Percutaneous unilateral biportal endoscopic discectomy for symptomatic lumbar disc herniation in geriatric patients

doi:10.21203/rs.3.rs-4635301/v1

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Percutaneous unilateral biportal endoscopic discectomy for symptomatic lumbar disc herniation in geriatric patients

https://doi.org/10.21203/rs.3.rs-4635301/v1

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Purpose

The purpose of this study is to investigate the surgical efficacy and safety of percutaneous unilateral biportal endoscopic discectomy(UBED)for symptomatic lumbar disc herniation (LDH) in geriatric patients.

Methods

72 geriatric patients with single or two-level LDH who underwent UBED from January 2020 to September 2022 were retrospectively analyzed. Ages of them ranged from 65 to 86 years (mean 73.2 years). Clinical outcomes were evaluated by operation time, total blood loss, hospital stay, visual analogue scale (VAS) score for leg pain, the Oswestry disability index (ODI) score, modified Macnab criteria and postoperative magnetic resonance imaging (MRI).

Results

Surgery was successfully treated in all geriatri patients with an mean operation time of 46 minutes (range: 32-68 minutes). All patients were followed up for a average duration of 14.2 ±1.9 months (range: 12-16 months). The leg pain VAS score was decreased from 8.37±1.21 preoperatively to 2.03±0.61, 1.56±0.32, 1.16±0.45 and 0.91±0.26 at immediately after surgery and 1, 6, 12 months postoperatively. The ODI score was also dropped from 61.21±11.06 preoperatively to 27.52±10.41, 19.12±7.05, 12.17±5.21 and 8.56±4.32 at immediately after surgery and 1, 6, 12 months postoperatively. Significantly statistical difference was observed in both VAS and ODI score at each follow-up time point when compared with the preoperative parameters (P<0.01). And there were 53 excellent cases, 12 good cases and 7 fair cases based on the modified MacNab criteria at 12 months postoperatively, with an excellent and good rate of 90.2%. Only 2 cases were found complicated with low extremity numbness, which were recovered via conservative treatment in three weeks. No infection or iatrogenic neurological deficit was occured in all patients.

Conclusions

We considered that UBED achieved satisfactory results and provided a minimally invasive, effective and safe alternative for the treatment of symptomatic LDH in geriatric patients.

unilateral biportal endoscopic discectomy

lumbar disc herniation

minimally invasive

geriatric

Symptomatic lumbar disc herniation (LDH) with low back pain and/or sciatica is a disturbing disease. ^[1] The radicular syndrome affects millions of people throughout the world. ^[2] Conservative treatment generally achieves a satisfactory result. Some studies also have reported that LDH can be naturally absorbed. ^{[3, 4]} But for those who failed in a period of conservative treatment, surgery seems necessary. ^[5] Mixter and Barr first attempted posterior laminectomy to decompress nerve roots and resect herniated discs for treating patients with symptomatic LDH in 1934. ^[6] On this basis, Caspar and Yasargil introduced microscope discectomy in the 1970s. ^[7] And then, open lumbar microdiscectomy (OLM) had been regarded as a standard surgery for symptomatic LDH. ^[8] Since the late 1980s, Kambin introduced endoscopic and arthroscopic equipment in lumbar decompressive surgery though transforaminal approach. ^{[9, 10]} Accompanied by improvements in optical equipments and surgical instruments, percutaneous endoscopic lumbar discectomy (PELD) has been widely implemented for LDH, lumbar spinal stenosis and other spinal disease. ^[11–14] In recent years, the minimally invasive technology named unilateral biportal endoscopic discectomy (UBED) also gained popularity in the treatment of lumbar disc disease. ^[15–17] UBED was performed via two independent channels on the unilateral side, one channel for the visualization and another for working instruments. Compared with OLM, UBED reduces the destruction of paraspinal muscles, while providing a clear and magnifed surgical field of vision, which improves operational fexibility, helps the surgeon to conduct precise and complete decompression. ^{[16, 18, 19]} Although UBED could achieve favourable results in treating LDH, the complications of this technology have been reported. ^[20] As things stand at present, the number of geriatric patients with symptomatic LDH has been increasing along with the deepening of aging process worldwide, but few studies explored surgical efficacy of UBED in olders. In the present study, we described the clinical efficacy and safety of UBED for geriatric patients with symptomatic LDH.

