Province prop answers Bok SOS
Oosthuizen suffered the fracture in his team's disappointing 23-all draw with Australia in Perth on Saturday.
He will be replaced by uncapped Wilco Louw of Western Province.
Oosthuizen sustained the injury in the second half of the encounter.
He will visit a specialist in Durban on his return to South Africa.
Louw is due to join the Springbok squad in Auckland on Monday.
Prop Coenie Oosthuizen suffered a broken arm in the 23-all draw with the Wallabies in Perth and to be replaced by Wilco Louw of DHL WP.
— South African Rugby (@Springboks) September 9, 2017
The draw means that the Springboks are now in second place on the Rugby Championship log – three points behind New Zealand, who they play next weekend in Albany.
Springbok coach Allister Coetzee said he was disappointed with the result, but pleased with the players' effort.
The Springboks fell behind 10-20 just after half-time, but showed great fighting spirit to grab a 23-20 lead towards the end.
A successful Wallaby penalty locked the scores at 23-all, while Springbok pivot Elton Jantjies had his drop-kick attempt charged down after the final hooter.
"The Springboks will never be happy with a draw," Coetzee told media at the post-match press conference.
"I am, however, satisfied with the overall performance, because the team showed great character in their fightback.
"We had three line-breaks and no reward in the last couple of minutes."
According to Coetzee, the most pleasing aspects of the match was his side's defensive effort, especially how the side adjusted their plan in the second half.
"We also continue to scrum well and our lineout also functioned well plus we saw a massive improvement in our mauling," added Bok coach.
"There's a lot of respect between the two sides and our results have always been very close. Australia are one of the top sides in the world and they gave us a great contest out there."
The Springboks travel to Auckland on Sunday and Coetzee will name his starting team to face the All Blacks, on Thursday.
