Background As a minimally invasive surgical approach for treating lumbar spinal stenosis, Unilateral Biportal Endoscopy (UBE) is receiving significant attention from clinical practitioners. Conventional UBE surgery involves the removal of the ligamentum flavum, and to date, there is no research on UBE techniques that preserve the ligamentum flavum. Method A retrospective analysis was conducted on 100 patients with lumbar spinal stenosis (LSS) who underwent UBE treatment from January 2022 to March 2024. The surgical techniques of decompression of the lumbar canal while preserving the ligamentum flavum using UBE technology were summarized. Patients were divided into two groups based on whether the ligamentum flavum was preserved during surgery: the preservation group with 40 patients, and the removal group with 60 patients. The intraoperative surgical time and blood loss of the two groups were compared, as well as perioperative Visual Analogue Pain Scores (VAS), Oswestry Disability Index (ODI), and complications such as dural tears and epidural hematoma. The difference in radiological decompression between the two groups was assessed using the cross-sectional area of the dural sac on lumbar MRI. Results The average surgery time for the group with the ligamentum flavum preserved was (50.13±8.45) minutes, and the intraoperative blood loss was (30.57±6.64) ml. For the group with the ligamentum flavum removed, the average surgery time was (66.47±7.26) minutes, and the intraoperative blood loss was (58.70±6.19) ml. Compared to the group with the ligamentum flavum removed, the group with the ligamentum flavum preserved had a shorter surgery time and less blood loss, with these results being statistically significant (P < 0.01). There was no difference in the VAS scores and ODI scores between the two groups at 3 days and 6 months postoperatively. The postoperative dural sac cross-sectional area for the ligamentum flavum preserved group and the ligamentum flavum removed group was 164.31±26.35 mm²and 170.92±27.68 mm², respectively, with no statistically significant difference (P = 0.24). The incidence of postoperative complications was 1.92% in the ligamentum flavum preserved group and 5.77% in the ligamentum flavum removed group, which was not statistically significant (P = 0.61). Conclusion The technique of unilateral biportal endoscopy (UBE) for lumbar spinal stenosis, which preserves the ligamentum flavum, can reduce complications, surgical time, and blood loss, while simultaneously providing favorable surgical outcomes. It is recommended to preserve the ligamentum flavum as much as possible when using UBE for the treatment of patients with lumbar spinal stenosis. Lumbar Spinal Stenosis Unilateral Biportal Endoscopy Ligamentum Flavum Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Background Lumbar spinal stenosis is a common disease among the elderly, primarily characterized by lower back and leg pain, and intermittent claudication. It significantly affects the quality of life of patients. [ 1 – 3 ]. For patients with severe lower back and leg pain, neurological impairment, and degenerative lumbar diseases that have failed conservative treatment, surgical intervention is required[ 4 ]. Traditional surgery is a common treatment for degenerative lumbar diseases; however, it extensively damages the paraspinal muscles and posterior ligamentous structures, leading to postoperative complications such as failed back surgery syndrome and muscle and nerve atrophy[ 5 ]. Unilateral Biportal Endoscopy (UBE) is a new technique for treating lumbar spinal stenosis. The UBE technique can achieve effective spinal decompression without compromising the integrity of the spine. UBE surgery can provide the same long-term clinical efficacy as open surgery while significantly reducing damage to spinal structures, decreasing the incidence of postoperative pain, and facilitating early and rapid recovery[ 6 – 8 ]. In conventional UBE surgery, decompression of the dural sac is achieved by removing the ligamentum flavum, but this removal increases the incidence of surgical complications. Previous studies have showed that epidural hematoma and dural tears are common complications of UBE surgery and are major factors reducing patient satisfaction[ 9 – 12 ]. Research by Kim et al. indicates that the longer the surgery and the more complex it is, the higher the incidence of epidural hematoma[ 13 ]. Removal of the ligamentum flavum prolongs the surgery time and disrupts the venous plexus between the ligamentum flavum and the dural sac, increasing the incidence of epidural hematoma. Dural tears also commonly occur during the process of removing the ligamentum flavum. Between the ligamentum flavum and the dural sac, there is a fine, net-like ligamentous structure known as the meningovertebral ligament, which serves to stabilize the dural sac. During lumbar ligamentum flavum resection, the meningovertebral ligament may be stretched, causing a dural tear[ 14 ]. Additionally, during the surgery, when both sides of the dural sac are subjected to the pressure of saline irrigation, a fold forms in the middle, concealed beneath the epidural fat, rendering it invisible to the surgeon. Thus, during the removal of the ligamentum flavum, it is easy to cause a dural tear at the site of the fold[ 15 ]. Furthermore, the area around the meningovertebral ligament has an abundance of epidural blood vessels, and bleeding can greatly interfere with the endoscopic field of view, increasing the risk of dural damage[ 16 ]. Due to the numerous defects resulting from the removal of the ligamentum flavum in UBE surgery, some scholars have proposed a surgical method that preserves the ligamentum flavum[ 17 ]. However, the ligamentum flavum is one of the compressive agents on the dural sac during lumbar spinal stenosis, and preserving the ligamentum flavum may affect the efficacy of neural decompression. To study the clinical effects of lumbar canal decompression while preserving the ligamentum flavum under UBE, we have summarized relevant surgical cases from recent years. Our objectives are: (1) to introduce the surgical techniques of UBE that involve preserving the ligamentum flavum; (2) to observe the therapeutic efficacy of UBE decompression for lumbar spinal stenosis when the ligamentum flavum is preserved. Materials and Methods Research Design This study is a single-center retrospective study approved by the Ethics Committee of Chongqing Liangping District People's Hospital, with written informed consent obtained from all patients before surgery. The study retrospectively analyzed patients with lumbar spinal stenosis (LSS) who underwent UBE treatment from January 2022 to March 2024. Inclusion criteria (1) patients presenting with intermittent claudication, experiencing lower limb pain and numbness after walking less than 50 meters; (2) imaging examinations indicating lumbar canal stenosis, primarily located at the intervertebral disc ligamentum flavum interspace; (3) patients with complete preoperative and postoperative imaging data, including X-rays, CT, MRI, etc. Exclusion criteria (1) Patients with a history of lumbar spine surgery; (2) lumbar instability (In the lateral radiographs of the lumbar spine with flexion and extension, an angle difference greater than 10 degrees between the inferior edge of the cephalad vertebral body and the superior edge of the caudad vertebral body, or a length difference greater than 4mm between the posterior edges of the adjacent vertebral bodies, is considered significant.); (3) lumbar scoliosis deformity; (4) patients with lumbar disc herniation requiring removal of the intervertebral disc during surgery; (5) patients with ossification of the ligamentum flavum. The study included a total of 100 patients with LSS treated with UBE, with 40 in the ligamentum flavum preservation group and 60 in the ligamentum flavum removal group. Surgical Procedure Preservation of the ligamentum flavum technique Taking the L4/5 intervertebral space on the left side as an example, the patient is positioned prone under general anesthesia, and the L4/5 segment is located under C-arm fluoroscopy. At the medial edge of the left pedicle, about 1.5 cm above and below the L4/5 space, two surgical incisions approximately 1.5 cm in length are made. Soft tissue is dissected using a soft tissue dissector, with the upper incision serving as the observation port and the lower incision as the working channel. Under endoscopy, a plasma radiofrequency knife is used to excise the soft tissue, revealing the lower edge of the L4 lamina, the ligamentum flavum, the root of the spinous process, and the medial edge of the facet joint. An osteotome is used to start resecting the lower edge of the left L4 lamina and the base of the spinous process from the junction of the spinous process and the lamina. The osteotome should be angled at 30° to the edge of the bone being resected, and the lamina is gradually removed in small amounts. The V-shaped junction of the bilateral ligamentum flavum at the cephalic midline is exposed. A curette is used to separate the ligamentum flavum on the ventral side of the right L4 lower articular process. On the dorsal side of the ligamentum flavum, an osteotome is used to remove the bone on the ventral side of the right L4 lower articular process. The upper part is exposed up to the starting point of the right L4 ligamentum flavum, and the right side is exposed to the inner edge of the upper L5 articular process. After removing the superficial layer of the ligamentum flavum, a curette is used to strip the attachment of the ligamentum flavum along the starting point of the right L4 and the inner edge of the upper L5 articular process and to remove part of the inner edge of the upper L5 articular process until the right L5 pedicle is exposed, completing the decompression of the right nerve root. The bone on the inner edge of the left L4 lower articular process is removed to expose the left ligamentum flavum at the starting point of the L4 lamina and the inner edge of the upper articular process. A curette is used to strip the attachment of the ligamentum flavum along the left side at the starting point of the L4 lamina and the inner edge of the upper articular process. Part of the inner edge of the upper articular process on the left side of L4 is removed until the left L5 pedicle is exposed, completing the decompression of the left nerve root. Now the ligamentum flavum is only attached to the L5 lamina, and the rest is freed. The ventral side of the dura mater beneath the ligamentum flavum is probed to confirm that the dura is bulging and decompression is adequate. Cancellous bone surfaces are treated with bone wax for hemostasis. No drainage tube is placed, and the incision is sutured (Fig. 1 ). Ligamentum flavum removal procedure Taking the left L4/5 intervertebral space as an example, the positioning and exposure steps are the same as those in the ligamentum flavum preservation procedure. An osteotome is used to start from the junction of the spinous process and the lamina to remove the lower edge of the left L4 lamina and the base of the spinous process, until the V-shaped junction at the midline head side of the bilateral ligamentum flavum is exposed. A