Consecutive Case Series of Uniportal Full‐endoscopic Unilateral Laminotomy for Bilateral Decompression in Lumbar Spinal Stenosis: Relationship between Decompression Range and Functional Outcomes

Abstract

Objective

Uniportal full‐endoscopic unilateral laminotomy for bilateral decompression (UFE‐ULBD) has been used to treat lumbar spinal stenosis (LSS) with satisfactory outcomes. However, a limited number of studies have investigated the relationship between decompression range and clinical outcomes. This study aimed to investigate the efficacy of UFE‐ULBD for single‐segment LSS and to explore the relationship between the decompression range and functional outcomes.

Methods

Single‐segment LSS patients who had undergone UFE‐ULBD using an interlaminar approach between November 2021 and February 2023 were retrospectively analyzed. Patient demographics, visual analogue scale (VAS) scores for leg and back pain, Oswestry disability index (ODI) scores, modified MacNab grades, and radiological outcomes, including the decompression ratio of the disc‐flava ligament space and osseous lateral recess, the enlargement ratio of superior articular process interval, lamina interval dural sac cross‐sectional area (DSCA), were collected. The independent sample t‐tests, paired sample t‐tests, chi‐square tests, Fisher's exact tests, and Pearson's and Spearman's correlation analyses were used.

Results

Forty patients (23 males, and 17 females) were retrospectively enrolled in this study. The mean follow‐up period was 12 months. At the last follow‐up, VAS scores for leg pain and back pain decreased from 6.0 ± 0.8 to 1.0 ± 1.9 (p < 0.001), and from 6.0 ± 0.8 to 1.2 ± 1.8 (p < 0.001) respectively; ODI score decreased from 71.7 ± 6.2 to 24.3 ± 21.3 (p < 0.001). According to the modified MacNab criteria, the results were excellent in 28 (70%), good in 5 (12.5%), fair in 6 (15%), and poor in 1 (2.5%), with an excellent‐good rate of 82.5%. The postoperative DSCA enlarged from 57.69 ± 21.86 to 150.75 ± 39.33 mm² (p < 0.001), with an enlargement ratio of 189.43 ± 107.83%. No difference in clinical or radiological parameters was detected between patients with excellent, good, fair, or poor outcomes based on the modified MacNab criteria.

Conclusion

UFE‐ULBD can provide satisfactory clinical and radiological outcomes in single‐segment LSS patients. With sufficient exposure to the dural sac boundary, the functional outcome was not related to the radiological decompression range in LSS patients who had undergone UFE‐ULBD.

Uniportal full‐endoscopic unilateral laminotomy for bilateral decompression (UFE‐ULBD) using an interlaminar approach can provide satisfactory clinical and radiological outcomes in single‐segment treat lumbar spinal stenosis (LSS) patients. With sufficient exposure of the dural sac boundary, the functional outcome was not related to the radiological decompression range in patients with lumbar spinal stenosis who had undergone UFE‐ULBD.

Introduction

Lumbar spinal stenosis (LSS) is a prevalent lumbar degenerative disorder and is a disabling cause of lower back pain, leg pain, and neurogenic claudication in older adults, affecting an estimated 103 million people worldwide. LSS patients who have received conservative treatment without satisfactory efficacy may require surgical treatment. ¹ In recent years, unilateral laminotomy for bilateral decompression (ULBD), a popular surgical procedure, has been used to treat LSS, with the advantages of minimal injury to the paraspinal musculoligamentous structures and enhanced postoperative recovery. ² , ³

Uniportal full endoscopy (UFE) is a minimally invasive technique used to treat lumbar disc herniation, cervical spondylopathy, and thoracic ossified ligamentum flavum. ⁴ , ⁵ , ⁶ Furthermore, uniportal full‐endoscopic ULBD (UFE‐ULBD) reportedly has excellent clinical and radiological outcomes in LSS patients. ⁷ , ⁸ , ⁹ A recent Bayesian network meta‐analysis revealed that endoscopic decompression is one of the most effective procedures for single‐segment LSS patients. ⁷ Other researchers found that the UFE‐ULBD technique could achieve lower visual analogue scale (VAS) and Oswestry disability index (ODI) scores, complication rates, blood loss, and shorter hospital stays than other decompressive techniques. ⁸ , ⁹

Although several studies have reported on UFE‐ULBD for treating LSS, only a limited number have investigated the relationship between the decompression range and clinical outcomes in LSS patients. Under the premise of achieving satisfactory clinical outcomes, it would be of certain value to explore the appropriate decompression range for spine surgeons to carry out UFE‐ULBD for LSS patients. Therefore, this study aimed to: (i) investigate the clinical and radiological efficacy of UFE‐ULBD for single‐segment LSS; and (ii) explore the relationship between the decompression range and functional outcomes after UFE‐ULBD operation.

