Lefort1 cut, ccw and nose altering

[jawguy123]

Very interesting. Do you have the measurements of the final result? Just interested since I see that these displacement measurements are made in mm with 2 decimal accuracy, and I have to wonder if such accuracy is even close to possible to reproduce at the actual result, or what kind of accuracy the surgeons work with. I would to some extent suppose that these are more like guidelines?

If you look at ISU1 (midline of upper incisor) planned movement you'll see relatively "neat" numbers -- 10.00mm advancement, 0.50mm left, 3.50mm up. This suggests that the surgeon "manually" planned/specified the movement of the upper incisor midline, and the other landmarks' numbers are generated (mostly) computationally.

Obviously 1/100th of a mm accuracy is not achievable. https://www.ncbi.nlm.nih.gov/pubmed/28950997 is one example of a study measuring accuracy in VSP cases.

I see e.g that your ANS is advanced less than your A point etc, is this the mechanics of the ccw rotation working?

Yes.

Is this considered a large advancement of the maxilla, or in what region are we? Looking at your pictures it's a noticeable change (you look great). Just asking because my surgeon haven't provided me with a real plan, just said "slight" maxillary advancement, and in my case, I think your 6mm would be too much for me.

I'd say ~7.5mm of anterior movement at A point is a relatively large advancement (not a "slight" one). However, I would say it's good practice to ask for your surgical plan before your actual surgery.

[Dogmatix]

If you look at ISU1 (midline of upper incisor) planned movement you'll see relatively "neat" numbers -- 10.00mm advancement, 0.50mm left, 3.50mm up. This suggests that the surgeon "manually" planned/specified the movement of the upper incisor midline, and the other landmarks' numbers are generated (mostly) computationally.

Obviously 1/100th of a mm accuracy is not achievable. https://www.ncbi.nlm.nih.gov/pubmed/28950997 is one example of a study measuring accuracy in VSP cases.


Yes.

I'd say ~7.5mm of anterior movement at A point is a relatively large advancement (not a "slight" one). However, I would say it's good practice to ask for your surgical plan before your actual surgery.

Interesting report. Basically in a context where people discuss jaw movements with mm or even more accurate, the reality is that the result is 1mm+-1 (roughly), so it can be 2mm difference within one standard deviation.

You say 7.5mm is a rather large advancement, but is it really sensible to discuss surgery if the deviations are smaller, given the accuracy you can operate at? I mean, giving a surgery where the planned advancement is 2mm, and at worst case you end up at 4mm, so you're basically at same situation as before, just at the other end.

I've been looking at a lot if surgery movies, and there doesn't seem to be much magic going around in the surgery room. They use same tools as I have in my toolbox, saw, hammer etc and it doesn't exactly seem to be laser precision.

[jawguy123]

You say 7.5mm is a rather large advancement, but is it really sensible to discuss surgery if the deviations are smaller, given the accuracy you can operate at?

I'd say it's important to consider the context of the deviations. I believe that the study only looked at the "absolute deviation" (made up term) -- the deviation of say point A from the planned position. I'd bet that the "occlusal deviation" (made up term) -- the deviation of the actual occlusal relationship from the planned occlusal relationship -- is less than the absolute deviation, due to the accuracy of the surgical splints.

Since the goal of orthognathic surgery is often to improve occlusion, those 1-2mm absolute deviations really don't matter so much.

Also, 1mm deviations don't have a significant effect on appearance. You give an example of a 2mm advancement, but no one would get a 2mm advancement for solely the sake of 2mm advancement.

[PloskoPlus]

At the end of the day the surgeon follows the occlusal splint. The best surgeons have 1mm accuracy.

[bex]

Very interesting. Do you have the meassurements of the final result? Just interested since I see that these displacement meassurements are made in mm with 2 decimal accuracy, and I have to wonder if such accuracy is even close to possible to reproduce at the actual result, or what kind of accuracy the surgeons work with. I would to some extent suppose that these are more like guidelines?

I see e.g that your ANS is advanced less than your A point etc, is this the mechanics of the ccw rotation working?

Is this considered a large advancement of the maxilla, or in what region are we? Looking at your pictures it's a noticeable change (you look great). Just asking because my surgeon haven't provided me with a real plan, just said "slight" maxillary advancement, and in my case, I think your 6mm would be too much for me.

