From my point of view as a resurfacing doc there is likely little to
be gained from an mri at this point. If you had a significant AVN it
would have shown up on the x-ray films your resurfacing surgeon saw
on your pre op appointment. If he viewed your films and felt a resurf
was possible don't worry. At worst he will find at the time of
surgery that your bone won't support a resurf and go with a MOM THR.
In my experience that can almost always be seen on plain x-ray so if
he didn't tell you about that you are likely a good resurf candidate.
Rather then speculate I would just contact your surgeon and ask.
As for knee pain that is common with hip arthritis but if it has
gotten worse a new hip x-ray can tell if your femoral head has
collapsed which might make a resurf harder. Many resurfs are done for
AVN with good results so don't worry about that.
Will Bone Cysts Keep Me from Having
Hip Resurfacing?
Cysts are very common in arthritic hips and can usually be
seen on x-rays. Most of the time they are not a problem with
resurfacing because they are small and in the part of the bone removed in
milling the femoral head for a resurf. Most larger ones can be filled
with a cement of bone chips and still do a good resurf. The only cysts
that are problematic are those that erode the superior femoral neck
weakening the bone at a critical place. This can lead to fracture
with a resurf and that is an indication for a THR instead. They can
usually be seen on a pre op x-ray so I can tell the patient that a resurf
may not be possible and a decision can be made at surgery. In the one
case I was surprised on the cyst was under a large osteophyte and was
obscured on the x-ray. The patient got a big head metal-metal THR and
is doing fine.
What is the Difference Between the Manufacturers Hip
Devices?
While all are high carbon cobalt chrome
alloys there is no way to know the slight variations if any in
the metals. The manufacturers are all very secretive about the
specifics for obvious reasons (to keep it out of the hands of
the competition). That said in the short term studies as well as
on the testing machines there haven't been many significant
differences between the different manufacturers products. I
think this will also be true over the long term but only time
will tell.
I feel the major differences will be in the instruments used to
guide the surgeon during the implantation. They should all be
adequate to make reproducible results but some may be easier
then others. I have been using the Conserve plus but so I can
make an informed decision plan on taking training with the other
two implants (Biomet and BHR) in the next few months. After
seeing them all in surgery I will then make a final decision
which I like best.
As far as a patient is concerned I would pick a surgeon you are
comfortable with and let them use the implant they are happy
with. By far and away the surgeons skills are more important
then the particular implant. I wouldn't worry about ranking the
devices because as of now there is no data to distinguish one as
better then the others.
Does Hip Resurfacing Remove More Acetabular Bone than a Total
Hip Replacement?
The acatabular component needs to have
an outside diameter to fill the acatabulum. Typically in a THR
you ream about 3-6 millimeters larger then the actual acatabular
size to get to good bone then fill the inside of the shell with
polyethylene to an inside diameter to match the femoral
component being used. In a resurf or a big head metal-metal THR
the inside of the acatabulum is 6-8 mm smaller then the outside
diameter and that is how much bone is reamed. The size in a
resurf is dictated by the femoral neck size which determines the
femoral head size (in M-M THR the acatabulum is selected on
anatomy and the head size selected to match).
All that said you see that reaming and acatabular size are
esentially the same for all types of implants. Hope that makes
it clear.
How much is reamed from the hip for the acetabular cup?
That is correct. The acatabular component needs to have an
outside diameter to fill the acatabulum. Typically in a THR you ream about 3-6 millimeters larger then the actual acatabular size to get to good bone then fill the inside of the shell with polyethylene to an inside diameter to match the femoral component being used. In a resurf or a big head metal-metal THR the inside of the acatabulum is 6-8 mm smaller then the outside diameter and that is how much bone is reamed. The size in a resurf is dictated by the femoral neck size which determines the femoral head size (in M-M THR the acatabulum is selected on anatomy and the head size selected to match).
All that said you see that reaming and acatabular size are esentially the same for all types of implants. Hope that makes it clear.
Will the neck capsule be preserved during my hip
resurfacing?
