Warning: Creating default object from empty value in /home/anterior/public_html/wp-content/plugins/wpsp/configs/default.php on line 27
hip arthroplasty | what bearing should you use? » hip arthroplasty

«

»

Print this Post

what bearing should you choose?

The area of contact between the femoral stem and the acetabulum in a total hip arthroplasty is called a bearing surface.  Just like the bearings in your car, this is the critical junction where all of the friction of movement must be reduced by smooth surfaces that glide easily with respect to each other.  There are several types of bearing surfaces that are currently used in total hip arthroplasty.  For the sake of this discussion we will describe bearings as X on Y, with X being the type of bearing on the femoral side of the hip replacement, called the BALL, and Y being the bearing on the acetabular side of the hip replacement, which is typically called the SOCKET or the CUP.  The most common bearings include:

  • Metal on Polyethylene (aka plastic)
  • Metal on Metal
  • Ceramic on Ceramic
  • Ceramic on Polyethylene

 

Metal on polyethylene bearings are by far the most common bearing used during hip replacement and most surgeons would consider a metal on polyethylene bearing to be the STANDARD bearing in total hip arthoplasty.  In a 2009 article in the Journal of Bone and Joint Surgery the authors researched the relative rates of usage of the most common bearing types.  By far, the most commonly used bearing was a metal on polyethylene bearing, which was used 51% of the time, followed by a metal on metal bearing,  used 35% of the time, and finally, a ceramic on ceramic bearing which was used only 14% of the time.

In this study on bearing usage in the United States, metal on polyethylene bearings were used most commonly in elderly female patients (patients who were medicare beneficiaries, aged sixty-five to seventy-four years old) whereas metal-on-metal and ceramic-on-ceramic bearings were used most commonly in younger male patients (less than sixty-five years of age) who also had private insurance.  This study also demonstrated that there is a lot of variation in types of bearing used during total hip replacement around the US: for example, the highest rates of standard metal on polyethylene bearing use occurred in the Northeastern United states and when surgery was performed in non-teaching hospitals, where as the highest rates of metal on metal bearing use occurred in the Southern United States and when surgery was performed at teaching hospitals.  These trends reflect the fact that many surgeons consider younger male patients to be better candidates for metal on metal bearing because they are more likely to subject the total hip replacement to increased stresses as a result of higher body mass, more physical activity, and a stubborn desire to return to all of the activities they were capable of prior to hip replacement, such as jogging.  Also, metal on metal bearing have typically been considered a “premium” implant or an “upgrade” over the conventional metal on polyethylene bearing, so surgeons are more likely to implant these bearings when the hospital may be able to recoup the increased costs of these bearings, which happens more commonly when private insurance is used to pay for the procedure.  The fact that metal on metal bearings were implanted more frequently in teaching hospital may reflect the fact that surgeons at teaching hospitals are more likely to have established relationships with the industry that manufactures total hip replacements and they are more likely to be actively engaged in the process of the trying out new materials and new bearing surfaces.

The complete reference for this article on the epidemiology of bearing surfaces is as follows:

J Bone Joint Surg Am. 2009 Jul;91(7):1614-20.  The epidemiology of bearing surface usage in total hip arthroplasty in the United States. Bozic KJ, Kurtz S, Lau E, Ong K, Chiu V, Vail TP, Rubash HE, Berry DJ. Department of Orthopaedic Surgery and Philip R. Lee Institute for Health Policy Studies, University of California, San Francisco, 500 Parnassus Avenue, MU 320W, San Francisco, CA 94143-0728

Recently, there have been several well publicized recalls of hip joints and bearings for a variety of reasons.  This has resulted in a lot of increased attention on bearing selection and has created a fair amount of anxiety in the minds of many patients.  Many orthopedic surgeons who perform total hip replacements would say that the safest choice for a bearing is a metal on polyethylene bearing since this bearing type has been implanted in the most number of people, has a very well established track record, has proved to be very durable, and the strategies for revision of this bearing should it wear out are well known and easily (relatively) achievable.

If a patient has a definite preference for a particular type of bearing, then I will usually accommodate their wishes once we have had a chance to discuss why they want a particular bearing.  If they have never researched the topic, or are open to suggestion, I typically try to steer them in the direction of a metal on polyethylene bearing since this has the longest track record, has been implanted in the largest number of patients, and is KNOWN to give years and years of faithful service.

Leave a Reply

Your email address will not be published. Required fields are marked *