1. Patient population

After the Institutional Review Board approval, we included a total of 72 geriatric patients (43 male and 29 female) with lower extremity radiculopathy due to LDH who were performed by UBED under general anesthesia in our spinal surgery department from January 2020 to September 2022. Ages of them ranged from 65 to 86 years (mean 73.2 years). The mean duration of clinical symptoms was 7.8 ± 4.1months, with a range from 2 to 12months. After identified by lumbar flexion and extension X-ray, computed tomography (CT) and magnetic resonance imaging (MRI), all enrolled patients were all diagnosed as single or two-level LDH, including 9 at L3-L4, 29 at L4-L5, 23 at L5-S1 level, 11 at L4-L5 and L5-S1 level. Among the 72 patients, 11 patients had internal medical comorbidities such as diabetes, hypertension and coronary heart disease. All patients had at least one year follow-up. Baseline characteristics of participants were present in Table 1.

Table 1

Baseline characteristics of the included patients
Patients (n = 72)
Male/female, No. (%)			43 (59.7)/29 (40.3)
Age, year			73.2 ± 8.5 (range: 65–86)
BMI, kg/m2			24.8 ± 2.7
Duration of symptoms, month			7.8 ± 4.1 (range: 2–13)
Duration of follow-up, month			14.2 ± 1.9 (range: 12–16)
Disc Level, No. (%, n = 83)
	Single-level	Two-level
L3-L4	9	0	n = 9 (10.8)
L4-L5	29	11	n = 40 (48.2)
L5-S1	23	11	n = 34 (41.0)
Type of herniation, No. (%, n = 83)
Central			n = 31 (37.3)
Paracentral			n = 52 (62.7)

2. Inclusive and exclusive criteria

Inclusive criteria: (1) the age of patient was greater than or equal 65 years old; (2) the cardinal symptom was leg pain with or without back pain due to single or two-level LDH; (3) positive nerve root tension sign; (4) imaging features of preoperative X-ray, CT scans and MRI images were in accordance with clinical symptoms; (5) failure of conservative therapy for at least three months; (6) sufficient clinical datas of the patients with at least 1-year follow-up. Exclusive criteria: 1) patient combined with lumbar instability or spondylolisthesis which confirmed by lumbar flexion and extension X-ray; 2) patients combined with infected lesions on the puncture path; 3) patients with history of lumbar spine surgery; 4) patients with serious physical illnesses, mental disorder or abnormal blood coagulation function.

3. Surgical procedures

All operations were performed under general anesthesia in the prone position with flexion of hip and knee. The target intervertebral space was confirmed via C-arm fluoroscopy. Two skin incisions centred around the target intervertebral space were made on the unilateral side. The endoscope and surgical instruments were placed respectively through the observational and working channel. Firstly, the soft tissue in surgical field of vision was cleaned by radiofrequency ablation and forceps, to create working space. And then, the junction between spinous process and vertebral plate at the target intervertebral space was identifed. Inferior lamina of the upper lumbar vertebral body and superior lamina of the lower lumbar spine were partially removed using abrasive drilling and vertebral plate rongeur. The ligamentum favum was dissected and removed carefully using Kerrison punches and radiofrequency probe. After identifying the dural sac and nerve root, the annulus of the protruding intervertebral disc was dissected and exposed. Be careful to stop bleeding, discectomy was then performed via nucleus forceps. A 90° hooked probe was used to confirm if there was any residual fragment present. Pulsation of the dural sac and decompression of the nerve root was confirmed finally. After meticulously arresting bleeding again, a rubber drainage tube was placed outside the lamina and the surgical incision was sutured.

4. Efficacy evaluation

Clinical efficacy was primarily evaluated by leg pain visual analogue scale (VAS) score and Oswestry disability index (ODI) score at immediately after surgery and 1, 6, 12 months postoperatively. Patient satisfaction was evaluated according to the modifed MacNab criteria (excellent, good, fair, and poor). And clinical evaluation also included operation time, postoperative MRI, complications with subsequent remedy, recurrence of symptoms, time of bed rest and duration of hospitalization.

