Dr Franz Birkholtz (Pretoria, South Africa)

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Quote from: Cooper on March 20, 2014, 09:19:03 PMDr. Franz,
You are awesome doctor. It will be my stupidity not to be your CLL patient. Can you please check on ERC device? I think it will be OK because patient in US are allowed to take it home.

It appears I might be your first patient unless someone beats me . I am looking forward to come in end of May.

Cheers!!!
I am teaching in Dallas end of may, but can slot you in as from first week june. Please confirm by email. I do not want to schedule official appointments via open forums.

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Quote from: Franz on March 20, 2014, 11:51:48 PMI am teaching in Dallas end of may, but can slot you in as from first week june. Please confirm by email. I do not want to schedule official appointments via open forums.

Yes Sir. Email already sent.

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Quote from: Franz on March 20, 2014, 11:51:48 PMI am teaching in Dallas end of may, but can slot you in as from first week june. Please confirm by email. I do not want to schedule official appointments via open forums.

You're coming to Dallas?! That's awesome! I live there

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So you guys know, Dr Birkholtz's contact e-mails and website have been updated on the first post of this thread.

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Quote from: Franz on March 23, 2014, 06:31:12 PMThe ratio is normally 0.8, ie tibia 80% of the length of the femur give or take.

So ideally, if one is able to do 2 LLs, one should aim to lengthen tibiae around 80% of the amount lengthened previously in the femurs to maintain the bio-mechanical ratio.

For example:

Femur: original length 40cm + 6cm of lengthening = 46cm final femur length

Tibia: original length 32cm + 4.8cm of lengthening = 36.8cm final tibia length

Original ratio: 32 / 40 = 80%

Increase ratio: 4.8 / 6 = 80%

Final ratio: 36.8 / 46 = 80%

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Quote from: Dingo on March 24, 2014, 01:00:29 PMSo ideally, if one is able to do 2 LLs, one should aim to lengthen tibiae around 80% of the amount lengthened previously in the femurs to maintain the bio-mechanical ratio.

For example:

Femur: original length 40cm + 6cm of lengthening = 46cm final femur length

Tibia: original length 32cm + 4.8cm of lengthening = 36.8cm final tibia length

Original ratio: 32 / 40 = 80%

Increase ratio: 4.8 / 6 = 80%

Final ratio: 36.8 / 46 = 80%

No. That would increase the ratio further. You can lengthen both equally and the ratio will be maintained.

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Quote from: Polycrates. on March 24, 2014, 06:37:30 PMNo. That would increase the ratio further. You can lengthen both equally and the ratio will be maintained.

You're wrong.

If your original dimensions are: tibia = 32cm and femur = 40cm >>> Tibia to femur ratio = 32/40 = 80%

If you increase the same amount, say 6cm on both tibia and femur you get >>> Tibia to femur ratio = (32+6)/(40+6) = 38/46 = 82,6%

To maintain the original ratio you have to increase the segments in proportion to the original ratio. This is basic math...

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Yeah, that was quite the blunder. Not only basic math but common sense. What I was trying to get at is that taking for instance, a lengthening of the femur 6cm, you can lengthen the tibia 6cm rather than 4.8cm and still have a ratio far closer to the original than you would create with adding just 6cm to the femur. With average limb lengths you'd probably change the ratio by 3% or so, as you've demonstrated, but the change becomes more drastic the shorter the original limbs are. With sensible lengthening in the 5-6cm range, I don't think maintaining the ratio to equality is needed at all, since most people lengthen one or the other and get away fine with a far different ratio than the original. Ideally, like you asked, I suppose you would if you wanted exactness. Nevertheless, you're completely correct and I'm quite the idiot for telling you that the opposite would be correct, and I'm sure your question was intended for Dr. Birkholtz anyway, so I'll let him answer.. Take it as a momentary lapse of reason. Sorry.

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double post...

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Quote from: Dingo on March 24, 2014, 01:00:29 PMSo ideally, if one is able to do 2 LLs, one should aim to lengthen tibiae around 80% of the amount lengthened previously in the femurs to maintain the bio-mechanical ratio.

For example:

Femur: original length 40cm + 6cm of lengthening = 46cm final femur length

Tibia: original length 32cm + 4.8cm of lengthening = 36.8cm final tibia length

Original ratio: 32 / 40 = 80%

Increase ratio: 4.8 / 6 = 80%

Final ratio: 36.8 / 46 = 80%

Absolutely correct. One of the reasons why we advocate 4-5 on tibias and 5-6 on femurs.