Femur Lengthening over 5-6 cm inevitably lead to malalignment

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I was reading this thread about mechanical and anatomic axis and saw that Dr Franz Birkholtz added something that I hadn't read before

http://www.limblengtheningforum.com/index.php?topic=413.0

Quote from: Franz on March 12, 2014, 07:09:54 PMYes with exfixes we lengthen along the mechanical axis which should correspond pretty much to patient height. With femoral nails, we tend to lengthen along the anatomic axis, which might not correspond perfectly to height gain (it is oblique). It is well described too that patients end up with 5-10 mm less than expected. I would suggest going 1cm beyond target length and then backing the nail up by 5mm. This would ensure quick consolidation. The downside of long lengthenings along the anatomic axis (like with precice, guichet, betzbone, iskd), is that we change the mechanical alignment of the femur, as we lengthen along a different axis. This means that intramedullary lengthenings in the femur beyond 5-6cm will inevitably lead to slight malalignment. This may in time lead to arthritis.
In short, keep to reasonable distances and go to a doc that understands this.
Standing xrays can be taken with Precice nails with certain precautions.

Is malalignment and potential arthritis just one of the prices to pay if you want to do 8cm femur? Is there any way around this?

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Quote from: Apprehensive Finance on October 24, 2020, 02:32:07 AMI wonder how this would be for people with bow legs. If the axis is changed I wonder if the malalignment would be reversed if it were already malaligned. Also idk if this is necessarily true in general. Doctors like Paley say they won’t risk functionality for extra cm.

No idea for bowlegs. I believe Dr Birkholtz was talking about patients who don't have deformities.

Many Paley patients have done 8cm femurs so I'm not sure if that's a good example as it's quite possible someone could still be functional with a certain degree of malalignment. As you previously mentioned bow legs and there are many people who are mildly bowlegged who are very athletic.

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Quote from: Khaleddefine on October 24, 2020, 10:41:31 AMThere is a new method to lenghten in the anatomical axis without messing it up. Yeah the  world is changing

Care to elaborate on this new method? What is it and which doctors have performed this method?

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Very interesting Kilo. At the moment the consensus is that soft tissue stretching too far is the main problem with excessive lengthening, I have no doubt that 6cm femur would have a better long term outlook than 8cm, ceteris paribus.

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Quote from: MakeMeTallAF on November 30, 2020, 07:51:38 PMThat still uses retrograde insertion just like the Reverse Planning Method

You risk knee pain. I think it's better to just go with antegrade insertion and deal with the slight misalignment.

By the time we are old we will have a cure for arthritis anyways

Other option is to not go over 6cm in femurs and you can avoid knee pain and misalignment.