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New Orthopedic Solution

Tue, 05/31/2005 - 6:12am
Providing a fast cure for a common problem, Wright Medical Technology created an intramedullary fixation device for distal radius fractures in just nine months. This exclusive article takes a look at the technology behind this innovative design.
Nearly 70 percent of casting procedures fail because they do not properly maintain alignment of the fracture.

AT A GLANCE

• Casting/plating problems reviewed

• MICRONAIL Device explained

• Software options examined

• Design cycle outlined

Dennis A. Schwartz is the director of engineering services at Wright Medical Technology, 5677 Airline Rd., Arlington, TN 38002. He has been in the field of orthopedics for more than 25 years, is an ADDA certified drafter, and holds an ASME senior level certification in geometric dimensioning and tolerancing. He also has a bachelor's degree from Christian Brothers University and a master's degree from the University of Arkansas. He can be reached at 901-867-9971. Information about NX and Teamcenter is available by contacting UGS, 5800 Granite Pkwy., Ste. 600, Plano, TX 75024 at 972-987-3000.

By Dennis A. Schwartz

The MICRONAIL Intramedullary Fixation Device is a minimally invasive device requiring a 2-cm incision over the radial styloid.
Fractures of the distal radius—the forearm bone on the thumb side—are the single most common bone fracture, with an estimated 300,000 occurrences in the U.S. each year. Fractures typically occur when people try to catch themselves when falling.

The two most common methods of distal radius repair are casting and plating.

Casting involves putting the patient in a cast for six to eight weeks while the fracture heals. Approximately 60 percent of distal radius fractures are treated with casts or a combination of casts and pins. Startlingly, nearly 70 percent of casting procedures fail because they do not properly maintain alignment of the fracture. This leads to patient discomfort and dysfunction.

The other alternative for distal radius repair consists of plates and screws. This process involves a surgical procedure that requires a five-inch incision and a plate with screws to hold the bone fragments together, which often leads to tendon irritation or rupture.

Obviously, both of these approaches have problems.

Wright Medical Technology Inc., a global orthopedic medical device company headquartered in Arlington, TN, set out to introduce an innovative product that would change the way distal radius fractures are repaired. Wright specializes in the design and manufacture of reconstructive joint devices and biologics. Its goal was to create a minimally invasive device that would reduce the number of days required for immobilization, minimize tendon irritation, and provide proper alignment of the fracture.

The new product is called the MICRONAIL™ Intramedullary Fixation Device, a minimally invasive device requiring only a 2-cm incision over the radial styloid. The device consists of four different-size nails, six pins, 13 screws, and 50 specialized instruments for implanting nails. The MICRONAIL Device is placed within the radius, greatly reducing the possibility of soft tissue complications, and uses locking pegs to provide buttressing support of distal fragment.
Digital Product Development
For this research and development effort, Wright required a unified solution for complete digital product development. Additionally, there was a need for every department within the company to have access to information while it was being created, enabling all departments to perform their tasks in parallel in order to bring the product to market ahead of the competition. Wright chose NX and Teamcenter solutions from UGS, a global provider of product lifecycle management software headquartered in Plano, TX, to meet its product development and data management requirements.

NX digital product development solutions enabled Wright to design, develop, test, manufacture, and advertise its product offering. The resulting product data was managed by Teamcenter, which captures and manages all product lifecycle information in a managed development environment.


The MICRONAIL Intramedullary Fixation Device consists of four different-size nails, six pins, 13 screws, and 50 specialized instruments for implanting nails.
Using NX, Wright developed fully parametric solid models of the nails, screws, pins, and instruments. Solid models of the radius bone were used to approximate the location and angle of the fixation holes in the nail. The advanced surfacing tools within NX allowed modeling of the complex curves and shapes. These models were then used to create rapid prototypes for initial evaluation by orthopedic surgeons.
Design Modifications
Since the models were fully parametric and the components were linked to each other in NX, design changes were completed quickly and efficiently. This was particularly relevant whenever the location or angle of a fixation hole in the nail was modified. As the drill guide instrument was linked to the nail implant, when a hole in the nail was changed, the corresponding hole in the instrument updated. Therefore, when feedback was received from the surgeons during the initial prototype stage, it was easily integrated into the designs and a new set of rapid prototypes was quickly created.

The next step involved creation of engineering drawings from the NX models. The models and drawings were then used to manufacture two full sets of prototype implants and instruments for cadaver evaluation. Changes were requested upon completion of the cadaver tests, but again, because the models were created parametrically and linked to each other—and drawings were linked to the same models—the changes were completed in a timely manner. In addition, two more sets of implants and instruments were easily created for evaluation.

Wright used NX digital simulation software to validate the integrity of all design iterations. The firm's engineers ensured proper mating conditions between components using NX and were easily able to calculate fits and tolerance stack-ups. This process continued until the engineers and surgeons agreed on a design for the soft (alpha) launch of the product. The alpha launch represented a limited distribution of the product to surgeons for use in practice.

The design was approved after completion of the second evaluation, just nine months from concept to alpha launch. Wright initiated the manufacture of a limited number of instruments and implants for this phase of the process. While manufacturing was taking place, the company also used the models created in NX to design surgical trays, which are used to securely carry the instruments and implants into surgery. The same solid models were used by the marketing department at Wright to produce training tools that explain how to use the MICRONAIL Intramedullary Fixation System.

After 20 surgeries were successfully completed, a final design was agreed upon. Some very minor changes to the design were requested, and these were quickly completed using NX. The final design models and drawings were released to full production two weeks after these changes were identified.
Collaborative Access

Engineers and surgeons agreed on a design for the alpha launch of the MICRONAIL Intramedullary Fixation Device. The alpha launch represented a limited distribution of the product to surgeons.
Throughout the process, the seamless integration of NX with data and process management capabilities ensured a continuously up-to-date and synchronized digital product model for the entire team to use. Teamcenter enabled Wright to collaboratively share design and manufacturing data between Wright's Arlington headquarters and its sites in Milan, Italy and Toulon, France. The software's built-in search capability made it easy for all departments to find the information they needed.

Before Wright deployed Teamcenter, information was not typically available until a product was completed and released. As a result, tasks were executed in a serial manner with each department waiting for another department to finish its task before it could begin. In contrast, Teamcenter allowed every department access to product information while it was being created. As a result, departments could perform tasks in parallel.
Beyond Engineering
Beyond the development of the MICRONAIL Device, Wright's quality engineering department used NX to design and create gauges that are used to inspect the MICRONAIL System. The manufacturing engineering department also used NX to program five-axis CNC machines to produce some of the components in the system. In addition, NX models were sent to suppliers to manufacture additional components not manufactured at Wright.

The same models were also provided to marketing and advertising to create surgical techniques, advertisements, promotional items, sample cases, and an animated video showing the implantation of the nail. For example, they were used to create radiographic templates used by surgeons to approximate sizing. In the past, many of these items could not be completed until actual parts were available because photographs of the parts were used for these purposes.
Market Demands
The seamless internal and external utilization of product lifecycle management software during the design of the MICRONAIL Intramedullary Fixation Device allowed Wright to bring a complete product system for distal fracture repair to market in a short amount of time—just nine months from concept to completed project—and provided the company with a competitive advantage. Previously, comparable product development efforts had averaged 12 to 18 months.

Since introducing the MICRONAIL Intramedullary Fixation Device, Wright has demonstrated it to surgeons throughout the country and the initial feedback is extremely promising.

ONLINE

For additional information on the technologies discussed in this article, see Medical Design Technology online at www.mdtmag.com or the following websites.

• www.wmt.com

• www.ugs.com
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