periosteal elevator is used to separate the ligamentum flavum on the ventral side of the bilateral lower articular processes. On the dorsal side of the ligamentum flavum, the osteotome is used to remove the bony part on the ventral side of the right L4 lower articular process, exposing the inner edges of the bilateral L5 upper articular processes. A curette is used to strip the ligamentum flavum from its attachment at the L4 lamina and the inner edge of the upper articular processes. The osteotome is then used to remove the bony part at the junction of the L5 lamina and the upper articular processes. A nerve dissector is used to peel off the chiseled bone block and its connected ligamentum flavum, exposing the neural structures. The camera is placed between the remaining ligamentum flavum and the upper edge of the L5 lamina. Then separate the remaining space between the ligamentum flavum and the neural tissue. A curette is used to separate the deep layer of the ligamentum flavum at the head end of the L5 lamina. Laminectomy punch are then used to completely remove the ligamentum flavum, exposing the dura mater. The bilateral edges of the dura mater are probed to confirm that the dura mater is bulging, indicating decompression is complete. The incision is then sutured (Fig. 2 ). Postoperative Related Treatment Within 72 hours post-surgery, 125ml of mannitol should be administered intravenously twice daily to prevent nerve root edema. Additionally, Take 0.5 milligrams of mecobalamin orally three times each time to promote nerve recovery. The patient is advised to engage in activities while wearing a lumbar back brace starting from the second day after the surgery, and to continue wearing the brace for six weeks. Clinical outcome and radiological assessment Clinical lumbar and leg pain was evaluated using the Visual Analogue Scale (VAS) at 3 days and 6 months post-operation, while lumbar spine function was assessed using the Oswestry Disability Index (ODI). The cross-sectional area of the dural sac at the level of the intervertebral disc in the decompressed lumbar MRI segments was measured before and after surgery (Fig. 3 ). All radiological assessments were performed by two senior spine surgeons with over five years of experience. Each surgeon measured three times to obtain an average value. If the difference in average values between the two assessors was less than 10mm, the mean of all six measurements was recorded. If the difference in average area values was 10mm or greater, a third senior spine surgeon with over five years of experience was invited to measure. All three surgeons used the same method to measure, and they consulted together to agree on each measurement result. The final average of the values included in the data was then recorded. Complications Surgical complications include postoperative wound infection, cauda equina nerve injury, and epidural hematoma, among others. The diagnostic criteria for epidural hematoma are: (1) new onset of lumbar distension pain, radiating pain in the lower limbs, or numbness after surgery; (2) postoperative MRI indicating the presence of a hematoma within the spinal canal (see Fig. 4 ); (3) after removal of the suture at the incision site and local drainage, the blood clots are observed. After the hematoma is drained, the patient's symptoms of lumbar soreness and swelling, as well as lower limb pain and numbness, are alleviated. Data Analysis All statistical analyses were performed using SPSS version 25.0 (IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp). Continuous data that followed a normal distribution were analyzed using the t-test and are presented as mean ± standard deviation (SD). For data not normally distributed, non-parametric tests were employed. Categorical data were expressed in frequencies and percentages (%) and compared using the Chi-square test. A p-value < 0.05 was considered to indicate a statistically significant difference between the two groups. Results Basic information Upon comparing the patients' age, gender, BMI, underlying diseases, and surgical segments, it was found that there were no statistically significant differences between the two groups (Table 1 ). Table 1 Comparison of baseline indicators between the ligamentum flavum preservation group and the ligamentum flavum removal group ligamentum flavum preservation group (n = 40) ligamentum flavum removal group (n = 60) P value Age(year) 66.37 ± 12.45 67.81 ± 11.74 0.56 Sex n(%) 0.81 male 19 27 - female 21 33 - BMI (kg/m 2 ) 23.13 ± 5.47 24.26 ± 2.85 0.18 Past-illnesses hypertension n (%) 20 29 0.87 diabetes n (%) 11 17 0.93 Osteoporosis n(%) 9 15 0.77 VAS score 6.94 ± 1.26 7.11 ± 0.87 0.43 ODI index 62.74 ± 12.88 63.39 ± 9.47 0.67 Segment n (%) 0.86 L3/4 12 21 - L4/5 21 30 - L5/S1 7 9 - Intraoperative indicator comparison The average surgical duration for the ligamentum flavum preservation group was (50.13 ± 8.45) minutes, with an intraoperative blood loss of (30.57 ± 6.64) ml. In contrast, the average surgical duration for the ligamentum flavum removal group was (66.47 ± 7.26) minutes, with an intraoperative blood loss of (58.70 ± 6.19) ml. Regarding surgical duration and intraoperative blood loss, the ligamentum flavum preservation group was superior to the ligamentum flavum removal group (P < 0.01). (Table 2 ) Table 2 Surgical duration and intraoperative blood loss ligamentum flavum preservation group ligamentum flavum removal group t P Surgical Duration (min) 50.13 ± 8.45 66.47 ± 7.26 10.21 <0.01 Intraoperative blood loss (ml) 30.57 ± 6.64 58.70 ± 6.19 21.62 <0.01 Postoperative outcome VAS score Three days postoperatively, there was no statistically significant difference in VAS scores between the group with preserved ligamentum flavum and the group with removed ligamentum flavum (P = 0.23). The ligamentum flavum preservation group's VAS score decreased from a preoperative 6.94 ± 1.26 to 3.73 ± 1.18 (t = 11.76, P < 0.01), while the ligamentum flavum removal group's score decreased from a preoperative 7.11 ± 0.87 to 4.05 ± 1.37 (t = 14.61, P < 0.01). Six months postoperatively, the VAS scores for the ligamentum flavum preservation group and the ligamentum flavum removal group decreased to 1.47 ± 1.01 and 1.39 ± 1.18, respectively, with no statistically significant difference (P = 0.73). ODI score Three days postoperatively, there was no statistically significant difference in the ODI score between the ligamentum flavum preservation group and the ligamentum flavum removal group (P = 0.12). The ligamentum flavum preservation group's ODI index decreased from a preoperative 62.74 ± 12.88 to 31.62 ± 5.37 (t = 14.10, P < 0.01), and the ligamentum flavum removal group's index decreased from a preoperative 63.39 ± 9.47 to 29.64 ± 6.61 (t = 22.64, P < 0.01). Six months postoperatively, the ODI index for the ligamentum flavum preservation group and the ligamentum flavum removal group decreased to 18.52 ± 10.14 and 15.73 ± 9.35, respectively, with no statistically significant difference (P = 0.16) (Table 3 ). Table 3 Postoperative outcome ligamentum flavum preservation group ligamentum flavum removal group t P VAS score 3 days 3.73 ± 1.18 4.05 ± 1.37 1.21 0.23 6 months 1.47 ± 1.01 1.39 ± 1.18 0.35 0.73 ODI Index 3 days 31.62 ± 5.37 29.64 ± 6.61 1.58 0.12 6 months 18.52 ± 10.14 15.73 ± 9.35 1.41 0.16 Imaging assessment Preoperatively, there was no statistically significant difference in the cross-sectional area of the dural sac at the intervertebral disc level between the two groups (P > 0.05). However, both groups showed significant improvement postoperatively (P 0.05) (Table 4). Table.4 Postoperative comparison of dural cross-sectional area cross-sectional area (mm 2 ) ligamentum flavum preservation group ligamentum flavum removal group t P preoperative 67.65 ± 14.28 65.73 ± 18.19 0.56 0.58 postoperation 164.31 ± 26.35 170.92 ± 27.68 1.19 0.24 t 20.40 24.60 P < 0.01 < 0.01 Complications None of the patients experienced serious postoperative complications such as surgical site infections or cauda equina syndrome. The incidence rates of postoperative complications in the ligamentum flavum preservation group and the ligamentum flavum removal group were 5% and 13.3%, respectively. No dural tears occurred in the ligamentum flavum preservation group, but 2 patients developed epidural hematomas. In the ligamentum flavum removal group, 2 patients experienced dural tears, and 6 patients developed postoperative epidural hematomas (Fig. 4 ). Although the incidence of complications was lower in the ligamentum flavum preservation group compared to the ligamentum flavum removal group, the difference was not statistically significant (P = 0.174). Discussion UBE is a minimally invasive surgical technique used to treat spinal stenosis, which has seen increasing clinical application due to reduced tissue dissection. Through a retrospective case analysis, we compared UBE patients who underwent surgery with and without the preservation of the ligamentum flavum. The results showed that the UBE decompression technique preserving the ligamentum flavum had a lower complication rate, shorter surgery time, and less surgical bleed loss, with equal surgical outcomes compared to those in the ligamentum flavum removal group. Therefore, we suggest that the ligamentum flavum should be preserved as much as possible when using the UBE technique to treat lumbar spinal stenosis. This study is the first to research the surgical method of preserving the ligamentum flavum during UBE surgeries, providing a basis for clinical doctors to select surgical mothods. The ligamentum flavum is considered an important anatomical barrier that prevents the formation of scar tissue postoperatively. Preserving the ligamentum flavum is beneficial in reducing the incidence of postoperative tissue adhesions[ 18 ]. The concept of preserving the ligamentum flavum was first proposed by Delamarter and was initially applied in microdiscectomy procedures. Microscopic discectomy offers advantages over open surgery, such as less trauma, quicker recovery, and thorough decompression. However, postoperative epidural fibrosis can affect the outcome of the surgery. Microscopic discectomy, compared to open surgery, has the advantages of less trauma, faster recovery, and more thorough decompression. However, postoperative epidural scar formation may affect the surgical outcome. To control the formation of epidural scars, surgeons have conducted extensive exploration during the surgical process, among which the technique of preserving the ligamentum flavum has achieved favorable results [ 19 ]. Rafet and colleagues conducted magnetic resonance imaging analysis on 93 patients who underwent microscopic lumbar discectomy, and found that preserving the ligamentum flavum during microscopic lumbar discectomy can reduce the formation of postoperative epidural scar tissue. [ 20 ]. When lumbar spinal stenosis occurs, the thickened ligamentum flavum is one of the compressive elements on the neural tissues[ 21 ]. Therefore, whether the decompression technique that preserves the ligamentum flavum in UBE surgery can achieve satisfactory clinical outcomes is currently not supported by relevant research. Intraoperative Indicators The results of this study show that the surgical