Methods

Subjects

This retrospective study was approved by the Ethics Committee of the Beijing Friendship Hospital, Capital Medical University (2023‐P2‐147‐01). Informed consent was obtained from all participants. The medical records of single‐segment LSS patients hospitalized at our spine center for surgical treatment between November 2021 and February 2023 were retrospectively reviewed. The inclusion criteria were: (i) diagnosed with LSS of single response levels; and (ii) predominant manifestation as neurogenic intermittent claudication and failed conservative treatment for at least 3 months. The exclusion criteria were: (i) age < 18 years; (ii) presence of lumbar spine tumor, infection, or trauma; (iii) presence of scoliosis, ankylosing spondylitis, or other spinal deformities; (iv) ≥II degrees lumbar spondylolisthesis or spinal instability; (v) history of surgery at the same surgical level; and (vi) incomplete medical records.

UFE‐ULBD through Interlaminar Approach

All procedures were performed in the prone position under 5 μg Sufentanil intravenously and local anesthesia (1% Ropivacaine 10 mL, 2% Lidocaine 15 mL, 0.9% Normal Saline 20 mL). An 18‐gauge spinal needle was inserted into the posterior ligamentum flavum, and the needle's location was confirmed at the midpoint of the interlaminar space by fluoroscopy. The guidewire, obturator, working cannula, endoscopic trephine, and endoscopic system were inserted sequentially. Bony decompression was achieved using a trephine or Kerrison punches, following the sequence of the ipsilateral upper lamina, upper spinous process, contralateral upper lamina, ipsilateral lateral recess, lower spinous process, and contralateral lateral recess. After detaching the insertion sites of the ligamentum flavum, the ipsilateral and contralateral ligamentum flavum were removed en bloc. All the decompression procedures were performed endoscopically. Decompression was completed when the compressed dura and nerve roots could be observed, and the bilateral nerve roots could be freely mobilized using a flexible probe (Figure 1).

FIGURE 1.

Endoscopic views of trephine‐assisted uniportal full‐endoscopic unilateral laminotomy for bilateral decompression (UFE‐ULBD) through the interlaminar approach. (A) bony decompression of cephalic lamina by endoscopic trephine; (B) detachment of ligamentum flavum on the cephalic side; (C) decompression of ipsilateral lateral recess; (D) decompression of caudal lamina and detachment of ligamentum flavum on the caudal side; (E) decompression of ipsilateral lateral recess; (F) complete decompression of dural sac.

Demographic Data Collection and Functional Assessment

Demographic data including sex, age, medical comorbidities, surgical level, discectomy, operation time, estimated blood loss, duration of postoperative hospitalization, and complications were systematically collected. The VAS scores for leg and back pain were evaluated preoperatively, one month postoperatively, and at the last follow‐up (at least 3 months). The ODI was assessed preoperatively and at the final follow‐up visit. The modified MacNab criteria were registered at the last follow‐up.

