Endoscopic discectomy through the intervertebral space approach

     Microscopic discectomy through minimally invasive channels is currently the most commonly used minimally invasive spinal surgery technique for the treatment of intervertebral disc herniation. MED minimally invasive lumbar discectomy is a new minimally invasive spinal surgery technique first developed by Foley and Smith in 1997. MED minimally invasive lumbar discectomy draws on the advantages of traditional posterior laminoplasty and endoscopic minimally invasive techniques. It establishes a surgical approach through a series of dilated channels and uses a 1.6-1.8cm diameter working channel to complete procedures such as laminoplasty, small joint resection, nerve root canal decompression, and intervertebral disc resection that were previously only possible through open surgery. Compared with traditional lumbar discectomy, this technique establishes a surgical approach through a series of dilated catheters, without the need for dissection and traction of paraspinal muscles, and completes all surgical operations within a 1.6-1.8cm diameter working channel. Therefore, it has the advantages of small surgical incision, mild paraspinal muscle injury, less bleeding, and fast postoperative recovery. Due to the advanced camera and video system, the surgical field of view is enlarged by 64 times, allowing for more accurate identification and protection of the dural sac, nerve roots, and vascular plexus within the spinal canal in the surgical area during surgery; At the same time, a clear surgical field ensures more accurate completion of various surgical operations, effectively avoiding the shortcomings of traditional surgical fields of deep vision and significant damage to the bone joint structure behind the spine. It maximizes the preservation of the integrity of the posterior ligament composite structure of the spine, thereby effectively reducing the occurrence of postoperative scar adhesion and lumbar instability.

　　The pathological changes in a specific area determine the placement of the work channel. Minimally invasive lumbar decompression surgery can provide sufficient decompression in the central spinal canal, lateral recess, and intervertebral foramen regions. In addition, the intervertebral disc tissue outside the intervertebral foramen can also be removed. Before performing decompression on different areas, it is necessary to plan the surgical pathway. For decompression of extraforaminal nerves, the working channel can be placed on the transverse process membrane between the transverse processes. Firstly, the transverse process membrane is determined, and the transverse process ligament is cut open to expose its deep exit nerve root. Once the exit nerve root is determined, the protruding intervertebral disc tissue can be found in the deep part of the nerve root. Recent studies have compared minimally invasive discectomy with traditional open surgery, and the results show that minimally invasive surgery has minimal tissue damage, minimal nerve interference, minimal blood loss, mild postoperative pain symptoms, short hospital stay, and fast recovery and return to work. A randomized controlled study between traditional open microsurgical discectomy and minimally invasive microsurgical discectomy through a minimally invasive channel showed that surgery through a minimally invasive channel is safer and more effective.

　　The new technology of intervertebral discoscopy (MED) developed by Foley and Smith is a perfect combination of minimally invasive microsurgical techniques and endoscopic techniques. MED surgery is similar to open microscopic discectomy and can be used for laminectomy, decompression, foraminotomy, and disc herniation surgery. The ease of operation, wide indications, and diverse functions of MED make it easier for surgeons to transition from traditional surgery to endoscopic surgery. Although endoscopic visualization not only provides a clear and enlarged surgical field of view, but also facilitates and is effective, it can only provide 2D images and is often obstructed by bleeding and unclear display, which is not as good as microscopic discectomy. The advancement of endoscopic imaging and endoscopic image fusion technology can help improve this issue.

　　Controlling bleeding is particularly important for any visualization technique, as excessive bleeding increases the risk of dural sac tear and nerve root injury. The bleeding outside the dura or around the small joints interferes with the surgeon's inability to further operate, but some traditional methods like microscopic discectomy can be used (fibrillar collagen gel, thromboxane gel, absorbable gelatin sponge and small cotton piece, etc.). Endius has developed a miniature bipolar electrocoagulation (MDS) device with a double-layer sheath, which can be applied for blunt separation, blood sucking, and electrocoagulation hemostasis. In addition, a dual light source endoscopic system (infrared/visible) is adopted, which adds an infrared channel to the current laparoscopic system. This system can detect small arterial bleeding in the environment of bleeding, identify the specific location of the bleeding, help the surgeon quickly burn to stop bleeding, and reduce repeated hemostasis operations when the bleeding point is unclear.

　　Currently, most spinal endoscopes claim to have a magnification of 20 x when using xenon or halogen light sources, and can reach 3 x 104 pixels. Recent visualization techniques can achieve 5 x 104 pixels through a 1.8mm fiber diameter, which is sufficient for most current surgeries. Future spinal endoscopic surgery will benefit from smaller fibers, providing more surgical space without compromising image quality. Another advancement is dual illumination. MGB endoscopy uses a telescope system called Shadow, which integrates two independent lighting sources onto a standard 30 ° surgical endoscope. Due to the structure of Shadow, it can provide good plasticity and contrast, which can be transformed into three-dimensional images, achieving high resolution and uniform clear surgical field of view. Another improvement in spinal endoscopy is the anti nebulization system, as re nebulization after external cleaning can lead to repeated interruptions in surgery. Maintaining clear vision is particularly important for the safe implementation of minimally invasive spinal surgery. In 1993, scholars studied adding an additional "sheath" (outer tube) to traditional endoscopes, which can clean and dry the optical lens at any time, so that the lens remains clean and does not need to be repeatedly removed from the patient's body. The added defogger can remove the smoke generated by high-frequency surgical electric knives. Unfortunately, the system is unable to prevent natural atomization caused by the imbalance between the temperature of the lens and the humidity in the working area. Some companies have attempted to add sensors and thermal resistance wires behind the lens to solve this problem. Based on the high-definition imaging (HDI) function of the CCD chip, it can provide 2 million pixels within the 1250 horizontal line, thus obtaining a clearer surgical field of view.

　　The advancement of computer technology and endoscopic technology has enabled three-dimensional reconstruction of virtual images, which are synthesized by combining preoperative images with intraoperative scans and then attached to intraoperative endoscopic images. Similar techniques have been used in craniocerebral surgery, which combines preoperative image reconstruction with intraoperative surgical microscope images. This can assist surgeons in confirming the boundaries of tumors and better removing them. Recently, Mississauga (Canada) developed a set of neuroendoscopic cannula, which can be used to observe the position of the endoscope based on MRI and CT data. Special software provides on-site endoscopic images and three-dimensional positioning of instrument positions. Another development is helmet display glasses, which are connected to surgical microscopes, allowing surgeons to observe transmitted display signals and surgical field of view. In the near future, this technology can also be used in spinal surgery endoscopes to compensate for the shortcomings of two-dimensional spinal endoscopes. The future improvements in imaging technology will also include better optical image resolution, better focusing like surgical microscopes, better elasticity and operability, greater working channel effects, and continuous improvement of 3D images. These improvements can take spinal endoscopic surgery to a whole new height.