Michael J. Higginbotham, Otto I. Lanz, and Claude Carozzo
Introduction
Innovation is an ongoing and evolving process in the field of surgery. Experience allows for more accurate incision placement, more precise dissection, and more skilled tissue manipulation. Accompanying this, the need for wide exposure diminishes. Minimally invasive techniques are widely accepted and routinely practiced in human neurosurgery. The trend toward less or minimally invasive surgery (MIS) has already been applied to several areas of veterinary surgery, including fracture repair, arthroscopy, thoracoscopy, and laparoscopy [1]. There have also been several MIS techniques recently described for veterinary neurosurgery.
We do not recommend complete abandonment of traditional, “open” surgical procedures as treatment for canine or feline disc herniation. It is much too premature to know whether these MIS techniques are necessarily better than traditional techniques. In this chapter, we will discuss the principles of MIS, introduce the concept of performing these, and review currently used MIS procedures employed in human and veterinary neurosurgery.
Principles of MIS
The ultimate goal of an MIS procedure is to accomplish the same surgical result as with traditional approaches but with better optical detail, less tissue trauma, and a smaller incision. As with any technique, there are indications and contraindications, as well as advantages and disadvantages.
There are few absolute indications for choosing MIS. However, severe dermatitis or the presence of other structural hindrances (e.g., tumor, scar tissue) may warrant a less invasive approach. Conversely, there are several, more straightforward, contraindications to MIS that must be considered. Hemodynamic instability, sepsis, coagulopathy, and inability to convert to an open procedure are all contraindications to proceeding with MIS [2].
The most commonly purported benefits to any MIS procedure include smaller incisions and less tissue dissection (and, therefore, presumably, less pain and inflammation), less perioperative bleeding, reduced need for postoperative analgesia, quicker and more complete recovery of normal function, decreased infection rate, shorter hospitalization, less reliance on ancillary support services (e.g., physical rehabilitation), and improved cosmesis [3–5]. Objective data are somewhat limited and only available for some of the aforementioned benefits. Other benefits appear to be subjective or anecdotal in nature, and some benefits may only be apropos in humans.
While magnifying loupes or operating microscopes are sometimes used, most MIS procedures are “video assisted.” This implies that an endoscope is used to provide visualization. Use of the video endoscope has several benefits. Besides the ease and speed of manipulation, technological advancements have led to stronger magnification, higher image quality, and stronger, more efficient illumination [6]. With endoscopy, the surgical site is viewed from a much closer perspective than that of the operating microscope. This eliminates the possibility of the surgeon’s hands obscuring the surgical field. Also, use of a surgical microscope has the disadvantage of requiring the surgeon (or assistant) to make multiple, fine adjustments to the microscope during the procedure in order to explore the surgical field. Endoscopy does not require constant refocusing.
While there are many advantages to MIS, there are also equally important disadvantages to this form of surgery that must be considered. First, the smaller overall field of view can result in failure to protect vital structures or to recognize abnormalities that are not directly within the field. Second, there is inherent difficulty in translating the three-dimensional surgical field familiar to all surgeons into a two-dimensional surgical field viewed on a video monitor. Third, absence or alteration in traditional feedback signals is also an important drawback to MIS [7]. Surgeons constantly utilize information (e.g., tissue texture, consistency, adhesion, etc.) from the surgical environment to make continuous adjustments to their performance. These tactile sensations are lost or changed in the process of using longer and smaller instruments while watching on a viewing monitor.
Learning to perform MIS procedures
Several important points must be considered when determining when and how to learn to perform MIS procedures. First, we must consider when to implement this training. If these procedures are to be taught and practiced during a residency training program, care must be taken that adequate training in non-MIS surgery is not compromised [8]. Alternatively, if these procedures are to be taught as part of a postresidency continuing education program or in a “short-course” environment, adequate prerequisite skill and standardization of training must be ensured [7, 9].
While a detailed discussion of learning MIS is beyond the scope of this chapter, a few key points should be recognized. The skill needed to properly perform an MIS procedure requires a proper understanding of image formation, three-dimensional orientation, and instrument manipulation, as well as a thorough knowledge of the regional anatomy. Learning and becoming proficient at MIS requires proper mentoring, continual practice, self-motivation and criticism, and dedication to self-improvement. It has also been suggested that the more traditional learning sequence of observation and incremental skill acquisition may not translate well to MIS [10].
