Hip Replacement surgery, also known as Total Hip Arthroplasty, is a procedure undertaken to alleviate pain and mobility issues associated with worn-out or damaged hip joints. The new joints are comprised of artificial parts made of metal, plastic, or ceramic. Candidates for hip replacement typically suffer from osteoarthritis, rheumatoid arthritis, or traumatic arthritis and do not respond to other types of treatments. In the United States, the number of hip replacements performed in recent years has increased substantially – especially in a growing number of young patients.  Physicians and clinicians believe hip replacement surgery is one of the most cost-effective ways to improve the quality of life in suffering patients.  However, while the technology holds tremendous promise not all hip replacement devices behave in the same way and precious few of the most popular device models have actually undergone the most rigorous testing and scrutiny under the U.S. Food and Drug Administration’s (FDA) Pre-Market Approval (PMA) process. Instead, it is common for hip joint manufacturers to instead opt for the FDA’s more lenient and expedient 510(k) Clearance process.

What Conditions Does Hip Replacement Typically Treat?

The hip is one of the largest joints in the human body and is dominated by a prominent ball-and-socket joint. The hip socket is formed by a part of the pelvis bone known as the acetabulum. The ball section is known as the “femoral head” and forms the upper part of the human femur (thighbone).  Over time, wear and tear as well as inflammation can cause acute pain and decrease in mobility. The most common causes of hip pain are:

• Osteoarthritis: This is akin to “wear-and-tear” in the hip joint.  The onset of osteoarthritis occurs typically in people 50 years of age or older and in those with a family history of arthritis. Sufferers experience a wearing away of the cartilage cushioning the bones so that they rub against each other causing pain and stiffness.
• Rheumatoid Arthritis: A chronic inflammation associated with autoimmune disease, Rheumatoid Arthritis (RA) is characterized by an inflammation of the synovial membrane which can damage the cartilage in the joint leading to pain and stiffness.
• Post Traumatic Arthritis: Cartilage in the hip joint can become damaged and inflamed following a serious hip injury or fracture.
• Osteonecrosis: Where a lack of blood to the hip joint, caused by an injury, dislocation, or fracture limits the supply of blood to the femoral head and causes the surface of the bone to collapse or arthritic inflammation.  Also known as “avascular necrosis”.

What Are the Types of Hip Replacement Surgery?

While considering options for hip replacement, surgical teams will consider either an anterior or posterior approach to the procedure.  

Posterior Approach

This surgical procedure involves a surgeon creating a 4-6 inch (or larger) along the outer buttock and splits the gluteus maximus muscle as well as detaching the two hip rotator muscles (they are reattached later). The head of the femur is then removed and a metal stem is placed in the hollow part of the femur, followed by the placement of a metal or ceramic ball on the top of the stem that acts as the new head of the femur. Once that is accomplished, the socket of the hip joint is removed and replaced with a new metal socket.

Anterior Approach

In the anterior approach, the surgeon actually makes an incision on the front part of the upper thigh, frequently removing the necessity to cut through muscle. Removal of the damaged joint and implantation is thereafter similar to the posterior approach. Anterior approaches may allow for an earlier return to activities because of a substantially lessened decrease in the risk of dislocation. However, it is also a more technically challenging surgery due to the proximity of a crucial nerve and the positioning of the patient during the procedure.

Once the approach is adequately considered, surgeons and patients will then decide on the nature and extent of the type of procedure. The three major types of hip replacement are:

Total Hip Replacement

The most common type of hip replacement surgery, total hip replacement involves the replacement of damaged sections of the patient’s hip with artificial implants. The hip socket is replaced with a durable plastic cup which may also include a titanium metal shell. The femoral head is removed and replaced with a ball made from ceramic or metal alloys. The new ball is then attached to a metal stem that is inserted into the top of the femur.

Partial Hip Replacement

Partial hip replacement (called “hemiarthroplasty”) involves only replacing one side of the hip joint – the femoral head (as opposed to both the head and the socket).  Partial hip replacements are more common in elderly patients who have suffered hip fractures.

Hip Resurfacing

Also known as “surface replacement”, hip resurfacing is an alternative to Total Hip Replacement for some patients, where appropriate. In the hip resurfacing procedure the natural femoral head is retained. The advantage to hip resurfacing is that patients avoid the risk of infection and hip dislocation. Furthermore, very active individuals may find that hip resurfacing can offer a more stable hip joint than Total Hip Replacement. However, hip resurfacing has its disadvantages as well, including the possibility for nerve damage or necessity for later hip revision surgery.

