Reliability Through Design Validation Testing

As orthopaedic devices become more advanced and less invasive, the design challenges and changes can become very intricate and cutting edge. Testing new designs becomes increasingly important as technology is continuously changing at a quicker rate. The ability to maintain an innovative competitive edge, and ensure reliable medical instruments backed by intensive testing analysis is where the value of the product is proven. Therefore, the challenge for suppliers and manufacturers of orthopaedic medical instruments is to ensure reliability by determining how long the product will function without malfunctioning over a set period of time.

In order for a manufacturer to prove their medical devices are safe and will function as intended over a specific time period, design testing analysis must be collected and documented. Medical device manufacturers are required to perform short-term design verification testing analysis on their medical instruments, and prove their performance adheres to safety regulations and requirements of the Food and Drug Administration. The FDA`s Center for Devices and Radiological Health (CDRH) specifically is responsible for regulating firms who manufacture, repackage, re-label, and/or import medical devices sold in the United States.

The challenge of the FDA is to monitor medical device safety and effectiveness in a twenty first century filled with emerging technology, while ensuring that these health enhancing products reach the medical community quickly. As a result, the goal of the FDA design verification testing is to ensure design results satisfy established design requirements, which are the basic standards of what manufacturers can actually do to ensure reliable and high performance medical device design done through testing analysis.

FDA Classification of Medical Devices to Ensure Quality Design Controls

In the United States, medical devices are rated using a three tiered class system. Class I devices are subject to the least regulatory control. They present minimal potential for harm to the user and are often simpler in design than Class II or Class III devices. Examples of Class I devices include elastic bandages, examination gloves, and hand-held orthopaedic surgical instruments.According to the FDA, all medical devices regardless of classification must be manufactured under a quality assurance program, be suitable for the intended use, be adequately packaged and properly labeled, and have establishment registration and device listing forms on file with the FDA.The requirements for medical device manufacturers are listed in The Quality System Regulation/Good Manufacturing Practices, which deals with the "requirements related to methods used in, and the facilities and controls used for: designing, purchasing, manufacturing, packaging, labeling, storing, installing and servicing of medical devices." Quality System Regulation (QSR)/Good Manufacturing Practices (GMP)In the table below, is a comparison of Medical Device Classifications.

-21 CFR Parts 808, 812, 820. Table 1. FDA Medical Device Classes Class

Description Of Classes

I. Class I devices are subject to the least regulatory control. They present minimal potential for harm to the user and are often simpler in design than Class II or Class III devices. Most Class I devices are exempt from the pre-market notification and/or good manufacturing practices regulation.Examples of Class I devices include elastic bandages, examination gloves, and hand-held surgical instruments.

II. Class II devices are those for which general controls alone are insufficient to assure safety and effectiveness, and existing methods are available to provide such assurances. In addition to complying with general controls, Class II devices are also subject to special controls. A few Class II devices are exempt from the pre-market notification. Examples of Class II devices include: ear, nose, and throat devices, powered wheelchairs, infusion pumps, and surgical drapes.

III. Class III is the most stringent regulatory category for devices. Class III devices are usually those that support or sustain human life, are of substantial importance in preventing impairment of human health, or which present a potential, unreasonable risk of illness or injury. Examples of Class III devices include: replacement heart valves, silicone gel-filled breast implants, and implanted cerebella stimulators.

Specifically, Class I medical devices are subject to "General Controls" as are Class II and Class III devices. An example of a Class I medical device, such as a manual hand-held surgical orthopaedic instrument is exempt from undergoing QSR testing, however it still must undergo the General Controls regulations listed below. (Title 21 of the Code of Federal Regulations (CFR), Parts 862-892). General Controls for all medical devices regardless of classification include:

1. Establishment Registration (use FDA Form 2891) of companies which are required to register under 21 CFR Part 807.20, such as manufacturers, distributors, repackages and re-labelers. Foreign establishments, however, are not required to register their establishments with FDA.

2. Medical Device Listing (use FDA Form 2892) with FDA of devices to be marketed.

3. Manufacturing devices in accordance with Good Manufacturing Practices (GMP) in 21 CFR Part 820.

4. Labeling devices in accordance with labeling regulations in 21 CFR Part 801 or 809.

5. Submission of a pre-market notification [510(k)] before marketing a device.

Medical Instrument Testing: Short-Term Verification vs. Long-Term Validation

When focusing on design testing, many OEM medical device manufacturers and suppliers of Class I Medical devices perform the minimum FDA requirements of short-term design verification testing for medical instruments. According to the FDA requirements, "design verification refers to the testing activities performed to ensure the results of a finished medical device design, which must meet the formally documented design input requirements. The design and development outputs must ensure that they have met the design and development input requirements. Besides requirements for design verification of medical devices, the Quality System Regulations require design validation testing documentation." Mainly, orthopaedic instrument design engineers are primarily interested in determining whether the device functions properly. As a result, most OEM manufacturers gather statistical analysis by using design verification for short-term testing on a very small number of the actual medical instruments samples during the process.

