I'm including the geometric gist of the tutorial I entered last night which was removed.
I shall assume you have some basic geometric familiarity underbelt as to relate to my explanations. That's because CCW-r, how it works, is based on a very fundamental geometric principle which is the ROTATION OF A TRIANGLE.
Although the Triangle is 'ABC', when we let A=ANS, B=PNS and C=pog point (outer most point on chin), it becomes the facial triangle that maxfax surgeons use to look at how applicable CCW-r posterior downgrafting is going to be depending on the patient because each person has pretty much a unique triangle constructed from points ANS, PNS and pog point.
Included is a diagram of a triangle; ABC rotated x degrees around fixed point A. The green triangle is a tracing of the blue triangle subsequent to a CCW rotation of x degrees.
The illustrations shows how the points B and C displace subsequent to the rotation. B drops down to B' and C goes outward to C'. So, how much C goes outward to C' is going to be directly proportional to how much B drops to B' via a CCW-r of X degrees. The obvious thing to note here is that the triangle does NOT change. It's the SAME triangle with the vertexes (and all the points on its lines (or 'legs') displaced by the rotation alone. The green triangle is the SAME triangle as the blue one. The blue one just shows where the green triangle would be after a CCW r of x degrees.
When we relate the displacements of the points (vertexes) of the triangle to a posterior downgraft, we can conceptualize something 'wedging down' to rotate the triangle by x degrees. So, the downgraft could be conceptualized as wedge ABB' where vertical linear distance between B and B'is the longest distance measure of the downgraft. (Surgeons give that mm meaure but usually don't relay the degree measure of the rotation). B going to B' via the rotation the downgraft affects causes C to go outward to C' (pog point to be advanced). So, how much C goes outward to C' is a function of the linear distance of BB'which in turn, is a function of the rotation the downgraft gives. Again, the obvious thing to observe is the triangle does NOT change in SHAPE. It only changes in POSITION when rotated. Hence, it is the rotation ALONE that shifts C outward to position C'. Since C=pog point, C'= pog point going outward via rotation of the trangle when we rename it; Triangle ANS PNS pog. (Keeping in mind that everyone has a DIFFERENT triangle.
OK. So, I thing you probably get the concept that the LARGER the posterior downgraft, the MORE outward distance the pog point will shift out via the rotation alone and how the basic concept of that is related to the fundamental geometric principle that describes the rotation of a triangle; ABC around a fixed point. (in this example I chose A). So, the principle is pretty straight forward (assuming again you have some geometry underbelt to ID with the principle). But surgeons look at the unique geometry of someone's FACE; in particular the CONSTRUCT of each person's unique triangle formed by ANS, PNS and pog.
How much the pog point can be brought outward is a direct function of how much they can shift the posterior maxilla DOWNWARD with the rotation. The larger the degree measure of the rotation, the more posterior maxilla shifts downward and the more the pog point goes outward.
So a limitation of how much to get the pog point to shift outward will be how much they can shift the posterior maxilla downward for that not to negatively affect the aesthetics of the smile or the function of the bite. In your case, excess posterior gummy smile and AOB are also part of your problem set in addition to the recessive mandible (and chin). Hence a large CCW-r via posterior downgraft with aim to maximize outward advancement at the pog point via the rotation of your triangle would tend towards shifting your excess posterior gum show MORE downward and contributing MORE to AOB. Whether or not the surgeon you consulted with does posterior downgraft, the limitations I mentioned are ones that surgeons who DO do the pdg (and significant ones at that) LIMIT the extent of them. So, 2 other things in your problem set LIMIT the 'solution' being that of a significant posterior downgraft solving the extend of all the recession to the mandible. That's why the BSSO and chin augment together are relied on to IMPROVE much of the recession.
As to combined impaction with a net CCW, THAT is a rotation but differs from that of rotating a triangle on which CCW posterior downgraft is based because unlike a triangle not being changed or altered, your triangle would be altered. For example AC (ans to pog) and BC (pns to pog) are made shorter by the impaction. I mention that just to point out that although you are getting a net rotation, the model on which posterior downgrafting is based on is that of a triangle that changes ONLY in position via the rotation but not it's shape.
As to rotation of the 'whole maxilla mandible complex', well, that's what basically happens with any rotation of the maxilla even when done with no posterior downgraft. A rotation of the mandible is effected via what ever rotation is done to the maxilla. In your case, both a posterior impaction and an anterior impaction will allow the mandible to rotate upwards and decrease it's angle of inclination. That, in turn, allows the BSSO to move 'forward' along less of a steep mandibular plane angle. Even posterior impactions alone gets the mandible to swing upwards when you consider it's the excess to the posterior maxilla thrusting the mandible downwards because it can't rotate up to close the bite.
As to pursuing posterior downgrafting, I don't mean to discourage about doing so given it's a good idea to get differing opinions. So, you would need to consult with doctors who do it. They will look at the entirety of your problem set in relation to what ever limitations it would have to maximizing the downgraft to maximize outshifting of the pog point.
