Medical Devices

Metal-on-Metal Hip Implant Systems

Metal-on-Metal (MoM) hip implants consist of a ball, stem and shell, all made of metal materials. MoM hip implants were designed to offer the following benefits:

  • Less device material wear is generated when the ball and socket rub against each other in comparison to other hip implants
  • Decreased chance of dislocation when the ball of the thighbone (femur) slips out of its socket in the hip bone (pelvis)
  • Decreased chance of device fracture

There are two types of MoM hip implants:

  • Traditional total hip replacement systems
  • Resurfacing hip systems

Traditional Metal-on-Metal Total Hip Replacement Systems

Metal-on-metal total hip replacement systems consist of a metal ball (femoral head), a metal femoral stem in the thighbone, and a metal cup in the hip bone (acetabular component). The ball attaches to the taper of the stem.

Drawing of a metal-on-metal total hip replacement system. The diseased parts of the hip are removed and replaced with a system comprised of a metal ball, metal stem and a metal

On February 18, 2016, the FDA issued a final order requiring manufacturers to submit a premarket approval application for two types of MoM total hip replacement devices: the hip joint metal/metal semi-constrained with a cemented acetabular component and the hip joint metal/metal semi-constrained with an uncemented acetabular component.

As summarized in the final order and given the known risks, the FDA believed there was insufficient evidence to conclude that general controls in combination with special controls would provide reasonable assurance of the safety and effectiveness of these devices. The FDA determined that these devices should remain Class III (higher risk) devices and premarket approval applications must be filed with the FDA by May 18, 2016 if a manufacturer wanted to continue marketing their metal-on-metal total hip replacement devices or market new metal-on-metal total hip replacement devices.

Prior to legally marketing any metal-on-metal total hip replacement devices, manufacturers are required to submit and get the FDA’s approval of a premarket application that includes: (1) any risks known, or that should be reasonably known, to the applicant; (2) the effectiveness of the device that is the subject of the application; and (3) full reports of all nonclinical and clinical information from investigations on the safety and effectiveness of the device for which premarket approval is sought.

Currently there are no legally marketed metal-on-metal total hip replacement systems in the United States.

Metal-on-Metal Resurfacing Hip Systems

Metal-on-metal resurfacing hip systems consist of a trimmed femoral head capped with a metal covering. Any damaged bone and cartilage within the socket are removed and replaced with a metal acetabular component.

Drawing of a metal-on-metal total resurfacing system. A metal cap is placed over the ball portion of the femoral head.

To date, there are two FDA approved metal-on-metal hip resurfacing systems through the premarket approval program. In each approved premarket application, the manufacturer demonstrated the safety and effectiveness of their metal-on-metal hip resurfacing system through non-clinical and clinical performance data. Links to the Summary of Safety and Effectiveness Data for both of the approved pre-market approvals are available below:


Page Last Updated: 11/16/2018
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