time and intraoperative blood loss in the group that preserved the ligamentum flavum were significantly lower than in the group that removed the ligamentum flavum. Ismail and colleagues compared the postoperative clinical outcomes of 149 patients who underwent microscopic lumbar discectomy. The results revealed that the average surgery time for patients who had the ligamentum flavum removed was 70.9 ± 5.2 minutes, while it was 42.3 ± 4.6 minutes for those who retained the ligamentum flavum. The average surgical blood loss was 91.1 ± 11.3 ml and 50.3 ± 7.4 ml, respectively. The differences were statistically significant[ 22 ]. In the UBE surgery, the ligamentum flavum is an important neuroprotective structure, as well as a crucial anatomical landmark during surgery[ 23 ]. The ligamentum flavum originates ventrally from the cephalad lamina and terminates dorsally at the caudal lamina. The decompression of the cephalad lamina is relatively safe and takes less time due to the protection afforded by the ligamentum flavum. In surgical techniques that involve the removal of the ligamentum flavum, it is necessary to detach the ligamentum flavum from the caudal lamina, which adds to the steps of the operation. Moreover, since this part of the procedure is performed close to the dural sac, there is a potential risk of dural damage, necessitating extra caution from the surgeon during the removal of the ligamentum flavum, which also contributes to the longer duration of the surgery. Besides the prolonged surgical time leading to increased blood loss, the dissection and removal of the ligamentum flavum itself can cause bleeding. As there are venous plexuses surrounding the ligamentum flavum, their rupture can occur during the ligament's removal, thus increasing the volume of surgical blood loss. Postoperative outcome Lee et al. conducted a retrospective study on 89 patients who underwent percutaneous endoscopic lumbar discectomy, finding no statistically significant differences in postoperative ODI and VAS scores between groups that preserved the ligamentum flavum and those that partially removed it [ 17 ]. This study primarily assessed the clinical efficacy of UBE surgery in patients with lumbar spinal stenosis, preserving the ligamentum flavum. The results showed no statistical difference in postoperative VAS and ODI indices between the ligamentum flavum preservation group and the removal group. Lumbar spinal stenosis is mainly caused by disc herniation and thickening of the ligamentum flavum, as well as facet joint hypertrophy, with the most common area of stenosis located at the intervertebral disc space. Therefore, as long as the neural decompression at the intervertebral disc space is achieved, the neural symptoms can be alleviated. In the ligamentum flavum preservation group, decompression was sufficient on the head side of the ligamentum flavum and the inner edges of the bilateral facet joints, leaving only the ligamentum flavum attachments on the caudal side of the lamina. This method of decompression can effectively expand the space of the spinal canal and relieve nerve compression. In the lumbar region, the lamina space is not directly opposite the intervertebral disc space level but is located caudally to it[ 24 ]. Therefore, preserving the caudal attachment of the ligamentum flavum does not affect the decompression effect at the intervertebral disc level. Changes in the cross-sectional area of the dural sac can provide more objective evidence for the effectiveness of decompression for lumbar spinal stenosis. Haruo et al. conducted a study on 88 patients with lumbar spinal stenosis and discovered that the cross-sectional area of the dural sac under axial load is significantly correlated with the severity of symptoms of lumbar spinal stenosis[ 25 ]. In this study, the preoperative cross-sectional area of the dural sac in the ligamentum flavum preservation group was 67.65 ± 14.28 mm², which increased to 164.31 ± 26.35 mm² postoperatively; in the ligamentum flavum removal group, the preoperative cross-sectional area was 65.73 ± 18.19 mm², which increased to 170.92 ± 27.68 mm² postoperatively. Both groups showed a significant increase postoperatively compared to preoperatively. However, there was no significant difference in the cross-sectional area of the dural sac between the two groups, indicating that the dural sac space could be enlarged regardless of whether the ligamentum flavum was preserved. Although the ligamentum flavum preservation group retained the ligamentum flavum, the bone on the dorsal side and the inner edges of the bilateral facet joints were removed, providing ample space for the dural sac. Complications Complications of UBE surgery include surgical incision infection, cauda equina nerve damage, dural sac tear, and epidural hematoma, among others. In this study, there were no occurrences of surgical incision infection or cauda equina nerve damage. Previous research has shown that the incidence of dural tears during UBE surgery is 3.95%, which often occurs dorsally during the removal of the ligamentum flavum due to reasons such as limited intraoperative visual field, and adhesions between the dural sac and the ligamentum flavum[ 26 ]. A dural sac tear can significantly impact endoscopic lumbar surgery, leading to spinal high pressure intraoperatively and cerebrospinal fluid leakage postoperatively. Based on preoperative MRI and intraoperative observations, we have found that many patients with spinal stenosis have a significant reduction in epidural fat, which leads to a decreased space between the ligamentum flavum and the dura mater, increasing the risk of dural sac tears during surgery. In this study, two cases of dural tears occurred in the ligamentum flavum removal group, with an incidence rate of 3.33%. There were no dural tears in the ligamentum flavum preservation group. When adhesions are present between the ligamentum flavum and the dural sac, it is easy to cause a dural tear while separating the space between them. At the midline attachment site of the ligamentum flavum and the caudal lamina, there is usually a meningovertebral ligament connecting the ligamentum flavum and the dural sac, which is prone to causing dural sac damage during removal. The surgical technique that preserves the ligamentum flavum omits this step, effectively reducing the probability of dural damage. An epidural hematoma refers to the accumulation of blood outside the dura mater within the spinal canal, which can cause nerve compression. Symptoms after UBE surgery typically include lumbar distension pain, lower limb pain and numbness, and perineal numbness. Liang and others conducted a retrospective study on 105 patients after UBE surgery and found that the incidence of symptomatic epidural hematoma was 6.7%[ 27 ]. The incidence rate of epidural hematoma in the ligamentum flavum removal group in this study was 10%, which is higher than that found in Liang's study. This discrepancy may be due to the use of osteotomes for decompression in this study, whereas Liang and others used bone drills. Bone drilling during decompression step can seal the trabecular spaces of cancellous bone, thereby reducing bone surface bleeding. Bone chiseling after bone removal, however, can lead to bleeding and the formation of an epidural hematoma. Therefore, it is recommended to use bone wax to seal the operative site after bone chisel operations to reduce the occurrence of epidural hematomas. We have summarized the key points of the operation to preserve the ligamentum flavum in UBE surgery. First, it is necessary to fully remove the bone at the base of the spinous process on the dorsal side of the ligamentum flavum and the superior lamina, initially exposing the "V" shaped convergence area of the bilateral ligamentum flavum on the cranial side. This serves as a starting point for decompression along the cranial starting point of the ligamentum flavum towards both sides. Second, when removing the ventrolateral osseous structures of the contralateral inferior articular process, it is necessary to create sufficient space, then expose the inner edge of the contralateral superior articular process. Decompression should be thorough, leaving space between the ligamentum flavum and the dural sac. Third, before resecting the inner edge of the superior articular process, it is necessary to remove the superficial layer of the ligamentum flavum to expose the apex of the superior articular process, the inner edge of the superior articular process, and the transition area between the inner edge of the superior articular process and the upper border of the lamina on the caudal side. Fourth, when removing the bone on the medial edge of the superior articular process, it should be close to the tip of the superior articular process. During the removal process, a nerve dissector can be used to probe the inner edge of the pedicle to ensure that the decompression range is sufficient. At last, preservation of the ligamentum flavum does not imply complete retention of the ligamentum flavum. The superficial layer of the ligamentum flavum and the sides of the ligamentum flavum need to be removed to ensure full decompression of the bilateral nerve roots and to prevent post-separation healing of the ligamentum flavum, which could lead to symptoms of nerve compression. (Fig. 5 ) This study has some limitations. Firstly, it is a single-center retrospective study with a small sample size, lacking large-scale, multicenter research, and the follow-up period is short, which introduces certain biases. Secondly, the included patients span different segments from L3 to S1, and due to the limited sample size, the study did not perform stratified comparisons based on specific segments. Despite these limitations, this study is the first to describe the UBE technique that preserves the ligamentum flavum, and it also confirms the effectiveness of this technique in treating lumbar spinal stenosis, providing a relevant basis for clinical surgeons. Conclusion The UBE technique for lumbar spinal stenosis that preserves the ligamentum flavum can protect the normal anatomical structures between the epidural space and other paraspinal tissues, reduce complications, surgical time, and blood loss, while also providing good surgical outcomes. It is recommended to preserve the ligamentum flavum as much as possible when using the UBE technique to treat patients with lumbar spinal stenosis. Declarations Human Ethics and Consent to Participate declarations All clinical investigations had been conducted according to the principles expressed in the Declaration of Helsinki. This study was conducted with approval from Ethics Committee of Chongqing Liangping District People's Hospital. Informed consent to participate in the study was obtained from the participant. Clinical trial number Not applicable Consent for publication Written informed consent for publication was obtained from all participants Availability of data and materials The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding The Funding of Baoding Self-raised Fund Project (Grant Number 2341ZF335)，the Funding of Affiliated Hospital of Hebei University (Grant Number 2023ZB01) Authors’ contributions Kepeng Li participated in the collection of experimental data. Bo Jiang designed the study. Ye Han wrote and revised the manuscript. Acknowledgements Not applicable. References Akosman I, Shafi K, Subramanian T, Kazarian GS, Kaidi AC, Cunningham M, Kim HJ, Lovecchio F. Left-digit bias in surgical decision-making for lumbar spinal stenosis. Spine J. 2024;24(8):1388-95. Zhu L, Sun Y, Kang J, Liang J, Su T, Fu W, Zhang W, Dai R, Hou Y, Zhao H, et al. Effect of Acupuncture on Neurogenic Claudication Among Patients With Degenerative Lumbar Spinal Stenosis : A Randomized Clinical Trial. Ann Intern Med. 2024. Åkerstedt J, Wänman J, Banitalebi H, Myklebust TÅ, Weber C, Storheim K, Hellum C, Indrekvam K, Hermansen E, Brisby H. Change in Lumbar Lordosis after Decompressive Surgery in Lumbar Spinal Stenosis Patients and Associations with Patient Related Outcomes 2 Years after Surgery. Radiological and Clinical Results from the NORDSTEN Spinal Stenosis Trial. Spine (Phila Pa 1976). 