Jamal Thompson, 19, struck Harvey Chilton with a power adapter with “steel edges” at the Quinton Court Shopping Centre, in Wardles Lane, hitting him on the arm and the head and kicked him as he tried to get away.
Mr Chilton’s right thumb was left “hanging off” and required surgery.
On May 17 last yea, Mr Chilton pulled his car into the shopping centre and went to speak to two friends he saw there.
Jamal Thompson, of St Mark’s Road, Tipton, approached him on foot, with another man on a bicycle, and confronted Mr Chilton about money in relation to damage to a friend’s vehicle.
Birmingham Crown Court heard that the mood changed, Thompson was “egged on” to “smack” Mr Chilton and pushed him off a wall which he had sat down on.
Thompson then pulled a computer charging adaptor with sharp edges from his waistband, raised it above his head and struck Mr Chilton on the arm and then the head.
When Mr Chilton tried to get away, Thompson struck him on the back of the head with the adapter and kicked him.
Mr Thompson was left needing surgery to his thumb, a metal plate in his wrist and stitches to repair arm and head lacerations he received in the attack.
In a witness statement made after the attack Mr Chilton, an engineer with West Midlands Ambulance Service, said he had been left unable to work and no longer left his home very often.
“When I do go out I feel I am looking over my shoulder,” he said.
“I have tried to face what has happened to me by talking to my friends but it is difficult to move on.
“Every single day seems slower than the one before.
“I struggle to get to sleep, and replay the events in my mind in the dark. I can’t help thinking about it.”
Since this statement was made the court was told Mr Chilton has returned to work part-time.
Thompson pleaded guilty to a charge of assault causing grievous bodily harm last November.
Sentencing Thompson to six years and nine months in a young offenders institution, Judge Samantha Crabb, said it was a “vicious and cowardly” attack.
“You were intent on causing trouble to Mr Chilton,” she said.
“You approached him, got in his face and pushed him off the wall before you launched your attack.
“You had a beef with Mr Chilton as a result of a previous encounter.
“You produced a black power adapter attached to a cable, raised it above your head and brought it down on his arm.
“You struck him again on the back of the head and hit him on a number of other occasions causing his injuries.
“When Mr Chilton was taken to hospital his right thumb was hanging off.
“You had just turned 19 at the occurrence of the offence.
“I have no doubt it was in no small part to your youth and immaturity.
“I am satisfied given the length of the sentence imposed there will be a good deal of maturing over the passage of time.”