I have a pic of his mommy and she has it too, so it's more genetic than anything else. My trimmer is a bit concerned that the coffin bone is tiltled down due to the high heel. She seems hell bent on getting the angle down to a textbook hoof angle. While I see why a high heel in a normal shaped foot is a bad thing, my gut tells me that my horse's high or club foot is what it is and not to mess with the angle too much. I'd rather let that one stay high and try to encourage more heel on the low foot.
Last question first - yes, there are a few good studies, but can't think of them off hand & no time to look now - shouldn't be here
- but if I recall, Pete Ramey had a reasonable article on it & I think barehoofcare.com also may.
While of course a deformity or such that causes it may be genetic, just because his mum was like that doesn't make it genetic. Of course, it's 'genetic' that many types/breeds of horse are long legged these days, requiring them to stand unevenly in order to graze at ground level, and as with us being 'right or left handed', there tends to be a habitual preference, which causes the 'back' foot to frequently bear more on the toe & less on the heel. He could also have had an injury that's caused him to be uneven - anywhere from shoulder or back, to something that caused heel sensitivity in that foot, leading him to develop more heel height on that foot.
I agree with you, that while 'textbooks' are indeed helpful, it's not a good idea to try to force live animals to conform to them & that attitude of your trimmer worries me. I would be trimming both feet to what they appear to need, based mainly on what the sole plane is 'telling' me. I would not attempt to 'build up' the low heel any more than lowering the high. I would want to find a good bodyworker that could help him even up, if that's possible for him, in which case his 'high' foot may come down of it's own accord.
Yes, those high feet do indeed often 'founder' with P3 'rotation', due to the extra pressure & leverage on the toe. Therefore I think it's important to alleviate & manage any flaring, keeping the toe short(meaning in front, not at ground surface - it's already short there), and I would also consider padding/booting is possibly going to be an ongoing necessity to protect & support the toe area.