FAQ Archives | Orthoped

Young for Total Knee Replacement

Curiously enough, high age is no obstacle for a total knee replacement, but low age is!

Studies demonstrated that:

  • only 25% surgeons were against total knee replacement operations in patients aged over 80 years, whereas
  • 65% surgeons were against total knee operations in patients younger than 50 years


Here are some answers: (more…)

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Hip Resurfacing Frequently Asked Questions

What are the major differences among the hip resurfacing implants?

The primary difference lies in the backing of the acetabular component. The BHR (Midland Medical Technology) uses a cast porous surface with a hydroaxiphate (HA) coating to promote bone ingrowth. The Wright Conserve Plus using a sintering process to affix cobalt chrome beads to the back surface. The Corin Cormet device has a plasma sprayed titanium backing with an HA coating. MidMedtech asserts that the heating of the device in the sintering or plasma spray process weakens the metal integrity. It has been shown in laboratory tests however, that when the machining tolerances are identical, the wear rate is not affected by the heat treatment. (more…)

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Cancer risks among total hip patients

“I am about to have a total hip in May. The thought of it is exhausting as I am only 30 years old. A big piece of metal would stay inside my body for many years! How will my body react to it? Perhaps, frightful thought, I may develop cancer around it?….”

Alloys used for manufacture of total hip prostheses contain materials which are potentially carcinogenic (can produce cancer) in animals.
It is also known that levels of some metals (Chromium, Nickel, e.g) are elevated both in the tissues around the total hip joint and in the blood of patients with total hips.
Also bone cement contains materials with potential carcinogenic effect that may enter into the circulation. (more…)

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Expectations and satisfaction from total hip surgery



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Total Hip Replacement Frequently Asked Questions

  • Which implant is the best?
    This is about as difficult a question to answer as “Which car is the best?”. There is a certain amount of individual preference to this decision. With new materials and stem designs now being introduced, there is a matter of judgement about risk of taking on improved designs that may be unproven in the human body. By trying something that is new and improved you may need to take on some of that risk. That said, even the “old devices” seem to be constantly changing so it may not be as clear-cut to accept past record as an indicator of future performance as it may seem.
  • My doctor said he is going to use a titanium implant, is that a good one?
    I’m not sure why it seems many doctors are telling their patients this. Perhaps because titanium sounds high tech and they feel the patients will be reassured he is using the best metal for golf clubs. Titantium can be used in hip implants in the stem and on the backing of the acetabular component to create a rough surface for bone ingrowth. When used in a stem it has the advantage over cobalt-chrome in that is more flexible, so it will flex more with the bone. As for longevity, the metal of the stem is probably less important than other details such as the composition of the articulating surfaces (junction of ball-and-socket). Titanium is never used for the articulating surfaces because it is too soft.
  • When is the right time to stop waiting and have surgery?
    For me I was having significant pain in certain situations more than 4 years before I had surgery. I waited until it had advanced to where I had severe pain and joint stiffness after any exertion (such as doing yardwork or a lot of walking). My range of motion had been affected so much that climbing stairs was a problem and I could no longer ride a bike. The decision came down to one of quality of life — in order to avoid situations with a lot of standing or walking I was passing up a lot of activities to the point I felt my life had become one of only avoiding pain. Although I wasn’t in pain all the time, it was enough that at times I felt it was affecting my personality.
  • How long will a hip implant last?
    There are many factors involved, its not unlike asking someone how long your car will last or how long the tires will wear. Your mileage will vary, but these are the controlling factors:

