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Hip replacement refers to the process in which a damaged hip joint is surgically replaced with an artificial implant. Patients require differing degrees of replacements, such as total or partial implants, and new hips are made from plastic, ceramic and metal. However, not all implants are safe, and some can cause serious complications.
A hip replacement, also called hip arthroplasty, is the surgical repair of a diseased or injured natural hip joint by replacing it with an artificial joint, or implant. Reasons for these surgeries usually involve a fracture or injury to the hip, wearing down of the joint over time or osteoarthritis, an age-related joint disease that can cause hip pain due to inflammation. Osteoarthritis is the most common reason why people have their hip replaced.
There are three common hip replacement procedures:
Marius Smith-Petersen, an American surgeon, made the first arthroplasty mold in 1925, and went on to create the first total hip replacement (THR), made with stainless steel. Since then, surgeons have performed more than 332,000 THRs, according to the Centers for Disease Control and Prevention. In 2015, U.S. surgeons performed an estimated 378,000 total hip replacements, and by 2020, that number will grow to more than 510,000, according to Medscape.
The average cost of a total hip replacement is about $30,000, but the individual cost varies depending on where a patient undergoes surgery, according to data reported by Blue Cross Blue Shield. For example, in Birmingham, Alabama the cost is $11,327. But in Boston, Massachusetts the cost is about $74,000. An expensive surgery does not necessarily mean higher quality or fewer complications.
The surgery takes about 1 to 2 hours, plus another 1 to 2 hours of prep time beforehand. The patient's size and overall health may also influence these estimates. After the surgery patients will stay a few days in the hospital and have to take blood thinners to prevent blood clots.
A total hip replacement uses an artificial joint to replace the entire hip structure. While the procedure is common, it is still a major surgery. During the procedure surgeons insert the hip stem into the patient’s femur for stability, replace the head of the femur with a ball and replace the socket with an artificial cup. Total hip replacements are the most popular type of hip replacement surgery.
Surgeons complete total hip replacements with a posterior approach (back of the hip) or an anterior approach (front of the hip). They often choose the posterior approach as it allows better visibility of the hip joint and is less invasive.
Special bone cement usually holds hip implants in place, but some surgeons use a cementless fixation technique. Devices meant for implantation without cement have a specially textured surface that encourages the bone to grow onto the implant and secure it in place. A hybrid total hip replacement uses a combination of both, implanting the cup without cement and setting the stem in place with cement.
Doctors recommend partial hip replacements (hemiarthroplasty) when only one part of a hip needs treatment. In most cases, the acetabulum (also known as the socket or cup) remains intact and a ball replaces the head of the femur. Some partial hip replacements only address the acetabulum. A partial hip replacement typically corrects a hip fracture at the neck of the femur.
Surgeons perform more than 100,000 partial hip replacements each year, according to the New York Times.
The primary goal of hip resurfacing is to avoid bone loss. The procedure can delay a total hip replacement in younger recipients, who are likely to outlive the original implant and require a second surgery later. It replaces the socket with an artificial cup and resurfaces the head of the femur instead of removing it. Surgeons cement a covering — usually made of metal —on top of the femur. This component has a short stem inserted into the neck of the femur. Doctors may also recommend hip resurfacing often to improve symptoms of arthritis.
This technique is not as popular among surgeons because of studies show this technique may lead to a higher level of metal ions released into the blood and surrounding tissues. The small stem may also break prematurely, causing dislocation or fracture.
Although there are varied designs and models of hips built by several manufacturers, there are three basic components of an artificial hip — a stem inserted into the femur (thighbone); a ball that attaches to the top of the femur; and a cup that attaches to the pelvis. When a person walks or moves their legs, the femoral head moves within the acetabulum in a similar fashion as a ball-and-socket joint. Device manufacturers design hip implants to mimic this natural movement as closely as possible.
Manufacturers make implants from a combination of materials, including plastics, ceramics and metals. Many of the most recent devices are metal-on-metal designs. Device makers marketed MoM hips to active, younger patients and claimed these devices are more durable and will last several years.
The primary differences among implants are their size and the material of the components. Hip implant components are made of polyethylene (plastic), metal, ceramic or a combination of these materials.
These are the most common type of hip implants and have been around since the 1960s. Plastic has a smoother surface finish that allows for less friction while the ball moves within the socket. However, MoP implants produce a lot of plastic debris, which will eventually cause the implant to fail and could lead to a condition called osteolysis.
