Joint Replacement Blog

Metal-on-Metal Bearings in Total Hip Replacement—Update 2012

Dr. William Barrett — Fri, 20 Jan 2012 16:57:32 +0000

At the beginning of the 21st century, metal-on-highly cross-linked polyethelene bearings were introduced, along with metal-on-metal bearings and ceramic-on-ceramic bearings. All of these “newer” bearings were introduced to try and combat wear associated with metal-on-conventional polyethylene, which in some patients would lead to significant bone loss around total hip replacement implants. Several mid-term studies revealed promising results utilizing metal-on-metal bearings in both hip replacement and hip resurfacing in younger, more active, individuals. However, over the last 3 to 4 years, studies have been published that revealed failures of metal-on-metal hips associated with an adverse tissue reaction felt to be associated with elevated levels of metal ion around the implants. These “adverse tissue reactions” can manifest as a small fluid collection, a cystic mass, or a solid mass referred to as a pseudotumor. This is a mass which is neither malignant nor infectious, can be small or large, and occurs in the soft tissue around hip replacement components. These adverse tissue reactions appear to be related to metal-on-metal bearing wear and may be an allergic reaction to low levels of wear debris or a toxic reaction to elevated levels of wear debris. Most likely, a combination of factors may be involved in these reactions. At present, there is no consensus as to what is the cause and why they occur.

Why does this happen?
All bearings utilized in hip replacements lead to wear between moving parts. This wear leads to particles in the surrounding soft tissue of the joint. The body reacts to different particles in a variety of ways. We know from experience in the 1980s and 1990s that polyethylene particles can lead to bone destruction by activation of cells that try to vacuum up the polyethylene particles. These cells release chemicals that lead to destruction of bone around the hip implants. Metal-on-metal particles, which are quite a bit smaller and in some cases dissolve in the fluid, are absorbed by cells and in some cases lead to a toxic reaction killing the cells. Therefore, the reaction of the cell to the particle is variable and varies from one patient to the next. The amount of wear of bearings used in total hip replacements is influenced by implant design and component placement. We know that smaller cup sizes may lead to greater wear or vertical cups may also lead to increased wear due to an edge-loading phenomenon where the edge of the socket articulates against the ball of the hip decreasing the contact area, decreasing the amount of coverage of the ball by the socket, all of which leads to less lubrication between the bearing surfaces and increased wear of the parts.

A central question in metal on metal bearings is why do some patients develop an adverse tissue reaction while others do not. It would appear that the level of wear and, therefore, wear debris influences this reaction. The patient’s response to wear debris is highly variable. Some patients with very low wear can develop a significant soft tissue reaction, while in other patients significant amounts of wear can lead to no reaction whatsoever. It, therefore, appears this is a combination of inflammatory and possibly allergic-type reaction to the debris.

What are the risks of different bearings?
It is important to realize that the overwhelming majority of hip replacements are highly successful. To date, metal-on-metal hip replacements still have greater than 90% success rate at followup available in 2012. Because of concerns about soft tissue reactions to metal debris, the number of metal-on-metal bearings implanted in the U.S. has dropped significantly. There has also been quite a bit of hyperbole in the press regarding patients who have had an adverse tissue reaction. While the complication in any one patient can be devastating, it is important to realize that the majority of patients continue to function quite well. Each bearing surface has its own set of potential complications and time will tell which bearing proves to be the most successful.

What should I do going forward?
If you have a hip replacement, you should follow up with your surgeon on a routine basis, usually at the first and second year at a minimum, then per the surgeon’s protocol thereafter. If you have a metal-on-metal hip, you should follow up with your surgeon on a yearly basis to check in to see if there is any change in the status of your hip. If you have symptoms, the most common of which are pain in and around the hip, a thorough history, physical exam, x-ray, and if appropriate, blood studies, will be ordered. If there is concern about an adverse tissue reaction to a metal-on-metal bearing, your surgeon may decide to measure your blood cobalt and chromium levels and/or check a specialized imaging study, such as an MRI or ultrasound, looking for soft tissue reaction around the implant. Like with any drug or implant, careful monitoring over time will help us better determine what is the appropriate use for specific devices.

