The 31-year-old Avintia rider has missed the past two races after injuring two fingers on his left hand in a crash at Barcelona.
Both fingers have been reconstructed by specialist Dr Xavier Mir, although the tip of his ring finger was amputated.
Spanish rider Javier del Amor was given a short-notice call to replace Aoyama for the Catalunya Grand Prix, while Ivan Silva stood in for him last time out in the Dutch TT.
Aoyama, who won at the Sachsenring in the 250 class in 2007, says he intends to compete but accepts he will only be able to fully evaluate his fitness once back on his bike.
"I am delighted that Dr Mir has given me permission to travel to Germany to participate in the grand prix," Aoyama said.
"I realise that we won't know exactly how I am until I climb on the bike and get going, but it means a lot just to be going there.
"The time I have had since the operation has allowed me to fully recover from injuries received in previous accidents; now we just need to keep an eye on the hand injuries and see how much they are going to limit me but, either way, I am very happy to be able to get back on my bike."
Aoyama's early-season preparations were also affected by injury, after he fractured his wrist in a motorcross fall in January.