5. statistical analysis

Statistical analysis was implement via SAS software (version 9.4). Dates were shown as mean ± standard deviation. The one-way ANOVA Dunnett t-test was used for comparison of leg pain VAS and ODI sores respectively. P < 0.05 was considered statistically significant.

Surgery was successfully operated in all geriatric patients with an mean operation time of 46 minutes (range: 32–75 minutes). Patients could stand on their feet with a lumbar brace after postoperative 2–6 hours of bed rest. The mean duration of hospitalization was 3.4 ± 0.7 days. All patients were followed up for a average duration of 14.2 ± 1.9 months (range: 12–16 months). The leg pain VAS score was decreased from 8.37 ± 1.21 preoperatively to 2.03 ± 0.61, 1.56 ± 0.32, 1.16 ± 0.45 and 0.91 ± 0.26 at immediately after surgery and 1, 6, 12 months postoperatively. The ODI score was also dropped from 61.21 ± 11.06 preoperatively to 27.52 ± 10.41, 19.12 ± 7.05, 12.17 ± 5.21 and 8.56 ± 4.32 at immediately after surgery and 1, 6, 12 months postoperatively. Significantly statistical difference was observed in both VAS and ODI score at each time point of follow-up when compared with the preoperative parameters (Table 2, Fig. 1–2). And there were 53 excellent cases, 12 good cases and 7 fair cases based on the modified MacNab criteria at 12 months postoperatively, with an excellent and good rate of 90.2%. Only 3 cases were found complicated with lower limb numbness, which were completely recovered via conservative treatment in 2–4 weeks. No infection or iatrogenic neurological deficit was occured in all patients. And no patient reported recurrent disc herniation during the follow-up period. Typical case was present in Fig. 3.

Table 2

Leg pain VAS and ODI score preoperatively and at each time-point postoperatively (* P < 0.01, score at each time-point postoperatively vs preoperative score).
	preoperative	immediately after surgery	Post-op 1 month	Post-op 6 month	Post-op 12 month
Leg pain VAS	8.37 ± 1.21	2.03 ± 0.61^*	1.56 ± 0.32^*	1.16 ± 0.45^*	0.91 ± 0.26^*
ODI	61.21 ± 11.06	27.52 ± 10.41^*	19.12 ± 7.05^*	12.17 ± 5.21^*	8.56 ± 4.32^*

Symptomatic LDH is the most common lumbar degenerative disease, which causes low back pain and/or sciatica. Conservative treatment is usually preferred and often achieves satisfactory results. With the deepening of the aging of the population in China, the number of elderly LDH patients is increasing. These patients often have a long course of disease, severe symptoms, and always combined with some medical diseases such as coronary heart disease, hypertension, diabetes, etc. If conservative treatment is ineffective, how to relieve their pain through simple and effective surgery and improve the prognostic quality of life is a problem that deserves our attention. A quite complex operation with larger trauma will increase the risk of perioperative complications for patients, and the incidence of adjacent vertebral diseases after intervertebral fusion surgery will also significantly increase. ^[21]

Nowadays, OLM has been considered as a gold standard surgical treatment for symptomatic LDH. ^{[8, 22, 23]} In recent years, minimally invasive techniques in spinal surgery and endoscopic instruments have been continuously developed, as well as the increasing demand from patients to reduce intraoperative injuries. PELD is widely used for symptomatic LDH. This technology has achieved excellent results, with the advantage of more preservation of bone, less soft tissue trauma, and faster recovery. ^{[24, 25]} However, PELD technology also has certain limitations, especially for beginners, as the flexibility during operation is limited due to the influence of single channels. At present, UBED technology is gradually emerging and used to treat lumbar degenerative diseases such as symptomatic LDH and lumbar spinal stenosis. ^{[16, 26]} And UBED has also achieved good therapeutic effects in the treatment of cervical and thoracic spinal diseases. ^[27–29] We personally believe that UBED compensates for the operational flexibility of PELD on the basis of minimally invasive and visualization, and for young physicians, the learning curve is relatively smooth. UBED was implemented using two independent channels on the unilateral side, one channel for the visualization and another for working instruments. The separation of visualizing and working portals facilitates surgical operation compared to single-portal endoscopic, which is convenient for the extraction of protruded disc. It provides a magnifed and clear surgical field of vision, while improves operational fexibility, helps the surgeon to conduct precise and complete decompression. ^{[16, 18]}