Who Is the Ideal Candidate for Hip Replacement Surgery?

The typical indications for people eligible for hip replacement are those who suffer from moderate-to-severe arthritis in the hip that causes pain and/or interferes with the activities of daily living.  Issues for suffers can include:

• Difficulty walking, going upstairs, and bending to get in and out of chairs
• Moderate-to-severe pain even while resting
• Stiffness that affects the hip’s range of motion during normal activities
• Symptoms not addressed by anti-inflammatories, physical therapy, steroid injections, or the use of an assistive device such as a cane or walker

Surgeons will carefully screen patients to help ensure that surgeries are successful and the risk of complications low. Eligibility for a hip replacement may be curtailed for those patients who pose a greater risk for postoperative complications or higher rates of infection. Typical reasons for ineligibility are:

• Existing Infections:  Serious cases of post-surgical infection can cause patients to be readmitted to the hospital and require long courses of intravenous antibiotics.
• Nicotine: Smokers and other tobacco users can face higher rates of complications and possibly the necessity of further follow-ups and revision surgery.
• Severe Osteoporosis: New joint prosthesis in the hip will exacerbate brittle bones which cannot support the new implants.
• Other Factors: Patients who are unable to follow-through with pre-and-post surgical instructions, such as those who suffer from dementia or alcoholism or are more prone to dangerous falls may be flagged as ineligible.

Hip Replacement Formats

Every hip implant has benefits and risks associated with its design and implantation. Every hip implant system has unique device design features such as size, shape and material, and dimensions. In the United States, there are currently four types of total hip replacement devices available with different bearing surfaces. These are:

• Metal-on-Polyethylene: The ball is made of metal and the socket is made of plastic (polyethylene) or has a plastic lining.
• Ceramic-on-Polyethylene: The ball is made of ceramic and the socket is made of plastic (polyethylene) or has a plastic lining.
• Ceramic-on-Ceramic: The ball is made of ceramic and the socket has a ceramic lining.
• Ceramic-on-Metal: The ball is made of ceramic and the socket has a metal lining.

Note: As of May 2016, there are no FDA-approved metal-on-metal total hip replacement devices marketed for use in the United States. However, there are some patients who received a metal-on-metal total hip replacement prior to that date.

Risks and Complications from Hip Replacement

Although there are generally many benefits to suffering patients from hip replacement surgery, as with any invasive procedure, there are risks and the possibility for complications. Some of the common risks associated with hip replacement surgery – and Total Hip Replacement in particular are:

Blood Clots Associated with Anesthesia

A serious medical complication arising from surgery is the potential for blood clot episodes tied to either Deep Vein Thrombosis (DVT) – a blood clot in the leg; or a Pulmonary Embolus (PE) – a clot that breaks off and travels to the lungs. Patients are typically urged (under physician supervision) to get out of bed shortly after surgery and take prescribed anti-clot medications to reduce the risk of blood clots.

Hip Dislocation

If a hip joint dislocates, the prosthetic ball can usually be re-seated in the socket without additional surgery, though anesthesia is frequently required during manipulation of the hip back into position. Dislocation is more prevalent in patients who are:

• Female
• Older
• Have had a previous hip surgery
• Have weak muscles surrounding the hip
• Have hip replacement surgery for a broken hip
• Have poor hip stability due to osteonecrosis

Infection

A deep infection in hospital settings, sometimes involving drug-resistant microbes is an issue of growing concern for patients and surgeons alike.  These infections can require a minimum of 1-2 additional surgical procedures to remedy.

Damage to Joint Structures

There exists a distinct possibility that soft muscle and joint tissue surrounding the hip will be damaged during surgery.  This damage, in some cases, can result in leg weakness or decreased feeling in the leg.

Loosening of the Prosthetic

A new hip joint should fit naturally with the existing bone and surrounding tissue.  However, over time, one or both ends of the replaced joint may loosen the bond to the natural bone causing pain or other problems. These issues may necessitate a repair surgery known as a Hip Revision. Revision surgery may also be recommended if an infection has developed in the tissue surrounding the joint.

Femur Fracture

While uncommon, it is possible for the thigh bone or femur to fracture during surgery during the dislocation process or during the fitting of the prosthetic stem inside the femur. A femur fracture will usually require additional surgery.