2024. Karlsson T, Försth P, Öhagen P, Michaëlsson K, Sandén B. Decompression alone or decompression with fusion for lumbar spinal stenosis: five-year clinical results from a randomized clinical trial. Bone Joint J. 2024;106-B(7):705-12. Martino Cinnera A, Morone G, Iosa M, Bonomi S, Calabrò RS, Tonin P, Cerasa A, Ricci A, Ciancarelli I. Artificial neural network analysis of factors affecting functional independence recovery in patients with lumbar stenosis after neurosurgery treatment: An observational cohort study. J Orthop. 2024;55:38-43. Sheppard WL, Getachew K, Zelalem T, Anderson D, Park DY. Global utilization of biportal spinal endoscopy: Case series on management of lumbar pathology in Soddo, Ethiopia. Int J Surg Case Rep. 2024;122:110046. Pao JL. Preliminary Clinical and Radiological Outcomes of the "No-Punch" Decompression Techniques for Unilateral Biportal Endoscopic Spine Surgery. Neurospine. 2024;21(2):732-41. Özer Mİ, Demirtaş OK. Comparison of lumbar microdiscectomy and unilateral biportal endoscopic discectomy outcomes: a single-center experience. J Neurosurg Spine. 2024;40(3):351-8. Meng H, Su N, Lin J, Fei Q. Comparative efficacy of unilateral biportal endoscopy and micro-endoscopic discectomy in the treatment of degenerative lumbar spinal stenosis: a systematic review and meta-analysis. J Orthop Surg Res. 2023;18(1):814. Wang B, He P, Liu X, Wu Z, Xu B. Complications of Unilateral Biportal Endoscopic Spinal Surgery for Lumbar Spinal Stenosis: A Systematic Review of the Literature and Meta-analysis of Single-arm Studies. Orthop Surg. 2023;15(1):3-15. Chen Z, Zhou H, Wang X, Liu Z, Liu W, Luo J. Complications of Unilateral Biportal Endoscopic Spinal Surgery for Lumbar Spinal Stenosis: A Meta-Analysis and Systematic Review. World Neurosurg. 2023;170:e371-371e379. Xu J, Wang D, Liu J, Zhu C, Bao J, Gao W, Zhang W, Pan H. Learning Curve and Complications of Unilateral Biportal Endoscopy: Cumulative Sum and Risk-Adjusted Cumulative Sum Analysis. Neurospine. 2022;19(3):792-804. Ahn DK, Lee JS, Shin WS, Kim S, Jung J. Postoperative spinal epidural hematoma in a biportal endoscopic spine surgery. Medicine (Baltimore). 2021;100(6):e24685. Wiltse LL. Anatomy of the extradural compartments of the lumbar spinal canal. Peridural membrane and circumneural sheath. Radiol Clin North Am. 2000;38(6):1177-206. Liu JJ, Zhu B, Chen L, Jing JH, Tian DS. [Efficacy comparison of unilateral biportal endoscopic decompression and extended interlaminar fenestration for lumbar lateral recess stenosis]. Zhonghua Yi Xue Za Zhi. 2022;102(11):801-7. Pao JL, Lin SM, Chen WC, Chang CH. Unilateral biportal endoscopic decompression for degenerative lumbar canal stenosis. J Spine Surg. 2020;6(2):438-46. Lee U, Kim CH, Kuo CC, Choi Y, Park SB, Yang SH, Lee CH, Kim KT, Chung CK. Does Preservation of Ligamentum Flavum in Percutaneous Endoscopic Lumbar Interlaminar Discectomy Improve Clinical Outcomes. Neurospine. 2019;16(1):113-9. de Divitiis E, Cappabianca P. Preserving the ligamentum flavum in lumbar discectomy: a new technique that prevents scar tissue formation in the first 6 months postsurgery. Neurosurgery. 2007;61(6):E1340. Lin HB, Dai JH, Li L, Xu ZX, Wang H. [Experimental study of reservation flaval ligament on prevention of peridural adhesion after operation on lumbar disc]. Zhonghua Yi Xue Za Zhi. 2009;89(11):766-70. Özay R, Ogur T, Durmaz HA, Turkoglu E, Caglar YS, Sekerci Z, Sorar M, Hanalioglu S. Revisiting Ligament-Sparing Lumbar Microdiscectomy: When to Preserve Ligamentum Flavum and How to Evaluate Radiological Results for Epidural Fibrosis. World Neurosurg. 2018;114:e378-378e387. Kim J, Kwon WK, Cho H, Lee S, Lee JB, Park JY, Jin DU, Jung EY, Hur JW. Ligamentum flavum hypertrophy significantly contributes to the severity of neurogenic intermittent claudication in patients with lumbar spinal canal stenosis. Medicine (Baltimore). 2022;101(36):e30171. Yüce İ, Kahyaoğlu O, Çavuşoğlu H, Aydın Y. Surgical outcome and efficacy of lumbar microdiscectomy technique with preserving of ligamentum flavum for recurrent lumbar disc herniations. J Clin Neurosci. 2019;63:43-7. Park DK, Weng C, Zakko P, Choi DJ. Unilateral Biportal Endoscopy for Lumbar Spinal Stenosis and Lumbar Disc Herniation. JBJS Essent Surg Tech. 2023;13(2):e22.00020. Wang Y, Zhang P, Yan X, Wang J, Zhu M, Teng H. The correlation between lumbar interlaminar space size on plain radiograph and spinal stenosis. Eur Spine J. 2023;32(5):1721-8. Kanno H, Ozawa H, Koizumi Y, Morozumi N, Aizawa T, Kusakabe T, Ishii Y, Itoi E. Dynamic change of dural sac cross-sectional area in axial loaded magnetic resonance imaging correlates with the severity of clinical symptoms in patients with lumbar spinal canal stenosis. Spine (Phila Pa 1976). 2012;37(3):207-13. Yu H, Zhao Q, Lv J, Liu J, Zhu B, Chen L, Jing J, Tian D. Unintended dural tears during unilateral biportal endoscopic lumbar surgery: incidence and risk factors. Acta Neurochir (Wien). 2024;166(1):95. Liang CX, Liang GY, Liu HF, Zheng XQ, Xiao D, Huang YX, Chen C, Yu T, Yin D, Chang YB. [Characteristics and risk factors of spinal epidural hematoma after unilateral biportal endoscopic lumbar interbody fusion]. Zhonghua Yi Xue Za Zhi. 2022;102(41):3267-73. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 29 Jan, 2025 Editor assigned by journal 28 Jan, 2025 Submission checks completed at journal 28 Jan, 2025 First submitted to journal 28 Jan, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5916963","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":408631801,"identity":"2cc4cf39-94f9-4bd5-a0b3-32801996f1e2","order_by":0,"name":"Kepeng Li","email":"","orcid":"","institution":"Chongqing Liangping District People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kepeng","middleName":"","lastName":"Li","suffix":""},{"id":408631803,"identity":"ea43f3e6-2f72-4684-8524-62e25d4ae20e","order_by":1,"name":"Bo Jiang","email":"","orcid":"","institution":"Chongqing Liangping District People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Jiang","suffix":""},{"id":408631805,"identity":"9d84bc21-1bda-4d71-8185-514e7d48a693","order_by":2,"name":"Ye Han","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIiWNgGAWjYBACAwhpI8fY3tj48APxWgrSjJl7DjcbSxCv5cPhxPYZ6W0CPMRoMWc/e0zigwEzY+/Mh20MEgx2croNBLRY9uSlSc4wYGOWnJ3Y9qCAIdnY7AAhhx3IMZPmMeBhM5yd2G4gwXAgcRtBLeffmEn/MZDgsb95sE2ChygtN4C2MBgYSDDOYCRayxtjyx6DBAPGnkRgIBsQ45fzOYY3fvz5X9/Yfvzhww8VdnIEtQABC1IEGhBWDgLMRCWTUTAKRsEoGMEAAN/HQ3APcP13AAAAAElFTkSuQmCC","orcid":"","institution":"Affiliated Hospital of Hebei University, Affiliated Hospital of Hebei University","correspondingAuthor":true,"prefix":"","firstName":"Ye","middleName":"","lastName":"Han","suffix":""}],"badges":[],"createdAt":"2025-01-28 07:53:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5916963/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5916963/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":75188152,"identity":"66889bfe-c709-44bf-8bfe-b0522d782580","added_by":"auto","created_at":"2025-01-31 18:00:21","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":333677,"visible":true,"origin":"","legend":"\u003cp\u003ePreservation of the ligamentum flavum technique. A and B. Preoperative CT/MRI reveals spinal canal stenosis. C. Intraoperative positioning at the junction of the inferior edge of the lamina and the root of the spinous process. D and E. Post-operation, the spinal canal area is increased, with the preserved ligamentum flavum visible. F. The preserved ligamentum flavum displayed at the end of the surgery, which is shown to no longer exert pressure on the dura mater beneath it. The blue arrow indicates the preserved ligamentum flavum.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/964f600741af1920381db13e.png"},{"id":75190523,"identity":"a06b5521-f0e9-4752-945f-608497b94d18","added_by":"auto","created_at":"2025-01-31 18:08:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":311780,"visible":true,"origin":"","legend":"\u003cp\u003eLigamentum flavum removal procedure. A and B. Preoperative CT/MRI shows spinal canal stenosis. C. Intraoperative localization of the lower edge of the lamina. D and E. Post-operation, the spinal canal area is enlarged; the ligamentum flavum is removed during the operation. F. At the end of the surgery, the image shows the dura mater after decompression.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/c1e772dea0fd5208c11794c9.png"},{"id":75188156,"identity":"45b71943-ee81-4210-99b4-6ae047b9de9d","added_by":"auto","created_at":"2025-01-31 18:00:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":215069,"visible":true,"origin":"","legend":"\u003cp\u003eThe cross-sectional area of the dural sac. A. The dura mater at the intervertebral disc level appears triangular before surgery. B. After decompression surgery, the dura mater area at the intervertebral disc level is semicircular.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/8623e30742729435585e6000.png"},{"id":75188166,"identity":"6c6c18a7-b544-4625-b5c6-e3c0ff11d14a","added_by":"auto","created_at":"2025-01-31 18:00:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":309025,"visible":true,"origin":"","legend":"\u003cp\u003eEpidural hematoma. A. Preoperative MRI indicates lumbar stenosis at the L4/5 level with significant hypertrophy of the ligamentum flavum. B. Postoperative MRI at the lumbar 4/5 level reveals an epidural hematoma, characterized by the signal of the hematoma replacing the original position of the ligamentum flavum (blue arrow indicator).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/d94d0b936b404ac7b730a552.png"},{"id":75190544,"identity":"5f8cc8e5-48dc-4d60-97d4-ffca308a415c","added_by":"auto","created_at":"2025-01-31 18:08:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":234870,"visible":true,"origin":"","legend":"\u003cp\u003eThe key steps of UBE surgery with preservation of the ligamentum flavum. A. Expose the intersection between the lamina and the base of the spinous process, and use an osteotome to chisel away the bone at the inferior edge of the lamina and the base of the spinous process starting from this point. B. Chisel away the inner edge of the ipsilateral inferior articular process. C. Remove the ventral bone of the contralateral inferior articular process at the attachment site of the cranial ligamentum flavum, and sever the attachment of the cranial and lateral aspects of the ligamentum flavum. D. The upper edge of the ligamentum flavum is free. E. After the removal of the bone on the inner edge of the inferior articular process on the same side, the articular surface of the inner edge of the superior articular process has been exposed. F. Chisel away the articular surface of the inner edge of the superior articular process with the osteotome. G. Use a curette to strip the attachment of the ligamentum flavum on the inner edge of the superior articular process and remove the inner edge of the superior articular process. H. Expose the outer edge of the nerve root, and the nerve root is fully released.