He says rehabilitation of the laminitic foot involves simple mechanics and is easy, the foot is trimmed to realign the hoof to P3 - just as TLS has been saying for some time!
The foot must be set up to relieve pressure on the sole under the tip of P3 and to decrease tension on the laminae.
The foundered foot typically grows a lot of heel, the toe becomes jammed up, there's a lot of pressure on the sole corium and coronary band at the toe - the foot needs to be set up for normal growth to take place.
The sole is designed to be a supporting structure as well as the laminae. The main goal is to thicken the sole depth and use the sole to support P3 while the laminae are compromised. Barefoot horses naturally bear weight on the sole and develop a tough and strong sole callus.
He says domestic (but perhaps this should be shod) horses often have a dysfunctional thin sole that will bend with thumb pressure, which provides no secondary support structure for P3, and which can quickly lead to a "train wreck" when the horse develops laminitis.
Laminitis isn't necessarily failure of laminae at the toe, laminae can fail at any point around the hoof.
The centre of pressure needs to be behind the apex of the frog - TLS recommends trimming the laminitic foot to maximise weight bearing in the back half of the foot.
I struggle to agree with Dr Morrison about the pull of the DDFT and the use of wedges and tenotomy - Pete Ramey's explanation that the DDFT cannot exert a rotational force and oppose the laminae if the sole is in ground contact (active) and the wall at the toe is out of ground contact (passive) seems to make perfect sense. On p 350 of Care and Rehabilitation of the Equine Foot Pete says that although elevating the heels may temporarily reduce tension in the DDFT in a standing horse (although the muscle will quickly adjust), it may increase tension when the horse moves. He believes that concerns about DDFT tension have held back vets and farriers, "preventing rotation reversal by leading people to stand P3 up on its tip and ultimately destroying the foot". Dr Eleanor Kellon and the ECIR group have similar views: http://www.ecirhorse.org/index.php/ddt-overview/ddt-trim
However Dr Morrison goes on to say that wedges and shoes "trash the heels" and he only uses them short-term to shift the centre of pressure back (which others would claim can be done with a good realigning trim) while he tries to fix the toe and develop sole depth, then he likes to rehabilitate laminitics barefoot to allow the heels to recover.
He made me smile when he said that the trim is really important, he never touches the sole, just cleans the frog slightly, trims the heels back to the widest part of the frog (or as far back as possible), rockers the toe and applies a good bevel to the wall all the way round - exactly as we have advised for all our successful rehabs!
He also says that the bars are very important and shouldn't be aggressively trimmed - they have a purpose in stabilising the heels and wall.
He points out that horses often can't stand with one foot up for long - seconds only. I would take this further and say that they should always be allowed to put their foot down (so nail on shoes are not appropriate), and trimmed when standing on a soft supportive surface.
There are some interesting x-rays of bone remodelling - Dr Morrison says that horses can usually handle a bit of remodelling of the tip of P3, but in his experience when there is a lot of erosion and demineralisation of P3, horses never become completely comfortable, and that once the surface of P3 is damaged, completely healthy laminae will never grow back. However, as long as P3 is healthy, he says feet can be amazingly rehabilitated following laminitis and rotation. This emphasises how important it is to get rotation realigned as soon as possible after a laminitis attack, to prevent changes to the bone from ever happening.
In conclusion, a very positive lecture stressing the importance of a mechanically correct barefoot trim, and whether you agree with everything he says or not, well worth spending an hour watching.