Saving the capsule is good with a THR
because it may decrease the rate of dislocation. In regular THR it can go either way saving or
not. Due to the technical needs of the resurf procedure the
capsule must be fully opened and partially removed. There is no
way to do a resurf and fully preserve the capsule. This is not a
problem though because the resurfs are more stable then a THR
and dislocations are very unlikely. I certainly wouldn't let the
need to sacrifice the capsule turn you off to resurfacing. The
anatomy of the resurf makes the capsule less necessary then in a
THR.
The capsule is the membrane connecting the rim of the
acetabulum and the base of the femoral neck. It helps stabilize the hip and
provides some of the blood supply to the femoral head. I may not
have been clear regarding how it is handled in a resurf. It is
cut all the way around to allow the head to be dislocated enough
to expose the head to resurface it. A small portion around the
neck is left to preserve the blood supply. The part near the
side of approach (posterior for most surgeons) is sometimes
removed. At the end the part that is assessable is usually
repaired and the rest scars back in. As for motion it is likely
that a good therapy program and activity does more to keep the
hip mobile then how much capsule is removed. That said I try to
retain as much as possible and still be able to do the job.
How difficult is it to revise a hip
resurfacing as compared to a THR?
Overall
it is much easier and less destructive to the bone revising a
hip resurfacing. Frequently it is easier on the soft tissues as well depending
how hard the THA femoral stem is to get out. As far as the
acatabular components are concerned they are the same in both
implants so there is minimal difference on that side of the joint.
One other point is that a resurfacing usually fails due to a fracture of
the femoral neck which leaves the bone below intact. Revising this
involves cutting the neck just below the implant leaving the surgeon
with the same bone configuration seen after the first cut in a
primary THA. The results of this revision are essentially the same as a
primary THA. On the other hand after removing a stemmed THA femoral
component there is frequently femoral bone loss and erosion. This
sometimes requires bone grafts or special custom components to
rebuild with results that have less longevity then a primary
component.
Can Computer Assisted Surgery by used for Hip
Resurfacing?
I was at the Annapolis conference
last week and listened with great interest to the discussions on this topic.
As you can well imagine the navigation companies have been trying
very hard to sell their equipment to the hospitals. I have
resisted thus far because I never felt the cost was justified in either
total knees or primary stemmed hips because the anatomy is easily
directly visualized and my accuracy was already excellent in placing
the components with the available instruments.
For resurfacing the anatomy is not so easily visualized
because the pin is placed in the center of the femoral neck and can't be directly visualized. Additionally the neck is not fully
visualized because the capsular attachments are preserved to maintain
blood supply to the femoral head.
I went back this week and reassessed my pin placements on my
first 50 resurfs and found that my pin placement was very accurate and
that all the pins that were more then 2 degrees off ideal (total of
2) were in the first 10 cases. That said there have been a few
times where although the pins were placed accurately I was a little
unsure until the post op x-ray confirmed things. There are a number
of ways to check placement with the neck feeler gauges prior to
reaming over the pin and once one learns how to do this it works well.
As I have done more I now rarely have those feelings of uncertainty
and would agree that computer navigation might not offer much at
this stage.
The role I see for navigation is in a surgeons early cases not
to be the only way to place the pin but rather as a way to check
placement of a conventionally placed pin to confirm proper position and
allow repositioning if needed. That would prevent misplacement in
the early cases while allowing a surgeon to gain experience and confidence in conventional pin placement.
Although I am now confident in my pin placements I am going to
try a navigation system once or twice just to see. After that the
hospital would need to buy the system and for now I don't think the
cost will be justified. I will keep everyone informed of my opinions
after I give it a try.
My operated hip leg feels too long
Not an uncommon feeling post op especially if the operated leg
was a tad short to begin with. With a resurf there is not much ability to alter the leg length so it more likely the feeling then an actual significant lengthening. Give it some time and the feeling usually will disappear.