Eun SS and his colleagues performed nucleus pulposus removal on 11 patients with LDH using UBED technology. After 14 months of follow-up, the results showed that the VAS score of leg pain decreased from preoperative (7.88 ± 1.24) points to postoperative (0.87 ± 0.64) points; and the ODI score decreased from preoperative (51.73 ± 18.57) to postoperative (9.37 ± 4.83), indicating the effectiveness and safety of UBED technology in treating LDH. ^[30] Soliman et al. ^[15] reported that 43 cases of symptomatic LDH were treated with UBED technology. At 24 months of postoperative follow-up, 95% of patients believed that the therapeutic effect was satisfactory. In our study, statistically significant difference was observed in both VAS and ODI score at each time point of follow-up when compared with the preoperative parameters (Table 2, Fig. 1–2). And there were 53 excellent cases, 12 good cases and 7 fair cases based on the modified MacNab criteria at 12 months postoperatively, with an excellent and good rate of 90.2%. A prospective study focused on 40 patients with single-segment LDH. ^[31] And the researchers treated the patients using UBED and PELD technology, respectively. After 6 months of follow-up, they found that the postoperative leg pain VAS and ODI score of both groups significantly decreased compared to preoperative parameters. However, the PELD group performed better in terms of intraoperative bleeding volume, surgical time, length of hospital stay, and short-term postoperative pain relief than the UBE group. Hengrui Chang et al. ^[32] reported that there was no signifcant diference in leg pain VAS or ODI scores at 12 months after surgery between UBED and OLM groups. But the UBED group had an advantage in immediate postoperative back pain. A systematic review presented the complications caused by UBED technology, such as incision or deep infection, iatrogenic nerve injury and tear of dural sac. ^[20] Only 3 cases were found complicated with lower limb numbness in our study, which were completely recovered via conservative treatment in 2–4 weeks. No infection or iatrogenic neurological deficit was occured in all patients.

Although the UBED learning curve is relatively flat, it still requires the basic skills of endoscopic operation. We have some insights and experiences in this technology. First, how to quickly seek a safe and effective operating space? We usually reach the junction point between the upper vertebral plate and the root of the spinous process in the first step to establish a base area. Second, the hydrostatic pressure showed be controlled to avoid intracranial pressure rise caused by high pressure. It is suggested that the hydrostatic pressure in lumbar surgery should be maintained at 25-30mm Hg. Third, for fear of air blockage during operation, attention should be paid to removing bubbles in the brine flushing pipeline. Forth, if the ligamentum flavum adheres to the dural sac, in order to avoid dural sac tear, only the superficial layer of ligamentum flavum can be stripped, leaving the adhesion area, so as to maintain the integrity of dural sac.

We considered that UBED achieved satisfactory results and provided a minimally invasive, effective and safe alternative for the treatment of symptomatic LDH in geriatric patients. Besides, a well-designed randomized controlled study with large sample, multicenter date and prolonged follow-up is required to verify the present results and to draw a more convincing conclusion.

UBED: Unilateral biportal endoscopic discectomy; LDH: Lumbar disc herniation; OLM: Open lumbar microdiscectomy; PELD: Percutaneous endoscopic lumbar discectomy; VAS: Visual analogue scale; ODI: Oswestry disability index

Acknowledgements

The authors thank all the participants who included in this study.

Author contributions

QRQ conceived the study design and drafted the manuscript. GAH, ZM and LHP was responsible of the methodology and data collection. ZP and ZB performed the investigation, statistical analysis and interpreted the results. ZRH and GZY contributed to the review of the manuscript. All authors read and approved the final manuscript.

Funding

There is no funding source.

Availability of data and materials

The data that support the findings of this study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

All participants were counseled about the purpose and other details of this study, and their participation was completely voluntary. Written informed consent was acquired from each participant.

Consent for publication

Written informed consent was acquired from the participants for publication of their clinical date and images.

Competing interests

The authors declare that they have no conflict of interest.