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/c55dd7ed2972d74d3c6d9e94.png"},{"id":75191045,"identity":"3b2d7357-a3d6-4e8e-9bbc-abaaab386ed9","added_by":"auto","created_at":"2025-01-31 18:16:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2432443,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5916963/v1/0436036b-8993-48cf-a16a-8d25db27a9d8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The clinical efficacy of unilateral biportal endoscopic treatment for lumbar spinal stenosis with preservation of the ligamentum flavum","fulltext":[{"header":"Background","content":"\u003cp\u003eLumbar spinal stenosis is a common disease among the elderly, primarily characterized by lower back and leg pain, and intermittent claudication. It significantly affects the quality of life of patients. [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. For patients with severe lower back and leg pain, neurological impairment, and degenerative lumbar diseases that have failed conservative treatment, surgical intervention is required[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Traditional surgery is a common treatment for degenerative lumbar diseases; however, it extensively damages the paraspinal muscles and posterior ligamentous structures, leading to postoperative complications such as failed back surgery syndrome and muscle and nerve atrophy[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Unilateral Biportal Endoscopy (UBE) is a new technique for treating lumbar spinal stenosis. The UBE technique can achieve effective spinal decompression without compromising the integrity of the spine. UBE surgery can provide the same long-term clinical efficacy as open surgery while significantly reducing damage to spinal structures, decreasing the incidence of postoperative pain, and facilitating early and rapid recovery[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn conventional UBE surgery, decompression of the dural sac is achieved by removing the ligamentum flavum, but this removal increases the incidence of surgical complications. Previous studies have showed that epidural hematoma and dural tears are common complications of UBE surgery and are major factors reducing patient satisfaction[\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Research by Kim et al. indicates that the longer the surgery and the more complex it is, the higher the incidence of epidural hematoma[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Removal of the ligamentum flavum prolongs the surgery time and disrupts the venous plexus between the ligamentum flavum and the dural sac, increasing the incidence of epidural hematoma. Dural tears also commonly occur during the process of removing the ligamentum flavum. Between the ligamentum flavum and the dural sac, there is a fine, net-like ligamentous structure known as the meningovertebral ligament, which serves to stabilize the dural sac. During lumbar ligamentum flavum resection, the meningovertebral ligament may be stretched, causing a dural tear[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Additionally, during the surgery, when both sides of the dural sac are subjected to the pressure of saline irrigation, a fold forms in the middle, concealed beneath the epidural fat, rendering it invisible to the surgeon. Thus, during the removal of the ligamentum flavum, it is easy to cause a dural tear at the site of the fold[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Furthermore, the area around the meningovertebral ligament has an abundance of epidural blood vessels, and bleeding can greatly interfere with the endoscopic field of view, increasing the risk of dural damage[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDue to the numerous defects resulting from the removal of the ligamentum flavum in UBE surgery, some scholars have proposed a surgical method that preserves the ligamentum flavum[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. However, the ligamentum flavum is one of the compressive agents on the dural sac during lumbar spinal stenosis, and preserving the ligamentum flavum may affect the efficacy of neural decompression. To study the clinical effects of lumbar canal decompression while preserving the ligamentum flavum under UBE, we have summarized relevant surgical cases from recent years. Our objectives are: (1) to introduce the surgical techniques of UBE that involve preserving the ligamentum flavum; (2) to observe the therapeutic efficacy of UBE decompression for lumbar spinal stenosis when the ligamentum flavum is preserved.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eResearch Design\u003c/h2\u003e \u003cp\u003e This study is a single-center retrospective study approved by the Ethics Committee of Chongqing Liangping District People's Hospital, with written informed consent obtained from all patients before surgery. The study retrospectively analyzed patients with lumbar spinal stenosis (LSS) who underwent UBE treatment from January 2022 to March 2024.\u003c/p\u003e \u003cp\u003eInclusion criteria (1) patients presenting with intermittent claudication, experiencing lower limb pain and numbness after walking less than 50 meters; (2) imaging examinations indicating lumbar canal stenosis, primarily located at the intervertebral disc ligamentum flavum interspace; (3) patients with complete preoperative and postoperative imaging data, including X-rays, CT, MRI, etc.\u003c/p\u003e \u003cp\u003eExclusion criteria (1) Patients with a history of lumbar spine surgery; (2) lumbar instability (In the lateral radiographs of the lumbar spine with flexion and extension, an angle difference greater than 10 degrees between the inferior edge of the cephalad vertebral body and the superior edge of the caudad vertebral body, or a length difference greater than 4mm between the posterior edges of the adjacent vertebral bodies, is considered significant.); (3) lumbar scoliosis deformity; (4) patients with lumbar disc herniation requiring removal of the intervertebral disc during surgery; (5) patients with ossification of the ligamentum flavum.\u003c/p\u003e \u003cp\u003eThe study included a total of 100 patients with LSS treated with UBE, with 40 in the ligamentum flavum preservation group and 60 in the ligamentum flavum removal group.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurgical Procedure\u003c/h3\u003e\n\u003cp\u003ePreservation of the ligamentum flavum technique\u003c/p\u003e \u003cp\u003eTaking the L4/5 intervertebral space on the left side as an example, the patient is positioned prone under general anesthesia, and the L4/5 segment is located under C-arm fluoroscopy. At the medial edge of the left pedicle, about 1.5 cm above and below the L4/5 space, two surgical incisions approximately 1.5 cm in length are made. Soft tissue is dissected using a soft tissue dissector, with the upper incision serving as the observation port and the lower incision as the working channel. Under endoscopy, a plasma radiofrequency knife is used to excise the soft tissue, revealing the lower edge of the L4 lamina, the ligamentum flavum, the root of the spinous process, and the medial edge of the facet joint.\u003c/p\u003e \u003cp\u003eAn osteotome is used to start resecting the lower edge of the left L4 lamina and the base of the spinous process from the junction of the spinous process and the lamina. The osteotome should be angled at 30\u0026deg; to the edge of the bone being resected, and the lamina is gradually removed in small amounts. The V-shaped junction of the bilateral ligamentum flavum at the cephalic midline is exposed. A curette is used to separate the ligamentum flavum on the ventral side of the right L4 lower articular process. On the dorsal side of the ligamentum flavum, an osteotome is used to remove the bone on the ventral side of the right L4 lower articular process. The upper part is exposed up to the starting point of the right L4 ligamentum flavum, and the right side is exposed to the inner edge of the upper L5 articular process. After removing the superficial layer of the ligamentum flavum, a curette is used to strip the attachment of the ligamentum flavum along the starting point of the right L4 and the inner edge of the upper L5 articular process and to remove part of the inner edge of the upper L5 articular process until the right L5 pedicle is exposed, completing the decompression of the right nerve root.\u003c/p\u003e \u003cp\u003eThe bone on the inner edge of the left L4 lower articular process is removed to expose the left ligamentum flavum at the starting point of the L4 lamina and the inner edge of the upper articular process. A curette is used to strip the attachment of the ligamentum flavum along the left side at the starting point of the L4 lamina and the inner edge of the upper articular process. Part of the inner edge of the upper articular process on the left side of L4 is removed until the left L5 pedicle is exposed, completing the decompression of the left nerve root.\u003c/p\u003e \u003cp\u003eNow the ligamentum flavum is only attached to the L5 lamina, and the rest is freed. The ventral side of the dura mater beneath the ligamentum flavum is probed to confirm that the dura is bulging and decompression is adequate. Cancellous bone surfaces are treated with bone wax for hemostasis. No drainage tube is placed, and the incision is sutured (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eLigamentum flavum removal procedure\u003c/p\u003e \u003cp\u003eTaking the left L4/5 intervertebral space as an example, the positioning and exposure steps are the same as those in the ligamentum flavum preservation procedure. An osteotome is used to start from the junction of the spinous process and the lamina to remove the lower edge of the left L4 lamina and the base of the spinous process, until the V-shaped junction at the midline head side of the bilateral ligamentum flavum is exposed. A periosteal elevator is used to separate the ligamentum flavum on the ventral side of the bilateral lower articular processes. On the dorsal side of the ligamentum flavum, the osteotome is used to remove the bony part on the ventral side of the right L4 lower articular process, exposing the inner edges of the bilateral L5 upper articular processes. A curette is used to strip the ligamentum flavum from its attachment at the L4 lamina and the inner edge of the upper articular processes. The osteotome is then used to remove the bony part at the junction of the L5 lamina and the upper articular processes. A nerve dissector is used to peel off the chiseled bone block and its connected ligamentum flavum, exposing the neural structures. The camera is placed between the remaining ligamentum flavum and the upper edge of the L5 lamina. Then separate the remaining space between the ligamentum flavum and the neural tissue. A curette is used to separate the deep layer of the ligamentum flavum at the head end of the L5 lamina. Laminectomy punch are then used to completely remove the ligamentum flavum, exposing the dura mater. The bilateral edges of the dura mater are probed to confirm that the dura mater is bulging, indicating decompression is complete. The incision is then sutured (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePostoperative Related Treatment\u003c/p\u003e \u003cp\u003eWithin 72 hours post-surgery, 125ml of mannitol should be administered intravenously twice daily to prevent nerve root edema. Additionally, Take 0.5 milligrams of mecobalamin orally three times each time to promote nerve recovery. The patient is advised to engage in activities while wearing a lumbar back brace starting from the second day after the surgery, and to continue wearing the brace for six weeks.