Radiological Measurement

All radiological parameters of the lumbar spine were measured by using computed tomography (CT) scans and magnetic resonance images (MRIs) of the lumbar spine. The degree of spinal stenosis was evaluated according to the Schizas grade by observing the morphology of the dural sac at the level of the intervertebral disc on axial T2‐weighted MR images. The facetectomy angle was calculated by measuring the angle of the inner facet of the articular process to the axial horizontal line on postoperative CT to evaluate facet undercutting. A < 90° angle indicates facet undercutting. The decompression ratio of the disc‐flava ligament space was calculated using the following formula: (1‐the postoperative superior articular process [SAP] width at the level of the intervertebral disc on axial CT scan/preoperative SAP width) × 100%. The decompression ratio of the osseous lateral recess was calculated using the following formula: (1‐the postoperative distance from the inner edge of the SAP to the inner edge of the pedicle on axial CT scan/preoperative distance) × 100%. The enlargement ratio of the SAP interval was calculated using the following formula: (postoperative distance between the internal margins of the bilateral SAPs/preoperative distance‐1) × 100%. The enlargement ratio of the lamina interval was calculated using the following formula: (postoperative distance between the midpoints of the medial plates of the bilateral lamina/preoperative distance‐1) × 100%. The dural sac cross‐sectional area (DSCA) was calculated by describing the boundary of the dural sac at the intervertebral disc level on axial CT scans. The DSCA enlargement ratio was calculated using the following formula: (postoperative DSCA/preoperative DSCA‐1) × 100% (Figure 2). All the above measurements were used to assess the radiological decompression range and effect. Radiological measurements of the spinal canal were performed and corroborated by an experienced spinal surgeon. These measurements have demonstrated good internal consistencies with Cronbach's alpha ranging from 0.86 to 0.92.

FIGURE 2.

Radiological measurements on computed tomography (CT) scans of the lumbar spine. (A, B) facetectomy angle was calculated by measuring the angle of the inner facet of the articular process to the axial horizontal line, A, facetectomy angle for ipsilateral side, B, facetectomy angle for ipsilateral side; (C, D) C, preoperative superior articular process (SAP) width, D, postoperative SAP width, decompression ratio of the disc‐flava ligament space was calculated: $\left(1-d/a\right)\times 100\%$; (E, F) E, preoperative distance from the inner edge of the SAP to the inner edge of the pedicle, F, postoperative distance from the inner edge of the SAP to the inner edge of the pedicle, decompression ratio of the osseous lateral recess was calculated: $\left(1-f/e\right)\times 100\%$; (G) SAP interval G was measured as the distance between the internal margins of the bilateral SAPs; (H) lamina interval H was measured as the distance between the midpoints of the medial plates of the bilateral lamina; (I) dural sac cross‐sectional area (DSCA) was calculated by describing the boundary of the dural sac.

Statistical Analysis

Categorical variables were grouped and presented as numerical values and continuous data were presented as mean value ± standard deviation. Data were compared between groups using independent sample t‐tests, paired sample t‐tests, chi‐square tests, and Fisher's exact tests, depending on the parametric qualities of the variables analyzed. Pearson's and Spearman's correlation analyses were used to determine the relationship between radiological features and clinical outcomes, including continuous and categorical variables, respectively. Statistical significance was set at p < 0.05. All data analyses were performed using SPSS version 25.0 software (IBM Corp., Armonk, NY, USA).

Results

Demographic Data

Forty LSS patients with a mean age of 68.2 ± 10.4 years old were enrolled in this study, and there were 23 male and 17 female patients. Thirty‐three (82.5%) patients had comorbidities, including hypertension, diabetes mellitus, coronary heart disease, and old cerebral infarction. Among the 40 patients, nine (22.5%) had surgical levels at L3‐4, 30 (75.0%) at L4‐5, and one at L5‐S1 (2.5%). Based on the Schizas grading of central stenosis, B‐type, C‐type, and D‐type stenosis were detected in four (10.0%), 12 (30.0%), and 24 (60.0%) patients, respectively. Only four (10.0%) patients underwent ULBD combined with discectomy because of obvious disc herniation. The mean duration of surgery, estimated blood loss, and postoperative hospitalization were 79.2 ± 19.8 minutes, 39.6 ± 23.1 mL, and 1.5 ± 0.7 days respectively. The mean follow‐up period was 12 ± 4.7 months (Table 1).

TABLE 1.

