Hip Replacements

hip replacement

Hip replacements are performed as a surgical procedure to remove a damaged hip joint and replace it with a new, engineered implant.  Hip replacement procedures are done for pain reduction and increased mobility.  In most cases the patient receives a new, more functional joint and experiences relief of pain.

In some cases however, the hip replacement device malfunctions for a number of reasons and can result in pain and suffering, loss of mobility and may require revision surgery.  Damage caused by hip implant failure is not always reversible and the revision surgery is often more invasive and requires significantly more time for recovery than the original surgery did.

There are three types of hip replacement surgeries that can be done, depending on the particular needs of the patient: total hip replacement, partial hip replacement, and hip resurfacing.

  • Total Hip Replacement – A total hip replacement is required when both sections of the hip joint have shown significant degradation.  The procedure involves the installation of a completely new engineered joint to replace both the femur head (ball) and the acetabular cup (socket).
  • Partial Hip Replacement – A partial hip replacement is recommended when only one of the hip components needs replacement.  In most cases, the femur head will be replaced with a new section and the acetabulum will be left intact.  In some cases however, the femur head may be in good condition but the cup section of the acetabulum requires replacement.  A partial hip replacement is also sometimes used to correct a broken hip that occurs at the femur neck.
  • Hip Resurfacing – Hip resurfacing can sometimes be used to prevent bone loss and delay a total hip replacement.  As a total hip replacement has a limited lifespan, hip resurfacing may five additional years of mobility before total replacement is required.  This increases the chance that a younger patient will outlive any total hip procedure that is required at a later date.  Hip resurfacing will include the implanting of a cup lining and femur head covering.  It is also used to help reduce mobility and pain issues associated with arthritis.

Types of Hip Replacement Products

Hip arthroplasty, the technical name for hip replacement can be done with a number of different implant types.  Each type mimics the physiology of the normal human hip.  The hip is a ball and socket type joint with the femoral head at the top of the largest leg bone acting as the “ball” and the acetabulum, a cup shaped area of the pelvis acting as the “socket”.  The hip joint can wear out after a period of time and require replacement with an implant that mimics natural movement to allow for continued mobility.

There are different materials used to manufacture hip replacement devices, each with attributes but also with complications.

Metal Ball with Plastic Cup (MoP)

This type of hip implant has been in use since the 1960s.  The plastic, made of polyethylene has a smooth surface which minimizes the friction as the ball moves in the socket.  The plastic used in the implant is fairly soft and does produce a lot of debris.  The breakdown of the liner can lead to osteolysis and will ultimately cause the device to fail as it has a limited lifespan.

Metal Ball with Metal Cup (MoM)

Metal-on-metal implants were designed to increase durability.  They use larger ball and socket shapes to provide maximum mobility and were marketed to a younger demographic as they could withstand greater wear and allow the patient to continue an active lifestyle without requiring a replacement surgery,  Metal-on-metal implants have been the focus of many recalls and investigations regarding design defects and failure rates.

Ceramic Ball with Plastic Cup (CoP)

The plastic used in the cup or lining of the socket is harder than that used in the MoP design.  The products have been fairly reliable but there is still potential for debris producing a risk of osteolysis.

Ceramic Ball with Ceramic Cup (CoC)

The all ceramic hip device design has been in use outside of the US since the 1980s but were not approved by the Food and Drug Administration (FDA) until 2011.  They are quite durable but have a history of squeaking and present a risk of shattering.

Ceramic Ball with Metal Cup (CoM)

The ceramic on metal was also approved in 2011.  It has been designed to reduce problems that have occurred with the MoM devices.  Postmarket studies regarding safety and performance are still underway.

Serious Adverse Events and Complications

The Zimmer Hip Implant Products

There have been hundreds of hip implant recalls since the devices were introduced to the US market.  The majority of these recalls have focused on the metal-on-metal construction in the ball and socket system.

Most of the problems associated with the devices have focused on the release of metal fragments into body tissues, resulting in toxicity or poor design causing the devices to have an inadequate seating to the bone tissue making the implant unstable.

Some studies have shown that despite manufactures claims of greater safety and stability from design and metal construction; advanced alloys are more toxic due to higher levels of metals such as chromium and cobalt.  Many patients have faces extreme pain and suffering along with revision surgery required to correct the failed procedure.