William P. Barrett, MD

Preoperative risk factors, their effect on total hip and knee replacement

Dr. William Barrett — Thu, 05 Jan 2012 22:40:10 +0000

At the 21st annual meeting of the American Association of Hip and Knee Surgeons in Dallas, Texas in November of 2011, a survey of joint replacement surgeons was presented. Within the past year, 82% of respondents stated they had discouraged patients from having a hip or knee replacement because of obesity. The cutoff value was a BMI greater than or equal to 44. Many of these surgeons referred their patients to a bariatric program for weight loss. Diabetic patients with an A1c greater than 7.5 were referred to their internists for better management of their diabetes prior to scheduling surgery.

The results of this survey are consistent with a growing trend among joint replacement surgeons to encourage patients to decrease their preoperative risk factors, particularly obesity and control of their diabetes and to have good control of their medical conditions prior to undergoing elective hip and knee replacement surgery.

The influence of these comorbidities or preop medical issues will be greater in the coming years when payments for care are bundled together to include many postop complications and readmissions.�
William P. Barrett, MD

Uncemented total hip replacement in patients less than 50

Dr. William Barrett — Thu, 05 Jan 2012 16:48:51 +0000

There were several papers presented at the 21st Annual meeting of the American Association of Hip and Knee Surgeons in Dallas, Texas in November of 2011. These papers demonstrated excellent long-term fixation both at 10 and 20 years using cementless femoral and acetabular components. Failures did occur due to wear at the bearing surface between the metal ball and polyethylene socket. Changes to the polyethylene, which were introduced over a decade ago, have improved the longevity of polyethylene inserts used for total hip replacements.

With the current concerns over metal-on-metal and ceramic-on-ceramic bearings, the most common bearing used today in the United States for younger and older individuals undergoing hip replacement is a metal ball mated with a crosslink polyethylene liner.

These studies confirm the durability of cementless fixation even in younger, more active individuals.

William P. Barrett, M.D.

Chronic narcotic use prior to total knee replacement

Dr. William Barrett — Tue, 29 Nov 2011 00:35:51 +0000

In a study reported in the American Journal of Bone and Joint Surgery in November of 2011, Dr. Zywiel and co-authors reviewed the results of patients who are using chronic narcotics prior to knee replacement and compared them to a group of patients not using narcotics prior to the knee replacement surgery. They noted that the patients in the preop narcotic use group had poorer outcomes, had longer length of stays in the hospital after surgery, had a higher rate of re-operation for manipulation of stiff knees, and a higher revision rate for pain.

With the increased use by primary care physicians of narcotics to treat the pain of osteoarthritis, this trend should be dampened somewhat by the poorer outcomes in patients who are taking narcotics prior to their knee replacement surgery. For this reason, if the patients fail to obtain pain relief with over-the-counter analgesics and oral anti-inflammatory medications, perhaps earlier referral to an orthopedic surgeon for evaluation of a painful, weightbearing joint would make sense prior to starting a patient on chronic narcotic use which may ultimately jeopardize the outcome of their subsequent joint replacement procedure. �
William P. Barrett, MD

Quad sparing total knee replacement versus conventional total knee arthroplasty, is there a difference?

Dr. William Barrett — Fri, 11 Nov 2011 00:34:33 +0000

Two studies presented at the 21st Annual American Association of Hip and Knee Surgeons in Dallas, Texas in November of 2011 reviewed the effect of surgical exposure, in particular use of quad sparing versus conventional total knee arthroplasty. They checked multiple variables including postoperative pain, quality of life, quadriceps strength postoperatively, gait, and function. One of the studies by Dr. Pagnano at the Mayo Clinic, was a prospective, randomized study dividing patients equally into a quad sparing and conventional total knee group. Patients and the evaluators were blind to which technique was used in the patients. Using objective measures postoperatively, they found no difference in the two groups, specifically no difference in pain control, quadriceps strength, gait, or function. In a second study presented at the same meeting, similar results were found. The bulk of data available in the orthopedic literature would support the fact that the surgical approach by itself has no significant impact on the outcome of knee replacement. Rather improved outcomes over the last several years would be attributed to multimodal pain management, preoperative education, and aggressive physical therapy. All of these components, when utilized together, lead to more rapid rehabilitation and earlier return to activity.

