Thursday, November 22, 2012

Wright Medical Hip Replacements

Wright Medical Technology Inc. is headquartered in Arlington, Tenn., and has been designing, manufacturing and marketing joint implants since 1950. About 60 percent of the company’s sales come from its hip and knee products. The company sells its products in more than 60 countries and had $480 million in worldwide sales for the first eight months of 2012. The company employs about 1,300 people globally and has branches in Canada, Japan and Europe.

While it is also known for its foot and ankle devices, the core of the Wright Medical product lineup has always been hips and knees; it controls about 2 percent of the U.S. hip and knee market. The company’s contributions to the innovation of hip replacements include its ceramic hip system, hard-bearing surfaces and proprietary neck modularity. Studies have shown that hard-bearing surfaces such as ceramic or metal produce less particle wear when paired with another hard-bearing surface as opposed to a soft-bearing surface like polyethylene plastic.

Wright uses alumina oxide ceramic to manufacture its LINEAGE liners and femoral heads to create an industry-leading ceramic-on-ceramic hip system. According to Wright, this particular coupling of ceramic parts generates less wear debris than ceramic-on-plastic or metal-on-plastic systems. Some studies have corroborated this data, revealing that after nine years, alumina-on-alumina hip prostheses had a 97.8 percent survival rate. Ceramic-on-ceramic prostheses are not without their problems, however. People who received these implants have reported squeaking in the joint, and ceramic has a tendency to fracture.

Wright has experienced success with its ceramic-on-ceramic products, though the same cannot be said for its metal-on-metal (MoM) products. Wright’s CONSERVE line of MoM hip replacement systems and its Profemur Z Stem have caused a number of complications in people who received these implants. Like other MoM implants, the CONSERVE hip system is prone to shed metal particles into surrounding tissues and the blood, leading to high levels of metal and metal toxicity. This may lead to metal poisoning (metallosis), tissue necrosis (death), loosening and other serious problems. The Profemur Z Stem is also under scrutiny because it is prone to fracture and fail early. A number of people have already filed lawsuits against Wright as a result of early device failure, pain, excessive metal ions in the blood and the need for expensive revision surgery because of the faulty design.

Wright Medical’s Hip Replacement Products

Wright Medical manufactures a wide variety of hip replacement devices, including components made from ceramic, metal and polyethylene plastic. The products are designed to be used to correct a variety of hip problems, from osteoarthritis to trauma and fractures. Wright’s hip replacements systems can be used with cemented or non-cemented techniques for primary and revision hip replacement surgery, and hip resurfacing.
CONSERVE Femoral Surface Replacement
CONSERVE PLUS Total Resurfacing Hip System
Acetabular Systems
DYNASTY Acetabular Cup System
GLADIATOR Bipolar Hip System
INTESEAL Acetabular Cup System
LINEAGE Acetabular Cup System (Polyethylene)
PROCOTYL E Acetablar Cup System
CONSERVE Total Hip with BFH Technology
CONSERVE Total A-CLASS Advanced Metal with BFH Technology
Femoral Stems
PERFECTA Plasma Spray Stems
PROFEMUR TL Total Hip System
PROFEMUR Total Hip System
PERFECTA Total Hip System
Revision Systems
LINK MP Reconstruction Hip Stem
PROFEMUR LX 5/8 Revision Stem
PROFEMUR R Revision Prosthesis

Wright Medical’s CONSERVE Hip System and PROFEMUR Z Stem

Wright Medical’s CONSERVE hip replacement line was created to respond to the demand for durable implants for younger, more active people. One of the greatest concerns that doctors face when younger patients develop hip problems is finding an implant that can withstand an active lifestyle. According to Wright Medical, its CONSERVE MoM implants provide excellent range of motion with low particle wear and long-term dependability. The larger femoral head (ball) size of the CONSERVE implants closely mimics the natural anatomy of the hip and allows up to 169 degrees of motion. In addition, the high-carbon, cobalt chrome cup and cobalt chrome ball are designed to reduce wear. This linerless design is referred to as a monoblock design because the acetabular cup and the liner come as one piece. The outside of the cup features a beaded, porous coating that encourages bone growth. The femoral heads range from 36mm to 54mm and are among the largest in the industry.

