I just want to add the front and sied view of the referenced before and after because it is much more useful (you can find the original on IG).
https://imgur.com/a/84uVctq
Good example. Same result (from front) not possible with only genioplasty in my opinion. It is a good example because it shows a case where someone does not have a very steep angle (I hope I see this correct) and who did not rotate the segment (or not much, not 100% sure by the scan) by lowering the back more. It looks like he lowered the whole segment almost equally and moved it forward.
Correct observation.
On this example, we have the before and after ( cuts on ceph) to observe and cross reference the BASIS of an opinion. Your opinion is based on observing the correct geometric relationships that apply to the example shown whereas the poster expressing the opinion that chin wings are just like someone elses normal sliding genio and/or are just 'invasive genios' belies he's not observing the cephs right in front of him, which clearly show the chin wing cut, in that particular person, is NOT at all like a genio. So, if he saw some photos of a person with a chin wing that looked no different to him than just a genio, he may have seen a photo of someone who had too high of an MPA to begin with which would have precluded getting a full chin wing cut that goes through the posterior jaw angles.
So, yes, indeed, there is a relationship between angle of inclination of the MPA and ability to make a chin wing cut all the way through the mandibular border. Lower MPAs allow for the cut to go all the way through the mandibular border to the posterior jaw angle where as higher MPAs only allow for what may be termed an 'extended genio'; something that doesn't cut all the way back through the posterior jaw angles. A vertically 'short' body of the mandible is also a factor.
What the chin wing doctors are looking at (or for) basically is whether or not the inclination of the MPA exceeds what ever inclination limit they have as to ability to cut through the mandibular border all the way through it and/or whether or not the mandible body is vertically long enough such that there is enough 'space' BELOW the NERVE to cut through safely without risk of nerve damage. Those with vertically short mandibular bodies and high MPA inclinations would be at high risk for nerve damage if they got a cut all the way back through the posterior jaw angles. Hence, there indeed is a relationship to be observed which IF actually observed (as you've done here) is sufficient to understand why some people START OUT with a type of 'bone geometry' that is very compatible with a full chin wing cut and some don't. The ones who do can get the most from the chin wing. Those that don't get the least from it.
In this example, the person is actually an IDEAL candidate for a chin wing. His MPA is inclined low enough for them to easily cut right through the mandible and there is enough vertical space to the body of the mandible for the nerve to be out of the way of the cut. The advancement of the whole segment is modest to minimal in this person because he doesn't need much chin advancement. What he needs is mostly what he got which is the 'drop down' to lower the border of the segment which you see on the ceph as something sandwiched in between the cut and the lower border of the mandible.