Metal-on-Metal Hip Implants and Metallosis

In Metal-on-Metal (MoM) hip implants, the metal ball and metal cup slide against each other during walking or running. This friction between the ball and socket can cause the release of metal particles that will wear off of the device and embed in surrounding tissue as well as metal ions of cobalt and chromium entering the bloodstream. Over time, this leaching of metal from the joint into surrounding tissue causes “Adverse Local Tissue Reaction” (ALTR) and/or “Adverse Reaction to Metal Debris” (ARMD).  The bottom line for patients implanted with MoM joints, however, is that they suffer damage and pain, device failure, loosening, and the need for revision surgery. Furthermore, patients implanted with MoM hip joints can also suffer from a condition known as “metallosis” – a potentially fatal complication arising from metallic erosion in the joint which induces pain around the joint, pseudotumors, and a noticeable rash.

Prior to 2016, MoM hip devices marketed in the United States were subject to the FDA’s less rigorous 510(k) clearance process which allowed them to be implanted in human patients without first subjecting them to the same standards of scientific review and lab testing as the FDA’s more rigorous Pre-Market Approval (PMA) process. In May 2016, following numerous recommendations, the FDA required all MoM manufacturers to immediately cease and desist from marketing MoM devices until they can be demonstrably approved under PMA conditions with valid supporting scientific evidence. It is worth noting that to-date, there are no FDA-approved MoM hip replacement devices marketed for use in the United States.

Recalls and Lawsuits Tied to Hip Replacement Devices

Smith & Nephew Metal-on-Metal and Hip Resurfacing

Smith & Nephew is a United Kingdom-based joint device manufacturer with operations in the United States.  In 2017, Smith & Nephew was named a defendant in Multidistrict Litigation (MDL-2775) occurring in federal court in Maryland before Judge Catherine C. Blake.  At the center of the litigation naming Smith & Nephew are several hundred claims alleging defects involving the company’s MoM Birmingham Hip Resurfacing (BHR) implants and its R3 hip joint products.  The BHR was the subject of a recall for all units implanted between 2006 and 2015 due to high rates of failure and revision surgeries as was the R3 in 2012 due to issues with erosion and metallosis.

Stryker LFIT V40 Femoral Head and Rejuvenate/ABG II Hip Implant

Stryker is a Michigan-based medical device manufacturer that traces its founding back to Dr. Homer Stryker, an orthopedic surgeon, and his device inventions dating back to 1941. Today Stryker is an international giant that claims $14.9 billion in sales in 2019. In 2016, Stryker announced a recall of its LFIT V40 femoral heads manufactured before 2011 following post-market surveillance showing a higher-than-average rate of failure with symptoms in patients similar to those suffering from metallosis. Similarly, Stryker recalled its Rejuvenate and ABG II implants in 2012 (after only 2 years on the market due to post-market research indicating issues common to MoM devices.  Both the LFIT V40 and the Rejuvenate/ABG II devices are the subject of ongoing multi-district litigation in federal court in Massachusetts (MDL-2768) and Minnesota (MDL-2441).

DePuy Orthopaedics ASR Hip Implant and Pinnacle Hip Implant

DePuy Synthes is a subsidiary of global pharmaceutical and medical device manufacturer Johnson & Johnson. In 2010, DePuy Synthes issued a voluntary global recall for its ASR Acetabular System following evidence that emerged through post-market surveillance that patients were suffering considerable pain, immune system reactions, inflammation, and the need for revision. The symptoms were consistent with MoM injury and potential design flaws. Similarly, Depuy Synthes’ Pinnacle MoM hip implant is alleged to cause a condition called “osteolysis” which occurs when bone surrounding the hip joint dissolves due to instability and metallosis. Pinnacle has not been the subject of a recall as of this date.  However, both the ASR Hip Implant and the Pinnacle Hip Implant are subjects of multi-district litigation in Ohio (MDL-2197) and Texas (MDL-2244).

Tracy Everhart

Tracy Everhart is the Editor for Drug Law Journal. A highly-trained and certified medical professional, Tracy is also an accomplished medical writer. After spending years on the front lines of the medical profession, Tracy now devotes her expertise and skills to researching and reporting on new drugs and devices that enter the market, as well as their side-effects and the real-life stories involved. Prior to joining Drug Law Journal, Tracy wrote for benchmark online healthcare resources focused on families and, in particular, women’s health issues. Tracy holds post-graduate degrees from both the American College of Healthcare Sciences and the Yale School of Nursing. She is also a graduate of both Hampshire College, where she studied microbiology and the University of South Carolina school of nursing.