Comparison of Outcomes Postoperation between Straight Leg Raising Test Negative and Positive Patients Who Underwent Percutaneous Transforaminal Endoscopic Discectomy for Lumbar Disc Herniation

Background: Percutaneous Transforaminal Endoscopic Discectomy is used increasingly in patients with Lumbar Disc Herniation. There is little knowledge on the related factors including SLR test influencing the operation. Therefore, we designed this prospective study to explore the relevant factors influencing postoperative effect of PTED surgery. Methods: Consecutive patients with LDH who came to our hospital from August 2015 to September 2016 and received PTED surgery. 4 kinds of scales including VAS (lumbar/leg), ODI and JOA were measured and reassessed at 1 day, 3 months, 6 months, 12months and 36 months after the PTED to assess their surgical outcomes. Results: All the patients had successful surgery. ODI and VAS (lumbar/leg) decreased in all patients and groups. And there was a statistically significant difference in each postoperative follow-up compared with that before surgery in every visit. In addition, the increase of JOA in postoperation was statistically significant compared with that before surgery. And, there is statistically significant difference between the three subpopulations (patients with SLR Positive (0°-30°), SLR Positive (31°-60°) and SLR Negative (61°-) in the changes of the scores of VAS(leg), ODI and JOA. However, there is no statistically significant difference between the three subpopulations (patients with SLR Positive (0°-30°), SLR Positive (31°-60°) and SLR Negative (61°--RRB- in the changes of the score of VAS(lumbar). Conclusions: PTED showed great effect on treating patients with lumbar disc herniation. And the main scale score such as VAS(leg). ODI and JOA showed that there is a statistically significant difference between the three subpopulations treated by PTED. Patients with SLR negative may get greater benefit from PTED.

Lumbar disc herniation(LDH) is one of the most common disorders whose prevalence is about 77.8% [1]. LDH is mainly due to compression of nerve by the nucleus pulposus, annulus fibrosis and cartilage plate, especially the nucleus purposes. After the degenerative changes of lumbar vertebra in different degrees, the intervertebral disc annulus fibrosis is broken under the action of external factors, and the nucleus pulposus enters the posterior vertebral canal, which then leads to the stimulation or compression of the nerve roots of the adjacent spinal cord. Then a series of clinical symptoms such as lumbar pain, numbness and pain in one lower limb or both lower limbs are produced.
Traditional open lumbar microdiscectomy (OLM) is considered the gold standard of LDH treatment for its good efficacy in long-term follow-up [2,3]. In recent years, minimally invasive techniques have developed rapidly and minimally invasive discectomy (MID) has been gradually applied in lumbar intervertebral disc herniation which is more minimally invasive and conducive to postoperative rehabilitation compared with open surgery [4].
Novel MID procedures have many Potential advantages over standard Microdiscectomy or open discectomy (MD/OD) including less blood loss, less postoperative pain, shorter hospitalisation and earlier return to work [5].
Straight leg raising(SLR) test is a common valuable examination method, which can reflect the severity of lumbar disc herniation and the degree of nerve root compression to some extent [6]. Jonsson's research showed that a SLR test has a strong correlation with various parameters of pain degree. And positive postoperative SLR test was associated with inferior outcome [7]. However, there are few studies on the related factors including SLR test influencing the operation, and there are few reports on which type of patients will benefit more from this kind of operation. Therefore, we designed this prospective study to explore the relevant factors influencing postoperative effect of PTED surgery, so as to provide a reference for clinical diagnosis and treatment. In this study, we collected preoperative and postoperative the Visual Analogue Scale(VAS) score, Oswestry Disability Index and Japanese Orthopaedic Association score (JOA) of patients and analyzed the relationship between these scores and SLR to find the influence of SLR on postoperative clinical results. It provides reference for clinical selection of surgical indications and contraindication.

Patients and follow-up
Methods: According to the strict inclusion and exclusion criteria, we selected 118 consecutive patients with LDH who came to our hospital from August 2015 to September 2016 and received PTED surgery. Only 96 of these patients had complete data and were followed up for three years. Their surgical outcomes were assessed using VAS(lumbar/leg). ODI and JOA. And patients completed these assessments one day before surgery. 4 kinds of scales including VAS(lumbar/leg), ODI and JOA were measured and reassessed at 1 day, 3 months, 6 months, 12 months and 36 months after the PTED. Our initial hypothesis was that the differences in 4 scaled score between patients between SLR positive and negative was statistically significant. The operation was performed by two doctors who have more than 10 years of spinal neurosurgery experience and has received professional training in spinal endoscopy.

