Hi,
Try to de-sensitize your dog by massaging his legs and paws while you speak gently and soothingly. After you get him to accept this, run the nail clippers over his feet, again while speaking soothingly. This may sound fast and easy, but it's not. It can take a long time, but one of the things you should do is stop when he starts getting overly anxious. Build the trust slowly. Then, just clip one toenail and stop there. It's so important that you do all of this in tiny increments so that you build up and then maintain his trust.
As for 'trussing' by groomers, I'm not sure what that means. Grooming is usually done on a table with an arm from which a loose 'noose' hangs. This is meant as a miminal kind of restraint that is more psychological for the dog than physical. Sometimes this system is supplemented by extra tethers that restrain the pet's movement further. This is in no way cruel to the dog- it restricts the movement for the safety of the dog, the groomer, and any other 'creatures' in the shop. Also, sometimes muzzles will be used- again for the safety of all involved.
Groomers are not miracle workers. There are no magic methods available to them for getting 'freaked out' dogs to allow their nails to be cut. Although some dogs are indeed much more well-behaved in a shop when the owner is gone, chances are also that if your dog freaks out at home while you attempt to cut his toenails, he will be the same way for a groomer. In extreme cases, some dogs actually have to be tranquilized to have their nails done. So it's to the benefit of all if that radical step can be avoided and the desensitizing can be done at home. If not, step 2 is at the groomer's with the necessary restraint. Restraining dogs is something that's necessary to all groomers. It's in no way cruel.