Will an x-ray show cysts
Many cysts can be seen on plain x-ray. For 3-D analysis a CT scan is much better then an MRI but rarely needed. If no cysts are seen on x-ray it is unlikely that clinically significant ones will be seen at the time of surgery. When I encounter larger cysts on x-ray I will sometimes get a CT but usually not. I will instead inform the patient that the cysts may make a resurf impossible depending on the size and location of the cyst. A final decision is made in surgery. Most cysts can be bone grafted or if smaller filled with cement. If cysts large enough to prevent a resurf are encountered then I proceed with a mig head M-M THR using the same acatabular component as for the resurf. Only once have I been surprised and needed to do a THR unexpectedly and that was a superior neck cyst that was hidden under an osteophyte. The other times I needed to go with a THR intraop I had predicted it on the pre op x-rays and counseled the patient accordingly.
As a patient I wouldn't worry about it because the anatomy is what it is. The anatomy will dictate the course us surgeons need to take. Just get a surgeon you trust and who is a fan of resurfs and let them do their job with the best judgement they know.
What can cause a dislocation?
From the sound of things I would expect her implant is not positioned correctly. This could have been because of improper placement at surgery or if a hemispherical cup without pegs was used it is possible for the cup to rotate and become misaligned later on. I would first get digital copies of her films or take digital photos of her films and e-mail them to one of us who give e-mail consults.
It would be unlikely to have dislocations of a resurf for another cause. In view of that a hip spica seems unlikely to solve her problem. She might benefit from a brace that keeps her from getting into a position where the hip can dislocate while the situation is studied but these are usually not comfortable enough to provide a long term solution. Usually revision is required. If the problem is on the cup side it may be possible to revise that and still keep the resurf.
Can I have an MRI after I had a hip resurfacing?
MRI is perfectly safe with any orthopaedic implant (joint replacements, fracture
hardware screws and others). The implants may degrade the picture quality in the
areas right near the implants but no harm will come to the implants or the surrounding bone.
Pacemakers are another story and are not safe with MRI. Other things that can be problematic are metal filings in the eye and vascular clips placed within 6 months.
Does a Surgeon need 100 Hip
Resurfacings to be experienced?
I ask everyone to consider that everyone needs to start somewhere and all
surgeons (even Gross, DeSmet and McMinn) had to do their first resurf and their
next 99 prior to reaching 100.
This issue is one that is difficult for me because I set very high standards
for myself and always want to do the best thing for my patients. That is why I
became interested in the resurf concept. As I went through my first 50 cases I
was always questioning my experience and analyzing the results to be sure I was
doing the best surgery I could. On the one hand you know you don't have the
experience that some others do. On the other hand there is no way to get it
without doing the cases. It is a very difficult issue for a surgeon.
I resolved it by training as follows:
While I realize the importance of experience as I hope most of my fellow
surgeons do we all must start somewhere. There is really no way to resolve that
issue.
As for an individual deciding where to have the procedure done there is no
easy answer. I would make sure first that you are comfortable with the surgeon
and your experience on your visit. Ask questions and be comfortable with the
answers. If you don't have a good feeling look elsewhere.
If you personally set a minimum number of cases for your surgeon that's fine.
But please don't insult the surgeons starting out by claiming them to be bogus.
Most are like me when I started. Worried to death about doing a perfect
performance every time while starting a new and difficult procedure. Doing their
best each and every time and beating themselves up for every mistake no matter
how minor. Ask my wife and she will tell you how much it bothers me every time
something doesn't go perfect in surgery, even if it is something that won't
affect the results. I take the responsibility and trust that patients give me
very seriously and I feel the majority of the orthopods do.
I hope that will give you all some insight into the moral dilema that faces a
surgeon starting with a new procedure. If some of us don't learn and gain
experience in resurfs then the procedure won't be widely available and many
resurf candidates will lose their heads needlessly due to lack of qualified
surgeons.
Remember we all had to crawl before we learned to walk and then stumbled
unsteadily before we learned to walk well. Thanks for reading this ramble.
