Implant sizes - how do surgeons calculate the correct size.

[happyhopper]

I wonder if anyone knows how surgeons work out the size of implant required in Hip Resurfacing or Total Hip Replacement.  I have heard that templating is one method.  If anyone can give further details that would be helpful.  Also what would the consequences be, if say the implant was a size too large?

[John C]

I believe that all surgeons template off the X-rays so that they know what sizes to have in the operating room, and what size to ream. Having said that, I believe that they also have other sizes available in the operating room in case they need to change plan due to bone defects or other issues.
Too large a size does have one definite negative consequence. We often talk about how HR saves bone on the femoral side, but it is also very important to save as much bone as possible on the acetabular side. If an unnecessarily large cup is put in, then there is that much less bone surrounding it in case the cup ever needs to be revised. Trying to revise a cup with insufficient pelvic bone stock is not a good place to be for the surgeon or the patient. This is one reason that many surgeons believe in using the smallest size appropriate for a patient, leaving as much pelvic bone stock as possible. It is also a reason that surgeons like the manufacturers to supply prosthesis in sizes as close together as possible, so that they never have a big jump up to the next size, thereby increasing the acetabular reaming.

[Baby Barista]

The components surgeons use is based first on the size and health of the femoral head. Then on the size of the femoral neck. They calculate once the bone is reamed and shaped, what will be the largest component they can install. The BHR cup is then based off of the head. It's why you'll always see surgeons prepare the head before they work on impacting the cup.

[Pat Walter]

Most I know do templating.  They also take one size larger and one size smaller into the operating room.  The medical rep is always there and can get a different size or give additional information or even call the company for very unusual problems.  I have watched live surgeries.

They do try to use a component that matches your one femur ball size. 

They better not size it incorrectly or you will have a lot of problems and a revision.  That has happened by some of the less experienced surgeons.  So use the top surgeons and they will size your device properly.

Pat

[Dannywayoflife]

I think BB and the others are right they template on X-rays and measure the femoral head when in theatre.

[happyhopper]

Many thanks for your responses.
Pat, as you have watched surgeries, would the size be worked out by the surgeon or his assistant?  Would there be any records kept of the calculations.  Also do the surgeons that you have seen operating make notes of what they find and what they do during surgery?
I also wonder what role does the assistant have during the surgeries you have seen.
I did, by the way, use a supposingly expert surgeon for my resurfacing!! 

[Dannywayoflife]

Happy hopper I see your in the uk. The easiest way to find out would be a freedom of information request to see your documents. Different surgeons will do things slightly differently and surgeons in the US will have different paperwork to do than NHS surgeons.

Where did you have your op done? Most hospitals have a foi department listed on their website.

[Pat Walter]

would the size be worked out by the surgeon or his assistant? - I watched Dr. Kusuma of OH and he does the sizing on the x-ray.  He discusses it with the medical rep which in this case was from Smith & Nephew.  I am pretty sure the surgeons do their own templating since this is very important and they are the ones with the hands on work.

 Would there be any records kept of the calculations - Dr. Kusuma had the templated x-rays taped to the wall where he would often look at it during the surgery. I don't know if he puts them back in the patient's folder.

Also do the surgeons that you have seen operating make notes of what they find and what they do during surgery - They don't make any notes during surgery since they are very busy.  This is something they do over and over, so they pretty much know what they are doing and don't make notes.

I also wonder what role does the assistant have during the surgeries you have seen - the assistant helps dislocate the leg and hands tools to the surgeon.  They do not do the surgery in the ones I have watched or the many, many videos I have seen at the courses.  There are a whole handful of people in the OR and they work quickly and very efficiently.  Each has a different job.  In most cases the surgeon does the more inner closing of the incision and the assistant finishes the upper layers of stitches or staple.  I think that varies some, but normally the surgeon does the inner work.

This is serious surgery and that is how it is approached in the OR.  Dr. Kusuma spent time studying the x-rays before surgery, too.  Then x-rays were taken after and he took a lot of time looking at those, too.  The medical representative is very important and is very knowledgeable.  They are in the OR too. 

I am sure each surgeon operates a little differently, but as far as I know and surgery videos I have seen at courses, they surgeon does the work.  The other people are there to aid him when needed.  The assistant can hold an instrument while the acetabular cup is placed.  Some surgeons hold it and tap it in place and others use an assistant to hold it so they can tap it with the hammer concentrating just on that part.  They use an assistant to dislocate the joint. 

Here is a full description of the surgery I watched

http://www.surfacehippy.info/observinglivesurgery.php

Pat

Pat

[happyhopper]

Many thanks Pat.
Thanks, also Danny, I already have received my medical notes from the hospital.

[Dannywayoflife]

I really truely hope you get sorted!

Danny

[keepmovin]

Hi All,
Just to add to this, you can also obtain the Operative Report from the hospital which documents the whole surgery from beginning to end, what they did, who did what, the attending surgeons, assistants, anesthesiologist, sizes of your components and much more.  Gives you a great understanding of what they were doing once inside!

Keepmovin