A hip replacement, or hip arthroplasty, is surgery that replaces a diseased or injured hip joint by with an artificial joint or implant. People usually receive hip replacements when arthritis causes severe hip pain and inflammation. Hip fracture and natural wear-and-tear are also common reasons for hip replacement surgery.
Hip replacements help millions of people regain mobility and find relief from joint pain, but hip replacement surgery is accompanied by some risk and requires months of recovery.
Prospective patients should know that implants don’t last forever, and some hip implants have a better safety record than others. They should take steps to be sure a hip replacement is right for them and that the device they’re receiving has a history of success.
An artificial hip has three basic components: a stem that is inserted into the femur, a ball that attaches to the top of the femur and a cup that attaches to a socket in the pelvis. The ball, also called a femoral head component, replaces the head of the femur. The cup, also called the acetabular component, is implanted into the pelvis.
Hip replacements are one of the most common joint replacement operations in the United States, with more than 300,000 performed in the country each year, according to the American Academy of Orthopaedic Surgeons. An estimated 2.5 million Americans were living with artificial hips in 2010, according to a study published in 2015 in The Journal of Bone and Joint Surgery.
Although hip replacement surgery is common, it is a major surgery that has a variety of risks. Complications during surgery or later in life can cause debilitating side effects. That’s why doctors and patients should consider the benefits and risks of the operation.
Candidates for Hip Replacement
The most likely candidates for hip replacement include people who experience pain that disrupts regular activities. In addition to people with osteoarthritis or hip injuries, people with rheumatoid arthritis, osteonecrosis or bone tumors may need hip replacements to relieve pain. People also receive hip replacements to increase mobility and improve overall quality of life.
Signs that You May Need a Hip Replacement
- Hip pain that prevents walking, bending, climbing stairs or doing daily chores
- Pain in your hip even when not walking or standing
- Stiffness in your hip that prevents lifting your leg
- Failure of non-surgical treatments to provide relief
- Depression or other changes in your mental health
- Your doctor rules out other health problems
Doctors will also consider the risk for each individual patient. Age, weight and medical conditions such as diabetes can affect a patient’s risk for complications following hip replacement, according to Dr. H. John Cooper, a board-certified orthopedic surgeon.
The risk of getting a specific complication “can be somewhere between 0 and 3 percent for somebody who’s healthy and in good shape,” Cooper told Drugwatch. “There are risk factors that are greater than 20 percent in patients with the wrong sort of combination of risk factors.”
People ages 50 to 80 have historically been the most common candidates for hip replacements. However, young teenagers with juvenile arthritis and people over the age of 80 have successfully undergone hip replacements.
Many people experience pain relief and improvements in daily living after receiving a hip replacement, but the devices are not miracle cures. Hip replacement surgery has a number of risks, and the implants wear out over time. To avoid complications, people who receive implants should not jog, run or participate in high-impact sports. They may be able to swim, bike or perform other low-impact activities.
Alternatives to Hip Replacement
Most doctors will ask patients to consider alternative methods for relieving pain or increasing mobility before recommending an artificial hip implant.
One such option called subchondroplasty attempts to promote natural bone growth to repair damaged hips. Doctors inject a bone substitute into the hip joint. The material fills gaps, voids and lesions in the bone. Over time, the body begins replacing the material with natural bone, which can sometimes lead to permanent repairs.
Alternative treatments usually tried before hip replacement include:
- Exercises that increase muscle around the hip
- Canes, walkers and other walking aids
- Over-the-counter medication for pain without inflammation
- Nonsteroidal anti-inflammatory drugs for pain with inflammation
- Osteotomy of the femur, a procedure that involves cutting and realigning the bone
But when alternative treatments do not provide relief, increase mobility or improve quality of life, doctors may consider a hip replacement procedure. They will analyze the patient’s medical history, take X-rays and perform physical exams to test hip mobility and strength. They may also conduct MRIs or CT scans.
Types of Hip Replacement Surgery
Surgeons perform hip replacements by using a posterior approach or an anterior approach. With a posterior hip replacement, the incision is made at the side or back of the hip. During anterior hip replacement, the surgeon makes the incision at the front of the hip.
The posterior approach is more common in part because it allows better visibility of the hip joint, though the anterior approach is becoming more prevalent. There is no significant difference between the procedures as far as recovery from surgery, but the anterior procedure may pose a higher risk of nerve damage that could cause numbness in the outer thigh.
