Design Validation is the testing of a product to ensure that it meets the user’s needs along with its expected intended uses by the engineers. Specified operation conditions must also be followed.

1) Slide- This product would benefit clinical trials because it is susceptible to user error. If the slide is not prepared the way it was engineered to be, different results could occur.
2) Bone plate- since this device would classify as a possible class 3 medical device, it would be a good idea for clinical trials to be performed. There is significant risk to the patient if failure of the device were to occur.
3) Suture- Clinical trials are not required if the material the suture is made of along with the antimicrobial used have previously underwent clinical trials in the past. There is no need to repeat costly trials required by the FDA.
4) Knee brace- clinical trials are not required because similar products have already been on the market for some time. This is not ‘new technology’ so trials have already been done on their predecessors.

http://www.mddionline.com/blog/devicetalk/design-validation-just-user-testing
http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm070627.htm