Groups of surgeons have traveled around the west toting more precise joint replacement and better outcomes as a result of “less invasive techniques”. The orthopedic literature does not support those claims, and while many claims are made, the objective data does not back up what some of the surgeons advertise.

As a patient, you want to look for a program that has a comprehensive approach to joint replacement surgery, evaluates and documents it’s outcomes in objective forms, and can back up it’s claims made with objective data.

William P. Barrett, MD

High flexion total knee replacement

Dr. William Barrett — Thu, 29 Sep 2011 23:05:14 +0000

Over the last few years, various device manufacturers have developed and marketed “High Flex knees”. The hope with these newer designs was that patients would gain greater range of motion with regard to postoperative flexion or bending of the knee. There have been several studies comparing conventional with High Flex knee designs over the last few years, and the majority of these studies have failed to demonstrate any improved range of motion with the newer designs. The new designs take into account continued articulation or “mating” of the thigh bone to the shin bone component past 140 degrees of flexion.

What has been learned from this is that range of motion following a total knee replacement is dependent on several factors. These include patient factors, specifically the amount of motion the patient had in the knee prior to the operation; the patient’s size, as a larger lower extremity can block motion by the soft tissue girth of the leg; and motivation of the patient to perform their postop physical therapy. Surgical technique can also influence range of motion. This can include the alignment and placement of the implants, removal of bone and soft tissue that can interfere with flexion at the time of surgery, and balancing of the soft tissue with the new knee implants. Lastly, the implant can have an influence, but it seems to be the least important of the factors noted above.

In summary, range of motion following knee replacement is influenced by the amount of motion the patient has before surgery, the participation of the patient in a rehab program after surgery, the surgical technique used by the surgeon which involves proper placement and alignment of the implants and balancing of the soft tissue, and to a lesser degree, the implant. The length of incision has nothing to do with range of motion after knee replacement.�
William P. Barrett, MD

Weight, wounds and exercise. How are they all related?

Dr. William Barrett — Tue, 06 Sep 2011 16:42:23 +0000

As aging baby-boomers begin to feel the aches and pains of arthritic joints, they may start to realize that their weight, their activity, and exercise regimen may impact outcomes of possible joint replacement procedures in their future. There are several factors that influence the outcome and survivorship of joint replacement procedures. These include the patient’s weight, activity level, and overall strength. There have been numerous scientific articles outlying the importance of maximizing your nutritional status, decreasing your body weight, and minimizing your complications following surgery. Arthritis can affect anyone, but, fortunately, is present only in roughly 10% of the population. Factors that tend to accelerate the onset of arthritis include genetic predisposition, prior injury to joints or adjacent bones, and obesity.

If your arthritis progresses to the point where surgical replacement of the joint is indicated, then there are several things you can do to increase your chances of success and decrease your risk of complication. These include losing excess weight and maximizing your nutritional health. One of the more common refrains I hear is that “I can’t lose weight doctor because I can’t exercise”. A greater portion of weight loss is associated with proper diet and avoidance of excess calories than it is with exercise. Recent articles in the New York Times have pointed out some of the potentially deleterious effects of modern diets and the use of high fructose corn syrup in many of the food items that we consume. Review of this article may be helpful to help you better plan a healthy diet. Losing excess weight will also decrease the risk of having wound healing complications. The first step in recovery from a joint replacement is securing safe healing of the surgical incision. This healing process is multifactorial and includes surgical technique and patient factors such as obesity and overall health status of the individual.