Demographic data of patients with LSS and functional outcomes of UFE‐ULBD.

	n = 40	p *
Age (year)	68.25 ± 10.483
No. males (%)	23 (57.5%)
Medical comorbidity (no. %)	33 (82.5%)
Surgical level (no. %)
L3‐4	9 (22.5%)
L4‐5	30 (75.0%)
L5‐S1	1 (2.5%)
Schizas grades (no. %)
B	4 (10.0%)
C	12 (30.0%)
D	24 (60.0%)
Discectomy (no. %)	4 (10.0%)
Operation duration (min)	79.2 ± 19.8
Estimated blood loss (mL)	39.63 ± 23.160
Length of postoperative hospitalization (day)	1.55 ± 0.783
Follow‐up (month)	12.00 ± 4.75
Functional outcomes
VAS score for leg pain
Preoperative	6.00 ± 0.828
Postoperative 1m	1.36 ± 1.693	<0.001
Final follow‐up	1.08 ± 1.977	<0.001
VAS score for back pain
Preoperative	6.06 ± 0.826
Postoperative 1m	2.67 ± 1.265	<0.001
Final Follow‐up	1.23 ± 1.832	<0.001
ODI score
Preoperative	71.75 ± 6.263
Final follow‐up	24.31 ± 21.395	<0.001
Modified MacNab grade (no., %)
Excellent	28 (70.0%)
Good	5 (12.5%)
Fair	6 (15.0%)
Poor	1 (2.5%)

Abbreviations: LSS, lumbar spinal stenosis; ODI, Oswestry disability index; UFE‐ULBD, uniportal full‐endoscopic unilateral laminotomy for bilateral decompression; VAS, visual analog scale

^*Paired t‐tests, comparison with preoperative value.

Functional Outcomes of UFE‐ULBD for LSS

The mean VAS score for leg pain significantly improved 1 month postoperative (1.3 ± 1.6 vs. 6.0 ± 0.8, p < 0.001) and at the last follow‐up (1.0 ± 1.9 vs. 6.0 ± 0.8, p < 0.001). Similarly, the mean VAS scores for back pain significantly improved 1 month postoperative (2.6 ± 1.2 vs. 6.0 ± 0.8, p < 0.001) and at the last follow‐up (1.2 ± 1.8 vs. 6.0 ± 0.8, p < 0.001) respectively, as compared to those at the preoperatively. There was a significant difference between 1 month postoperative and the last follow‐up VAS scores for back pain (p < 0.001), while no significant difference was found in terms of the VAS score for leg pain. The mean preoperative and the last follow‐up ODI score was 71.7 ± 6.2 and 24.3 ± 21.3, showing a clinically significant improvement (p < 0.001). At the last follow‐up, based on the modified Macnab criteria, the following results were obtained: excellent, 28 (70%); good, good (12.5%); fair, six (15%); and poor, one (2.5%). No perioperative complications were observed and no reoperations were performed during follow‐up (Table 1).

Radiological Outcomes of UFE‐ULBD for LSS

After UFE‐ULBD, the mean angle of facetectomy of the ipsilateral facet joint was 95.8 ± 7.0°, larger than 90°; while the contralateral was 63.8 ± 9.0°, less than 90°. The decompression ratio of the disc‐flava ligament space on the ipsilateral side was 20.3 ± 10.5%, and the contralateral was 5.1 ± 6.2%. The decompression ratio of the osseous lateral recess on the ipsilateral side was 32.0 ± 27.4%, and the contralateral was 7.7 ± 8.5%. The enlargement ratio of the SAP interval and lamina interval was 21.48 ± 15.22% and 68.53 ± 32.12% respectively. The postoperative DSCA was significantly enlarged compared with that before surgery, from 57.69 ± 21.86 to 150.75 ± 39.33 mm², with an enlargement ratio of 189.43 ± 107.83% (Table 2).

TABLE 2.

Radiological outcomes of UFE‐ULBD for LSS

	n = 40	p *
Angel of facetectomy (°)
Ipsilateral	95.803 ± 7.0271
Contralateral	63.851 ± 9.0957
Decompression ratio of disc‐flava ligament space (%)
Ipsilateral	20.38 ± 10.55
Contralateral	5.15 ± 6.25
Decompression ratio of osseous lateral recess (%)
Ipsilateral	32.03 ± 27.45
Contralateral	07.74 ± 8.51
Enlargement ratio of SAP interval (%)	21.48 ± 15.22
Enlargement ratio of lamina interval (%)	68.53 ± 32.12
DSCA (mm2)
Preoperative	57.69 ± 21.86
Postoperative 1 m	150.75 ± 39.33	<0.001
Enlargement ratio (%)	189.43 ± 107.83

Abbreviations: DSCA, dural sac cross‐sectional area; LSS, Lumbar spinal stenosis; SAP, superior articular process; UFE‐ULBD, uniportal full‐endoscopic unilateral laminotomy for bilateral decompression

^*Paired t‐tests, comparison with preoperative value.

