Van Ryn sustained a concussion and broken nose and hand. He is expected to be out at least a month.
Kostopoulos received a five-minute boarding penalty and game misconduct when he hit Van Ryn from behind during the Maple Leafs' 6-3 win Saturday. Van Ryn remained on the ice for several minutes.
"While it is my determination that Kostopoulos did not deliver a check to an unsuspecting opponent, his actions caused injuries," NHL vice president Colin Campbell said in a statement.
Kostopoulos will be eligible to return Nov. 16 at St. Louis. His salary of nearly $33,000 for the three games will go to the NHL players' emergency assistance fund.