Hip implants that fail can cause serious adverse events such as:

  • Severe Pain and Inflammation – pain is the most common side effect from a failed implant.  The pain can be caused by the implant’s failure to properly adhere to the hip and leg bone, becoming dislodged.  Pain also occurs due to metal releasing small fragments into surrounding tissue causing inflammation, tissue death, and toxicity.
  • Hip Instability and Lack of Mobility – when a hip joint replacement device malfunctions and does not seat correctly, it may become dislocated and produce instability.  This makes movement very difficult or impossible as the implant may grate against the bone resulting in severe pain.  The ball and socket may also become dislocated which prevents proper movement and may cause the patient to be unable to move the leg correctly.  This is generally reversible when revision surgery is performed but damage to surrounding tissue and bone may be permanently damaged and not correctible with revision surgery.
  • Revision Surgery Requirement – a surgery to correct a failed implant may be required due to severe pain from metal toxicity.  Hip implants that become dislocated will also cause extreme pain and immobility.  The hip implant will require removal and replacement with a new device.  This may require significant reconstruction to replace damaged bone.  The recovery period from hip revision surgery may be a great deal longer and more painful than the original surgery.  In addition, not all of the tissue damage may be reversible, resulting in permanent injury.

Other severe adverse events that may be caused by hip replacement products:


tissue toxicity caused by metal degradation.  The metal-on-metal grinding of some hip implants may cause pieces of the metal to flake off and become deposited in surrounding areas including the bone.

Osteolysis and Osteonecrosis

tissue dissolution or death in areas surrounding the implant due to toxicity from metal fragments or plastic.  This may result in a requirement to perform reconstructive surgery in addition to the revision surgery.

Tissue Ossification

as bone disruption occurs, bone tissue may begin to grow in soft tissue surrounding the injured joint.  This will calcify creating damage to the local tissue which is extremely painful and may result in permanent tissue damage.

Periprosthetic Fracturing

as the bone around the implant weaken, small fractures may form, making the bone fragile.  This fracturing may require reconstructive surgery in addition to the revision surgery.

Less serious, but still significant events that may be caused by the Zimmer hip replacement device:

  • Pain or inflammation in the thigh, hip or groin area
  • Instability in the joint
  • Muscle tissue loss
  • Generalized body inflammation due to metal toxicity, tissue breakdown or infection which can lead to rashes, headaches, fatigue and other symptoms

Metal-on-metal Hip Implants and the 510(k) Approval Pathway

The FDA classifies medical devices into three categories based on patient risk.  Class I and II devices present less risk to the patient while a Class III device such as an implanted device presents a much greater risk in the event of a malfunction and are capable of causing permanent changes.  Hip implants are Class III devices which would normally require an application for Premarket Approval (PMA) in order to be offered for use in the US market.

PMA applications require that clinical studies of efficacy and safety are completed and submitted to the FDA along with numerous other documents regarding design, components and manufacturing information.  The FDA has an alternative pathway known as 510(k) which is generally used only for Class I and II devices unless the manufacturer of a Class III device shows that a new product is substantially similar to and not substantially different from products that are already approved for use.

This pathway is generally intended for upgrades and minor manufacturing improvements.  Unfortunately, the FDA allowed the manufacturer of the first metal-on-metal hip implant device was exempt from PMA requirements and could be submitted on a 510(k).  The manufacturer, Stryker, claimed that their new design of metal-on-metal was based on already approved devices and allowed the device to be manufactured and used in the US without performing costly clinical studies which could have identified design defects and adverse events.

After the first MoM device was allowed on the market, manufacturers of new metal-on-metal hip implants were allowed to claim 510(k) exemption based on the marketing approval of the Stryker device.  Even though the Stryker device was recalled and has resulted in thousands of injuries and a multitude of lawsuits, not all similar devices have been recalled.  This has resulted in a flood of additional lawsuits related to other hip implant devices after device failure and injury.

In May of 2011, 21 manufacturers were ordered by the FDA to conduct postmarket studies relating to the safety of their hip implants.  In 2012, an FDA panel convened to address the issues surrounding hip implants and concluded that there was little reason for the continued use of MoM systems.  Despite this conclusion, the FDA has yet to act on the panel’s recommendation and MoM systems are still in use, many of which have created severe adverse events related to device failure.