Relationship of Functional and Radiological Outcomes in UFE‐ULBD

To investigate the possible factors underlying the unsatisfactory outcomes of UFE‐ULBD in LSS patients, demographic data and radiological parameters were compared between patients with excellent/good outcomes and those with fair/poor outcomes according to the modified MacNab criteria. Although not statistically significant, patients reporting fair/poor outcomes at the last follow‐up seemed to have a lower decompression ratio of the contralateral osseous lateral recess (5.63 ± 5.98 vs. 15.28 ± 12.09, p = 0.081) or less enlargement ratio of SAP interval (12.67 ± 6.91 vs. 23.85 ± 16.04, p = 0.084), than those of patients with excellent/good outcomes. However, no differences in the other clinical or radiological parameters were observed between the two groups (Table 3).

TABLE 3.

Clinical and radiological parameters between patients with excellent/good and fair/poor outcome

	Excellent/good group (n = 33)	Fair/poor group (n = 7)	p
Age (year)	67.85 ± 10.438	70.14 ± 11.320	0.605 #
No. Males (%)	17 (51.5%)	6 (85.7%)	0.205 #
Medical comorbidity (no., %)	28 (84.8%)	5 (71.4%)	0.355 #
Surgical level (no., %)
L3‐4	5 (15.2%)	4 (57.1%)	0.078 #
L4‐5	27 (81.8%)	342.9 (%)
L5‐S1	1 (3.0%)	0 (0%)
Schizas grades (no., %)
B	4 (12.1%)	0 (0%)	0.282 #
C	8 (24.2%)	4 (57.1%)
D	21 (63.6%)	3 (42.9%)
Discectomy (no., %)	4 (12.1%)	0 (0%)	1.000 #
Operation duration (min)	78.91 ± 18.996	80.83 ± 25.965	0.831*
Estimated blood loss (mL)	38.79 ± 22.432	43.57 ± 27.946	0.626*
Length of postoperative hospitalization (day)	1.55 ± 0.833	1.57 ± 0.535	0.938*
Radiological parameters
Angel of facetectomy (°)
Ipsilateral	95.789 ± 6.7056	95.857 ± 8.8021	0.982*
Contralateral	63.89 ± 9.40	63.69 ± 8.44	0.958*
Decompression ratio of disc‐flava ligament space (%)
Ipsilateral	20.66 ± 11.73	19.38 ± 4.85	0.673*
Contralateral	5.86 ± 6.67	260 ± 3.80	0.228*
Decompression ratio of osseous lateral recess (%)
Ipsilateral	41.13 ± 36.53	29.48 ± 24.68	0.329*
Contralateral	15.28 ± 12.09	5.63 ± 5.98	0.081*
Enlargement ratio of SAP interval (%)	23.85 ± 16.04	12.67 ± 6.91	0.084*
Enlargement ratio of lamina interval (%)	67.63 ± 31.35	71.88 ± 37.28	0.762*
Enlargement ratio of DSCA (%)	191.96 ± 113.13	180.40 ± 93.62	0.807*

Abbreviations: DSCA, dural sac cross‐sectional area; SAP, superior articular process

^*Independent sample t‐tests

^# Chi‐squared or Fisher exact tests.

To further determine the relationship between the radiological parameters and clinical outcomes, a correlation analysis was performed. The results revealed no significant correlation between radiological parameters and modified MacNab criteria‐based clinical outcomes; however, a negative correlation was detected between the contralateral osseous lateral recess decompression ratio and clinical outcomes (r = −0.321, p = 0.073).

Discussion

Our study demonstrated that an excellent‐good rate of 82.5% based on the modified MacNab criteria could be achieved in single‐segment LSS patients who had undergone UFE‐ULBD using an interlaminar approach, with a combination of significant improvement in VAS scores for leg pain and back pain, ODI score and DSCA. While, no difference in clinical or radiological parameters was detected between patients with excellent, good, fair, or poor outcomes based on the modified Macnab criteria. It indicated that the functional outcomes of UFE‐ULBD for LSS were not related to the decompression range based on radiological measurements under the condition of sufficient exposure to the dural sac boundary.

