Femur lengthening and mechanical/anatomical axis angles

Hi,
I’ve been reviewing information about various LL clinics with affordable prices and was considering Turkish ones. They quite often prefer to do Femurs as it allows to gain more height – 8 to 10cm. However, as an engineer I’m bothered with one question.

While tibia is perpendicular to the ground and leg overall, femur has this Q angle that technically positions it diagonally from outer side of your leg going to inner one (from top to bottom). Femur lengthening over nail (both LON or precise) is performed over your anatomical axis. It means that if you simply lengthen the femur bone, the more you lengthen it, the more it forwards “inside” to inner space between your legs. In other words – making your knees to be closer and breaking the mechanical angle.

To represent it visually I prepared a picture with comparison that I made myself.

 First comparison shows shift in mechanical angle, second one compares space between legs from pre-surgery to after-surgery, last one is same as second one but vice-versa.

I thought that maybe there’s a way in which doctors fix this mess by using a nail that is not fully straight for example, but found some articles and researches saying that there’s 1* angle change by each 1 cm of lengthening. And while natural angle is 6 degrees you can calculate how it is changed by lengthening femurs for 8cm.
Article 1: The effect on mechanical axis deviation of femoral lengthening with an intramedullary telescopic nail
Article 2: Effect of lengthening along the anatomical axis of the femur and its clinical impact

Now, can anyone explain why am I not seeing such information anywhere and not hearing others to speak about it loud? Does patients just prefer height over straight legs with healthy knees? I even wrote to couple of doctors directly, but they replied that 1) yes, they lengthen over anatomical axis 2) no, somehow magically mechanical axis is not changed (no proves ofc.)

I’d like to hear others opinions as I want to decide for myself if Femur is a no go and I should chose tibia no matter what or there’re clinics that do lengthening and correct the angle/axis to be the same by adding small curve (bend) to the segment of bone that gets extended. I do not trust doctors anymore (at least turkish ones) as it looks like they just want money and will blindly claim that everything will be great without any details or explanations.

Thanks!

 Bump. This needs to be adressed.

Nice.
This is for someones who believe that 8-10 cm in femurs is a piece of cske while they swear that everyrhing more than 5cm on tibias will ruin your legs.
I never understood why even some doctors like Betz, who have good reputation (I don't know why) let their patients do some crazy amounts like 10-12 cm on femurs and most of them ended up with terrible knee pain etc. These pictures explain a lot.

So, of course femur LL is not safer than tibia one. Easier maybe (with internals only of.course) but no way safer in the long run.

What about lengthening up to 5 cm? Or up to 6.5 cm? Of course 10 cm is too much and it might produce visible changes in femur curvature but at least with conservative amount of lengthening, the mechanical axis won't deviate that much.

I'm too worried about this issue as I want to lengthen my femurs first since they're quite short and lengthening my tibia only for 5 or even 6 cm won't do that much for my starting height of 165 cm. I want to lengthen at least 6.5 cm on my femurs and at least 5 cm on my tibia for meaningful height gain of 11.5 cm and get long legs. Without doing femur and only doing tibia, I won't look good and the height gain won't be enough.

There are atleast 4 people on this forum with proven 11/12 cm femur. It takes much more time to recover for sure, but still noone of them had problems like some people in Turkey after 5-6 cm. I think it's just the best way if you want to have one surgery in your life and foreget about everything + you want to be quite mobile during the lengthening.

There's no way you can get away without doing tibia too after you lengthen past 5 or 6.5 cm on femurs, it will just look very bad when nked and biomechanics will be ruined too.

IMO, for most people who have about 0.80 tib/femur ratio, the best split is something like 6.5 cm on femur and 5 cm on tibia or 8 cm on femur and 6 cm on tibia if one needs to lengthen within the maximum possible safe limits. Minimum is 5 on femur and 4 on tibia to be worthwhile but 6.5 / 5 split is decent and lies in the middle of conservative and upper safe limits. 11.5 cm is half a head (assuming 23 cm is average head length of males) so 50% head length increase is a significant height increase IMO.

Quote from: lucindaris on August 09, 2024, 12:13:36 PMThere are atleast 4 people on this forum with proven 11/12 cm femur. It takes much more time to recover for sure, but still noone of them had problems like some people in Turkey after 5-6 cm. I think it's just the best way if you want to have one surgery in your life and foreget about everything + you want to be quite mobile during the lengthening.

11-12cm are never the best way. Sooner or later you are going to have problems, epsecially knee pain.
Tall who did 11cm with Betz after a few years had terrible knee pain and did tibia LL also (while he didn't want as he was almost 1.90 after femur LL) trying to restore some of the femur-tibia ratio and fix his pain, I don't know if he made it though after tibia LL.
And also with 11-12 cm on femurs you'll look terrible.
So your advice is pure catastrophical. Noone should ever go for more than 8cm.

Quote from: Body Builder on August 09, 2024, 03:07:38 PM11-12cm are never the best way. Sooner or later you are going to have problems, epsecially knee pain.
Tall who did 11cm with Betz after a few years had terrible knee pain and did tibia LL also (while he didn't want as he was almost 1.90 after femur LL) trying to restore some of the femur-tibia ratio and fix his pain, I don't know if he made it though after tibia LL.
And also with 11-12 cm on femurs you'll look terrible.
So your advice is pure catastrophical. Noone should ever go for more than 8cm.

Knee pain is really unpredictable imo and could happen to anyone doing LL due to obvious strain but most of the times it will eventually go away.

What matters here is not how much you decide to lengthen, but how the amount you lengthen changes the shape of your legs and whether doctors are able to prevent that during the surgery.

This was brought up some years back. This thread also made some interesting points:

http://www.limblengtheningforum.com/index.php?topic=2090.msg33657#msg33657

Quote from: KiloKAHN on August 10, 2024, 01:34:00 AMThis was brought up some years back. This thread also made some interesting points:

http://www.limblengtheningforum.com/index.php?topic=2090.msg33657#msg33657

In your opinion, which method allows to minimize malalignment and knock knees? Taylor, LATN, LON, or internals like Precice? Or is it solely dependent on the technique used by the surgeon?