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Image-Guided Surgery: Space Age Technology Enters the Operating Room

Introduction
Advances in spine surgery during the past 10 years have been nothing short of brilliant! In fact, anyone who undergoes spine surgery today will benefit from new technologies that have improved imaging, anesthesia, surgical technique and instrumentation.

One of the greatest advances has been the emergence of image-guided surgery. Image-guided surgery enables spine surgeons to see and navigate through the patient's anatomy three-dimensionally (3D) in real time before and during surgery!

This remarkable development is the result of a combination of futuristic technologies including computers, sophisticated software, specialized surgical tools, and precision position-measurement systems. The use of such technologies results in greater surgical accuracy and increased ability to apply minimally invasive surgical techniques. Consequently, the patient outcome is better!

Image-Guided Spine Surgery: Brief History
To appreciate where we are today - technologically speaking, we have to take a couple of 'historical' steps backward. In fact, almost 100 years back when x-rays were first discovered. You could say that x-rays were the most basic form of image-guided surgery!

Traditionally, a surgeon examined the patient's x-rays and relied on his wealth of knowledge and skill to perform the procedure. The surgeon was limited by 1) what he could see on the x-ray, and 2) the anatomy exposed by surgically opening the patient.

This was hardly image-guided surgery, as it is known today. This might be compared to driving a car. You have been trained how to drive safely (knowledge, skill), you know the neighborhood (anatomy), but you don't actually know what is ahead until you get there (tumor). A map (x-ray) is helpful, but cannot reveal what is ahead in 'real time three-dimensionally'.

Progress really started to be made when computers came on the scene as well as the development of ways to measure the location of an object very precisely. An example of this is Global Positioning Systems (GPS), originally designed for military use. These technologies as well as Computed Tomography (CT Scanning) and Magnetic Resonance Imaging (MRI) began to combine forces in the 1970's and 1980's.

Another step forward was the development of 'frameless stereotaxy'. Stereotaxy means a stationary device (frame) assists in the precise guidance of a surgical instrument (taxy or tactic). The first forms involved attaching a frame to a patient's head, taking x-rays (map of the patient's anatomy), and using the frame as a guidance system to find the location within the brain. At that time it was called 'framed stereotaxy'.

Bringing it All Together
By the early 1990's scientists, surgeons and other experts were beginning to draw together the technologies described above to develop comprehensive frameless image-guidance systems for surgery. The forerunner in this breakthrough and a leader in the field today is the StealthStation™. Let's take a look at the StealthStation™ to better understand how image-guidance helps surgeons.

The components of the StealthStation™ include a high-performance computer, sophisticated software, touch-screen monitor, a camera to recognize light emitting diodes (LEDs), and several specialized instruments fitted with LEDs. LED technology is similar to your television remote control. When you press a button to change the channel, a small red light communicates your request to the television and the channel changes.

Several days before surgery, the necessary images (CT Scans and/or MRIs) of the patient's spinal anatomy are prepared. The images are then 'downloaded' into the StealthStation™ computer and the system creates three-dimensional images of the spinal anatomy. The 3D images can be rotated, enlarged, flipped, angled, or manipulated in a variety of other important ways. This allows the surgeon to accurately pre-plan the surgical procedure including determining the type and size of instrumentation (e.g. screws) and implant placement and trajectory. Such pre-planning is helpful to ensure a successful surgical outcome, especially for patients with spinal deformity whose anatomy often does not match that in a textbook.

During surgery the instruments communicate with the computer and surgeon in real time. This means the spine surgeon can watch on a computer monitor as he precisely operates on the spine. Looking at the computer monitor, the surgeon can see the position of the instrument as it relates to portions of the patient's anatomy that are beneath the surface of skin, hidden from the surgeon's direct view.

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Additionally, the advent of image-guidance has enabled greater use of minimally invasive techniques. For example, the StealthStation™ can help a surgeon see 'through' the skin; therefore, the surgeon does not need to make a large incision just to expose and see the anatomy underneath the skin.

Technically Speaking - This is How it Works
The first and most important step is 'registration'. A special probe fitted with LEDs is used to teach the computer the exact location of the patient. The camera tracks the LEDs emitted by the probe as the surgeon touches different points on the patient's spinal anatomy. This builds a one-to-one relationship between the computer and patient.

During surgery, the patient's spinal anatomy moves, such as during breathing. The 'connection' between patient and computer established during registration enables the StealthStation™ to automatically update images each time the anatomy moves!

Throughout the surgery, the computer can generate images of the patient's anatomy as it relates to the surgeon's instrument. All this power is at the surgeon's fingertips using a touch-screen or a mouse!

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Conclusion
Image-guided surgery systems are valuable for spine surgeons for pre-operative planning, navigating complex spinal anatomy, surgical precision, injury prevention and patient safety. Systems such as the StealthStation™ have been used for thousands of patients in the United States and Europe with successful results proven by a wealth of data.

Updated on: 01/19/10
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