Author details

¹Department of Spinal Surgery, Gaoyou People’s Hospital, Yangzhou, Jiangsu, 225600, China. ²Department of Orthopedics, The Third Clinical Medical College of Yangzhou University, Yangzhou, Jiangsu, 225600, China. ³Department of Medical Image, Gaoyou People’s Hospital, Yangzhou, Jiangsu, 225600, China. ⁴Department of Orthopedics, Gaoyou Hospital of Integrated Traditional Chinese and Western Medicine, Yangzhou, Jiangsu, 225600, China.

Da VDW, Simons E, Riphagen II, Ammendolia C, Verhagen AP, Laslett M, et al. Physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain. Cochrane Database Syst Rev. 2010;65(2):D7431.
Koes BW, van Tulder MW, Peul WC. Diagnosis and treatment of sciatica. BMJ (Clin Res Ed). 2007;334(7607):1313-1317.
Cribb GL, Jaffray DC, Cassar-Pullicino VN. Observations on the natural history of massive lumbar disc herniation. J Bone Joint Surg Br. 2007;89(6):782-784.
Benson RT, Tavares SP, Robertson SC, Sharp R, Marshall RW. Conservatively treated massive prolapsed discs: a 7-year follow-up. Ann R Coll Surg Engl. 2010;92(2):147-153.
Daffner SD, Hymanson HJ, Wang JC. Cost and use of conservative management of lumbar disc herniation before surgical discectomy. Spine J. 2010;10(6):463-468.
Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of spinal canal. Journal of Neurosurgery. 1934, 211(5):210-215.
Caspar W. A New Surgical Procedure for Lumbar Disc Herniation Causing Less Tissue Damage Through a Microsurgical Approach. In: Wüllenweber R, Brock M, Hamer J, Klinger M, Spoerri O, eds. Lumbar Disc Adult Hydrocephalus. Advances in Neurosurgery. Berlin: Springer; 1977:74-80;4.
Perezcruet MJ, Foley KT, Isaacs RE, Ricewyllie L, Wellington R, Smith MM, et al. Microendoscopic lumbar discectomy: technical note. Neurosurgery. 2002;51(5 Suppl):129-136.
Kambin P. Percutaneous lumbar diskectomy. JAMA. 1989;262(13):1776.
Kambin P, Casey K, O'Brien E, Zhou L. Transforaminal arthroscopic decompression of lateral recess stenosis. J Neurosurgery. 1996;84(3):462-467.
Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome, and complications in 307 consecutive cases. Spine. 2002;27(7):722-731.
Ruetten S, Komp M, Merk H, Godolias G. Full-endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine. 2008;33(9):931-939.
Hsu HT, Chang SJ, Yang SS, Chai CL. Learning curve of full-endoscopic lumbar discectomy. Eur Spine J. 2013;22(4):727-733.
Choi KC, Kim JS, Park CK. Percutaneous Endoscopic Lumbar Discectomy as an Alternative to Open Lumbar Microdiscectomy for Large Lumbar Disc Herniation. Pain Physician. 2016;19(2):E291-300.
Soliman HM. Irrigation endoscopic discectomy: a novel percutaneous approach for lumbar disc prolapse. Eur Spine J. 2013;22(5): 1037-1044.
Heo DH, Son SK, Eum JH, et al. Fully endoscopic lumbar interbody fusion using a percutaneous unilateral biportal endoscopic technique: technical note and preliminary clinical results. Neurosurg Focus. 2017;43(2):E8.
Kim SK, Kang SS, Hong YH, Park SW, Lee SC. Clinical comparison of unilateral biportal endoscopic technique versus open microdiscectomy for single-level lumbar discectomy: a multicenter, retrospective analysis. J Orthop Surg Res. 2018;13(1):22.
Aygun H, Abdulshaf K. Unilateral biportal endoscopy versus tubular microendoscopy in management of single level degenerative lumbar canal stenosis: a prospective study. Clin Spine Surg. 2021;34(6):E323-328.
Zhixiang Huang, Guochao Li, Weiming Deng, Meng Liu, Tianwang Li. Lumbar DiscHerniation Is a Nonnegligible Factor For the Degeneration of Sacroiliac Joints. Pain Physician. 2021;24(3):E357-E365.