Wright also claims its CONSERVE hip replacement designs reduce the chance of soft tissue impingement, which can lead to dislocation. Some studies have shown that increasing the size of the ball results in fewer dislocations.
The products included in this line of hip replacement products are:
  • CONSERVE Plus Total Hip Resurfacing System (2009)
  • CONSERVE Total Hip with BFH Technology (2003)
  • CONSERVE Total A-CLASS Advanced Metal with BFH Technology (Patent pending)
The CONSERVE Total Hip acetabular cup and ball are designed to be used with a number of stems, including the PROFEMUR Z. The PROFEMUR Z is a modular neck and stem system that is made of titanium alloy. The femoral stem fits inside the thigh bone and connects to the neck, which in turn connects to the ball. The PROFEMUR Z is designed for use with a minimally invasive surgical technique and simplifies insertion into the bone. The stem is dual tapered, and the upper half of the stem is rectangular in shape. The surface of the stem is grit-blasted to create a rough surface that allows better bonding with the bone.

The PROFEMUR Z system includes the stem and a choice of six interchangeable neck pieces available in two lengths. Modular necks and stems allow surgeons to customize length for each patient to provide a better fit, especially in complex revision surgeries. However, there is growing concern in the orthopaedic community regarding the stability and design integrity of modular stems. In fact, metal necks and metal stems can create friction and problems similar to the metal ball-metal cup issues.

Problems with CONSERVE Plus and PROFEMUR Z System

Wright Medical claims that its CONSERVE line of hip replacement systems offers superior design that reduces wear and dislocation rates. However, the CONSERVE Plus Total Hip Resurfacing System has demonstrated higher than normal failure rates. The Food and Drug Administration (FDA) has received reports of more than 200 adverse events of device failures, severe pain in the hip and groin, loosening and high metal toxicity in the blood because of the metal-on-metal design of CONSERVE Plus implants.

While no recall has been issued yet, the CONSERVE Plus bears a striking resemblance to the DePuy ASR. The ASR was recalled after a high number of device failures caused severe complications in a number of people. Many who received the ASR device have since filed lawsuits against DePuy. Like the DePuy ASR, Wright’s CONSERVE Plus is a cementless, monoblock device with a cup and large femoral head made from cobalt chromium. The cups of both implants feature beaded porous coating. These two systems are also marketed to active individuals. Another similarity between these devices is the unusually high revision rate. According to the National Joint Registry of England and Wales, the five-year revision rate for the CONSERVE Plus is 8.36 percent. This rate is second only to the DePuy ASR, with a rate of 9.63 percent.

Because of its metal-on-metal design, the CONSERVE Plus system can cause a number of problems.
The FDA warns that metal-on-metal hip devices like Wright’s CONSERVE hip replacement systems can cause the following adverse effects:
  • Pain in the groin, hip or leg
  • Limp or decrease in ability to walk
  • Swelling in or near the hip joint
In addition, metal-on-metal implants are known to cause metallosis. This is a condition caused by an excessive amount of metal particles in the blood.
The FDA warns that metallosis can cause problems involving other parts of the body such as the heart, nerves, thyroid and kidney, including:
  • Chest pain, shortness of breath
  • Numbness
  • Changes in vision or hearing
  • Fatigue
  • Feeling cold
  • Weight gain
  • Urinary trouble
The PROFEMUR Z stem is also a source of concern for many hip replacement recipients and their doctors. According to a report from the Australian National Joint Registry, 1 in every 9 patients who received a PROFEMUR Z stem has been forced to undergo revision surgery due to device failure. Complications such as corrosion, femoral neck fracture and fretting were reported. Fretting occurs when two opposing surfaces rub together and cause wear damage. Several lawsuits have already been filed, claiming negligence and faulty design. When the CONSERVE Total Hip is used with a PROFEMUR Z stem, the resulting complications can be exponentially worse.

Wright Medical Hip Replacement Lawsuits

Both the CONSERVE Plus and PROFEMUR Z stem have been implanted in thousands of people, some of whom have filed lawsuits after having to undergo revision surgery to correct painful complications such as metallosis, loosening, severe pain, device failure and device fracture. One man filed suit against Wright in 2011 after the titanium neck of his PROFEMUR Z stem fractured while he was getting dressed for work. He had to have emergency surgery when his hip suddenly gave out and he suffered intense pain. Surgeons had to remove the fractured bits of titanium from his body.
Many suits have also been filed against Wright Medical for problems with the CONSERVE hip replacement systems. These lawsuits were consolidated under one judge in the U.S. District Court for Northern Georgia. The complaints allege that the device releases high levels of metal particles in the blood that can cause loosening and device failure because of Wright’s faulty metal-on-metal design.
Wright is no stranger to lawsuits. After an investigation that started in 2007, the federal government sued the company for questionable business practices involving bribing doctors to use their products. In order to avoid admitting any wrongdoing, the company agreed to pay $7.9 million in fines in 2011.

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