Pacioretty sustained a "severe concussion" and a fractured vertebrae, head coach Jacques Martin told reporters, according to C.J. Stevenson. The injury is a non-displaced fracture of the fourth vertebrae.
Earlier Wednesday, RDS' Renaud Lavoie originally reported the possibility of a fracture.
The Canadiens announced Tuesday night that Pacioretty was conscious, could move his hands and feet and was talking.
Pacioretty, 22, is a native of New Canaan, Conn. He played high school hockey at The Taft School in Watertown, Conn. He is in his third NHL season after playing one year at Michigan.