Dylan McNulty had approached the victim's home in an "aggressive manner", following an earlier row over the phone, and slammed the french door she was standing at onto her arm.
Newcastle Crown Court heard the woman needed surgery and may be left with long term nerve damage as a result.
Prosecutor Ellen Wright said the mum saw the 24-year-old approach her home and she stood at the french doors as he approached.
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Miss Wright added: "The defendant moved quickly towards the door and barged it with his shoulder, causing the door to slam into her left arm.
"She describes screaming, in instant pain."
The court heard McNulty left and the woman contacted the police.
An officer who arrived at the house described the victim as being "in agony" and was taken to South Tyneside District Hospital.
The woman said the injury and the surgery she required had a "huge impact" on her life and caused her to be off work for 11 weeks.
She said in a victim statement: "I feel useless and gutted I can't continue with usual day to day life."
McNulty, of Albert Road, Jarrow, admitted causing grievous bodily harm.
Judge Amanda Rippon told him: " You lost your temper and because you lost your temper you slammed the door onto her arm and broke her wrist.
"You didn't intend to break her wrist but you still slammed her arm in a door and broke her wrist."
The court heard McNulty had previous convictions and his last offence was for assault.
The judge warned if he continued to offend "someone will eventually throw away the key".
McNulty was sentenced to 12 months imprisonment, suspended for two years, with rehabilitation and programme requirements plus a £50 fine for breach of a previous suspended sentence.
Nicholas Lane, defending, said McNulty is "ashamed of his behaviour" and had struggled to deal with the end of the relationship, which was his first serious one.
Mr Lane said McNulty has been in employment and hopes to return to work.