What is New in Joint Replacement Surgery
of the Knee and Hip?

Much has changed in joint replacement surgery over the past decade.  Some good and some not so good.  The brief discussion which follows should get the reader not only the knowledge to know what is out there, but also to make an educated decision on what is right for them.  With so much on the internet, billboards, and the shared information among friends, it is sometimes hard to filter what is real and what is not.

One of the more impressive and still developing technology is a custom made and custom inserted total knee replacement.  Several venders have the availability of such appliance and the promise is to minimize differences in dimensions that would otherwise not be appropriately fit by the off-the-shelf model.  An example of this is that women's and men's shoes are different. Yet it goes beyond the shoe fit to specifically address certain anatomical variations such as different size and dimensions.  We are not all alike and we come from different heritages such as African-American, Asian, European, Native American to name a few, and all of these make a difference in the way that our bones are shaped.  This specific technology addresses that in the design of the implant. After the knee replacement is reconstructed there are instruments that are specifically designed to fit the patient's anatomy with which to make more accurate the insertion of the total knee replacement.  Differences that exist in different implant lines often are not universally appropriate for all patients. In a response to the demands for more accurate implants, the majority of vendors now offer better solutions for variabilities of both genetics and anthropology.

Shorter rehabilitation is at this point in time not only a possibility, but it should be expected by patients. That being said, the expectations for short lengths of stay range from 24 hours to three days, which gives a rather large target to hit. Taking advantage of current technologies and of pharmaceutical agents, there really is no reason to expect hospitalization beyond 24 hours. In some cases and for a highly motivated and educated patient population, returning home the same day as a total joint procedure is now possible. This fast recovery also extends into the recovery time where 72% of the patients are done with their rehabilitation and their total knee at three weeks. What used to be a three month recovery program is now 3 weeks. At the conclusion of this recovery, the patient is expected to have full extension (or the knee straight), and 120 degrees of bend, (better known as flexion). If the outcomes are not retrievable by physicians that you consult with, you might want to continue you’re shopping.

Metal sensitivity is a recent topic of discussion with regards to implants.  Specifically, one implant that is able to deliver a hypoallergenic implant is the total knee replacement.  However, it has not been able to be mass produced for the hip.  That being said, women have a more than twice the likelihood of having allergies to metal because of jewelry and cosmetic exposure.  If you have a metal sensitivity, it is important that your physician test you for it and/or use an implant that has no metal exposed so that you do not develop further symptoms in the knee that could be construed as a metal byproduct allergy.

HIP REPLACEMENT

Out With the New, Back with the Old.

Ever heard of hip resurfacing?  There are a lot of physicians and patients who wish they never had.  For 35 or 40 years there has been an enthusiasm for minimizing the amount of bone resection when performing total hips.  What initially looked appealing became the worst nightmare over the last decade that one can recall in recent times.  Numerous recalls and revision surgeries have been the result of this and excluding certain brands and surgical techniques, it has been a very disappointing attempt at improving something that worked perfectly well.  Before you embark on a metal-on-metal or resurfacing operation, please check with your physician regarding his outcomes and the literature that is very abundant on these types of hip replacements.

If the vehicle body is the hip implant then the wheels are the bearing surface.  The bearing surface is where the movement occurs at the socket joint and recently there have been some interesting and very progressive developments on types of materials used in the construction of the ball and socket joint.  The recognized leaders are ceramic-on-ceramic, ceramic-on-polyethylene, and cobalt-chrome or molybdenum on polyethylene.  What is not felt to be ideal is metal-on-metal for the reasons stated above due to metal byproducts and metal sensitivity.  Many older versions have the metal-on-metal utilized in the bearing surface and for those functioning well there should not be any real concern, but certainly strict adherence to follow up to the physician who put it in is important to make sure that the complications associated with this do not occur.  Ceramic-on-ceramic has demonstrated to be the superior surface with one major downside and that is the noise or squeaky sound that it sometimes has after some use.  For this reason, many of the vendors have decided not to supply this and in reality, while it does not hurt anything, it is very disheartening to have a hip that makes noise or a squeaking sound when using it under normal conditions.  The solution for this is a ceramic-on-polyethylene liner and that has been the industry favorite for a premium bearing surface.  The standard traditional low demand ball is still made from cobalt-chrome and other sub-metals used in constructing in the socket assembly.

The most comforting outcomes in total hips is the incredible relief of pain they provide in patients who have been debilitated crippling arthritis of the hip.  Not only is it a speedy and fast recovery, but it truly is one where you often forget that you had a total hip.

A good source of information to extend beyond this brief glimpse is www.AAHKS.org or www.dlionbergermd.com where you can find an abundance of information on a variety of orthopaedic topics.

Dr. Lionberger is a fellowship trained clinical professor at UT Bryan College Station, with an office in the Texas Medical Center in Houston. Telephone (713) 790-1818.