I took a look at the link Post Bimax gave at time frame 5:57 where they show the bone model.It's because with the BSSO cut a GAP is left and with healing, bone growth fills in this gap. Looks like a 2mm gap on each side can be there which would explain the statistical average of 4mm bigonial increase in width. The observed much wider bigonial distance (BGD) they cite in the EARLY stages of healing (like a day after or so) would be swelling of bone while it's initiating the inflammatory/healing response.Keep in mind the observation was made via direct X-ray focus on the posterior mandible. Looking at someones (outer) face post surgery or self assessments of posterior jaw looking more narrow most likely could kick up optical illusion based on RELATIVE distances. That's because when the anterior part of the mandible is moved forward, that area will look WIDER because it's being brought MORE into the foreground. Because that is so, the width increase at posterior mandible might not look visually obvious or could look relatively more narrow depending on how much forward the anterior mandible is advanced.
I mean looking at this image from the article, it looks like an actual substantial increase in width and not just the perception of it. https://www.semanticscholar.org/paper/Posterior-mandibular-widening-secondary-to-sagittal-Sigaux-Lahon/7ba8b84eeef2c292ef09a21455a049333d5559b7/figure/8
If thats the case, wouldn't everyone getting BSSO have wider, squarer jaws? There are plenty who's angles don't change at all or actually become more narrow.
What a great result he had though. Jeeze
If you look at the scatterplot you'll notice BGD actually decreased in some patients, so it's not a guaranteed thing.