In addition to routine short-term design verification testing requirements for medical devices, performing long-term design validation studies can more accurately determine the functionality of instruments through gathering hard statistical results. The advantage of long-term validation studies is the testing of multiple sample instruments, (up to 30 test units) rather than just 1-2 instruments, which are used in the traditional short-term testing process. Design validation is required by the FDA for Class II and Class III medical devices, and includes testing of production units under actual or simulated use conditions. Design validation is performed under defined operating conditions on initial production units, lots, or batches, or their equivalents.

As some of the Class I medical devices, such as a hand-held orthopaedic surgical instrument are becoming more technologically advanced, medical OEM device companies should search out manufacturers who go beyond the basic design verification testing on their devices. Many medical device suppliers and manufacturers often overlook the importance of routinely including and performing long-term design validation testing on a larger number of instruments for increasing the accuracy of design performance parameters statistics. Likewise, a large number of OEM medical companies choose to outsource the design of medical instruments through manufacturers playing the role as the supplier. Therefore, major OEM medical device companies, who purchase from suppliers, and brand the products under their own company name are relying solely on the supplier to validate the medical device's reliability.

Advantages of Performing Design Validation Testing for Class I Medical Devices

Ultimately, companies designing and engineering innovative Class I medial devices, such as hand-held medical instruments have a competitive advantage in their industry by performing thorough validation testing and analysis prior to launching their new products in the marketplace. Predicting reliability of a medical instrument in the beginning of the design process dramatically decreases liability for the entire supply chain, and especially for the surgeons, who perform surgery using the devices.

Medical devices manufacturers and suppliers, who decide to voluntarily perform additional design control testing procedures for their Class I medical devices may need to invest in a considerable amount of technology testing resources, and a large quantity of sample devices used for testing purposes. However; the value of ensuring proven reliability to a customer could be priceless. The data analysis gained from a well-planned, long-term validation test study can provide the necessary statistical information about the performance of the instrument.

For example, an interesting advancement in Class I hand-held orthopaedic medical devices is a combination of a torque-limiting driver and a ratchet driver mechanism, normally used in two separate instruments, now engineered together to create one surgeon-friendly device. Although the components of the device have been used for decades in its most basic design elements, the combination of the two mechanisms working together in one device is fairly new to the market.

A hand held Class I medical device, such as a torque-limiting instrument is typically used in an orthopaedic surgical implant procedure to secure a bone screw into place while attaching a plate to a bone. The instrument allows the surgeon to use one instrument to both ratchet and secure the bone screw to the pre-specified amount of torque. The torque limit setting is set specifically, so that the screw will not be driven too tightly or too loosely.

An orthopaedic medical device such as the torque limiting instrument can benefit from undergoing long-term validation testing and analysis, which can reveal any mechanical issues affecting the performance early in the design process. Ultimately, implementing a long-term design validation testing program ensures the manufacturer's ability to pre-determine device failure during the design process prior to a new medical instrument's launch to the marketplace, and equally as important is planning to routinely perform on-going testing to continuously improve a product for optimal design.

Design Validation Testing Through Life Cycle Simulation

One of the main benefits of performing tests on a large quantity of instruments over a longer periods of time vs. 1-2 instruments of a short period of time is it will give a very precise average for the instrument's life cycle (duty interval). This invaluable testing analysis done during the development stage of a medical instrument is achieved by simulating the actual "day in the life of conditions" for the typical medical instrument.

The life cycle or (duty interval) of an orthopaedic medical instrument is the time period in which the instrument will operate under its' intended use during surgery, and the sterilization conditions after a surgical procedure. Due to the mechanical nature and wear limitation of the torque-limiting device routine design validation testing can help determine the medical devices' duty interval cycle between the times the torque setting is calibrated during the manufacturing process, to the return of the instrument for the 6-month re-calibration service.

How does the manufacturer accurately determine the time period (duty life cycle) of a hand held medical instrument? To improve upon reliability and accuracy of variable setting torque-limiting products, the life cycle of the medical device will need to be tested through simulation testing to show the instruments are capable of holding a specific tolerance level to set the initial torque calibration by the manufacturer prior to shipping the instrument.

The medical instrument's life cycle is the point in time when the device undergoes average usage during surgery and routine sterilization in an autoclave steam sterilization system used in the medical industry. The key factor affecting a torque-limiting medical device is the failure rate versus the time period of its mechanical function, which sustains the device's performance.

A major influence on the life cycle of a torque-limiting medical instrument is the harsh sterilization procedures necessary after its use by a surgeon. The main external contributor to performance degradation in the mechanism of a torque-limiting device is the exposure to high temperatures during autoclaving.

A hospital's standard sterilization procedure for a torque-limiting medical instrument is to start the cleaning process with a liquid sterilization detergent solution, and then placing it in an autoclave to kill any bacteria, which cannot be reached. The instruments are immersed in a heated, pressurized chamber of an autoclave, which uses water to create elevated temperatures, and pressure by heating water into steam at a temperature of 270 degrees Fahrenheit.

Going the Extra Mile by Performing Long-Term Validation Testing

Many manufacturers and suppliers of medical instruments may view long-term design validation testing on their products to be burdensome in addition to the FDA guidelines of short term testing for ensuring their products performance adheres to safety regulations. As testing programs become more stringent in the industry, a successful manufacturer will seize this trend, and view it as a positive direction for their company to move towards, since thorough testing and analysis allows for the opportunity to provide customers with what they want, which is long-term reliability and dependable medical instruments.