Clinical Efficacy of UFE‐ULBD for LSS

Several studies have reported satisfactory outcomes with UFE‐ULBD in the treatment of LSS patients. ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ , ¹⁵ Lee et al. retrospectively investigated the clinical outcomes of full‐endoscopic decompression using a uniportal, unilateral approach in the lumbar canal or lateral recess stenosis patients, and excellent or good results were obtained in 93.8% of the patients based on the modified MacNab criteria. ¹³ Meng et al. reported the preliminary outcomes of a fully endoscopic 360° decompression technique for LSS combined with disc herniation; the overall excellent rate of the modified MacNab criteria was 89.7%, accompanied by 10.3% complications. ¹⁶ Another prospective cohort study by Wu et al. indicated that endoscopic ULBD could achieve comparable outcomes for LSS with or without degenerative spondylolisthesis or degenerative scoliosis, showing an overall 85% excellent‐good outcome based on the modified MacNab criteria. ¹⁴ Hasan et al. also reported that full‐endoscopic ULBD could achieve similar functional outcomes for LSS with mild‐to‐moderate degenerative scoliosis or spondylolisthesis compared to minimally invasive surgery, while the endoscopic approach demonstrated a favorable rate of complications. ¹⁵ Süner et al. compared the long‐term results of LSS patients who underwent tubular and uniportal endoscopic approaches and found that the long‐term results were similar between these two techniques, of which the PE group had the advantage of less blood loss during surgery. ¹⁷ In this study, the VAS scores for leg and back pain and ODI scores improved significantly after UFE‐ULBD and remained good at the last follow‐up. The overall excellent‐good rate of the modified MacNab criteria was 82.5%, accompanied by an obvious enlargement of the DSCA with a mean ratio of 189.4%. These findings support the satisfactory outcomes that could be achieved by the UFE‐ULBD technique through an interlaminar approach in LSS patients.

Advantages of UFE‐ULBD over Other Decompressive Surgery

Moreover, UFE‐ULBD showed some advantages over other decompression techniques for LSS. Komp et al. reported two prospective results of UFE‐ULBD for LSS patients, indicating that the decompression results were equal to those of conventional procedures; however, UFE‐ULBD brought advantages in complications, traumatization, and rehabilitation. ¹¹ , ¹² Percutaneous uniportal endoscopic decompressive surgery for LSS offers the advantage of reduced immediate postoperative pain compared with conventional microsurgical decompression. ¹⁸ The paraspinal muscles along with the posterior ligamentous complex can be preserved after endoscopic ULBD with adequate neural decompression, thereby improving the stability of the motion segment and resulting in better postoperative outcomes. ¹⁹ However, the UFE technique is imperfect. Wu et al. conducted a prospective cohort study comparing the clinical efficacy and safety of uniportal and biportal endoscopic ULBD for LSS and found that both techniques had the same efficacy; however, biportal endoscopy had potentially lower risks of intraoperative complications, inadequate decompression, and conversion to open surgery during the early period of the learning curve. ²⁰

