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[gettingtaller]

People talk about 6cm being the safe limit for femurs. I'm already way past that and I've met lots of other betz patients who have passed that and have or are having a good recovery.  So where does this safe limit originate? Do the surgeons who advise this do it because their nails or techniques do not allow them to go much beyond that? Is it their insurance companies telling them to say this to cover their asses against future liability claims? Are there documented cases of really bad things happening? Fwiw I got minor nerve damage beneath my knee at 5cm, since then everything has been fine. I'm at 8cm and could easily go more (my body isn't freaking out). I hear people on this forum refer to it as though it's some kind of gospel thus perpetuating this (what could be) a theoretical or "finger in the air" safe limit. Just wanted to hear what people think.

[Claude]

Hi. There are some papers about this safe limit and i think it's more about 7.5 cm for the tibia. But as it is an average limit it only means that most people shoudln't do more. And it should mean that the "safe" limit is also a little more if you do femurs. As i said its only around 7 cm for most people, but you can do 9 cm and be ok, or more. It depends on the technique used i think also (external or not). Well this is my POV.

[BilateralDamage]

Good question, I believe a lot of doctors suggest this limit, but there's no real studies or evidence to show that it's unsafe to go beyond the amount.  Doctors generally recommend at most 5 cm on tibias, but then you have other doctors who are willing to do 12 cm on the tibias without any concern.  Guichet has a 10 cm limit because that's as long as his nail will go and Paley has an 8 cm limit for the same reason.

I think everyone's bodies are physiologically different and some people can go above and beyond what others do.  It's all about how your body responds to the lengthening.

[theuprising]

I highly recommend reading the Dr Birkholtz thread and Dr Lee on old forum  where they discuss this.
Other than obvious proportion issues it has alot to do with your soft tissues, they can only be stretched
to a certain point before they become permanently weakened. Dr Lee suggests you should ideally lengthen 15% of original bone length however up to 20% is possible. I don't think they are just
saying it to cover their asses rather what offers the safest and most  reliable recovery for the patient.
Dr Birkholtz also mentions that the greater the distance lengthened the higher the likelihood for arthritis
later on. As I mentioned earlier he explains it far better than I can in his thread so check it out.

[TRS]

I guess the safe limit is an individual matter. Some people can go for further lengths while others may not. Some doctors say not to go beyond 5 cm in any segment, some say you can do moderate lengthening upto 7.5 cm while other doctors do permit beyond 8 cm. Dr.Lee suggests 15% of the original bone length so people with longer bone will be able to lengthen more.
But then again, most doctors usually encourage people to stick with small targets as possible, maybe due to higher risk of early arthritis from the added pressure on the adjacent joint (more length=more pressure). Another possible reason is that internal femur lengthening is along the anatomical axis which causes a change in the mechanical axis. Here is the quote from Dr.Birkholtz

 

Great question,

Yes 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.

So from this perspective, the "safe" limit not only tries to reduce risk from the complications that may arise during lengthening but also tries to reduce the risk of developing arthritis in the long term.

[Claude]

Good question, I believe a lot of doctors suggest this limit, but there's no real studies or evidence to show that it's unsafe to go beyond the amount.

There are some studies. Anyway you just have to listen to your body (feel the vibe  ).

[theuprising]

Gettingtaller want to know why you are asking now and not before you started lengthening?

[Hanna84]

This question will be answered 100% honestly, when other doctor's devices will be able to lengthen more than they can now... ;-) Paley used to say that 6,5cm is safe... That's what precice 1 was able to lengthen.
In general, it depends a lot on your individual body and healing capacities

[gettingtaller]

Gettingtaller want to know why you are asking now and not before you started lengthening?

Uprising, why do you assume I didn't??

[theuprising]

Uprising, why do you assume I didn't??

Obviously since you are already way past the recommended limit. Second obvious one
is that you made this thread.

My thinking was exactly like yours when I first found LL wanting to do the maximum amount
and finding a surgeon who would do it. The more I researched you realise that just because
something can be done doesn't mean it should. This being said good luck with recovery if
you had a tall enough starting height you should have a better time of it.

[gettingtaller]

Obviously since you are already way past the recommended limit. Second obvious one
is that you made this thread.

My thinking was exactly like yours when I first found LL wanting to do the maximum amount
and finding a surgeon who would do it. The more I researched you realise that just because
something can be done doesn't mean it should. This being said good luck with recovery if
you had a tall enough starting height you should have a better time of it.

Of course I asked before lengthening, your question was just bizarre.  You'd be brain dead if you didn't.
This is a forum of people with a shared interest and I'm curious about what the LL collective thinks about this.

[theuprising]

Of course I asked before lengthening, your question was just bizarre.  You'd be brain dead if you didn't.
This is a forum of people with a shared interest and I'm curious about what the LL collective thinks about this.

Gettingtaller as it appears from your response that you have already asked about safe lengthening limits prior to asking it here
for the benefit of the forum can you please post any medical sources of where lengthening your femur 9 to 10 cm is recommended as being safe
and leading to no longer term problems.