Surgical Techniques
After the success of the anesthesia, patients were in the prone position. We choose at 8 to 10 cm away from the spine puncture, puncture Angle of 10 ° for L2/3 and L3/4, and at 8 to 10 cm away from the spine puncture, puncture Angle of 30 ° for L4/5 and L5 / S1 (

Statistical Analyses
The statistical analysis of this study was performed with the statistical package SPSS, version 23.00 (SPSS Inc, Chicago, Illinois). Data is shown as meaning ±standard deviation(SD). Then independent t-test, Mann-Whitney U test, Chi-square test, and Fisher's exact test were used to compare the differences of clinical and radiological outcomes. P values < 0.05 were accepted as statistically significant.

Discussion
PTED is considered as a secure and effective method for the treatment of soft disc herniation. The advantages of this technology include the preservation of the posterior disc structure which has less impact on the stability of the spine and the effectiveness similar to that of traditional open discectomy [8,9]. In recent years, PTED has undergone significant technological evolution and the indications of PTED are also expanding [10][11][12].
There several randomized controlled studies have demonstrated that the new method showed great effectiveness in the treatment of LDH which is consistent with our study [8,13,14]. While PTED brings great benefits to most patients, a small number of them have poor outcomes or complications [15,16]. Therefore, we need further research to explore the best indications for PTED so as to bring the greatest benefit to patients with LDH.
SLR test serves as a valuable common examination method, which can reflect the severity of lumbar disc herniation and the degree of nerve root compression to some extent [6].
Jonsson's research showed that the SLR test has a strong correlation with various parameters of pain degree. And positive postoperative SLR test was associated with inferior outcome [7]. However, there are few studies on whether SLR test could influence the operation, and there are few reports on which type of patients will benefit more from this kind of operation. Therefore, we designed this research to compare the prognostic differences between patients with SLR positive and negative who have LDH after PTED surgery. Our study showed that patients with PTED had a very good prognosis after surgery, and patients with very severe cases could take care of themselves and gradually return to a normal life after surgery. This is similar to most reports on the efficacy of PTED procedure [17,18]. There was no statistically significant difference in preoperative VAS(lumbar/leg). JOA, ODI, etc. among three groups we selected, ensuring that the comparison was reliable and valuable. It is assumed that this is of great significance for postoperative recovery of patients. And the changes of VAS(lumbar/leg), JOA and ODI are greater in patients with SLR negative than those in patients with SLR positive. This may show that SLR negative patients had more benefits from the operation, although there was a statistically significant difference among the three groups in the main scaled scores. In brief, PTED as a novel technique showed an excellent effect in the treatment of LDH. And there is a study performed by Hyeun that has shown that PTED works well for all types of lumbar disc herniation, including extremely difficult cases [18]. Overall, there was statistically significant difference in postoperative changes among SLR Positive (0°-30°), SLR Positive (31°-60°) and SLR Negative (61°-). Therefore, there is an obvious difference in the effect of PTED surgery between patients with SLR positive and SLR negative.
Surgery-induced instability is a common consequence of OLM which may occur as much as to 22% after OLM [19]. Instability of the spine results from the removal of small lumbar This study has several limitations. For design reasons, there is no suitable control group, because the purpose of this study is not to emphasize the possible advantages of PTED over other surgeries, but to show the improvement of patients after receiving this surgery and the relationship with SLR. In addition, for many reasons, some patients lost follow-up and did not complete the study.
While there have been many studies of PTED for LDH, none have looked at differences in improvement and postoperative recovery in the terms of SLR. According to our findings, PTED seems to be a safe and effective technique. Patients with SLR negative may have good outcomes according to VAS(leg). ODI and JOA. In a word, there was significant difference among the three groups. All in all, these have important clinical impact. But whether SLR plays a role in the outcome requires large, multicenter, randomized, controlled studies. This study laid the foundation for a multicenter randomized controlled study.

Conclusions
PTED showed great effect on treating patients with lumbar disc herniation. And the main scale score such as VAS(leg). ODI and JOA showed that there is a statistically significant difference between the three subpopulations treated by PTED. Patients with SLR negative may get greater benefit from PTED.

Declarations
The datasets generated and/or analysed during the current study are not publicly available due to the need to protect individual privacy but are available from the corresponding author on reasonable request.

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