Examples of applying the definitions

The following section explains how the definitions operate in practice, including examples, for devices which:

Replace or substitute for the articulating surface of the joint

Under paragraph (b)(i) of the joint replacement definition, the articulating surface of joints would be a Class III medical device. It includes devices that replace:

• the ball and/or socket of the hip;
• the two condyles of the femur and the corresponding surface of the tibia and/or the patella or trochlear groove of the femur;
• the ball and/or socket of the shoulder.

Examples include:

Provide primary fixation

Under paragraph (b)(ii) of the joint replacement definition, devices which provide primary fixation of the joint replacement to the patient's bone would be a Class III medical device.

Examples include:

* If femoral or tibial knee stems are intended by the manufacturer to provide primary fixation to the bone they are to be classified as a Class III medical device. However, if these stems are intended by the manufacturer to be used where the individual requirements of the patient make it appropriate to do so, the device is not to be classified as a Class III medical device.

Intrinsic elements of the joint replacement

Under paragraph (b)(iii) of the joint replacement definition devices that connect directly or indirectly with the articulating surface and/or primary fixation and operates as an intrinsic element of the joint replacement would be a Class III medical device.

Examples include:

Devices that are intrinsic elements of the joint replacement may be directly or indirectly connected to the articulating surface and/or primary fixation. The example to the right shows a hip joint replacement:

• The bipolar head replaces the articulating surface, so would be a Class III medical device.
• The cemented stem provides primary fixation, so would be a Class III medical device.
• The proximal femoral device directly connects to the bipolar head (the articulating surface) and indirectly to the cemented stem (primary fixation) and without this device the hip joint replacement would not operate as intended, so it would be a Class III medical device.
• The extension pieces would not be classified as a Class III medical device as these are intended by the manufacturer to be used to provide bone substitution or accommodate anatomical requirements of the patients and are only used appropriate to the individual requirements of a patient. As a result these devices fall within the definition of an ancillary device (outlined below).
• These classifications are not changed by the fact that, for this device, the Class IIb extension pieces are located between two Class III devices.

Ancillary medical devices

The joint replacement definition specifically excludes ancillary devices. While ancillary devices may be required to enable the shoulder, hip or knee joint replacement medical device to operate as intended by the manufacturer, they do not replace the articulating surface of the joint, provide primary fixation or operate as an intrinsic element of the joint replacement and are therefore not classified as Class III medical devices.

Ancillary medical devices may provide additional stability either alone or together with other implantable medical devices, or provide bone substitution or additional fixation to assist in the implantation of the joint replacement where the individual requirements of a patient make it appropriate to do so. Screws, plates and wedges are specifically cited as ancillary devices.

Examples include:

* If femoral or tibial knee stems are intended by the manufacturer to provide primary fixation to the bone they are to be classified as a Class III medical device. However, if these stems are intended by the manufacturer to be used where the individual requirements of the patient make it appropriate to do so, the device is not to be classified as a Class III medical device.