\u003c/p\u003e \u003cp\u003eClinical outcome and radiological assessment\u003c/p\u003e \u003cp\u003eClinical lumbar and leg pain was evaluated using the Visual Analogue Scale (VAS) at 3 days and 6 months post-operation, while lumbar spine function was assessed using the Oswestry Disability Index (ODI). The cross-sectional area of the dural sac at the level of the intervertebral disc in the decompressed lumbar MRI segments was measured before and after surgery (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). All radiological assessments were performed by two senior spine surgeons with over five years of experience. Each surgeon measured three times to obtain an average value. If the difference in average values between the two assessors was less than 10mm, the mean of all six measurements was recorded. If the difference in average area values was 10mm or greater, a third senior spine surgeon with over five years of experience was invited to measure. All three surgeons used the same method to measure, and they consulted together to agree on each measurement result. The final average of the values included in the data was then recorded.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eComplications\u003c/p\u003e \u003cp\u003eSurgical complications include postoperative wound infection, cauda equina nerve injury, and epidural hematoma, among others. The diagnostic criteria for epidural hematoma are: (1) new onset of lumbar distension pain, radiating pain in the lower limbs, or numbness after surgery; (2) postoperative MRI indicating the presence of a hematoma within the spinal canal (see Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e); (3) after removal of the suture at the incision site and local drainage, the blood clots are observed. After the hematoma is drained, the patient's symptoms of lumbar soreness and swelling, as well as lower limb pain and numbness, are alleviated.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eData Analysis\u003c/h2\u003e \u003cp\u003eAll statistical analyses were performed using SPSS version 25.0 (IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp). Continuous data that followed a normal distribution were analyzed using the t-test and are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD). For data not normally distributed, non-parametric tests were employed. Categorical data were expressed in frequencies and percentages (%) and compared using the Chi-square test. A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered to indicate a statistically significant difference between the two groups.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eBasic information\u003c/p\u003e \u003cp\u003eUpon comparing the patients' age, gender, BMI, underlying diseases, and surgical segments, it was found that there were no statistically significant differences between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of baseline indicators between the ligamentum flavum preservation group and the ligamentum flavum removal group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eligamentum flavum preservation group (n\u0026thinsp;=\u0026thinsp;40)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eligamentum flavum removal group (n\u0026thinsp;=\u0026thinsp;60)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge(year)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.37\u0026thinsp;\u0026plusmn;\u0026thinsp;12.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e67.81\u0026thinsp;\u0026plusmn;\u0026thinsp;11.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.81\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003emale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003efemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003cp\u003e(kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23.13\u0026thinsp;\u0026plusmn;\u0026thinsp;5.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e24.26\u0026thinsp;\u0026plusmn;\u0026thinsp;2.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePast-illnesses\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ehypertension\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.87\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ediabetes\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOsteoporosis\u003c/p\u003e \u003cp\u003en(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.94\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e7.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.43\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eODI index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e62.74\u0026thinsp;\u0026plusmn;\u0026thinsp;12.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e63.39\u0026thinsp;\u0026plusmn;\u0026thinsp;9.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.67\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSegment n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL3/4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL4/5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL5/S1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIntraoperative indicator comparison\u003c/p\u003e \u003cp\u003eThe average surgical duration for the ligamentum flavum preservation group was (50.13\u0026thinsp;\u0026plusmn;\u0026thinsp;8.45) minutes, with an intraoperative blood loss of (30.57\u0026thinsp;\u0026plusmn;\u0026thinsp;6.64) ml. In contrast, the average surgical duration for the ligamentum flavum removal group was (66.47\u0026thinsp;\u0026plusmn;\u0026thinsp;7.26) minutes, with an intraoperative blood loss of (58.70\u0026thinsp;\u0026plusmn;\u0026thinsp;6.19) ml. Regarding surgical duration and intraoperative blood loss, the ligamentum flavum preservation group was superior to the ligamentum flavum removal group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSurgical duration and intraoperative blood loss\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eligamentum flavum preservation group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eligamentum flavum removal group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical Duration (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50.13\u0026thinsp;\u0026plusmn;\u0026thinsp;8.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e66.47\u0026thinsp;\u0026plusmn;\u0026thinsp;7.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative blood loss (ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.57\u0026thinsp;\u0026plusmn;\u0026thinsp;6.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e58.70\u0026thinsp;\u0026plusmn;\u0026thinsp;6.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ePostoperative outcome\u003c/p\u003e \u003cp\u003eVAS score\u003c/p\u003e \u003cp\u003eThree days postoperatively, there was no statistically significant difference in VAS scores between the group with preserved ligamentum flavum and the group with removed ligamentum flavum (P\u0026thinsp;=\u0026thinsp;0.23). The ligamentum flavum preservation group's VAS score decreased from a preoperative 6.94\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26 to 3.73\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18 (t\u0026thinsp;=\u0026thinsp;11.76, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while the ligamentum flavum removal group's score decreased from a preoperative 7.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.87 to 4.05\u0026thinsp;\u0026plusmn;\u0026thinsp;1.37 (t\u0026thinsp;=\u0026thinsp;14.61, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Six months postoperatively, the VAS scores for the ligamentum flavum preservation group and the ligamentum flavum removal group decreased to 1.47\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01 and 1.39\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18, respectively, with no statistically significant difference (P\u0026thinsp;=\u0026thinsp;0.73).\u003c/p\u003e \u003cp\u003eODI score\u003c/p\u003e \u003cp\u003eThree days postoperatively, there was no statistically significant difference in the ODI score between the ligamentum flavum preservation group and the ligamentum flavum removal group (P\u0026thinsp;=\u0026thinsp;0.12). The ligamentum flavum preservation group's ODI index decreased from a preoperative 62.74\u0026thinsp;\u0026plusmn;\u0026thinsp;12.88 to 31.62\u0026thinsp;\u0026plusmn;\u0026thinsp;5.37 (t\u0026thinsp;=\u0026thinsp;14.10, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and the ligamentum flavum removal group's index decreased from a preoperative 63.39\u0026thinsp;\u0026plusmn;\u0026thinsp;9.47 to 29.64\u0026thinsp;\u0026plusmn;\u0026thinsp;6.61 (t\u0026thinsp;=\u0026thinsp;22.64, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Six months postoperatively, the ODI index for the ligamentum flavum preservation group and the ligamentum flavum removal group decreased to 18.52\u0026thinsp;\u0026plusmn;\u0026thinsp;10.14 and 15.73\u0026thinsp;\u0026plusmn;\u0026thinsp;9.35, respectively, with no statistically significant difference (P\u0026thinsp;=\u0026thinsp;0.16) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePostoperative outcome\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eligamentum flavum preservation group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eligamentum flavum removal group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVAS score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 days\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.73\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.05\u0026thinsp;\u0026plusmn;\u0026thinsp;1.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6 months\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.47\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.39\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.73\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eODI Index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 days\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31.62\u0026thinsp;\u0026plusmn;\u0026thinsp;5.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.64\u0026thinsp;\u0026plusmn;\u0026thinsp;6.