An 82-year-old man suffered a broken back after he was dragged to the ground by three men who ripped jewellery from his wrist.
Ahmet Dobran, who uses a walking stick, was grabbed by the neck by one man while the others hit his back and arms before the trio pinned him down to steal his gold bracelet and Longine watch.
The robbery, which happened just before 7pm on Sunday August 27 in Sussex Road, Newham, east London, left the pensioner with three fractured vertebrae.
Mr Dobran, who had also been undergoing treatment for cancer, is still in a serious but stable condition in hospital.
The attack has aggravated other conditions he had, such as Parkinson's.
Pc Sam Bush, the investigating officer, said: "How three grown men can be so vicious in attacking and robbing an 82-year-old man with a walking stick is beyond comprehension.
"He was out shopping at the time of the attack and had bags of shopping in his hands, which made him even more vulnerable.
"The callous men who attacked Ahmet swore at him throughout the attack.
"He is understandably in a state of shock and in a serious but stable condition in hospital.
"We need to catch these vicious thugs before they target anyone else as they clearly have utter disregard for their victims and do not hesitate to use violence."
Police have released images of three men they would like to speak to in connection with the attack.
Anyone who can help should contact police on 101.