Development status of minimally invasive spine surgery technology

In recent decades, with the tremendous progress in spinal surgical concepts and scientific technology, the popularity of minimally invasive spinal surgery has greatly increased. Minimally invasive spinal techniques are designed to minimize the risk of surgical complications while achieving the same results as traditional open surgery. Minimally invasive spine surgery advocates avoiding or reducing tissue damage related to the surgical approach as much as possible, preserving normal anatomical structures within the surgical scope as much as possible, while allowing for rapid postoperative recovery and better quality of life.

Starting from lumbar disc microresection technology, various revolutionary minimally invasive techniques continue to emerge and gradually replace open surgery. The development of modern surgical auxiliary equipment such as endoscopes, navigation and robots has further expanded the scope of indications for minimally invasive spinal surgery, making it suitable for many complex spinal lesions. For example, using a microscope or endoscope can not only perform routine nerve decompression/fusion operations more safely, but can also significantly improve the feasibility and safety of operations related to spinal metastatic lesions, complex spinal infections, and complex spinal trauma.

01  Surgical procedure

So far, minimally invasive spine surgeries include minimally invasive anterior lumbar interbody fusion (MIS-ALIF), minimally invasive posterior lumbar interbody fusion (MIS-PLIF)/minimally invasive transforaminal lumbar interbody fusion fusion (MIS-TLIF), oblique lateral lumbar interbody fusion (OLIF) and extreme lateral lumbar interbody fusion (XLIF), as well as endoscopic fusion technology that has been initially developed in recent years. Throughout the development process of various minimally invasive spinal techniques, it is the historical process in which scientific development drives the development of surgical concepts and technologies.

 Since Magerl first reported percutaneous pedicle screw placement in 1982, minimally invasive spinal technology has officially entered the development stage.  In 2002, Foley et al. first proposed MIS-TLIF. In the same year, Khoo et al. reported MISPLIF for the first time using a similar working channel. These two surgeries paved the way for the development of minimally invasive posterior spinal surgery. However, to reach the spinal area through the posterior approach, it is inevitable to peel off muscles and remove part of the bone structure, and the degree of exposure of the surgical field will affect the amount of bleeding, infection rate, and postoperative recovery time.  ALIF has the potential advantages of not entering the spinal canal, avoiding epidural scar formation, completely preserving the musculo-osseous tissue structure of the posterior spine, and reducing the risk of nerve damage.

 In 1997, Mayer reported a modified lateral approach to ALIF, using a retroperitoneal/anterior psoas approach at the L2/L3/L4/L5 levels and an intraperitoneal approach at the L5/S1 level.  In 2001, Pimenta first reported a method of spinal fusion through the lateral retroperitoneal space and dividing the psoas major muscle. After a period of development, this technique was named XLIF by Ozgur et al. in 2006.  Knight et al. first reported direct lateral lumbar interbody fusion (DLIF) through the psoas approach similar to XLIF in 2009.  In 2012, Silvestre et al. summarized and improved Mayer's technology and named it OLIF. Compared with XLIF and DLIF, OLIF uses the anatomical space in front of the psoas major muscle and does not interfere with the muscle and the nerves below it. It can not only effectively avoid the risk of vascular damage caused by ALIF, but also avoid the psoas major injury caused by XLIF/DLIF. Plexus injury, reducing the incidence of postoperative hip flexion weakness and thigh numbness.

On the other hand, with the continuous improvement of surgical instruments and the gradual maturity of technology, patients' demand for minimally invasive surgery has increased.  In 1988, Kambin et al first tried and introduced endoscopic spine surgery. Up to now, the most representative method is single-incision or double-incision endoscopic laminectomy to treat lumbar spinal stenosis, lumbar disc herniation, etc. On this basis, endoscopic lumbar interbody fusion came into being. According to the characteristics of the endoscope, it is divided into full endoscope, microendoscope and double-hole endoscope. Through the transforaminal approach or interlaminar approach for spinal fusion. So far, endoscopically assisted lateral lumbar interbody fusion (LLIF) or TLIF has been clinically used to treat degenerative spondylolisthesis and lumbar spinal stenosis accompanied by spinal instability or foraminal stenosis.

02 Surgical auxiliary equipment

 In addition to improvements in minimally invasive surgical concepts and approaches, the application of a large number of high-precision surgical auxiliary equipment also facilitates minimally invasive surgery. In the field of spine surgery, real-time image guidance or navigation systems provide greater safety and accuracy than traditional free-hand techniques. High-quality intraoperative navigation CT images can provide a three-dimensional intuitive view of the surgical field, allow three-dimensional real-time anatomical tracking of implants during surgery, and reduce the radiation exposure risk of surgeons and patients by more than 90%.

 On the basis of intraoperative navigation, the application of robotic systems in the field of spine surgery has been increasing in recent years. Pedicle screw internal fixation is a representative application of robotic systems. By combining with navigation systems, robotic systems are theoretically expected to achieve Perform pedicle screw internal fixation more accurately while reducing soft tissue damage. Although there is insufficient clinical data on the utility of robotic systems in spine surgery, several studies have shown that the accuracy of pedicle screw placement with robotic systems is superior to manual and fluoroscopic guidance. One of the most important advantages of robot-assisted spine surgery is that it overcomes the mental and physical fatigue of the surgeon during the operation, thereby providing better and more stable surgical operations and clinical results.

 In the process of minimally invasive spine surgery, it is crucial to choose the right indications and ensure patient satisfaction with the treatment results. The combination of artificial intelligence (AI) and machine learning will help spine surgeons improve preoperative planning, surgical execution plans and optimize patient selection to ensure improved postoperative outcomes and patient satisfaction.

03 Outlook

Although minimally invasive spinal technology has made great progress and is currently the most widely accepted advanced concept in clinical practice, we should still be aware of the limits of minimally invasive surgery. The development of minimally invasive technology has greatly reduced the exposure of local anatomical structures during surgery. At the same time, it has placed higher requirements on the surgeon's skills and understanding of anatomical structures. Many spinal surgeries, such as spinal correction surgeries for severe deformities, are already very difficult to perform even under maximum exposure conditions. Full exposure of the surgical field is helpful for operating instruments and intraoperative operations, and full exposure of nerve and vascular structures is also difficult. Can effectively reduce the risk of complications. Ultimately, the primary goal of spine surgery is to ensure that the procedure is performed safely.

 In summary, minimally invasive surgery has become an inevitable trend in the development of spinal surgery concepts worldwide. The main goal of minimally invasive spinal surgery is to minimize the soft tissue damage associated with the approach and preserve the normal anatomical structure, speed up the postoperative recovery process and improve the quality of life without affecting the surgical effect. Over the past few decades, major advances in surgical concepts and scientific technology have enabled minimally invasive spine surgery to continue to move forward. Various surgical approaches allow physicians to perform 360° minimally invasive decompression and fusion around the spine; endoscopic technology greatly expands the intraoperative anatomical field of view; navigation and robotic systems make complex pedicle screw internal fixation easy safer.

 However, minimally invasive surgery also brings new challenges:
 1. First of all, minimally invasive surgery significantly reduces the exposure range, which may make it very difficult to deal with intraoperative complications, and may even require conversion to open surgery.
 2. Secondly, it relies heavily on expensive auxiliary equipment and has a steep learning curve, which increases the difficulty of its clinical promotion.

 We look forward to providing patients with more and better minimally invasive options through further innovation in surgical concepts and continuous development of science and technology in the future.