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Out of CAOS Comes Order

Wed, 10/11/2006 - 7:40am

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The need for accuracy in surgical procedures is fundamental. The precision with which a surgeon plies his trade has direct and critical ramifications in the quality of life—even the continuance of life—of the patient in each case he performs. This is especially true in the field of orthopedics. For orthopedic surgeons engaged in reconstructive surgeries from bone setting to joint replacement, a misalignment measuring the smallest fraction of an inch can mean the difference between a patient painlessly walking again and being relegated to a wheelchair.

In the past decade, technological advancements have provided surgeons with a new type of tool that can essentially map various structures of the human body and ensure the accuracy of instrument and implant placement, cuts and alignments in a myriad of minimally invasive surgical procedures. These tools, surgical navigation systems, function as a kind of global positioning system for the human body. The passive systems have no actual interaction with the patient, but rather inform the surgeon of the positioning of instrumentation and implantable devices in relation to the patient’s anatomy. While recent innovations have brought these systems into prominence in procedures ranging form neurosurgical to ENT surgery, this article will be focusing on one specific incarnation of surgical navigation: computer-assisted orthopedic surgery (CAOS) systems.

The image-free OrthoPilot from Aesculap helps surgeons achieve perfect alignment without CT and MRI scans.
The basic principle behind computer-assisted orthopedic surgery is relatively simple. Digital images of the patient’s anatomy are gathered pre- or intraoperatively and provide the surgeon with anatomical landmarks on which to base bone cuts and final placement of orthopedic implants. In most systems the actual surgical instrumentation can also be incorporated into the digital model, allowing for precise positioning and movement that surgeons are not generally afforded in minimally invasive procedures. The benefits provided by CAOS are increased accuracy in implant placement, reduced outliers in surgical outcome and the ability to employ less invasive surgical techniques.

In general, CAOS systems can be broken down into three categories. Preoperative image-based systems usually utilize computer tomography (CT) scans to provide a 3D digital image of the patient’s anatomy prior to the surgical procedure. The digital model is then loaded into the OR’s computer and visualization system, providing an anatomical map for the surgeon to follow throughout the procedure. Intraoperative image-based systems generally rely on a composite of two dimensional images provided by fluoroscopic imaging equipment after the patient is actually positioned on the operating table. The final and newest category is image-free systems that require no pre-scanning of the patient, thereby eliminating the added cost and patient transport required for CT and fluoroscopic scanning. The image-free systems provide real time anatomic information intraoperatively based on a constant collection of landmark locations being updated to the software supporting the digital model.

As CAOS and the systems that the technique employs have only been in use for a few years, the technology, hardware and software is still in its infancy. Nonetheless, there are a variety of CAOS systems and platforms currently on the market with proven results.

One such system, the imaging-free OrthoPilot® Navigation System from Aesculap, was specifically designed to provide integration within the surgical workflow and minimize the strain on patients caused by the navigation procedure. The main goal of the system is to help surgeons achieve perfect implant alignment without having to perform preoperational examinations or take radiation-intensive and expensive CT or MRI scans.

The user-friendly OrthoPilot is easily integrated into existing surgical techniques and is offered with ergonomic instruments for specific procedures. To drive the system, Aesculap also provides the KneeSuite™ and HipSuite™ software packages. KneeSuite includes applications for total knee arthroplasty (TKA), conventional or less invasive procedures, ACL reconstruction and high tibia osteotomy (HTO), uni-compartmental knee arthroplasty and revision knee application. HipSuite provides applications for Total Hip Arthroplasty (THA) for different approaches, conventional or minimally invasive techniques and a wide variety of Aesculap cup and stem implants.

Another prominent marketer of surgical navigation technology is BrainLAB AG. BrainLAB provides solutions across a broad range of specialties and offers a selection of navigation systems specifically for the orthopedic market. With a focus on the surgeons who will be using the systems, BrainLAB designs platforms that offer easy-to-use functionality, touchscreen control, simplified workflows and versatile instrument integration.