MoM implants are very durable and can withstand the active lifestyle of younger patients. They have less wear and can accept larger bearings than implants made of other materials. However, their durability comes at a price. MoM hip implants shed metal particles that studies linked to a number of serious health issues like metallosis — a condition that causes bone and tissue. MoM implants came under fire because of design flaws and early failure rates. Several manufacturers – including DePuy and Stryker — have recalled one or more all-metal hip implant products.
Unlike the plastic used in the MoP device, the plastic used in these devices is very dense. Although these materials are reliable and provide for a very smooth surface, there is still the issue of wear debris and the potential for osteolysis.
All-ceramic hips are known for their durability and reliability. They have been around since the early 1980s, but the FDA only recently approved for use in the United States. Although the femoral ball is made from very hard clay that is wear-resistant, these devices have a history of producing a squeaking noise and shattering.
The first ceramic-on-metal hip received FDA approval in 2011. The goal is to avoid the problems of metal-on-metal hip implants. Postmarket studies are underway.
Recovery time after hip replacement varies from several days to several weeks depending on factors including the patient's age, weight and type of hip surgery. After surgery, discharge from the hospital can take anywhere from 1 to 4 days if there are no complications.
Patients who cannot accomplish these tasks may have to spend some time in a rehab facility. After discharge, nurses and doctors will explain recovery exercises and how to recognize complications.
As with any surgery, complications can arise following hip replacement. Patients or doctors may detect some problems immediately, while others may not surface for years. Serious situations may require patients to undergo a second surgery, called revision surgery. In some cases, patients may need several revision surgeries to treat complications.
The design of an implant may contribute to complications and early implant failure. For instance, metal-on-metal implants can lead to metallosis, which is a serious condition that occurs when metallic debris builds up in the soft tissue of the body. Metallosis can lead to bone and tissue death. Osteolysis, the loss of bone around the implant, can occur when body works to remove foreign particles produced by the device during normal movement. This can lead to loosening and failure of the implant.
|Other complications can include:|
|Implant dislocation||Avascular necrosis (bone death)|
|Infection||Loosening of the implant|
|Heterotopic ossification (soft tissue becomes calcified)||Fracture|
Following up to 10 percent of hip replacement surgeries, patients require one or more revision surgeries to correct complications. In the case of some implants such as the DePuy ASR, patients need surgeries just a few years after the original operation.
Doctors perform revision surgery to replace one or more artificial hip components that have loosened, worn out, become dislocated or fractured. These procedures are tougher for surgeons and patients alike, since typically there is more bones loss and tissues are inflamed when doctors place the new components. The mortality rate also rises. For original hip replacement procedures, the death rate is 1 percent; for revision surgeries, the rate is 2.5 percent.
Metal-on-metal implants have some of the highest failure rates among all types of hips. Studies show these hip implants produce metal ions that enter a recipient's bloodstream, creating metal poisoning known as metallosis. Other complications with these implants include a loosening of the hip implant, joint dislocation and joint squeaking.
Many people with these problematic artificial hips opt for revision surgery to receive a new hip implant. Many of those same patients — and others — opt for legal action by suing device manufacturers, claiming the companies knew their hip systems were defective.
The U.S. Food and Drug Administration (FDA) must approve all hip replacement systems before manufacturers can market them in the United States. The FDA classifies metal-on-metal hip systems as Class III (higher risk) devices but regulates them under the 510(k) premarket notification program. The program allows the companies to get their products on the market without rigorous testing. Now, several makers of MoM implants face thousands of lawsuits in state and federal courts.
In May 2011, the FDA ordered 21 manufacturers of MoM products to conduct postmarket studies. A year later, an FDA panel found that there is little reason for surgeons to continue to use these implant systems. The FDA states that "a decision on the proper classification of metal-on-metal hip systems is forthcoming."
Dozens of medical device manufacturers sell hundreds of different hip components, and they often advertise their products directly to the consumer. Orthopaedic surgeons, however, are the most qualified to make the decision about which implant components to use in surgery. Most hip implant systems come with several options for surgeons — including different materials, modular necks and stems and a variety of femoral ball sizes.