Also for your consideration from the Dr. Donghoon Lee thread

4. What are the lengthening limits for your procedures?
There are no limits to bone lengthening itself, but in reality there are limits because of soft tissues. To minimize various complications resulting from limb lengthening, it is recommended that lengthening is performed under 20% of the original bone length. 15% will be even better.
Limb lengthening is a process that involves not only the bone but also the soft tissue surrounding the bone. Especially when muscle is lengthened, even after recovery, sports ability (especially when playing vigorous sports) might not return 100%. The more the bone is lengthened, the more probability sports ability will not fully recover.
According to Park’s report (Park HW et al, JBJS,2008 ), 25% of the people who lengthen the tibia(6cm in average) was found to have some difficulties in persuing vigorous activity.
If both Tibia and Femur are lengthened sequentially, the maximum to be 10cm in total. But, one more important thing is to consider body ratio. So, I recommend to decide the target considering the safety, recovery of sports activity and body ratio.
 
http/www link edit -   http://www.limblengtheningforum.com/index.php?topic=145.0 

[theuprising]

Noticing you asked about safe lengthening in the Birkholtz thread he had already answered your question on Page 16.


Question asked by handy
Dr. Birkholtz-  Why would lengthening 5-6cm be any safer than 6.1-8cm in terms of only malalignment? If lengthening along the anatomic axis with internal nails causes malalignment, since you're not lengthening along the mechanical axis, wouldn't any amount of lengthening then cause malalignment? What is it about lengthening 5-6cm and malalignment that makes it any safer than 6.1-8cm if all internal lengthening causes malalignment?

Birkholtz reply:
You are right. ANY lengthening along the anatomic axis will cause malalignment. As with most things in life, it is the magnitude that counts. Smaller distances will cause smaller malalignments and larger distances may lead to significant malalignments.



Which is why it keeps being stated on here that the more you lengthen along the anatomic axis (femurs) the larger your malalignment is and the more likely problems will be down the track. Not that you will definately get them but you are more likely to than someone who lengthened a more sensible distance.

[onedayillgrow]

So basically lengthening 5-6cm or aroundabout the 15-20% original bone length is good? Like the recovery is not guaranteed, i understand that, but it is a pretty damn good chance you'll recover quite well with adequate care, doctor and practice? If so that is such good news because i only want to lengthen 11-12 cm, 6cm femur and 5.5 - 6cm tibiae. Does that sound like a good ratio for recovery?

[gettingtaller]

Noticing you asked about safe lengthening in the Birkholtz thread he had already answered your question on Page 16.


Question asked by handy
Dr. Birkholtz-  Why would lengthening 5-6cm be any safer than 6.1-8cm in terms of only malalignment? If lengthening along the anatomic axis with internal nails causes malalignment, since you're not lengthening along the mechanical axis, wouldn't any amount of lengthening then cause malalignment? What is it about lengthening 5-6cm and malalignment that makes it any safer than 6.1-8cm if all internal lengthening causes malalignment?

Birkholtz reply:
You are right. ANY lengthening along the anatomic axis will cause malalignment. As with most things in life, it is the magnitude that counts. Smaller distances will cause smaller malalignments and larger distances may lead to significant malalignments.



Which is why it keeps being stated on here that the more you lengthen along the anatomic axis (femurs) the larger your malalignment is and the more likely problems will be down the track. Not that you will definately get them but you are more likely to than someone who lengthened a more sensible distance.

Thanks uprising. This isn't very clear to me however. Reduced function I kinda get but the good dr doesn't really go into specific examples of problems. From the consultations I had before my surgery, it came down to how much your body could stretch during lengthening before it gave up or you fell over from intolerance. The other consideration was cosmetic proportion. I'm not so naive to think that changing something like this isn't going to have an impact but going from 6cm to 9cm? What more damage are you actually doing? I've met some patients that went to 9 or 10 who came back for nail removal and they appeared to be doing just fine. You wouldn't think they'd had LL. Both betz and guichet advocate long lengthening as long as your body can handle it e.g. Your IT bands don't go to hell leaving you looking like John Wayne. As I write I'm at 8.7 on my left leg so will hopefully stop clicking it in 3 days...so far (touch wood) I can say it's not been as hard as I was expecting, maybe this is the big difference between internals and externals.

[theuprising]

Hey gettingtaller if you don't mind me asking how old you are as your LL has
gone so smoothly I'm guessing you are 25 or under? Also what is your wingspan?

It has a big effect on how much lengthening can be done and look ok.

[gettingtaller]

Lol. I started my ll at 39 and turned 40 a month into it. I have amazing bone consolidation too. Betz nearly fell off his chair when he saw how much bone cloud I had I'll upload an X-ray tomorrow.

[rickybobby]

gettingtaller,

did dr. b say anything about knee pain if you get to a certain point?

[gettingtaller]

He said it's very likely after 8cm and I have if now but only at night when my leg is jb the sane position for too long. It's temporary. Goes away after you stop clicking and your body adjusts. Takes about a week after clicking.

[hanshi]

Lol. I started my ll at 39 and turned 40 a month into it. I have amazing bone consolidation too. Betz nearly fell off his chair when he saw how much bone cloud I had I'll upload an X-ray tomorrow.

Hello Gettingtaller,

it would be nice if you actually posted that x-ray. It would be quite interesting to see those 2 diffent nails.
Thank you in advance.

[gettingtaller]

Kinda busy with family at the money but will upload when I get back in front of a pc.

[hanshi]

Kinda busy with family at the money but will upload when I get back in front of a pc.

Hello, are still planning to upload those x-rays or not?

[Astronomy]

Thats the puzzle I used to be eager to figure out.
I think only number cant foresee how much you can elongate by.
The limit,in my narrow opinion,is legisated when you feel hell of pain and cant go on.
So two popular saying like"u cant go over 20％ of your bone lengthen"and"8cm for femur,5 cm for tibia"aint logical and critical.It just depends.