Mark Hanretty hurt his shoulder when he fell as the couple got into position on Sunday night.
He had to receive medical attention before it was confirmed that he was able to take part in the dance-off.
A worried Oona was called over by presenter Phillip Schofield as medics treated her partner.
She said: "I'm sure it was my fault because he's the most amazing skater in this show."
Mentor Jayne Torvill added: "You know when a professional can't get up like that it's pretty serious."
The duo performed to the hit Just The Two Of Us after Mark's shoulder was popped back in.
But they lost out to rugby star Gareth Thomas and his partner Robin Johnston who danced to the Queen track Somebody To Love.
Three of the four judges voted to save Gareth after the dramatic skate-off.
Earlier the celebrity skaters had taken part in "duels", as two couples battled on the ice at the same time.
The judges then voted for the best couple in each "duel", making them immune from the public vote.
Oona lost her duel with gymnast Beth Tweddle, while Gareth lost out to actor Matt Lapinskas.
Ashley Roberts told both couples they had put on "amazing performances", while Jason Gardiner said it was "definitely one of the most dramatic skate-offs we've ever had".
Head judge Robin Cousins told Oona: "Against anyone else, a skate of that calibre would easily have taken you through."
Schofield told the former Labour MP that she and her partner had "given us a very dramatic moment".
The politician said she "adored" the experience. "I loved learning how to skate," she said.
Referring to her injured partner, she added: "I feel really devastated for him."
Mark then joked: "I didn't expect to have as much fun as I had with a politician."
The injury came after Coronation Street actress Samia Ghadie suffered from bruised ribs during rehearsals, while Olympian Beth Tweddle was rushed to hospital with severe abdominal cramps.
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