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  6. General Information about Hip Implants
  1. Metal-on-Metal Hip Implants

General Information about Hip Implants

Hip implants are medical devices intended to restore mobility and relieve pain usually associated with arthritis and other hip diseases or injuries. Every hip implant has benefits and risks. Every hip implant system has unique device design features such as size, shape, and material, and dimensions. In addition, the same hip implant system may have different outcomes in different patients. There are several factors that may influence the outcome and longevity of a hip implant including the device design features, surgeon experience and implantation technique, and individual patient characteristics such as age, sex, weight, activity level and overall health.

Although hip replacement is typically successful, it is important to know that hip implants may need to be replaced eventually.

Materials Used in Hip Implants

In the United States, there are currently four types of total hip replacement devices available with different bearing surfaces. These are:

  • Metal-on-Polyethylene: The ball is made of metal and the socket is made of plastic (polyethylene) or has a plastic lining.
  • Ceramic-on-Polyethylene: The ball is made of ceramic and the socket is made of plastic (polyethylene) or has a plastic lining.
  • Ceramic-on-Ceramic: The ball is made of ceramic and the socket has a ceramic lining.
  • Ceramic-on-Metal: The ball is made of ceramic and the socket has a metal lining.

An orthopaedic surgeon should determine which hip implant will offer the most benefit and least risk for each patient.

As of May 16, 2016, the effective date of the final order requiring premarket approval applications for these devices, there are no FDA-approved metal-on-metal total hip replacement devices marketed for use in the US. However, there are some patients who received a metal-on-metal total hip replacement prior to May 16, 2016. The FDA's Metal-on-Metal Total Hip Replacement Implant webpage provides specific information on metal-on-metal total hip replacements.

Surgical Risks

Hip surgery, like any medical procedure, has risks. The risks of surgery include:

  • A reaction to the anesthesia
  • Heart attack
  • Wound infection
  • Excessive bleeding
  • Blood clots

There may be adverse events after surgery, regardless of the type of hip system implanted, including:

  • Hip dislocation, when the ball of the thighbone (femur) slips out of its socket in the hip bone (pelvis)
  • Bone fracture
  • Joint infection
  • Local nerve damage with numbness or weakness
  • Device loosening or breakage
  • Difference in leg lengths
  • Bone loss (osteolysis)
  • Various types of local or systemic reactions to particles or ions generated from the use of the implant1

Patients who have hip implants should be aware of potential symptoms that may occur three or more months after surgery that may indicate that their device is not functioning properly. Symptoms may include:

  • Pain in the groin, hip or leg
  • Swelling at or near the hip joint
  • A limp or change in walking ability
  • Noise (popping, grinding, clicking or squeaking) from the hip joint

Depending on the severity of the adverse event(s), additional surgery may be necessary.
Many of the recommendations, warnings and contraindications outlined on this website are from the manufacturers' labeling.

1 This local response is sometimes referred to as an "adverse local tissue reaction (ALTR)"; the systemic and local responses are referred to as "adverse reaction to metal debris (ARMD)."

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