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6 months\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18.52\u0026thinsp;\u0026plusmn;\u0026thinsp;10.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.73\u0026thinsp;\u0026plusmn;\u0026thinsp;9.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eImaging assessment\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ePreoperatively, there was no statistically significant difference in the cross-sectional area of the dural sac at the intervertebral disc level between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, both groups showed significant improvement postoperatively (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). There was also no statistically significant difference in the postoperative cross-sectional area of the dural sac between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;4).\u003c/p\u003e \u003cp\u003eTable.4 Postoperative comparison of dural cross-sectional area\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecross-sectional area (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eligamentum flavum preservation group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eligamentum flavum removal group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epreoperative\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e67.65\u0026thinsp;\u0026plusmn;\u0026thinsp;14.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e65.73\u0026thinsp;\u0026plusmn;\u0026thinsp;18.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epostoperation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e164.31\u0026thinsp;\u0026plusmn;\u0026thinsp;26.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e170.92\u0026thinsp;\u0026plusmn;\u0026thinsp;27.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003et\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eComplications\u003c/p\u003e \u003cp\u003eNone of the patients experienced serious postoperative complications such as surgical site infections or cauda equina syndrome. The incidence rates of postoperative complications in the ligamentum flavum preservation group and the ligamentum flavum removal group were 5% and 13.3%, respectively. No dural tears occurred in the ligamentum flavum preservation group, but 2 patients developed epidural hematomas. In the ligamentum flavum removal group, 2 patients experienced dural tears, and 6 patients developed postoperative epidural hematomas (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Although the incidence of complications was lower in the ligamentum flavum preservation group compared to the ligamentum flavum removal group, the difference was not statistically significant (P\u0026thinsp;=\u0026thinsp;0.174).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eUBE is a minimally invasive surgical technique used to treat spinal stenosis, which has seen increasing clinical application due to reduced tissue dissection. Through a retrospective case analysis, we compared UBE patients who underwent surgery with and without the preservation of the ligamentum flavum. The results showed that the UBE decompression technique preserving the ligamentum flavum had a lower complication rate, shorter surgery time, and less surgical bleed loss, with equal surgical outcomes compared to those in the ligamentum flavum removal group. Therefore, we suggest that the ligamentum flavum should be preserved as much as possible when using the UBE technique to treat lumbar spinal stenosis. This study is the first to research the surgical method of preserving the ligamentum flavum during UBE surgeries, providing a basis for clinical doctors to select surgical mothods.\u003c/p\u003e \u003cp\u003eThe ligamentum flavum is considered an important anatomical barrier that prevents the formation of scar tissue postoperatively. Preserving the ligamentum flavum is beneficial in reducing the incidence of postoperative tissue adhesions[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The concept of preserving the ligamentum flavum was first proposed by Delamarter and was initially applied in microdiscectomy procedures. Microscopic discectomy offers advantages over open surgery, such as less trauma, quicker recovery, and thorough decompression. However, postoperative epidural fibrosis can affect the outcome of the surgery. Microscopic discectomy, compared to open surgery, has the advantages of less trauma, faster recovery, and more thorough decompression. However, postoperative epidural scar formation may affect the surgical outcome. To control the formation of epidural scars, surgeons have conducted extensive exploration during the surgical process, among which the technique of preserving the ligamentum flavum has achieved favorable results [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Rafet and colleagues conducted magnetic resonance imaging analysis on 93 patients who underwent microscopic lumbar discectomy, and found that preserving the ligamentum flavum during microscopic lumbar discectomy can reduce the formation of postoperative epidural scar tissue. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. When lumbar spinal stenosis occurs, the thickened ligamentum flavum is one of the compressive elements on the neural tissues[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Therefore, whether the decompression technique that preserves the ligamentum flavum in UBE surgery can achieve satisfactory clinical outcomes is currently not supported by relevant research.\u003c/p\u003e \u003cp\u003eIntraoperative Indicators\u003c/p\u003e \u003cp\u003eThe results of this study show that the surgical time and intraoperative blood loss in the group that preserved the ligamentum flavum were significantly lower than in the group that removed the ligamentum flavum. Ismail and colleagues compared the postoperative clinical outcomes of 149 patients who underwent microscopic lumbar discectomy. The results revealed that the average surgery time for patients who had the ligamentum flavum removed was 70.9\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2 minutes, while it was 42.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6 minutes for those who retained the ligamentum flavum. The average surgical blood loss was 91.1\u0026thinsp;\u0026plusmn;\u0026thinsp;11.3 ml and 50.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4 ml, respectively. The differences were statistically significant[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In the UBE surgery, the ligamentum flavum is an important neuroprotective structure, as well as a crucial anatomical landmark during surgery[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The ligamentum flavum originates ventrally from the cephalad lamina and terminates dorsally at the caudal lamina. The decompression of the cephalad lamina is relatively safe and takes less time due to the protection afforded by the ligamentum flavum. In surgical techniques that involve the removal of the ligamentum flavum, it is necessary to detach the ligamentum flavum from the caudal lamina, which adds to the steps of the operation. Moreover, since this part of the procedure is performed close to the dural sac, there is a potential risk of dural damage, necessitating extra caution from the surgeon during the removal of the ligamentum flavum, which also contributes to the longer duration of the surgery. Besides the prolonged surgical time leading to increased blood loss, the dissection and removal of the ligamentum flavum itself can cause bleeding. As there are venous plexuses surrounding the ligamentum flavum, their rupture can occur during the ligament's removal, thus increasing the volume of surgical blood loss.\u003c/p\u003e \u003cp\u003ePostoperative outcome\u003c/p\u003e \u003cp\u003eLee et al. conducted a retrospective study on 89 patients who underwent percutaneous endoscopic lumbar discectomy, finding no statistically significant differences in postoperative ODI and VAS scores between groups that preserved the ligamentum flavum and those that partially removed it [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This study primarily assessed the clinical efficacy of UBE surgery in patients with lumbar spinal stenosis, preserving the ligamentum flavum. The results showed no statistical difference in postoperative VAS and ODI indices between the ligamentum flavum preservation group and the removal group. Lumbar spinal stenosis is mainly caused by disc herniation and thickening of the ligamentum flavum, as well as facet joint hypertrophy, with the most common area of stenosis located at the intervertebral disc space. Therefore, as long as the neural decompression at the intervertebral disc space is achieved, the neural symptoms can be alleviated. In the ligamentum flavum preservation group, decompression was sufficient on the head side of the ligamentum flavum and the inner edges of the bilateral facet joints, leaving only the ligamentum flavum attachments on the caudal side of the lamina. This method of decompression can effectively expand the space of the spinal canal and relieve nerve compression. In the lumbar region, the lamina space is not directly opposite the intervertebral disc space level but is located caudally to it[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Therefore, preserving the caudal attachment of the ligamentum flavum does not affect the decompression effect at the intervertebral disc level.\u003c/p\u003e \u003cp\u003eChanges in the cross-sectional area of the dural sac can provide more objective evidence for the effectiveness of decompression for lumbar spinal stenosis. Haruo et al. conducted a study on 88 patients with lumbar spinal stenosis and discovered that the cross-sectional area of the dural sac under axial load is significantly correlated with the severity of symptoms of lumbar spinal stenosis[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. In this study, the preoperative cross-sectional area of the dural sac in the ligamentum flavum preservation group was 67.65\u0026thinsp;\u0026plusmn;\u0026thinsp;14.28 mm\u0026sup2;, which increased to 164.31\u0026thinsp;\u0026plusmn;\u0026thinsp;26.35 mm\u0026sup2; postoperatively; in the ligamentum flavum removal group, the preoperative cross-sectional area was 65.73\u0026thinsp;\u0026plusmn;\u0026thinsp;18.19 mm\u0026sup2;, which increased to 170.92\u0026thinsp;\u0026plusmn;\u0026thinsp;27.68 mm\u0026sup2; postoperatively. Both groups showed a significant increase postoperatively compared to preoperatively. However, there was no significant difference in the cross-sectional area of the dural sac between the two groups, indicating that the dural sac space could be enlarged regardless of whether the ligamentum flavum was preserved. Although the ligamentum flavum preservation group retained the ligamentum flavum, the bone on the dorsal side and the inner edges of the bilateral facet joints were removed, providing ample space for the dural sac.