Manufacturers and Models of Hip Implants with Pending Actions

There are hundreds of hip implant devices on the market, many of which function as intended.  In general it is up to the orthopedic surgeon to choose the correct implant for a particular patient.  The surgeon makes his choice based on the patient’s physiology, but also on the aspects of the available implants.  When a manufacturer has made claims with regard to safety and performance that are misleading or turn out to be incorrect, the patient pays the price with pain and suffering.  In most cases this is directly related to the device performance and the manufacturer’s practices.

DePuy Orthopaedics

a division of Johnson & Johnson, the largest medical and pharmaceutical products company in the world, developed three hip replacement systems that have shown a high failure rate.  The device failure of each system is primarily due to its metal-on-metal construction.

  • Pinnacle Hip Replacement System
  • ASR XL Acetabular System
  • ASR Hip Resurfacing System

The two ASR systems were recalled in 2010 but court documents from 2013 show that DePuy expected up to 40 percent of the devices to fail within five years.  DePuy has agreed to settle 7,500 lawsuits for a total of $2.5 billion but faces nearly 5,000 more.  Additional lawsuits are expected to follow.

Stryker Orthopaedics

Stryker introduced the first metal-on-metal hip implant system through the 510(k) approval process.  Two of the hip implant products have resulted in complications including both implant loosening and metallosis.

  • Rejuvenate Hip System
  • ABG II modular-neck hip stem

In 2012, both of the systems were recalled a few months after Stryker had issued warnings to physicians about metallosis, necrosis and other complications that would result in revision surgery.  The first lawsuit was filed in New Jersey in 2012 and federal cases were consolidated into multidistrict legislation (MDL).  Many more lawsuits have followed and more are expected.

Zimmer Holdings Inc.

Zimmer will be the second largest orthopedics company in the US after completion of its acquisition of Biomet.  Zimmer manufactures a number of modular hip implants systems, one of which has received multiple complaints of improper seal of the implant due to a plasma coating that is used in place of the cement normally used for other implants.  The dislocation of the cup has caused a requirement for numerous revision surgeries.

  • Durom Acetabular Component (Durom Cup)

Zimmer introduced the implant device in 2006 and by 2007, reports began to surface of failure within one year after implant.  The Durom Cup was briefly recalled in 2008 after Zimmer claimed that any failures were due to improper surgical technique.  The implant device was re-introduced with labelling additions and a new physician training program.  Thosands of US patients have received the implant and Zimmer faces multiple lawsuits. The company set aside $69 million, but has already paid $400 million and expects to pay at least $200 million more.  Zimmer’s own estimates show that up to 5.7 percent of the implants will require revision surgery.

Smith & Nephew

Smith & Nephew introduced a metal lined modular hip replacement device in 2012 which was the first of its kind.  Nearly 8 thousand patients have received the device and may be at risk for revision surgery which has shown a failure rate of over 6 percent.

  • R3 Acetabular System

The device was recalled in 2013 due to poor performance.  The device has been reintroduced but now contains a plastic cup with a proprietary metal alloy or ceramic head.  The device originally contained metal-on-metal which has resulted in severe effects for many MoM implants and the Smith & Nephew device has shown an alarming failure rate.  Smith & Nephew has been the subject of multiple lawsuits which have not yet been settled.

Biomet Inc.

Biomet manufacturers a number of hip devices, including MoM hip implants. They have claimed long-life span as a primary advantage of their systems but by 2011, multiple complaints of failure had been reported to the FDA, all of which occurred within the first two years after implant.

  • M2a-Magnum Hip Implant

Biomet is battling numerous lawsuits related to the M2a implant and also faced claims by the Securities and Exchange Commission (SEC) regarding the Foreign Corrupt Practices Act. Biomet was found guilty of bribing doctors in China, Brazil, and Argentina to use its hip replacement devices between 2000 and 2008. To settle the claims, Biomet paid $22.9 million in 2012.  Biomet federal lawsuits were consolidated in MDL and have been settled for $56 million, however additional cases have been filed.

Wright Medical Technology Inc.

Wright Medical Technology has manufactured hip implant devices that are similar to DePuy products subject to investigations and lawsuits including MoM systems.  Despite complaints of failure, the devices have not yet been recalled and over 10 thousand have been implanted in patients in the US.

  • CONSERVE Plus Hip Devices

Wright faces numerous personal injury lawsuits from patients across the US for injuries including metallosis, infections and necrosis of bone and tissue.  The company also paid $7.9 million to settle allegations of bribing surgeons to use their devices. Wright devices may require revision surgery in over 8 percent of patients within the first five years of implant.  Additional lawsuits are expected regarding device failure.

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