Recurrent lumbar disc herniation is a common cause of postoperative low-back pain in addition to postoperative scars and surgical site infections. It refers to the disappearance or alleviation of the patient’s low back and leg pain symptoms after open surgery or minimally invasive surgery, but after a time, the recurrence of nucleus pulposus herniation of the same segment of the lumbar disc is observed, which compresses the corresponding nerve root or dural sac and induces back and leg pain. For the diagnosis and treatment of recurrent lumbar disc herniation, the average cost per patient is 39,386 US dollars, which is significantly higher than that of patients undergoing conservative treatment, putting a financial burden on the patients . The current definition of recurrent lumbar disc herniation is still controversial. First, some scholars hold that after the initial surgery, an asymptomatic interval of at least 6 months is needed for recurrent lumbar disc herniation to be diagnosed . Alternatively, recurrent lumbar disc herniation can be diagnosed if intervertebral disc herniation recurs at the same segment after the postoperative symptoms are relieved for more than 1 month . Therefore, in this study, we defined recurrent disc herniation as the recurrence of leg pain symptoms after they had disappeared or were significantly alleviated for more than 1 month after the initial surgery for lumbar disc herniation, which was confirmed by imaging of a herniated nucleus pulposus in the same segment.
The recurrent herniation of the nucleus pulposus after surgery and the recurrence or aggravation of the symptoms are correlated with body mass index (BMI), age, sex, smoking, the size of the herniation, and the degree of degeneration of the lumbar intervertebral disc [24,25,26]. Yao et al.  found that patients aged ≥ 50 years were more likely to relapse after surgery because the degree of degeneration of the lumbar intervertebral disc increases with age. After the intervertebral disc is under pressure, the nucleus pulposus may herniate again, and BMI is one of the most important risk factors for postoperative recurrence. Therefore, patients undergoing TESSYS due to lumbar disc herniation should be guided to maintain good living habits, control their body weight, and avoid excessive pressure on the spine in order to maintain the treatment effect of the surgery.
At present, recurrent intervertebral disc herniation is still treated mainly by traditional open surgery and minimally invasive interventional treatment [27,28,29]. Although traditional open surgery is more thorough in removing the herniation and ensuring the stability of the spine after fusion surgery, it will also lead to an increase in the surgical risk, operative time, intraoperative blood loss, and medical cost . In recent years, the TESSYS technique, as an endoscopic spinal surgery method, has emerged as a new way to treat recurrent lumbar disc herniation. The TESSYS technique has a small working channel diameter, reduces the exposure of bony landmarks, does not need to damage the lamina of the surgical segment, and ensures the stability of the spine. The technique is performed under direct endoscopic vision, which facilitates the clear identification of scars, nerve roots, blood vessels, the nucleus pulposus, and other tissues. The use of local anesthesia can effectively reduce the likelihood of intraoperative dural sac and nerve root injury through timely communication with the patient. Hoogland et al.  reported that 262 cases of recurrent lumbar disc herniation were treated under an endoscopic transforaminal approach, and the good-to-excellent rate of this approach was 85.7%. In this study, 31 patients with recurrent lumbar disc herniation were followed up for 2 years. The good-to-excellent rate of TESSYS was 83.9%, which was similar to that reported earlier. Postoperative pain symptoms were still present, or the degree of symptom relief was low in 6.45% of patients. On the one hand, this may have been due to the presence of extensive adhesions in the original lumbar spine surgery segment during the reoperation. To avoid nerve damage and other risks, intraoperative decompression can be incomplete. On the other hand, due to the long course of the disease, long-term pain in the lower back and lower extremities can affect the structure and function of the central nervous system and promote central sensitization during peripheral nociceptive stimuli to produce chronic neuropathic pain . These cause anxiety and depression, which makes the treatment effect poor.
Although the TESSYS technique, as a minimally invasive procedure, has the advantages of less trauma, less bleeding, and faster postoperative recovery, it should be noted that it has relatively limited ability to repair the annulus fibrosus with ruptured intervertebral discs, and the nucleus pulposus preserved in the intravertebral space may still become herniated again. Poor life and work habits of the patient after surgery may also lead to an increase in the degree of intervertebral disc degeneration, leading to reherniation of the nucleus pulposus. In this study, during our 2-year follow-up, no patients had recurrence of symptoms or reherniation of the nucleus pulposus. These findings may be related to their decrease in high-intensity physical activity and their avoidance of poor lifestyle habits after surgery.
This study has several limitations. Firstly, the sample size is not large enough that longer follow-up duration with more cases is needed. Secondly, we only focused on the results of TESSYS for recurrent lumbar disc herniation, the data of traditional open surgery for recurrent lumbar disc herniation should be collected and compare the TESSYS with the traditional open surgery in the treatment of recurrent lumbar disc herniation, which will be our future research focus. Finally, this study is a single-center retrospective study, a multiple center clinical study could be suggested for further study.