I recently made another thread on this forum with the subject title 'Soft tissue adaptation is the biggest obstacle found in limb lengthening' in which I put forward 2 questions regarding soft tissue for discussion by members, which I had originally put to Dr Birkholtz in his respective thread. I thought people would be interested in seeing his answers so I will post them here.
3) Soft tissue is one of the largest issues in regards to limb lengthening. Is there a medical consensus on why soft tissue doesn't adapt the same way it does during natural bone growth? We are all aware that after growth plates fuse no more growth can occur even under the same hormonal conditions but why does the same issue of growth of soft tissue occur where they technically have no 'end point' similar to plate fusion? Could one not accurately reproduce the hormonal conditions in soft tissue growth to mimic that found in natural growth? I believe I have read some studies that refer to issues with cell reproduction of soft tissue in regards to this.
The main difference in soft tissue adaptation to growth during normal growth vs CLL growth, is the rate at which it occurs. It seems like one of the ways that soft tissue adapts to growth is because of a constant distraction force which triggers gene expression and provides soft tissue growth. In normal growth, this rate of elongation is quite slow and as a result the tissues grow at the optimal rate and can 'keep up'. In limb lengthening we have to speed up the process because the bone will consolidate prematurely if we stretch too slowly. If we could drop distraction rates down to 0.1-0.3mm per day, we will probably have soft tissues that will adapt better. In addition there is probably some form of genetic trigger that switches off after normal adolescent growth, similar to a growth plate closing. Lastly, the predominant protein in soft tissue is collagen. It does become less supple as time goes on, and this is a result of aging. This causes more resistance to stretching as well.
4) A second question regarding soft tissue, after leg lengthening, does the body ever truly recover to the stretching even several years after combined with consistent physical therapy (if lengthened to reasonable standards rather than over lengthening leading to plastic deformation which I assume is permanent), creating new tissue as found in someone with legs of that natural length or does the body just adapt and become more flexible rather than truly recovering, with the soft tissue always being stretched to accommodate the new bone?
Although distraction histiogenesis does cause new tissue to form (ie grow properly), there is an element of elongation through stretching. One of the reasons why realistic lengthening goals should be borne in mind.
6) Is there truly such thing as 100% recovery in regards to cosmetic leg lengthening when the soft tissue is stretched any amount reasonable or not or will it always limit maximum athletic potential even if its imperceptible?
I think that with current technologies available, athletic potential is definitely affected regardless of lengthening amount. Whether it is noticeable in an individual would depend on factors like pre-op status, flexibility, genetics, lengthened amount, technique etc etc.
I hope you find this information as interesting and enlightening as I did, there are some other answers in the thread about biomechanics and ratio etc. that I would advise reading if you are interested. These answers seem to go against some of the more optimistic views which often are just wishful thinking in regards to such a serious surgery. It seems there will always be a permanent athletic trade off in LL regardless of amount lengthened.
Perhaps technology will advance to the point where some system can be put in place to stretch soft tissue prior to any surgery over the course of a year or so at a much slower rate meaning that the tissue will have been stretched at a much more reasonable speed and amount and be already be at the correct length for the increase in bone, delay union to lengthen at a slower rate or use stem cell/hormonal therapy to repair the damaged tissue. The future can't arrive soon enough.
Thoughts?