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Author Topic: actual femur lengthening amount?  (Read 963 times)

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lovinglonglegs

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actual femur lengthening amount?
« on: May 25, 2023, 08:47:31 PM »

i remember femur is not upright that the lengthening amount is not 100% going to your height, and i heard there's a formula to calculate this for your final height expectation. Does anyone know about that estimator?
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NailedLegs

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Re: actual femur lengthening amount?
« Reply #1 on: May 25, 2023, 11:19:05 PM »

Take a look at the video HJ did



tldr;

It doesn't generally matter, the difference will only be about .2cm - .4cm if you lengthen 8cm total. Don't worry about it.
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"Welcome to the worst nightmare of all... reality!"

Current LL plan:
QLL in Early 2025 using the PRECICE nail with Dr. Birkholtz.
4cm tibia, 4cm femur. One year later, re-break for another 4+4. 167cm -> 175cm -> 183cm

lovinglonglegs

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Re: actual femur lengthening amount?
« Reply #3 on: May 27, 2023, 09:01:55 PM »

thanks men
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Body Builder

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Re: actual femur lengthening amount?
« Reply #4 on: May 27, 2023, 09:34:48 PM »

The difference is about 10%. For instance you lose about 0,8cm for 8cm lengthening.
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lovinglonglegs

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Re: actual femur lengthening amount?
« Reply #5 on: May 28, 2023, 02:02:01 AM »

The difference is about 10%. For instance you lose about 0,8cm for 8cm lengthening.

you sure? i searched and most say it's only less than 0.5cm
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jerrytheman

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Re: actual femur lengthening amount?
« Reply #6 on: May 28, 2023, 05:57:12 AM »

when you stand up straight optimally and recovered from duck ass and stuff then 0. Think about it, when someone is 6 feet when they are optimally straight  and legs straight when measuring, they're not actually 6 feet when their legs are shoulder length apart, but they're still a 6 feet person. so who cares. You are exactly 8cm taller if that is what you lengthen.
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JON SNOW

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Re: actual femur lengthening amount?
« Reply #7 on: May 28, 2023, 05:34:25 PM »

average femur length is around 46 cm and the angle between the anatomical and mechanical axis or Q-angle, is 13-15 degrees in males

So:      {(y + x)(cos(14))}-{(y)(cos(14))}= ¨actual femur lengthening¨ or  anatomical axis length gain

where  y=femur initial length (cm)
          x=Limb Lengthening (cm)


           {(46cm + 8 cm)(cos(14))}-{(46cm)(cos(14))}=¨actual femur lengthening¨ = 7.76 cm   

           or   -.24  of less of actual height gain

PD:This would be on avg

« Last Edit: May 28, 2023, 06:57:09 PM by JON SNOW »
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JON SNOW

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Re: actual femur lengthening amount?
« Reply #8 on: May 28, 2023, 05:41:18 PM »

about 0.1 cm is gained with the osteotomy

and maybe a little more depending on the technique of the surgeon when inserting the nail

So the actual lengthening and height gain are a very close
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