Lin G-X, Huang P, Kotheeranurak V, Park C-W, Heo D-H, Park C-K, et al. A systematic review of unilateral biportal endoscopic spinal surgery: preliminary clinical results and complications. World Neurosurg. 2019;125:425-432.
Ren C, Song Y, Liu L'et al. Adjacent segment degeneration and disease after lumbar fusion compared with motion-presenring procedures: a meta-analysis. Eur J orthop Surg Traumatol. 2014;24(Suppl 1):S245-253.
Casal-Moro R, Castro-Menéndez M, Hernández-Blanco M, Bravo-Ricoy JA, Jorge-Barreiro FJ. Long-term outcome after microendoscopic diskectomy for lumbar disk herniation: a prospective clinical study with a 5-year follow-up. Neurosurgery. 2011;68(6):1568-1575.
Rongqing Qin, Baoshan Liu, Jie Hao, Pin Zhou, Yu Yao, Feng Zhang, et al. Percutaneous Endoscopic Lumbar Discectomy Versus Posterior Open Lumbar Microdiscectomy for the Treatment of Symptomatic Lumbar Disc Herniation: A Systemic Review and Meta-Analysis. World Neurosurg; 2018;120:352-362.
Rasouli MR, Rahimi-Movaghar V, Shokraneh F, Moradi-Lakeh M, Chou R. Minimally invasive discectomy versus microdiscectomy/open discectomy for symptomatic lumbar disc herniation. Cochrane Database Syst Rev. 2014;2014(9):CD010328.
Gempt J, Jonek M, Ringel F, Preuss A, Wolf P, Ryang Y. Long-term follow-up of standard microdiscectomy versus minimal access surgery for lumbar disc herniations. Acta Neurochir (Wien). 2013;155(12):2333-2338.
Jin Hwa Eum, Dong Hwa Heo, Sang Kyu Son, Choon Keun Park. Percutaneous biportal endoscopic decompression for lumbar spinal stenosis: a technical note and preliminary clinical results. J Neurosurg Spine. 2016;24(4):602-607.
Park JH, Jun SG, Jung JT, Lee SJ. Posterior percutaneous endoscopic cervical foraminotomy and diskectomy with unilatera lbiportal endoscopy. Orthopedics. 2017;40(5):e779-e783.
Kim J, Heo DH, Lee DC, Chung HT. Biportal endoscopic unilateral laminotomy with bilateral decompression for the treatment of cervical spodylotic myelopathy. Acta Neurochir (Wien), 2021;163(9):2537-2543.
Yue Deng, Mingzhi Yang, Chao Xia, Yong Chen, Zhong Xie. Unilateral biportal endoscopic decompression for symptomatic thoracic ossification of the ligamentum flavum: a case control study. Int Orthop. 2022;46(9):2071-2080.
Eun SS, Eum JH, Lee SH, Sabal LA. Biportal endoscopic lumbar decompression for lumbar disk herniation and spinal canal stenosis: a technical note. J Neurol Surg A Cent Eur Neurosurg. 2017;78(4):390-396.
Jie Hao, Jiaqi Cheng, Huawei Xue, Feng Zhang. Clinical comparison of unilateral biportal endoscopic discectomy with percutaneous endoscopic lumbar discectomy for single L4/5-level lumbar disk herniation. Pain Pract. 2022;22(2):191-199.
Hengrui Chang,Pain Pract Jiaxin Xu, Dalong Yang, Jiayuan Sun, Xianda Gao, Wenyuan Ding. Comparison of full‑endoscopic foraminoplasty and lumbar discectomy (FEFLD), unilateral biportal endoscopic (UBE) discectomy, and microdiscectomy (MD) for symptomatic lumbar disc herniation. Eur Spine J. 2023;32(2):542-554.

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You are reading this latest preprint version

Percutaneous unilateral biportal endoscopic discectomy for symptomatic lumbar disc herniation in geriatric patients

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

1. Patient population

2. Inclusive and exclusive criteria

3. Surgical procedures

4. Efficacy evaluation

5. statistical analysis

Results

Discussion

Conclusion

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1