In episode 478 of the Boruto anime, Naruto and Sasuke had a final battle. Their battle was a battle to settle their unfinished business and to prove their friendship. The two fought for the honor of Konoha, their beliefs, and their friendship.
It was during this fight that both Sasuke and Naruto lost an arm. This happened when their Chidori and Rasengan attacks collided together, blowing off an arm from each side of the duo.
In the Boruto anime, we learn that Naruto was offered a prosthetic arm by Tsunade. However, he declined it.
He was not willing to let his limb be replaced because it reminded him of the past and his crimes. He also felt that growing a new arm would inhibit his growth as a person.
In the anime, Sasuke is a powerful and strong ninja. His Kekkei Genkai allows him to activate the Eternal Mangekyou Sharingan. His katana is extremely deadly, and his Sharingan is extremely powerful.
He believes that his missing arm symbolizes the wrongs he committed in his past, the lives he destroyed, and his path to darkness. This led to his decision not to grow an arm and instead pursue a life of reconciliation.
In the manga, Sasuke refuses to use a prosthetic arm because he thinks that it is not necessary and that it could hinder his growth as a person. He views his arm as a reminder of his past and wants to lead a life that is focused on the redemption of all his sins.
