A Medical Device Daily

Zimmer Holdings (Warsaw, Indiana) said that the first electromagnetic computer-assisted solutions knee replacement procedure was successfully performed last week at Methodist Hospital (Houston).

David Lionberger, MD, an orthopedic surgeon at Methodist, performed three successful navigation-assisted procedures using the Zimmer Minimally Invasive Solutions (MIS) Quad-Sparing Total Knee Replacement Procedure and Medtronic Navigation's (Louisville, Colorado) StealthStation with the AxiEM electromagnetic computer assisted system.

Zimmer and Medtronic Navigation, which have an exclusive partnership for MIS surgical navigation solutions, developed the system, which involves computer-assisted equipment, software and Zimmer instruments. The companies are demonstrating the electromagnetic system at the American Academy of Orthopaedic Surgeons (AAOS; Rosemont, Illinois) meeting in Washington this week, and plan to officially launch the system worldwide in July.

Centerpulse, which Zimmer acquired in 2003, had previously been involved in development of electromagnetics for orthopedic navigation, but the Zimmer/Medtronic collaboration is the first to produce a successful system for widespread commercialization.

In January, a 510(k) was cleared, allowing the Zimmer system to be used in conjunction with orthopedic knee procedures.

“With the launch of our electromagnetic system, we have taken a great step forward in enabling a significant number of orthopaedic surgeons to provide patients the benefits of MIS Quad-Sparing Knee Replacement, and later this year we will launch, along with Medtronic Navigation, a similar electromagnetic system for Zimmer MIS hip replacements,“ said Ray Elliott, Zimmer chairman, president and CEO.

Elliott said the system was designed to give the surgeon leg alignment and other anatomical information about the knee during surgery to help improve patient outcomes. “We will offer the system on a portable platform and with economics that make navigation accessible to more of our hospital customers,“ he said. “Our electromagnetic system is a perfect fit for our MIS surgical techniques that entail less visibility.“

Electromagnetic tracking systems are an alternative that enables “significantly more minimally invasive surgical techniques than the use of infrared camera technology,“ Zimmer said. It noted that the term “electromagnetic“ refers to the method used to locate and track the implants and instruments relative to patient anatomy.

The technology consists of an electromagnetic field transmitter that generates a local magnetic field around a specific area of anatomy. The localization system, armed with magnetic sensors, is able to identify the position of instrumentation. The system's ability to track the implant and instrument positions is not related to line of sight relative to the emitter. Electromagnetic mini reference trackers are attached to the patient's bones and the surgical instruments, producing a real-time, 3-D video display of the surgical procedure.

Lionberger, who performed the first orthopedic electromagnetic procedures, has used other computer-assisted equipment and described the AxiEM system as a “great advance“ for patients and surgeons. “This system delivers what we, as orthopaedic surgeons, have been waiting for,“ he said. 'The potential patient benefits of minimally invasive joint replacement are tremendous, but the techniques involved are new and often more difficult, and can be especially challenging with limited visibility. Now we have a means of accurately determining proper implant alignment and placement even while working through much smaller incisions such as minimally invasive surgical procedures.“

Zimmer's MIS Quad-Sparing procedure has as its goals several benefits to patients, including: less tissue trauma; faster and less painful rehabilitation; smaller incisions; less scarring; a shorter hospital stay; and a faster return to work and leisure activities.

Medtronic Navigation is the world's leading supplier of integrated surgical navigation solutions. With nearly 2,000 StealthStation Systems installed worldwide, Medtronic Navigation surpasses the combined installed base of all other manufacturers of navigation solutions.

Wright Medical Group (Arlington, Tennessee) introduced its Odyssey Minimally Invasive Knee Instruments at the meeting. The knee instrumentation is part of Wright's Odyssey Tissue Preserving Initiative, a minimally invasive surgery program for hip, knee and total joint resurfacing procedures.

The company said that while many orthopedic manufacturers have developed minimally invasive instruments and techniques, it has concentrated on offering a minimally invasive instrument system that does not require surgeons to radically change their current surgical techniques.

