After such an injury, for which there's nothing to do but tape and bear it, I switched to cables. There's not an alpine or tele skier out there who hasn't tweaked a thumb at least once from touching a hand down at speed. Train yourself to make a fist as you fall so your thumb isn't exposed. Collarbones are known to snap loudly as you reach out stiff-armed to break a fall. Learn to tuck and roll.
Shoulders suffer impact from overly aggressive pole plants.
Use your poles to initiate your turns and as balance points rather than as dynamic supports. Hate to say it, but backcountry skiing is a helmet sport. Tree-skiers should consider their odds accordingly. Backpackers Knife cuts and burns from fires and camp stoves are extremely common. Be prepared with sterile dressings.