\u003c/p\u003e \u003cp\u003eComplications\u003c/p\u003e \u003cp\u003eComplications of UBE surgery include surgical incision infection, cauda equina nerve damage, dural sac tear, and epidural hematoma, among others. In this study, there were no occurrences of surgical incision infection or cauda equina nerve damage. Previous research has shown that the incidence of dural tears during UBE surgery is 3.95%, which often occurs dorsally during the removal of the ligamentum flavum due to reasons such as limited intraoperative visual field, and adhesions between the dural sac and the ligamentum flavum[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. A dural sac tear can significantly impact endoscopic lumbar surgery, leading to spinal high pressure intraoperatively and cerebrospinal fluid leakage postoperatively. Based on preoperative MRI and intraoperative observations, we have found that many patients with spinal stenosis have a significant reduction in epidural fat, which leads to a decreased space between the ligamentum flavum and the dura mater, increasing the risk of dural sac tears during surgery. In this study, two cases of dural tears occurred in the ligamentum flavum removal group, with an incidence rate of 3.33%. There were no dural tears in the ligamentum flavum preservation group. When adhesions are present between the ligamentum flavum and the dural sac, it is easy to cause a dural tear while separating the space between them. At the midline attachment site of the ligamentum flavum and the caudal lamina, there is usually a meningovertebral ligament connecting the ligamentum flavum and the dural sac, which is prone to causing dural sac damage during removal. The surgical technique that preserves the ligamentum flavum omits this step, effectively reducing the probability of dural damage.\u003c/p\u003e \u003cp\u003eAn epidural hematoma refers to the accumulation of blood outside the dura mater within the spinal canal, which can cause nerve compression. Symptoms after UBE surgery typically include lumbar distension pain, lower limb pain and numbness, and perineal numbness. Liang and others conducted a retrospective study on 105 patients after UBE surgery and found that the incidence of symptomatic epidural hematoma was 6.7%[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The incidence rate of epidural hematoma in the ligamentum flavum removal group in this study was 10%, which is higher than that found in Liang's study. This discrepancy may be due to the use of osteotomes for decompression in this study, whereas Liang and others used bone drills. Bone drilling during decompression step can seal the trabecular spaces of cancellous bone, thereby reducing bone surface bleeding. Bone chiseling after bone removal, however, can lead to bleeding and the formation of an epidural hematoma. Therefore, it is recommended to use bone wax to seal the operative site after bone chisel operations to reduce the occurrence of epidural hematomas.\u003c/p\u003e \u003cp\u003eWe have summarized the key points of the operation to preserve the ligamentum flavum in UBE surgery. First, it is necessary to fully remove the bone at the base of the spinous process on the dorsal side of the ligamentum flavum and the superior lamina, initially exposing the \"V\" shaped convergence area of the bilateral ligamentum flavum on the cranial side. This serves as a starting point for decompression along the cranial starting point of the ligamentum flavum towards both sides. Second, when removing the ventrolateral osseous structures of the contralateral inferior articular process, it is necessary to create sufficient space, then expose the inner edge of the contralateral superior articular process. Decompression should be thorough, leaving space between the ligamentum flavum and the dural sac. Third, before resecting the inner edge of the superior articular process, it is necessary to remove the superficial layer of the ligamentum flavum to expose the apex of the superior articular process, the inner edge of the superior articular process, and the transition area between the inner edge of the superior articular process and the upper border of the lamina on the caudal side. Fourth, when removing the bone on the medial edge of the superior articular process, it should be close to the tip of the superior articular process. During the removal process, a nerve dissector can be used to probe the inner edge of the pedicle to ensure that the decompression range is sufficient. At last, preservation of the ligamentum flavum does not imply complete retention of the ligamentum flavum. The superficial layer of the ligamentum flavum and the sides of the ligamentum flavum need to be removed to ensure full decompression of the bilateral nerve roots and to prevent post-separation healing of the ligamentum flavum, which could lead to symptoms of nerve compression. (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis study has some limitations. Firstly, it is a single-center retrospective study with a small sample size, lacking large-scale, multicenter research, and the follow-up period is short, which introduces certain biases. Secondly, the included patients span different segments from L3 to S1, and due to the limited sample size, the study did not perform stratified comparisons based on specific segments.\u003c/p\u003e \u003cp\u003eDespite these limitations, this study is the first to describe the UBE technique that preserves the ligamentum flavum, and it also confirms the effectiveness of this technique in treating lumbar spinal stenosis, providing a relevant basis for clinical surgeons.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe UBE technique for lumbar spinal stenosis that preserves the ligamentum flavum can protect the normal anatomical structures between the epidural space and other paraspinal tissues, reduce complications, surgical time, and blood loss, while also providing good surgical outcomes. It is recommended to preserve the ligamentum flavum as much as possible when using the UBE technique to treat patients with lumbar spinal stenosis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eHuman Ethics and Consent to Participate declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll clinical investigations had been conducted according to the principles expressed in the Declaration of Helsinki. This study was conducted with approval from\u0026nbsp;Ethics Committee of Chongqing Liangping District People's Hospital. Informed consent to participate in the study was obtained from the participant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent for publication was obtained from all participants\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Funding of Baoding Self-raised Fund Project (Grant Number 2341ZF335)，the Funding of Affiliated Hospital of Hebei University (Grant Number 2023ZB01)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eKepeng Li participated in the collection of experimental data.\u003c/p\u003e\n\u003cp\u003eBo Jiang\u0026nbsp;designed the study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eYe Han wrote and revised the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAkosman I, Shafi K, Subramanian T, Kazarian GS, Kaidi AC, Cunningham M, Kim HJ, Lovecchio F. 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[Characteristics and risk factors of spinal epidural hematoma after unilateral biportal endoscopic lumbar interbody fusion]. Zhonghua Yi Xue Za Zhi. 2022;102(41):3267-73.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Lumbar Spinal Stenosis, Unilateral Biportal Endoscopy, Ligamentum Flavum","lastPublishedDoi":"10.21203/rs.3.rs-5916963/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5916963/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs a minimally invasive surgical approach for treating lumbar spinal stenosis, Unilateral Biportal Endoscopy (UBE) is receiving significant attention from clinical practitioners. Conventional UBE surgery involves the removal of the ligamentum flavum, and to date, there is no research on UBE techniques that preserve the ligamentum flavum.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethod\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA retrospective analysis was conducted on 100 patients with lumbar spinal stenosis (LSS) who underwent UBE treatment from January 2022 to March 2024. The surgical techniques of decompression of the lumbar canal while preserving the ligamentum flavum using UBE technology were summarized. Patients were divided into two groups based on whether the ligamentum flavum was preserved during surgery: the preservation group with 40 patients, and the removal group with 60 patients. The intraoperative surgical time and blood loss of the two groups were compared, as well as perioperative Visual Analogue Pain Scores (VAS), Oswestry Disability Index (ODI), and complications such as dural tears and epidural hematoma. The difference in radiological decompression between the two groups was assessed using the cross-sectional area of the dural sac on lumbar MRI.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe average surgery time for the group with the ligamentum flavum preserved was (50.13±8.45) minutes, and the intraoperative blood loss was (30.57±6.64) ml. For the group with the ligamentum flavum removed, the average surgery time was (66.47±7.26) minutes, and the intraoperative blood loss was (58.70±6.19) ml. Compared to the group with the ligamentum flavum removed, the group with the ligamentum flavum preserved had a shorter surgery time and less blood loss, with these results being statistically significant (P \u0026lt; 0.01). There was no difference in the VAS scores and ODI scores between the two groups at 3 days and 6 months postoperatively. The postoperative dural sac cross-sectional area for the ligamentum flavum preserved group and the ligamentum flavum removed group was 164.31±26.35 mm²and 170.92±27.68 mm², respectively, with no statistically significant difference (P = 0.24). The incidence of postoperative complications was 1.92% in the ligamentum flavum preserved group and 5.77% in the ligamentum flavum removed group, which was not statistically significant (P = 0.61).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe technique of unilateral biportal endoscopy (UBE) for lumbar spinal stenosis, which preserves the ligamentum flavum, can reduce complications, surgical time, and blood loss, while simultaneously providing favorable surgical outcomes. It is recommended to preserve the ligamentum flavum as much as possible when using UBE for the treatment of patients with lumbar spinal stenosis.\u003c/p\u003e","manuscriptTitle":"The clinical efficacy of unilateral biportal endoscopic treatment for lumbar spinal stenosis with preservation of the ligamentum flavum","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-31 18:00:17","doi":"10.21203/rs.3.rs-5916963/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-01-29T12:29:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-01-28T13:09:24+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-01-28T13:07:06+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2025-01-28T07:46:45+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"969c01ac-3512-497e-9999-106423e61c5a","owner":[],"postedDate":"January 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-10T04:53:26+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-31 18:00:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5916963","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5916963","identity":"rs-5916963","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}