The Odyssey Knee Instruments are designed for use with Wright's Advance series of knee products. Included in the line are the Advance Medial Pivot Knee, which allows natural knee motion and a high level of stability when a patient's posterior cruciate ligament is damaged or resected, and the Advance Double-High Knee, which the company said offers both high stability and high flexion without sacrificing the patient's posterior cruciate ligament.

Designed to more closely mimic the kinematics of the natural knee, the Advance family of knee implants has more than seven years of clinical success, according to the company. With the introduction of the Odyssey instrumentation, it said surgeons and patients “can now experience the known benefits of this innovative knee line through a less-invasive surgical approach.“

Aldo Denti, vice president and general manager of Wright's OrthoRecon Division, said, “Our goal in designing the Odyssey knee instrument system was to provide patients the advantages of minimally invasive knee surgery and provide surgeons a technique that is consistent with their training and experience with a knee system backed by a strong clinical history.“

In another product announcement, Wright and BrainLAB (Munich, Germany), an innovator in image-guided medical technology, reported release of BrainLAB's software for Wright's Advance Knee System on the VectorVision surgical navigation platform. The CT-free knee application will allow surgeons to implant the Advance Medial Pivot Cruciate-Sacrificing, Double-High Cruciate-Preserving and Posterior Stabilized knees. By adapting the software to the clinical workflow, this software integration will allow surgeons to use navigation effectively for all relevant steps of the procedure, the companies said. In addition, surgeons can use BrainLAB's VectorVision with Wright's Advance knees in both traditional and minimally invasive approaches to total knee arthroplasty. BrainLAB's VectorVision navigation system helps surgeons optimize total joint replacement surgery through exact positioning of the implant and precise alignment of the leg axis.

Also at AAOS:

• SpineVision (Paris) said it has received FDA clearance to market its PediGuard instrument as a Class II device. The company said this is the first FDA-cleared device for real-time detection of possible penetration outside the vertebral pedicle, a continuing issue in spine surgery.

SpineVision said published rates of intraoperatively “misplaced“ pedicle screws range from 10% to 40%. Of that number, 2% to 10% have resulted in pathological consequences such as spinal cord damage, including paraplegia or quadriplegia.

The company describes PediGuard as the first wireless, handheld instrument capable of accurately detecting changes in tissue type, thus alerting surgeons to potential pedicular or vertebral breaches during pedicle screw site preparation.

PediGuard is a drilling instrument that constantly monitors the electrical conductivity of the tissue at its tip throughout the drilling process. It measures and translates the electrical conductivity into an audio and visual feedback.

Its sensitivity allows the surgeon to know whether the tip is in contact with cortical bone, cancellous bone, soft tissues or blood. The surgeon is immediately informed through variations of sound cadence, sound pitch and LED flashes, when and if the electrical conductivity at the distal part of the instrument changes.

• Orthovita (Malvern, Pennsylvania), a developer of orthopedic biomaterials, reported that a poster titled “A Prospective Multi-Center Pilot IDE Study on the use of Cortoss in Vertebroplasty-Report on the First 20 Cases“ was exhibited at the meeting.

Hyun Bae, MD, of the Spine Institute at Saint John's Health Center (Santa Monica, California), led the study. Other investigators included Philip Maurer, MD, of the University of Pennsylvania Hospital (Philadelphia), as well as Erik Westerlund, MD, Timothy Peppers, MD, and Raymond Linovitz, MD, of CORE Orthopedic Medical Center (Encinitas, California).

The pilot investigational device exemption (IDE) study was intended to provide preliminary information about the use of Cortoss Synthetic Cortical Bone to treat osteoporotic vertebral compression fractures. The study results suggested that a relatively small volume of Cortoss may be able to reinforce the vertebrae and achieve symptomatic relief, as compared to the larger volumes reported in the literature for polymethylmethacrylate (PMMA) bone cement.

Cortoss appeared to have an interdigitated fill pattern, which is intended to create trabecular reinforcement. The study results appear to be consistent with the results obtained in a prospective vertebroplasty study using Cortoss conducted in Europe, Orthovita said.

A larger, prospective, multi-center IDE study is under way in the U.S. designed to demonstrate that Cortoss is safe and effective for the treatment of osteoporotic vertebral compression fractures.