The Pamplona-based club needed to win and hope that either Getafe or Granada lost as they bid to survive relegation from La Liga on the season's final day, but the match was marred by the incident after Osasuna's first goal.
Midfielder Oriol Riera fired the hosts into a 12th-minute lead against already relegated Betis, but as fans celebrated, a restrictive barrier gave way and dozens of supporters spilled onto the side of the pitch.
The match was subsequently delayed for 35 minutes, as were the league's other games at half-time to avoid some fixtures finishing earlier than others.
During that period, medical staff attended the injured and security officials removed the rest of the faulty railing.
After the match, the Navarre Red Cross confirmed through Osasuna that a total of 68 supporters suffered injuries, including a 66-year-old who suffered a fractured femur.
Despite the 2-1 win, Osasuna were subsequently relegated as both Getafe and Granada emerged from their matches, beating Rayo Vallecano and Real Valladolid respectively.
