Metal on Metal Hip Replacement
Metal on Metal (MoM) hip implant devices were designed to be longer lasting and more durable than other types of artificial hip joints which are made of metal and plastic. While most MoM device procedures will result in relief of pain and return to mobility, the design of the devices can result in serious medical injuries.
Metal-on-Metal Hip Design Faults
MoM hip replacement devices were intended to be more durable, corrosion resistant and longer lasting to be used in a “younger” patient who was more active. Most were designed as modular systems, intended to make implantation easier and using all metal surfaces to be corrosion and fatigue resistant.
They are constructed of cobalt, chromium and titanium metals which may grate against one another at the joint where the two components meet. This may result in the release of toxic metal ions and debris into surrounding tissues causing a condition known as metallosis. Their design has however proven to be troublesome.
All of the metal-on-metal hip implant devices on the market were approved under a U.S. Food and Drug Administration (FDA) shortcut pathway known as 510(k). This shortcut allows device manufacturers to skip costly and lengthy clinical trials in human patients by claiming that a new device is similar to devices already on the market. Most MoM hip implant devices were never tested in humans before being offered for sale in U.S. patients.
Hip Replacement Metal Corrosion
All hip implants can cause serious side effects, but Metal on Metal devices have been the cause of a higher than average rate of failure due to fritting and corrosion of the metal. When surfaces of metal components grate against one another, metal fragments and ions may be released into the surrounding joint space and may be absorbed by tissues or taken up into the bloodstream.
Metallic fritting and shedding of metal fragments may result in:
- Metallosis –poisoning due to metal fragments and ions
- Necrosis – tissue or bone death due to localized reaction to metal
- Osteolysis – dissolution of dead or necrotic bone tissue, mainly caused by metal toxicity
- Bone fractures – bones near the joint may weaken and fracture
- Pseudotumors – false “tumor” formation caused by inflammation which surrounds joint
- Systemic metal poisoning – body-wide inflammation due to metal ions being taken up into the blood stream
- Revision Surgery – to remove and replace implant due to pain or severe inflammation
- Reconstructive surgery – to repair weakened bone tissue resulting in fractures of femur or pelvis
Systemic inflammation or excessive immune response due to body-wide poisoning may cause symptoms such as rash, headache, fatigue or other “flu-like” symptoms.
Metal On Metal Revision Surgery
In many cases of severe metallosis, surgery will be required to correct or treat the complications caused by metal poisoning.
There are two basic procedures that may be needed:
- Revision surgery will remove the faulty or corroded implant and replace with a new artificial joint, possibly of a different type
- Reconstructive surgery will repair damage caused by metallosis or a malfunctioning device. Repairs that may be needed include broken bones, degraded or porous bone, necrotic tissue, and damage caused by joint destabilization.
A hip revision surgery is often more complicated than the first joint replacement surgery. Revision surgery, particularly if it involves reconstruction, may result in more pain and post-surgical inflammation and will require a longer recovery period.
Some patients who require revision surgery will need separate reconstruction surgeries, in some cases more than one. Each additional surgery places the patient at greater risk for anesthesia complications, infection risk and will have its own recovery period.
People who must undergo revision surgery due to metallosis will be at even further risk for future complications due to tissue damage and other issues, even after a new joint has been placed as tissue and bone may be weaker and more likely to wear down or fracture.
Other Metal on Metal Hip Side Effects
In addition to serious side effects or complications, patients who receive MoM implants may experience side effects which are less severe such as:
- Pain and inflammation in hip area, groin and abdomen
- Mobility difficulties while standing or walking, due to hip instability
- Loss or atrophy of muscle mass due to joint immobility
- Loss of function and inability to move due to pain
- Hip dislocation
Even if side effects are not severe, revision surgery may still be required to restore mobility and relieve pain. Each surgery will carry the same risks for pain and infection and other complications.
Metal on Metal Hip Lawsuits
Stryker Corporation is facing numerous lawsuits for injuries related side effects of its hip implant devices. People or loved ones of those who have been injured, required revision surgery or experienced severe side effects due to a Stryker hip implant should seek legal assistance.