Hip Resurfacing Surgery as a Replacement Alternative

Hip resurfacing is an alternative to standard hip replacement surgery used for the treatment of severe hip arthritis. Hip resurfacing is not a new surgery. Hip resurfacing surgery has been performed since the early 1970s. However, recent changes in hip resurfacing implant design have led to a new interest in this procedure.

Candidates

Hip resurfacing surgery is a possible consideration for patients with severe hip arthritis. Hip resurfacing has been recommended for patients who are younger and may face multiple surgeries over the course of their lifetime. No studies have shown that hip resurfacing is better for young patients, but there are theoretic advantages that have led some healthcare providers to pursue this possibility.

Why Did Hip Resurfacing Fall out of Favor in the 1970s?

Hip resurfacing was a popular procedure several decades ago. The implants used at that time were made of metal and plastic. Unfortunately, these implants had significant problems and often failed in the first several years following surgery. These patients often required additional surgery, even within a short time following their initial hip resurfacing.

What Led to the Recent Increase in Hip Resurfacing Surgeries?

In the 1990s, new hip resurfacing implant designs were introduced. The hip resurfacing implants are now made entirely of metal, with two separate pieces. One of the metal implants is a "cap" placed on the ball of the ball-and-socket hip joint, and the other side of the implant is a metal cup that forms the socket of the joint. These implants have not shown the high rate of early failure seen in the metal and plastic implants of the 1970s and 80s.

Some surgeons have advocated hip resurfacing implants because of several potential advantages.

Maintenance of Normal Bone

Hip resurfacing surgery removes less bone than a standard hip replacement. In a standard hip replacement, the entire ball of the ball-and-socket hip joint is removed. In a hip resurfacing surgery, instead of removing the ball, a metal cap is placed around where the cartilage has worn off. Because the bone around the implant is supporting the metal cap, this bone tends to remain healthy and strong. The bone around a standard hip replacement can become thin and weak if the hip replacement implant supports the entire load. This problem is called "stress shielding," and is seen less commonly in hip resurfacing.

Less Risk of Dislocation

Hip resurfacing implants better replicate the normal anatomy of the hip joint and, therefore, have a lower risk of dislocation following surgery. Especially in younger, more active patients, dislocation can be a significant risk of hip replacement surgery.

Easier Revision

If the hip resurfacing surgery does not last the entire life of the patient, the revision (repeat) replacement is not as difficult. Every time a revision procedure is performed, a larger surgery and larger implant must be used. By minimizing the bone removed, and using a smaller implant, the revision surgery following hip resurfacing surgery can be more like performing a standard hip replacement.

The Best Patients for Hip Resurfacing

The ideal patient for a hip resurfacing procedure is a young (less than 60 years old) patient with strong bone around the hip joint. Young patients are of particular concern to joint replacement surgeons because of the chance they will need additional replacements (revision hip replacement) at some point later in life. The hip resurfacing procedure is thought to preserve more bone and prevent possible complications associated with revision hip replacement surgery.

Poor Candidates for Hip Resurfacing

Patients with problems in the bone around the hip joint should not undergo a hip resurfacing surgery. These include patients who have bone loss as a result of their arthritis, patients with osteoporosis, and patients with cysts within the bone. Any of these conditions can weaken the bone around the hip joint, and lead to complications of hip resurfacing surgery.

Other factors may sway patients away from considering a hip resurfacing procedure. These factors include:

• Age: Patients over the age of 60 should carefully consider standard hip replacement surgery. While hip resurfacing provides some theoretic advantages, we know that most patients over the age of 60 will do extremely well with a standard hip replacement. Revision surgery (repeat hip replacement) becomes much less commonly necessary in patients over 60 years old, and therefore, standard hip replacement is usually favored.
• Women: Women have been shown to have a higher rate of complication from hip resurfacing surgery. The exact cause of this is not known, but it is thought to be due in part to the strength of the bone supporting the hip resurfacing implant. Women have been shown to have up to double the risk of fracture around the implant following hip resurfacing surgery.
• Obesity: Patients who are overweight have also experienced a higher rate of complication following hip resurfacing surgery. Some of this problem is thought to be due to increased force on the bone supporting the implant, as well as technical difficulty in the surgery on a larger patient.
• Inflammatory Arthritis & Osteonecrosis: Patients with inflammatory arthritis, such as rheumatoid arthritis, or osteonecrosis causing their hip problems, should consider a standard hip replacement. These patients often have bone abnormalities that could lead to problems supporting the hip resurfacing implant. Your healthcare provider may order special tests to determine if there is an adequate bone to support the hip resurfacing implant.

Hip resurfacing surgery is performed through an incision similar to a standard hip replacement. The arthritic joint is exposed, and the remaining cartilage is removed, but most of the bone stays in place. A metal cap is then placed on the ball, and a metal socket is placed in the pelvis.

Possible Complications

There are a few major concerns with hip resurfacing surgery, and unfortunately, no one knows the long-term results of the implants that are currently being used. Therefore, no one can definitively say that this surgery is better or worse than a standard hip replacement. The current implants used in hip resurfacing have only been used for about ten years, and the only data available is on so-called short-term (less than one year) and mid-term (1 to 10 years) follow-up. No long-term data are available for hip resurfacing surgery.

Possible complications include:

• Fracture: The risk of fracture of the bone supporting the hip resurfacing implant has led some healthcare providers to question if this surgery should be done on any patients. While studies have varied, the risk of fracture of the bone seems to be between 1% and 20% of patients. Fractures are more common in patients who have poor bone quality, obese patients, and women. Also, fractures are more common for surgeons who have done this surgery less frequently.
• Loosening: Similar to standard hip replacements, hip resurfacing implants can become loose over time. If the implant loosens, a standard hip replacement usually needs to be performed.
• Metal Ions: All implants inserted into the body slowly wear out over time. Metal implants used in hip resurfacing surgery have been shown to wear less than plastic implants, but the metal implants do release metal ions into the body as they wear. These metal ions can be detected throughout the body in patients who have had metal-on-metal hip replacements or hip resurfacing surgery. The effect of these metal ions in the body is not known. There are concerns about causing hypersensitivity reactions and possible carcinogenic (cancer-causing) effects. Fortunately, there is little data to show this is a problem, but it is a theoretic concern.

Recovery

The recovery following hip resurfacing surgery is similar to that following hip replacement surgery. Patients have a lower risk of dislocation of the implants, so the precautions placed on the patient may be less significant.

During the first year after surgery, all impact activities and heavy lifting must be avoided. This is the time frame when the bone holding the implant is most susceptible to fracture. Therefore, current recommendations are to avoid running, jumping, and lifting for the first 12 months after surgery.

Will You Need More Surgery at a Later Date?

It is not known how long on average hip resurfacing implants will last. With better-designed implants, they seem to be functioning well at the 10-year mark. However, that is still not as good as what is known about standard hip replacements.

If the hip resurfacing implant does develop problems, or if it does wear out, additional surgery may be recommended. Because the initial hip resurfacing surgery removed less bone than a standard hip replacement, the revision (repeat) surgery is usually less complicated following a hip resurfacing procedure. The usual procedure is to convert the worn out hip resurfacing implant to a standard hip replacement.

For More Information

The most commonly used implant for hip resurfacing in the United States is called the Birmingham Hip Resurfacing implant or BHR Hip from Smith & Nephew. Other systems have been approved by Stryker Corporation and the Conserve-Plus hip resurfacing system by Wright Medical Technology. You can find information about this implant, and surgeons who perform this procedure by going to their website.

Other companies are also designing and testing hip resurfacing implants, so more options will be available in the coming years.