I'm admittedly a hell of a lot less knowledgeable than others in this thread about the more technical aspects of the surgery, but I'll try to answer what I can (all, please feel free to correct any info that I've misunderstood/is inaccurate)

• (1) I don't have the final measurements, but when my surgeon debriefed me post-op, he reminded me that the VSP is not 100% exact, but they try to adhere to the plan as much as possible. Because the plates you see in the VSP (see below) are custom to my face, it more or less requires that the movements here adhere to the plan. I can't imagine that the movements differed too much from the plan that I shared, aside from the pogonion advancement.
• (2) Yes, that sounds right. I also included the VSP visuals below, if that helps to visuals the movements.
• (3) As I mentioned, this surgery was a medical necessity. My bite was perfect, but my airway was collapsing when I slept and exercised, and the lack of oxygen was causing some serious health issues. It's my understanding that in order to have this surgery covered by insurance (as mine was), your surgery must require pretty significant advancement. So - that being said, I think you're correct in your assumption that 6mm is much greater than your surgeon's idea of a "slight" advancement.

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[Dogmatix]

At the end of the day the surgeon follows the occlusal splint. The best surgeons have 1mm accuracy.

Yes, but correct me if I'm wrong. The occlusal splints say noting about the relationship to the skull, just the relationship between the jaws themself. In case if a bimax you fracture both jaws so they basically move freely. The occlusal splints give the surgeon the exact teeth match, but the other part is how you attach the maxillomandibular complex back to the skull which gives the aesthetics, and seems far less accurate and more of a free hand work.

[jawguy123]

Yes, but correct me if I'm wrong. The occlusal splints say noting about the relationship to the skull, just the relationship between the jaws themself. In case if a bimax you fracture both jaws so they basically move freely. The occlusal splints give the surgeon the exact teeth match, but the other part is how you attach the maxillomandibular complex back to the skull which gives the aesthetics, and seems far less accurate and more of a free hand work.

Bex's surgeon actually used custom made plates (though her surgeon is in the minority) to get more precise movement. These plates guide the maxilla directly in relationship to the skull. Check out the picture "VSP - KLS Plates.jpg" she posted.

[april]

Bottom line is that any displacement to ANS-PNS will also be a displacement to ANS and therefore a displacement to the base of the nose whether it's noticeable or not. Good surgeons anticipate the possible UNFAVORABLE very noticeable nose changes and can do a variety of techniques to mitigate those types.

Would ANS reduction/shaving be one of those techniques?

Do you know in which situation that would be most indicated? An already open nasolabial angle pre-surgery?

[kavan]

Would ANS reduction/shaving be one of those techniques?

Do you know in which situation that would be most indicated? An already open nasolabial angle pre-surgery?

Sometimes.

When there is too much tension to the upper lip nose angle giving an OPEN angle. So it would be done to make the angle LESS.

[wigglewiggle]

The displacement of the ANS is what would be seen as a change to the base of the nose and sometimes right under the base of the nose at where the upper lip area (or labial ledge) is close to the base of the nose. So, when ANS-PNS is along a positive slope line, moving 'forward' with linear advancement will bring forward the base of the nose and the tip area is advanced and can rotate up slightly. For someone with a narrow nose base and a dorsal hump, it would improve the nose contour. But if they had a wide nose base and already upward tilted nose, it would just exaggerate that particular aesthetic problem.

Could you explain what type of ANS-PNS movement would be considered "moving forward" resulting in bringing forward the base and tip of the nose?

More specifically I'm wondering if my planned maxillary movement would fall into your description.

Thanks!

[PloskoPlus]

Could you explain what type of ANS-PNS movement would be considered "moving forward" resulting in bringing forward the base and tip of the nose?

More specifically I'm wondering if my planned maxillary movement would fall into your description.

Thanks!

Looks like setback.

[Dogmatix]

Could you explain what type of ANS-PNS movement would be considered "moving forward" resulting in bringing forward the base and tip of the nose?

More specifically I'm wondering if my planned maxillary movement would fall into your description.

Thanks!

You have a negative sign on your A-P movement of ANS, meaning to move the ANS back. So this is the opposite of advancing the base of the nose.

Am I right that you have a rather large overjet and some gummy smile?

[kavan]

Could you explain what type of ANS-PNS movement would be considered "moving forward" resulting in bringing forward the base and tip of the nose?

More specifically I'm wondering if my planned maxillary movement would fall into your description.

Thanks!

With reference to the maxilla, displacement in the Anterior-Posterior (A-P) direction that is  denoted by a + sign, before the number denoting the millimeter displacement, refers to ADVANCING an area 'forward'.

Look at the SIGN (+ or -) before the number denoting the millimeter displacement on your chart and it should be self explanatory whether or not you planned maxillary movement would fall into my prior description.

[Post bimax]

Add-on question to this thread- does anyone know if a setback of the maxilla would actually narrow the nose (opposite of the widening effect when advancing)?.  Intuitively it seems this would be unlikely; just as when certain materials are 'stretched out' they do not revert to their original form on release of tension.

[GJ]

I don't think so, because what causes the widening is cutting the muscles. This is why the stitch is useful keeping the muscles in place.
Maybe it's possible to go in and try to reattach those muscles. That I don't know.