Emphasis on Testing & Inspection
By Luther Johnson and Steve Trout
This exclusive report examines the importance of testing and modeling as an integral part of a structured design process. It takes a look at how testing in the orthopedic device market has become an essential part of the design process and promises to continue to grow as more complex products are developed for patient needs.

By integrating testing processes at all stages of the development cycle, medical device manufacturers are able to perfect designs more quickly.

As this spine test system demonstrates, multiple degree-of-freedom control technology, increased processor speeds, and sophisticated test algorithms afford device designers the multi-channel control and better compensation required to test complex orthopedic devices.
• Entrepreneurial approach’s limits

• Structured design approach’s advantages

• The “aerospace/automotive” connection

• Hip, knee, and spine applications

The medical device industry has expanded rapidly over the past 20 years, driven in no small part by entrepreneurial medical professionals who have conceived innovative, next-generation orthopedic products that have helped improve patient quality of life worldwide. Talented surgeons, engineers, and scientists have served as the engine behind this rapidly growing industry, devoting enormous energyand taking considerable risksto bring thousands of new ideas and designs to the market. But as larger medical device manufacturers acquire these products and designs, making them available to ever larger populations of patients in need, it has become apparent that the entrepreneurial model is not fully suited to meet the full range of their product development needs. The entrepreneurial approach is the genesis of many of today’s successful orthopedic devices, but due to its high risks and extended development times, it cannot fully meet the market demands of larger manufacturers. Most prominent among these demands are the need to more efficiently manage the risks inherent in the device approval process and the need to bring products to market as fast as possible.

In response to these pressures, large manufacturers have increasingly followed the example of their counterparts in the aerospace and automotive industries, choosing to augment the innovative entrepreneurial model with a more elegant and structured device development path. This “elegant development path” affords manufacturers the engineering wherewithal to conduct meaningful testing earlier and more frequently throughout the development process to better mitigate risk and integrate advanced modeling techniques to perfect designs more quickly.
Integration of Testing
In addition to the emergence of more structured device development programs, the orthopedic device industry is seeing an increasing sophistication in patient quality of life needs and subsequent growth in the complexity of the devices designed to meet them. Testing capabilities have evolved to meet the design challenges of these devices, and more and more design engineers are integrating testing throughout the development process from initial concept stages to clinical validation. This evolution of testing capabilities is best exemplified by the progression in orthopedic device testing needs from hip to knee to spine applications:

Hip Simulator
• Simple hip applications require three controller-driven channels and involve relatively few soft tissue considerations.

• More complex knee applications require four controller-driven channels and must account for greater soft tissue influence.

• Extremely complex spine applications require up to eight controller-driven channels and must account for a very high influence of soft tissue.

And this evolution of testing capabilities will certainly continue. As device complexity and impact on patient quality of life increases, the full integration of testing throughout the development of materials, components, and full devices will become the norm.

One way that test system suppliers have been able to match the increasing sophistication of orthopedic device designs is to leverage advanced test technologies and techniques pioneered originally for the aerospace and automotive industries. Multiple degree-of-freedom (DOF) control technology, increased processor speeds, and more sophisticated test algorithms afford device designers the multi-channel control and better compensation they require to test today’s most complex orthopedic devices.

By integrating testing processes at all stages of the development cycle, medical device manufacturers are able to perfect designs more quickly, resulting in reduced costs and decreased time-to-market. Design engineers also are able to develop safer, more reliable products using the data generated from their tests. In fact, the FDA has increasingly recognized the tight link between testing and clinical studies, using test data from the development process to validate results observed in clinical studies.
Rise of Virtual Modeling
As in the more structured development approaches employed in the automotive and aerospace industries, virtual modeling also is becoming increasingly commonplace in medical device development. Modeling offers several major benefits to design engineers, including acceleration of the development process, reduction in time-to-market, and improvements to the quality, effectiveness, and safety of the final product. However, modeling and analysis are capabilities that require considerable resources to achieve critical mass. Once these capabilities are in place in a larger corporation, they can be leveraged efficiently across many products.This rise in the use of modeling will result in the need for more device testing, not less. As medical devices become more sophisticated, more complex models will need to be developed. And as these models progress in complexity, they will need to be reconciled, or correlated, with data gleaned from regular and frequent physical testing. Thus, there will be a need for “discovery” testing earlier and more often, model validation test throughout, and more targeted “verification” testing undertaken at the end of the development process. Typically, numerous iterations of a model will be developed and tested to create confidence in the design and provide background data that can be submitted to validate results seen in clinical studies.
Emergence of Technological Driver

Knee Simulator
Testing has become an essential part of the development process in the orthopedic device industry and promises to increase in sophistication and frequency as modeling plays a more prominent role in the development of more complex products. Testing has gained such a foothold that test engineers are actively being recruited from other industries to keep pace with demand and to assist in formalizing test procedures and processes. Test equipment manufacturers also are being pulled into the mix at a much earlier stage than ever before, working with medical professionals and entrepreneurs to incorporate testing equipment needs into venture capital proposals. And while the orthopedic device industry currently relies on testing and modeling technologies developed originally for automotive and aerospace industries, it may soon emerge as a primary innovator of these technologies. Several unique attributes of the orthopedic device industry will drive this innovation. For example, the rapidly growing familiarity with advanced testing and modeling technologies among clinicians and designers will push the device innovation envelope. Aging populations and expectations for higher quality of life make this an extremely lucrative market, poised for explosive growth worldwide. And the emergence of biologics for use in applications, such as spine, where soft tissues are a significant factor will open an entirely new arena for testing and modeling applications.

Luther Johnson, BSME, PE, is a product manager for MTS Systems Corp. and has more than 20 years of materials and component testing experience. Steve Trout is the biomaterials and biomechanics application specialist for MTS Systems Corp. with more than 25 years of materials and component testing experience. He is also an active member of the ASTM F04 Medical and Surgical Materials and Devices Committee. MTS Systems Corp., 14000 Technology Dr., Eden Prairie, MN 55344, is a global supplier of mechanical testing and simulation equipment in many product design verticals including medical devices. Johnson and Trout can be reached at 800-944-1687.
For additional information on the technologies discussed in this article, see Medical Design Technology online at or MTS Systems Corp. at