Initial interest in minimally invasive spine surgery dates back several decades and has since been based on the primary goal of finding novel techniques in order to facilitate similar or better clinical outcomes to those of conventional open spine surgery. This concept is driven by the theoretical benefits of less injury to nerves, vessels and muscle around the spine, decreased blood loss, decreased post-operative pain, smaller incisions, decreased scarring, shorter length of stay and faster recovery times. However, there is still a lack of clear evidence that minimally invasive spine surgery has truly better long-term outcomes than traditional open surgery.

The modern tools and techniques used in minimally invasive spine surgery have been adapted from technology used in many other surgical fields. Despite the level of sophistication of current imaging, limited exposures and specialized tools, it is imperative that the surgeon ensures that the proposed goals of the surgical procedure are actually achieved. Current advances in minimally invasive spine surgery can be divided in to four main topics: microscopic technique, small incisions, specialized tools, and special imaging.

The goal of all minimally invasive techniques is to perform the necessary procedure with minimal injury to soft tissue. Thus, the basic tenet of this type of surgery is to accomplish your goal through the smallest window possible. The adaptation of the operating microscope in spine surgery dates back to the late 1960s and, since that time, it has been used in a variety of minimally invasive spinal procedures because it provides superior lightening and magnification power in addition to providing both the surgeon and assistant with a three dimensional view of the operative site. Such technology has facilitated the surgeon to perform the most delicate tasks in very tight spaces and supported the use of very fine sutures and microscopic instruments.

To accomplish the goal of adequate visualization with minimal soft tissue injury, there have been several advances in obtaining smaller incisions. These technologies range from fiberoptic cameras and video systems to special tube retractors placed through small incisions. Specialized instruments need to be used in conjunction with tube retractors given the limited working area. These microsurgical approaches have allowed access to the spinal cord, spinal nerves, disk spaces, and vertebral bodies.

Procedures performed with these techniques include both cervical and lumbar discectomy and decompression of pinched nerve roots, and in limited circumstances fusion procedures in the cervical, thoracic, and lumbar spine. Some studies suggest that this affords the patient minimal invasion, decreased surgical time, less blood loss, lower morbidity, better cosmesis, and decreased length of hospitalization, while others suggest that there does not seem to be a definitive advantage over mini-open exposures.

Because of the limited access available for the surgeon to work, specialized tools have been developed to adapt to these minimally invasive techniques. Such developments have made discectomies and decompressions commonly performed procedures, however, further innovation in spinal implants has now made fusions with screws possible. Percutaneous screw systems combined with tube retractors play a major role in minimally invasive spine surgery and have facilitated the spine surgeon to perform spinal fusion through small incisions. While some of the newer technologies and techniques are still in need of long-term clinical data and support, the interest and use of these systems is increasing.

Because of the complexity of spinal anatomy and low margin of error in spine surgery, image guidance technology has been viewed as an ideal application for minimally invasive spine surgery. The theoretical benefits of this technology are increased accuracy and safety of minimally invasive procedures through limited surgical incisions while decreasing exposure of the patient and surgeon to harmful radiation. Computer assisted navigation systems involve real-time tracking of sensors on virtual surgical tools to help identify anatomic landmarks. Although still under development, this technology has been adopted throughout orthopedics, particularly in joint replacement and spine surgery. Intra-operative CT scanning is yet another technological advance in imaging that may change the landscape of both traditional and minimally invasive spine surgery. This technology would allow the surgeon to obtain circumferential data not otherwise obtainable with intra-operative X-rays. The role of intra-operative CT in spine surgery is not completely defined and still requires scientific evidence to determine the benefits, safety, and efficacy over more traditional imaging modalities.

Enthusiasm over recent developments in minimally invasive spine surgery should be both welcomed and cautioned. As with all advances, we must continue to scrutinize our efforts in order to ensure patient safety and the efficacy of progress. It is also important to consider the changes that might make this technology viable for the future. Learned skills in this area will help the surgeon adapt to further progress in the field as outcome data prove the benefits of minimal access spine surgery. Lessons learned from previous advancements have taught us that new technology brings new problems and struggles. Despite the level of sophistication of current imaging, smaller incisions and specialized tools, it is imperative that the surgeon ensures that the proposed goals of the surgical procedure are achieved while maintaining patient safety.

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