Patients who are younger than 50, have a normal body mass index or who are in overall good health may be candidates for minimally-invasive surgery. During this surgery, the incision is smaller and recovery time after the surgery is shorter.
Special bone cement is commonly used to hold hip implants in place, but some surgeons use a cementless fixation technique. Devices that do not require cement have a textured surface that allows the bone to grow onto the implant and secure it. A hybrid total hip replacement involves implanting the cup without cement and setting the ball in place with cement.
Total Hip Replacement
Total hip replacement is the most common hip surgery. It uses artificial components to replace the entire hip structure. During the procedure, surgeons insert a stem into the patient’s femur, or thighbone, for stability. They replace the head of the femur with a ball and replace the natural socket in the hip joint with an artificial cup.
Partial Hip Replacement
Partial hip replacement removes and replaces the patient’s femoral head, which is the ball at the top of the femur, or thighbone. It does not replace the socket. A ceramic or metal ball is attached to the top of a stem that’s inserted into the hollow center of the femur. Surgeons typically perform this surgery to repair certain types of hip fractures.
Hip resurfacing helps relieve pain from cartilage loss. A surgeon trims damage from the natural bone ball at the top of the thighbone. He or she then resurfaces it with a smooth metal covering. The surgeon also lines the natural bone socket of the hip with a metal lining or shell.
Bilateral Hip Replacement vs. Staged Hip Replacements
If both hips require replacement, surgeons may choose a staged hip replacement. They replace one hip at a time, letting the patient recover from the first surgery before doing the second one. Alternatively, the patient may undergo a bilateral hip replacement in which both hips are replaced at the same time.
A bilateral hip replacement can mean a single trip to the operating room and the potential for less overall recovery time. But it doesn’t work for all patients.
The risk of blood loss during surgery is greater with bilateral hip replacement and patients are under anesthesia for twice as long — up to four hours. Patients are also more likely to require longer hospitalization or inpatient rehab.
Bilateral replacements usually involve younger, healthy and active patients who can handle more rigorous physical therapy and exercise following hip replacements.
Types of Implants
Device manufacturers design hip implants to mimic the natural movement of the body. The primary differences between implants are their size and the material of the components.
Hip implant components are made of polyethylene (plastic), metal, ceramic or a combination of the materials.
One of the most common types of hip implant, metal-on-polyethylene has been used since the 1960s. The ball is made of metal and the socket has a plastic lining or is made entirely of polyethylene. Plastic has a smooth surface that causes little friction while the ball moves within the socket. However, MoP implants can produce plastic debris, which can eventually cause the implant to fail. Wear debris from the breakdown of materials could lead to a condition called osteolysis, which occurs when inflammation destroys the bone and the implant in the bone loosens.
Metal-on-metal hip devices are no longer available in the United States, though thousands of people may have been implanted with them. Around the turn of the century, many new hip implants were made from metal-on-metal components, meaning the ball, stem and socket were all made out of metal. Manufacturers believed the metals were more durable than other materials. However, MoM hip implants can shed metal particles that may cause a number of serious health issues, including a type of metal poisoning called metallosis. Several models of metal-on-metal hips were recalled or taken off the market.
Ceramic-on-polyethylene devices couple a ceramic ball with a socket made from plastic. They may also substitute the plastic socket for a polyethylene lining in the natural socket. With plastic parts, there is still a risk of wear that causes debris that leads to osteolysis.
Ceramic-on-ceramic devices combine a ceramic head with a ceramic lining in the hip socket. A 20-year follow up study found that overall survivorship of CoC implants was 88 percent. It increased to 91 percent when researchers looked only at failures related to materials, according to Dr. Laurent Sedel, who presented the study at the SICOT XXV Triennial World Congress 2011. The most common failures were loosening of the lining and component fractures.
The U.S. Food and Drug Administration approved the first ceramic-on-metal hip device in 2011, making the design relatively new. The ball is made of ceramic and the socket has a metal lining.
Hip Replacement Risks and Complications
Most people who have hip replacement surgery do not experience major complications. Dislocation and loosening are the most common complications of hip replacement, according to the National Institute of Arthritis and Musculoskeletal and Skin Disease.
Problems after hip surgery can include:
- Loosening of implant
- Blood clots
- Bone growth beyond normal edges of the bone
Some complications occur at much higher rates with specific implant designs, said Cooper, who is an assistant professor of orthopedic surgery at Columbia University Medical Center. He categorizes device-specific concerns into two major groups.
