Defined by the USFDA a medical device is an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory intended for use in the diagnosis of disease which does not achieve any of its primary intended purposes through chemical action within or on the body.

The Food and Drug Administration has recognized three classes of medical devices:

Class I devices present minimal potential for harm to the user and are often simpler in design than Class II or Class III devices. These devices are subject only to general controls.

Class II devices are those for which general controls alone are insufficient to assure safety and effectiveness, and additional existing methods are available to provide such assurances. Therefore, Class II devices are also subject to special controls in addition to the general controls of Class I devices.

A Class III device is one for which insufficient information exists to assure safety and effectiveness solely through the general or special controls sufficient for Class I or Class II devices. Such a device needs premarket approval, a scientific review to ensure the device's safety and effectiveness, in addition to the general controls of Class I. Examples of Class III devices which require a premarket approval include replacement heart valves, silicone gel-filled breast implants, implanted cerebral stimulators, implantable pacemaker pulse generators and endosseous (intra-bone) implants (with the exception of root-form endosseous dental implants which were recently reclassified as Class II). WHL has provided design and engineering services for a wide variety of projects varied medical devices systems.