Several of the world’s largest hip implant manufacturers – including DePuy, Stryker and Zimmer — have been forced to recall some of their most popular products after early failure rates and other complications. Smaller brands – including Smith & Nephew, Biomet and Wright – also are under fire for selling defective implants. Some problematic implants remain on the market without a recall.
DePuy, a division of Johnson & Johnson, developed three hip replacement designs since 2000 with high failure rates: the Pinnacle Hip Replacement System, the ASR XL Acetabular System and the ASR Hip Resurfacing System. The problems with all three systems arise from their metal-on-metal components, and DePuy recalled the two ASR systems in mid-2010. According to evidence presented at the first ASR trial in January 2013, DePuy knew at the time of the recall that the all-metal ASR device would fail within five years in 40 percent of patients.
DePuy is facing an estimated 12,000 lawsuits from patients who received one of its ASR hip implants. According to Bloomberg, DePuy has agreed to pay $2.5 billion to settle 7,500 of those lawsuits.
In July 2012, Stryker recalled two hip replacement systems: the Rejuvenate and the ABG II modular-neck hip stems. These two hip designs have been associated with complications such as loosening of the implant and metallosis. The first plaintiff filed a lawsuit against Stryker for its hip design in New Jersey on August 7, 2012.
The recall came just a few months after Stryker issued warnings to surgeons about the hazards associated with these two products. Stryker listed metallosis, tissue death and a number of other complications that could require revision surgery. While not recalled, new studies suggest Stryker's line of titanium TMZF femoral stems and LFIT cobalt-chromium femoral head can also cause the same problems as the ABG II and Rejuvenate. These compoments include the Accolade TMZF, Citation TMZF and Meridian TMZF.
Zimmer is facing lawsuits over its Durom Acetabular Component (Durom Cup), a hip socket made of metal. This one-piece socket uses a plasma coating instead of cement to promote bone growth and remain in place, but the implant does not always properly attach to the bone and can cause excruciating pain if it loosens.
Zimmer briefly recalled the Durom Cup in 2008 to revise the instructions, but it returned to the market. Thousands of U.S. patients received the component between its debut in 2006 and the recall.
Smith & Nephew recalled the metal liner component of its modular R3 Acetabular System on June 1, 2012. About 3,000 to 4,000 Americans received the faulty metal liner between 2009 and 2012, and these patients may be at an increased risk for revision surgery. If a patient has undergone revision surgery or a doctor has recommended it, compensation for medical expenses and injuries may be available.
On November 15, 2016, the company recalled its Modular SMF and Modular Redapt Revision Femoral Hip Systems. The company issued a recall when it noticed higher than anticipated complaint and adverse events trends. "In the worst case scenario implanted patients are symptomatic and exhibit adverse tissue reaction to metal debris which may lead to revision surgery," the company said in its Urgent Field Safety Notice.
In addition to the R3, Smith & Nephew's Birmingham Hip and its Emperion Hip System are also under scrutiny. A 2016 study by Stronach et al. in Arthroplasty Today described the fracture of an Emperion hip stem 6 years after implantation.
Biomet manufactures a metal-on-metal hip implant called M2a. It’s a modular device with many options, including M2a-Magnum, M2a-38, M2a-Taper, M2a-28mm, Stanmore and Exceed ABT. The metal-on-metal design can result in high failure rates and patients who received a defective Biomet hip implant may suffer from metallosis or another complication.
Wright Medical manufactures two hip implant products that are similar to DePuy’s ASR hip replacement systems. One is the Conserve Plus Total Resurfacing Hip System, which features a metal-on-metal ball and socket. The other is the Profemur Z Hip Stem, which is a modular metal product. Since 2003, patients received about 10,000 of these hip replacement products. Because of their similarities to DePuy hip implants, these products may be associated with higher failure rates.
OMNI, also known as OMNIlife science, Inc. is a medical device company based in Taunton, Massachusetts. The company designed the Apex K2 Hip Implant System to interlock with several other parts for a custom fit. But, problems with the system surfaced when the Australian equivalent of the U.S. FDA, the Australian Register of Therapeutic Goods, pulled the implant from the market in 2012.
According to the Australian agency, the implant had an above-average revision rate — more than 9 percent of hips could fail and need additional surgery within three years. Its metal-on-metal design also caused metal particle to leak into patients' blood, leading to swelling and deterioration of bone and tissue.
The FDA has not yet recommended a recall, but attorneys are investigating claims on behalf of injured patients.