LSS characterized by intermittent claudication is a common degenerative disease of the lumbar spine. With the progression of disease, the patient's walking distance is gradually decreased, which will seriously affect the quality of life of the patient eventually [12]. It is the main cause of low back pain and even bilateral lower limb paralysis in the elderly [13]. The main causes of LSS in elderly patients are the dysfunction of blood circulation caused by compression and the effects of inflammatory factors. Due to the morphological transformation of lumbar bone and its surrounding soft tissue, the increase of intraspinal pressure results in the compression of spinal cord or nerve root, which in turn leads to the aggravation of the disease [14]. Conservative treatment and surgical treatment are used in the clinical treatment of LSS. Conservative treatment, such as oral analgesics, transforaminal epidural block and selective nerve root block can potentially allow for the spontaneous total resolution of symptoms in young patients [15]. The surgical treatment includes traditional posterior open surgical and minimally invasive channel therapy. The safety of surgery is particularly critical in elderly patients as these people are often complicated with a variety of medical diseases, and their physiological function is significantly deteriorated, making it poorly tolerated, with high surgical risks, high complication rates, and a greater chance of dural injury. Therefore, it is necessary for the operator to make a reasonable choice of surgical approach according to the surgical indications, so that elderly patients can also receive surgical treatment. Due to a large exposed area of traditional open surgery, the patients are prone to great bleeding, increasing the risk of infection, and destroying the structure of facet joints, which harms the stability of the patient's spine and greatly increase the chance of postoperative low back pain. As a result, it is difficult to be tolerated by elderly patients and was not conducive to their recovery. Therefore, orthopedic doctors urgently need to find a new surgical method to make up for the shortcomings of open surgery.
With the development of medical technology, minimally invasive channel surgery has gradually developed. Minimally invasive microscopic or endoscopic decompression surgery can fully expand the spinal canal which can avoid the shortcomings of traditional posterior open surgery such as large openings and incomplete decompression [16]. At present, there is still a great debate about the surgical treatment of LSS in the elderly. Compared with traditional posterior open surgery, Quadrant channel open decompression has the advantages of shorter operation time, less intraoperative bleeding, less postoperative lumbar spine slippage and degeneration, and lower postoperative infection rate [17]. Besides, Quadrant channel open decompression creates a working channel through the continuous expansion using the working trocar needle, which can eliminate the need for extensive dissection of the paravertebral muscles to reveal skeletal landmarks [18], making it one of the effective treatment methods for LSS. Due to the large pressure on the surrounding soft tissues during the placement of the step-by-step expansion channel, however it is easy to cause local skin and subcutaneous tissue necrosis at the operation site if the operation is performed for a long time, which will affect the healing of the incision [19]. In addition, when the channel is installed, muscle and joint capsule tissue will be left to varying degrees at the bottom of the channel due to the influence of the articular process. To obtain a better exposure, therefore, the soft tissue at the bottom of the channel needs to be removed inevitably during the surgery, which may lead to the injury of the muscle attachment points and joint capsule of the surgical segment, and easily result in postoperative chronic low back pain. At the same time, due to the limitation of the channel, the surgical field of vision is small, coupled with intraoperative blood seepage, and the clarity and comfort of the surgical field of vision is poor, so it is often necessary to use a special surgical microscope. Besides, the requirements for accuracy in positioning are more stringent, and the operation time is relatively long, which is easy to cause muscle fatigue of the operator [20], thus increasing the technical difficulty of the operation for the surgeon. Some researchers have suggested that a “precise” fenestration operation should be performed under the intervertebral foraminal microscope for decompression, which aims to effectively alleviate the disease with minimal trauma [21], so percutaneous transforaminal endoscopic technique has emerged [22]. However, the intervertebral foraminal microscope cannot fully reduce the pressure for the severe LSS. The emergence of Delta large channel endoscopy technology responds to the requirements of development. The Delta endoscope is further optimized and improved on the basis of the traditional foraminal endoscope, and the scope of decompression under the endoscope is further expanded by expanding the working channel [23]. It also has a large diameter, simple operation, and has a field of view similar to that of open surgery [24], as well as equipped with a larger grinding drill that is large enough to easily remove excess bone and enlarge synapses [25], which avoids the shortcomings of the limited field of view in Quadrant channel open decompression. Moreover, with a large operation space and less damage to the muscle attachment point and joint capsule of the surgical segment, the risk of postoperative low back pain is greatly reduced. The report of Wu et al. showed that the Delta large channel endoscopy technology has a significant effect on the treatment of LSS [26], which can not only release the compression of the nerve by the dural sac and the bone around the nerve root, but also release the compression of soft tissues such as the intervertebral disc, posterior longitudinal ligament and ligamentum flavum, and without obvious damage to the lumbar spine [27], thereby effectively alleviating the the patient's low back and bilateral lower extremity radiological pain and improving the body function of the patient. Moreover, it can shorten the operation time and reduce the amount of intraoperative bleeding, and uses water as the operating medium, which can make the field of vision clearer [28]. During the operation, continuous normal saline irrigation can flush out various inflammatory mediators around the diseased intervertebral disc and the by-products left by electrocoagulation, which can relieve postoperative pain [29].
In this study, all the 40 patients successfully completed the surgery. 19 out of the 20 patients in the observation group had no postoperative complications, and 1 case of surgical site infection occurred, which was cured after symptomatic treatment with anti-inflammatory and standard drug change. In the control group, 15 out of 20 patients had no postoperative complications. 1 case of cerebrospinal fluid leakage occurred, which was cured after bed rest and conservative treatment with antibiotics; 3 cases of low back pain were cured after treatment with anti-inflammatory and analgesic drugs; 1 case of limited necrosis at the skin edge of the surgical incision was cured after drug change. Ultrasonic bone knife was used during the Quadrant channel open decompression operation, whose vibration would generate heat. Due to the small incision, it was inevitable to contact the skin during the operation. Therefore, the heat generated by the ultrasonic bone knife might burn the skin in contact, which resulted in skin infection and necrosis.
In summary, Quadrant channel open decompression can shorten the operation time, reduce intraoperative bleeding, and reduce surgical trauma [30]. It has a short learning curve, and has a strong three-dimensional sense and overall sense during the operation. However, the surgical field of view is small, special operating microscopes are required, and the probability of postoperative chronic low back pain is high.
The emergence of Delta large channel endoscopy has made up for the shortcomings of the Quadrant channel open decompression, with less damage to the patient and a better curative effect and obvious advantages in relieving back and leg pain and improving patients' daily life status. It greatly shortens the bed rest and hospitalization time, and has a low incidence of complications, which greatly ensures the quality of life of patients, and is worthy of clinical promotion. Although the Delta large channel endoscopy has a long learning curve and certain limitations [31]; for example, when the interlaminar approach is placed in the working channel, the dura mater is sometimes compressed, and the nerve root is stretched and injured and excessive saline flushed too fast intraoperation can lead to increased epidural pressure. However, as a modification and optimization of the total spine endoscopy, it has more potential for development in terms of trauma, visual field and work efficiency. There were still some shortcomings in this study. For example the sample size was small and the clinical observation time was short. There might be some deviations in the report on the treatment effect, which needed to be further studied at a later stage. In addition, the treatment should be comprehensively considered according to the patient's body condition and economic conditions.