As we enter into the final months of summer, it is important to take stock in yourself and look in the mirror and decide what it is you can do to help your overall health status, decrease your risk of arthritis, and if surgery becomes necessary, maximize your chances for a successful outcome. �
William P. Barrett, MD

Getting ready for surgery

Dr. William Barrett — Mon, 08 Aug 2011 16:07:32 +0000

I had the pleasure of going on a recent bike trip with a 75-year-old gentleman named Earl. Earl had some of the most deformed knees I have seen in a long time with bone-on-bone changes in the inside or medial compartment of each knee. He was told he has severe osteoarthritis and is going to undergo bilateral knee replacements. Earl has run 40 marathons in his lifetime, now bikes 40 km a day. On this recent bike trip, we would average over 30 miles a day riding on hilly terrain. Despite the severe arthritis, Earl was able to keep up with us despite his severe arthritis. When I asked him if it hurt, he said his pain has become a part of his life that he has gotten used to. He took no anti-inflammatory medications and he is looking forward to getting his knees fixed. While Earl may be an exception, most people with osteoarthritis are able to engage in some form of exercise to help maintain their strength and improve their flexibility.

A story like Earl’s underscores the importance of taking as good a care of your body as you can, particularly as you face the prospect of impending surgery. Thirty percent of most Americans are overweight and this contributes to the significant increase in the instance of osteoarthritis of the hip and knee. Reducing caloric intake and maintaining at least a minimal exercise routine is important to improve the success of your surgery and decrease your risk of complications.

— William P. Barrett, MD

It’s summertime. Are you getting back in shape?

Dr. William Barrett — Wed, 27 Jul 2011 22:27:38 +0000

With the return of nicer weather to the Pacific Northwest, many people turn to the outdoors for exercise. But, really keeping yourself in shape is a year-round commitment to your health, your well-being, and your future. With national obesity rates exceeding 30%, it is time to take stock in who you are and what you eat and how you take care of yourself. I am always amazed at the number of patients who tell me they will begin exercising once we fix their joints, because they can not exercise now. The reality is, weight loss is not simply about exercise, but analyzing what you eat and how much you eat. The majority of us can lose a substantial amount of weight by simply decreasing our intake, analyzing exactly what we eat, and finding a healthier diet. Many individuals have a fairly fixed caloric intake, but as they develop arthritis, they begin to exercise less and less. As a result, the amount of calories they burn decreases and the national tendency is to gain weight. So, as we burn fewer calories, we have to decrease the amount of calories we take in. This is a concept that is often lost on individuals, but so important to our overall health.

So, my advice for the summer, take a moment, look at what you’re eating, how much your eating, and ask yourself, are you doing what’s best for you?

— William P. Barrett, MD

Anterior approach versus posterolateral approach total hip replacement.

Dr. William Barrett — Fri, 15 Jul 2011 15:49:44 +0000

We recently completed our prospective randomized study evaluating the differences between anterior approach and posterolateral approach total hip replacement. There was a statistically significant difference in the amount of postoperative pain, return to work, and function between the two groups. The anterior approach hip recovered faster, got back to work sooner, and had an earlier return of function when compared to the patients in the posterolateral group. At one year, the differences between the two groups seemed to be minimal, supporting the fact that total hip replacement is an excellent operation with very gratifying, long-term results. While there were certain exclusion criteria in the study, such as morbid obesity and age over 75, these groups were otherwise very well matched and similar to the general total hip replacement population. Evaluating these two approaches and having done them both for many years, it is clear that certain patients are better suited for one approach versus the other. Certainly, individuals who have a large “beer belly” or pannus of adipose tissue are less desirable for an anterior approach as it interferes with the exposure and can potentially complicate healing. Certain bone conditions also will favor a posterior approach as there are more options for implant selection. For motivated, more-fit individuals, the anterior approach offers some advantages.

— William P. Barrett, MD