Relationship between Clinical Outcomes and Decompression Range in UFE‐ULBD

One MR radiological study by Kim et al. investigated the remodeling pattern of the spinal canal after full‐endoscopic ULBD with a minimum follow‐up of 26 months and found that despite achieving sufficient decompression immediately 6 months postoperative, varying severities of asymptomatic restenosis were found in postoperative MRI without clinical significance. ²¹ Restenosis of the ULBD during follow‐up might remind surgeons to achieve sufficient decompression during surgery. Several researchers have mentioned that the checkpoint of sufficient decompression obverts free and pulsatile neural elements, and adequate bony decompression of the cephalad/caudal lamina and ipsilateral/contralateral facet joint to expose the margin of the ligamentum flavum and resect the ligamentum flavum is important. ²² , ²³ , ²⁴ Moreover, Huang et al. thought that detachment of the ligamentum flavum from the origin to the insertion site could ensure adequate decompression and reduce the incidence of iatrogenic durotomy due to normal saline flowing into the epidural space, acting as an effect of fluid‐aided neurodissection. ²⁵ Our study achieved sufficient bony decompression using the UFE‐ULBD technique based on postoperative radiological measurements, accompanied by good functional outcomes. Further analysis of patients with different functional outcomes showed no significant difference in radiological parameters, especially DSCA enlargement. However, patients reporting fair/poor outcomes seemed to have a lower decompression ratio of the contralateral osseous lateral recess and a lower enlargement ratio of the SAP interval than those with excellent or good outcomes. A negative correlation between the contralateral osseous lateral recess decompression ratio and the modified MacNab grade was detected in our study. These results indicated a possible correlation between unsatisfactory outcomes and insufficient decompression of the contralateral lateral recess. While, insufficient bony decompression of the contralateral lateral recess might be related to the limitations of the coaxial hard work channel, small visual field, and few types of instruments in the UFE system. ¹⁸ Based on our clinical experience at a single spine center, patients with radiologically sufficient decompression of the contralateral lateral recess did not necessarily show better clinical outcomes than those with less bony decompression (Figure 3). However, excessive facetectomy aimed at achieving sufficient decompression of the lateral aspects may not be recommended, considering the possibility of postoperative iatrogenic instability. ² , ¹² , ²⁶ Therefore, further studies focusing on the risk factors for unsatisfactory outcomes and the precise determination of the decompression range may be needed for the UFE‐ULBD technique.

FIGURE 3.

Differences in the degree of bony decompression for contralateral lateral recess might not lead to differences in clinical outcomes in uniportal full‐endoscopic unilateral laminotomy for bilateral decompression (UFE‐ULBD) for lumbar spinal stenosis patients. (A–C) One 65‐year‐old male patient with L3/4 stenosis underwent UFE‐ULBD with radiologically sufficient bony decompression for contralateral lateral recess and reported a “good” outcome based on the modified MacNab criterion after surgery, and the contralateral facet joint was resected partially to allow the endoscope to reach the dorsal side of the contralateral nerve root during the operation. (D–F) Another 73‐year‐old male patient with L4/5 stenosis underwent UFE‐ULBD without radiologically sufficient bony decompression for contralateral lateral recess, and a “good” outcome was also achieved; while the contralateral facet joint was nearly not resected but the contralateral nerve root could be confirmed without compression under endoscopic view intraoperatively.

Strengths and Limitations

To our knowledge, this is one of the few studies to investigate the relationship between functional outcomes and the radiological decompression range in LSS patients who underwent UFE‐ULBD. However, the current study has some limitations. First, this is a retrospective study with a relatively small sample size and no control group. Further prospective studies with larger sample sizes are warranted to confirm these findings. Second, the average 18‐month follow‐up period is relatively short for assessing the long‐term prognosis of clinical outcomes and their relationship with the radiological decompression range. Continuous long‐term follow‐up is required in these patients. Moreover, considering that MR was not performed in most patients during the follow‐up period, radiological measurements from the CT scans were not confirmed. MR will be performed during further follow‐up in this LSS cohort.

Conclusion

UFE‐ULBD using an interlaminar approach can provide satisfactory clinical and radiological outcomes in single‐segment LSS patients. Under the condition of sufficient exposure to the dural sac boundary, the functional outcome was not related to the radiological decompression range in LSS patients who had undergone UFE‐ULBD. This article was expected to guide spine surgeons to perform appropriate decompression range during UFE‐ULBD for LSS, achieving satisfactory clinical outcomes, and avoiding excessive resection of bone structures.

Conflict of Interest Statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics Statement

The Ethics Committee of Beijing Friendship Hospital, Capital Medical University has approved the research (BFH20220602013). Patients agreed to participate in this study. Informed consent was obtained from patients before the study.

Author Contributions

All authors had full access to the data in the study and took responsibility for the integrity of the data and the accuracy of the data analysis. Conceptualization, H.T. and B.Z.; Investigation, H.T. and L.Y.; Resources, G.Z. and B.Z.; Writing‐Original Draft, H.T. and X.X.; Writing‐Review & Editing, N.L. and Y.Y.; Supervision, X.L. and Y.Y.; Funding acquisition, H.T. and B.Z.

Authorship declaration

All authors listed meet the authorship criteria according to the latest guidelines of the International Committee of Medical Journal Editors, and all authors are in agreement with the manuscript.