neuro-regeneration in ACL graft

[truthseeker]

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There was some suggestion that there might be some neuroregeneration of ACL grafts in animal models years ago. I looked in the resources that I have access to but haven't found any new information. If it happens, it would provide further evidence for having ACL reconstruction vs not having it done.

Does anyone know of any recent research that either suggests it does occur or doesn't occur? I had a patient ask me about it, I did my search and came up empty. I figured you all would have access to journals that I don't.

 

[skiz knot]

There was some suggestion that there might be some neuroregeneration of ACL grafts in animal models years ago. I looked in the resources that I have access to but haven't found any new information. If it happens, it would provide further evidence for having ACL reconstruction vs not having it done.

Outcomes in patients and return to sport is reason to have ACL surgery, not because some disorganized, non-functioning tissue is, or is not present.

 

[truthseeker]

Outcomes in patients and return to sport is reason to have ACL surgery, not because some disorganized, non-functioning tissue is, or is not present.

You didn't answer my question.

The lack of size of the ACL and most other ligaments do not support their role as an end range restrictor, but rather a mechanoreceptor vessel that inform the rest of the system to get the limb out of a dangerous position.

Good outcomes result from good proprioception among other things. An injury to a graft can repair itself because it revascularizes. I am asking has there been any new research into humans that suggest that mechanoreceptors also grow into allografts or autografts. I suggest that if outcomes with surgery are better than without, is it because the proprioception input from the properly placed graft returns.

 

[skiz knot]

You didn't answer my question.

The lack of size of the ACL and most other ligaments do not support their role as an end range restrictor, but rather a mechanoreceptor vessel that inform the rest of the system to get the limb out of a dangerous position.

Good outcomes result from good proprioception among other things. An injury to a graft can repair itself because it revascularizes. I am asking has there been any new research into humans that suggest that mechanoreceptors also grow into allografts or autografts. I suggest that if outcomes with surgery are better than without, is it because the proprioception input from the properly placed graft returns.

Many biomechanical studies have shown strength of the native ACL as well as strength of allo/autograft reconstructed ACLs are strong enough to withstand the physiologic loads placed on it during daily and sport activities, provided they joint is not placed into at risk positions (valgus, rotation, etc...) No biologic tissue is able to fully prevent injury when extreme stresses are placed through it. I agree that proprioceptive nerve fibers of ligaments play an important and incompletely understood role in normal joint. It is known that normal knee kinematics do not completely return after ACL reconstruction, placing additional strains on secondary stabilizers of the knee (meniscus, capsule, IT band, MCL, etc...). The kinematic alteration has been postulated to be a factor explaining the observation that knee arthritis rates are similar in ACL reconstructed knees and chronic ACL deficient knees. Some studies have even suggested lower rates of OA in non-reconstructed knees. This is, as I'm sure you are aware, a very controversial area.

I am not aware of research that shows if nerve regenerates into the graft, but I do not think that is a major contributing factor to good patient outcomes after ACL surgery (I could be wrong, I'm not an expert). I would postulate that any improved outcomes (return to sport/lack of subjective instability) is more likely a result of the mechanical constraints of the graft than any contribution from any ingrowth of proprioceptive nerve fibers.

 

[truthseeker]

thanks

 

[skiz knot]

You're welcome. I think the topic you bring up is an interesting subject and worthy of future research. Someday graft neuroregeration may be an important adjunct to treatment as surgical and rehab protocols continue to improve.

 

[truthseeker]

I have read more research that supports the ACL as a sensor than I have as a rope. Successful rehab currently entails training the remaining sensory systems to make up for the loss of the proprioception from the torn/grafted ACL.

Using the same rationale of the graft as a scaffold that becomes ligament-like by allowing re-vasularization I would think would allow re-innervation.

To me, if there were neural regeneration, it would better explain why reconstruction is better than remaining ACL deficient. I would think that those who did the revascularization studies could look back at the histology of the slides they took and see if there is any neural tissue.

 

[skiz knot]

Successful rehab currently entails training the remaining sensory systems to make up for the loss of the proprioception from the torn/grafted ACL.

To me, if there were neural regeneration, it would better explain why reconstruction is better than remaining ACL deficient.

It makes perfect sense to undergo proprioceptive training to prevent recurrent injury, as well as to prevent injury (in women at least).

As for the second statement, you have to define "better." ACL reconstruction is "better" than no reconstruction for those that desire return to high level sporting activities and in those with symptomatic instability. Many people will have perfectly acceptable outcomes without ACL reconstruction and can do sporting activities that don't require significant cutting/pivoting without having to undergo surgery/rehab. Long term outcomes with ACL reconstruction and chronic deficiency are otherwise equivocal (and controversial).

 

[truthseeker]

I guess my question would be: What makes a reconstructed knee have a better result for an athlete than rehab alone? I don't buy that the ligament/graft is structurally strong enough to handle a big pivot episode. So, it would lead me to believe that it is enhanced proprioception that primarily improves outcomes/performance. I suspect that the suggestion of the return of mechanoreceptors may actually imply the return of the graft to its primary role of proprioceptor. I think the structural role is secondary.

I don't think the right studies have been done to prove or disprove that theory. IF that study is done, AND it supports my hypothesis, then surgery would probably be deemed less necessary for athletes.

Right know, if my son or daughter tore their ACL I would encourage them to have the surgery. I do think, however, that the rehab that occurs in both scenarios may be more important that the reconstruction itself. This opinion is obviously biased by my point of view as a PT/ATC and not a surgeon.

 

[skiz knot]

I guess my question would be: What makes a reconstructed knee have a better result for an athlete than rehab alone? I don't buy that the ligament/graft is structurally strong enough to handle a big pivot episode. So, it would lead me to believe that it is enhanced proprioception that primarily improves outcomes/performance. I suspect that the suggestion of the return of mechanoreceptors may actually imply the return of the graft to its primary role of proprioceptor. I think the structural role is secondary.

I don't think the right studies have been done to prove or disprove that theory. IF that study is done, AND it supports my hypothesis, then surgery would probably be deemed less necessary for athletes.

Right know, if my son or daughter tore their ACL I would encourage them to have the surgery. I do think, however, that the rehab that occurs in both scenarios may be more important that the reconstruction itself. This opinion is obviously biased by my point of view as a PT/ATC and not a surgeon.

What is the point of your post? To give your opinions and conjecture? You have access to pubmed, right? Yes, you do. Go to your local library, if you're no longer affiliated with an academic institution, and ask them to obtain a copy of any article in which you are interested. It is free.

 

[truthseeker]

What is the point of your post? To give your opinions and conjecture? You have access to pubmed, right? Yes, you do. Go to your local library, if you're no longer affiliated with an academic institution, and ask them to obtain a copy of any article in which you are interested. It is free.

I suppose thats part of it, but really what I would like is to spark some interest in doing research into the matter by someone who has access to a much larger population than I do.


I looked back and found that yes, I am the only one who has given their opinion.