The BrainLAB VectorVision® Computer-Assisted Surgery Platforms utilize the company’s Passive Marker Technology and operate without cumbersome wires and LEDs. Versatile enough to accommodate multiple medical specialties, the platforms are fully upgradeable for newly developed software modules. In addition, the BrainLAB open platform design provides surgeons the flexibility to work with a variety of implant vendors, allowing easy integration with the newest implants and technologies. There are currently three different VectorVision system designs for orthopedic applications.

The VectorVision®2 is an image-guided surgery system that can be directly operated by the surgeon as an intraoperative tool and is designed for constant clinical use. Its full hardware and software modularity make it easily expandable to additional features and applications. The VectorVision® Compact combines all the advantages of BrainLAB wireless passive marker technology in a minimal footprint of 40 cm by 60 cm, making it ideal for surgical suites where space is at a premium. The system’s two cameras are mounted to a vertical column with a spring-loaded arm. A rotating LCD monitor is attached below the camera arm and a large shelf is mounted in the middle of the column to provide space for additional equipment. The third design, the VectorVision® Sky, is conveniently ceiling-mounted to make equipping multiple ORs with surgical navigation easy and affordable. The articulated arms of the VectorVision Sky offer maximum flexibility for the use and positioning of the touchscreen and camera, while improving workplace ergonomics and patient safety. BrainLAB also offers a variety of instrumentation and software packages for navigation in a number of orthopedic procedures.

The ORTHOsoft Navitrack TotalKnee system tracks instruments, knee structure and knee implants in real time.
ORTHOsoft, a leader in CAOS technology, manufactures the Navitrack® Navigation System, which helps improve the results of total knee and total hip replacement surgery by combining advanced computer technology with a surgeon’s skill. The Navitrack system acts as a surgical assistant to surgeons, providing them with support and guidance to precisely align hip and knee implants. The surgeon first attaches small pins called Trackers to a patient’s bones and then to the instruments to be used in the procedure. Throughout the surgery, the surgeon is able to identify several landmarks on the bones, allowing the computer to identify the best alignment for the implant. The system tracks the surgeon’s instruments, showing on-screen the implant’s actual position.

The Navitrack system is available in two configurations, the Navitrack TotalKnee™ and the Navitrack TotalHip™. TotalKnee utilizes imaging technology that does not require CT or MRI scans. It is a CAOS application that tracks the main surgical instruments, the knee structure and the knee implants relative to the patient’s body. The information and images that TotalKnee collects provides data that makes it easier and more precise to determine leg movement. With computer animations, it offers detailed views of the patient’s knee, while showing key tasks to be performed. The TotalHip System was designed to integrate completely into the surgical workflow, thereby minimizing extra steps the surgical team may have to take. The system tracks and displays bone structures and instruments on a workstation screen, giving real-time, 3D visual and numeric information. This provides the surgeon with precise measurements of leg-length changes during surgery.

Once again, while surgical navigation technology and CAOS systems in particular are still in their relative infancy, these advanced systems are just the tip of the iceberg. The systems covered here provide a brief overview of the variety of surgical navigation systems currently available for orthopedic applications, but there are a number of other offerings on the market for specific orthopedic procedures as well as other specialties. Medtronic Navigation, Inc. markets the extensive line of StealthStation Navigation Systems for neurosurgery, orthopedics, spine and ENT, while Stryker Corporation, a world leader in orthopedic technology, offers the Stryker® Navigation System built on a solid foundation of over six years of development, testing and research. GE Healthcare also has an extensive arsenal of image guided surgery equipment with advanced surgical navigation capabilities. And this is just to name a few.

Naturally, as the technology continues to advance, so will the available hardware and software that can help surgeons strive for perfect accuracy and precision in every procedure. And as the technological competition starts to heat up, once again it will be the patients that invariably win in the end.
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