The first involves certain implants with metal-on-metal bearings that are associated with a higher risk for failure and metal release from the bearing’s surface. The other major class of concern involves metal-on-polyethylene bearings that release metal debris where the pieces of the stem or head come together.
“The reactions are similar: inflammation around the joints, fluid collections, and in more advanced cases, tissues damage, bone loss or some of the more rare but serious complications like blood vessel constriction or compressions,” Cooper said.
A couple of the devices have been recalled and are no longer commonly used in the United States or across the world. But there are still plenty of patients in the United States who have these devices inside of them, Cooper said. Some patients in the United States are walking around with implants that were not available in the United States but were available in Europe or in other countries, and they are having the same kinds of problems.
Most hip implants last for 10 years to 15 years, but the devices wear out more quickly if the patient has an active lifestyle. Some implants wear out faster than others, requiring revision surgery to remove, repair or replace the device. An estimated 10.4 percent of hip replacements require revision surgery, according to a 2016 study published in Arthroplasty Today.
Hip Implant Recalls
A hip replacement recall usually happens when the implant causes complications in large number of people implanted with the device. Several leading device makers have issued large recalls related to hip complications.
Johnson & Johnson subsidiary DePuy Orthopaedics issued a global recall for the company’s ASR and ASR XL Acetabular Cups in 2010. The reason given was the company’s “ongoing post-market surveillance,” meaning the company was reviewing reported problems. DePuy never recalled its metal-on-metal versions of its Pinnacle hip but quietly pulled them off the market. People have filed more than 20,000 lawsuits over DePuy’s ASR and Pinnacle metal-on-metal hips.
Stryker recalled 9,003 ABG II Modular hip stems in April 2012 after reports of fretting and corrosion. These devices were not metal-on-metal ball and socket components. The problem came from the connections in the stem that held the implant to the femur. The Stryker devices came with different sized and angled necks that allowed surgeons to customize fit for patients. The junction where these connected shed particles into patients’ tissue.
United Kingdom-based Smith & Nephew recalled all 6,266 lots of its Modular Redapt Hip Systems in 2016 due to “a higher than anticipated complaint and adverse event trend.” Just a year earlier, the company had recalled almost 6,000 Birmingham Hip Resurfacing, or BHR, components due to “revision rates which were higher than established benchmarks.”
Zimmer recalled 19,000 Durom cup components in 2008 because of false and misleading labeling. And Wright Medical recalled shells for its Conserve and Dynasty hip replacement lines in 2016 due to metal debris causing the need for revision surgeries in patients with the devices.
What to Know About Metal-on-Metal Implants
The FDA classifies metal-on-metal hip systems as Class III, higher risk medical devices, but many of them were cleared for sale in the United States through the agency’s 510(k) premarket notification process. Under the process, companies need only to show that their products are “substantially equivalent” to other devices already approved by the FDA before they can start selling their products.
“Metal-on-metal implants were commonly used up to a third of the time in hip replacement in the early and mid-2000s,” Cooper said.
The devices had higher than expected failure rates. Problems led companies to recall some models. Others were simply pulled off the market.
Today, there are no FDA-approved metal-on-metal hip implants available in the United States. There are only two FDA-approved metal-on-metal resurfacing systems available. And any company that wants to sell metal-on-metal hips can no longer rely on the 510(k) process. Companies have to provide scientific evidence that their devices are safe and effective.
“The patients with these more problematic or riskier implants need regular follow-up with an orthopedic surgeon familiar with hip or knee replacements.”
Studies and data from national registries showed metal wear debris from metal-on-metal hip implants can cause inflammation around the joints and local tissue damage with what doctors call adverse local tissue reactions, or ALTR.
“Often in these patients when these kinds of reactions develop, if caught early, the bearing surface can be changed so permanent damage is not typically done,” Cooper said.
But if the problem goes unaddressed for a period of time, then patients can suffer irreversible, permanent tissue damage or bone loss. In extreme cases, patients may experience nerve compression or compression of blood vessels. In very extreme cases, the metal being released from these joint replacements can get to high systemic levels in the blood and can potentially cause concern about systemic side effects that affect the patients’ heart, vision or hearing.
“The patients with these more problematic or riskier implants need regular follow-up with an orthopedic surgeon familiar with hip or knee replacements,” Cooper said. “If they haven’t been within the past year, I would recommend making an appointment with their surgeon who put the device in.”
Many people with these problematic artificial hips have opted for revision surgery to receive a new hip implant. Some patients filed lawsuits against hip implant manufacturers, claiming the companies knew their hip systems were defective.
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