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[10–12]. 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 muscles attached to the lamina and the removal of the facet joints. Patients with PTED have less possibility of instability because these structures are preserved in this kind of surgery. A short-term retrospective study performed by Lee demonstrated that no patients in the PELD group developed instability, but 3.4% of patients who underwent OLM developed instability on final follow-up[20].
PTED has incomparable advantages over other technologies, only resecting part of the superior articular process bone and most structures preserved so as not to damage the biomechanical structure of the spine, local anesthesia, small incision, less bleeding, short operation time and early ground access[21–23]. And there are three systematic reviews that suggest that PELD seems to be a safe and effective LDH intervention with similar clinical efficacy compared with traditional open microdiscectomy[24–26].
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.