    1. “Miles” per year. With the polyethelyne liners, wear of the liner is a function of use. Less use gives you more time before it wears through. For the hard bearing surfaces (metal-n-metal and ceramic-on-ceramic) the wear rate is so small it is not expected that “wear-through” will be the limited factor — which is not to say the wear debris can’t cause problems (see items 5 and 6 below).
    2. Years. Polyethylene oxidizes in-vivo and there is some evidence it then becomes more brittle with age, this would increase the wear rate per “mile”. Some surface defects on ceramic-ceramic joints may grow with time, though the newer materials attempt to minimize this. Metal-on-metal articulation, through a self polishing process, actually can have less wear-per-mile as it gets older.
    3. Age of patient. This is correlated with item #1 above. Younger people are harder on their joints and walk more steps per day.
    4. Sex of patient. Males are harder on their joints and statistically put on more miles.
    5. Response of your body to debris. Some people have a very strong osteolysis response to debris particles, some people don’t. Response, on average, is stronger for large particle sizes (from polyethelyne) as macrophage response is stronger for larger and more debris. The size of the particles is much smaller for metal-on-metal and ceramic-on-ceramic articulation.
    6. Mechanical strength of bone-implant interface. This is somewhat related to the previous item as the osteolysis can cause loosening of the joint, but it can also happen from mechanical stresses, soft bones, failure to get good ingrowth (uncemented) or failure to get proper cement mantle (cemented).
    7. Loading of the implant. The distribution of forces that the implant provides on the bone can affect the strength of the surrounding bone. This is known as Wolff’s Law: bone that is not stressed has a tendency to resorb (or dissolve). Resorbed bone can lead to weakness at the implant-bone interface or result in cracks where debris may lodge and osteolysis begin. Loading is function of implant design, installation and body geometry.
  • Did you do anything special to prepare for surgery?
    If you have time you can do what you can to be in the best shape you can be by your surgery date. I did some upper body work (home gym) to lose a few extra pounds (nothing serious in my case) that I had gained because I had a period of less physical activity due to hip pain avoidance. The upper body strength then helped when I had to move myself in/out of bed using mostly my arms and also helped somewhat with the crutches.
  • Will I have a permanent 90-degree bending restriction?
    Generally, no. The advice about bending restrictions seems to vary a lot among surgeons, and may also depend on your own circumstances. If you have hip dysplasia or unnatural shape to your femur you may be more likely to dislocate and the surgeon will factor that in. Generally the 90-degree rule will apply only for the first 6-12 weeks. After that time your hip capsule should have healed, the muscles around the joint strengthened and the implant should have established good bone ingrowth (in the case of uncemented components).If you are concerned about this type of restriction limiting your activities you should strongly consider hip resurfacing or metal-on-metal THR with a large diameter femoral head.
  • What physical restrictions do you have after hip resurfacing surgery?
    I will not be allowed to jog or play basketball for recreation. I think downhill skiing on groomed trails will be allowed, but I don’t think I’ll risk that. The lifetime of any implant would better be described in terms of “miles” than years. Or a better measure would be number of cycles times the force of each (combination of the patient’s weight and the vigor of the step, walking vs. jogging). So, regardless of what is “OK’ed”, one still has to be aware of the wear factors.
  • Do hip implants set off the metal detectors at the airport?
    Since the Transportation Security Administration (TSA) took over the security screening at the airports, I have had a pretty consistent experience with the metal detectors — that is my hips (one resurfaced, one large head metal-on-metal THR) always set off the walk-through detector.This is not such a big problem, it just makes the screening process take a little longer. If you set off the detector you will be directed to a separate line and inspected with a wand-like handheld detector. Even if you’re going to set off the detector, its best to remove all metal beforehand so that you aren’t asked to repeatedly remove things and walk through. Just mention that you have some metal in your hips and they will check you by hand. You’ll have to first sit down and the security inspector will check your legs and feet in the sitting position, then stand and he/she will check your body while standing. If the detector goes off, they will pat down the area of the signal with the back of their hand. Its best not to have anything in your pants pockets then they can immediately determine that you aren’t carrying a weapon. After a couple minutes you’ll be on your way.

    One additional tip: If you’re traveling with someone its best to go first and have your companion go through the same x-ray line. They can attend to the items that you sent through the x-ray machine while you’re getting hand inspected. At some airports one of the TSA people will bring your things over to you so you can keep an eye on them while being checked by hand.

    TSA Home Page with more travel tips

  • Should I get a card or letter from my doctor to take with me to the airport?
    I think such cards are not of much use. I do not have one, and have never found the need. Since there is not a standard, verifiable, implant card, the airport screener will have to check out the claim of an implant anyway. Terrorists have access to computers and printers and could probably make a nifty card themselves. Same with any sort of written documentation. The one situation I could see it being useful is if you had to explain to someone in another language about the implant, and a picture is worth a thousand words, quite literally in that case.
  • All this information on implants is good, but why not just let the doctor choose the implant?
    Letting the surgeon choose sounds like a good idea if you are willing to let him make all the judgements and risk assessments for you. Keep in mind that many surgeons and hospitals may be tied to one or two manufacturers for their parts, so their range of options may not be complete. I recommend seeing at least two surgeons from different groups, and different hospitals, if possible, to get an idea of the consensus for your particular situation.

    If you are young and considering some of the newer technologies you may want to visit with a surgeon who has research experience and might be better able to judge preliminary research findings.

  • What is the best way to find a good surgeon?
    It is best to talk to those in your community who see the results of the surgeries for themselves first hand. That would be the physical therapists in the rehab centers and the nurses in the orthopedic ward. When asking for a recommendation you may ask them about their results with patients in your situation (in terms of age, weight, general health and activity level).There is a high correlation between surgical skill and the outcomes. Skill comes, in part, from experience and continuous practice. I would make sure the surgeon does a lot of hips in a year, probably at least 50-100 (1-2 per week). The more experience the surgeon has with patients like you, the better.
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