A New York City doctor who performed unnecessary surgeries on desperately poor patients as part of a $31 million scheme to scam insurance and lawsuit money pleaded guilty to federal fraud charges on Thursday, prosecutors said.

Dr. Sady Ribeiro, 72, is looking at a maximum five-year prison sentence on charges of mail fraud and conspiracy to commit wire fraud, said the Manhattan U.S. Attorney’s office.

Prosecutors say Ribeiro has also agreed to forfeit $513,000 in proceeds from the crime to the government, and to pay $3.98 million in restitution to the victims, who include businesses and insurance companies.

Some of the 400 patients of Ribeiro and other doctors in the scheme were so broke, they asked for food when they showed up for appointments, the feds said in an indictment.

“Many of the patients did not have sufficient clothing to keep them warm during the wintertime, and had poor quality shoes,” the indictment said. Many were drug addicts, and were recruited from homeless shelters, said the feds.

Ribeiro denies federal prosecutors’ claim that the treatments were “surgeries.”

“The procedures were minimally invasive and took between five to 10 minutes,” said his lawyer, Kenneth Abell. “In Dr. Ribeiro’s assessment, they presented zero risk to the individuals and, to his knowledge, no one suffered any adverse effects from them.”

Abell said Ribeiro “is a good doctor and person who has spent years helping patients.” State records show he still has his medical license.

Ribeiro’s patients were referred to him by a group of lawyers and other “scheme participants” who asked the patients to stage or claim to have suffered trip-and-fall accidents. The feds say the scheme operated from 2013 to 2018.

The purported accidents were cited in lawsuits and insurance claims that yielded money for the lawyers, doctors and a firm run by another defendant, Adrian Alexander, that provided money to fund the scheme, say the feds.

The patients got little in return for undergoing the needless treatment.

Many of the patients were offered personal loans at 100% interest or loans to cover the costs of their medical care at 50% interest — rates so high that the scheme’s operators ended up with nearly all the proceeds from the slip-and-fall lawsuits, said prosecutors.

Alexander, 77, pleaded guilty for his role in the scheme in August and also faces up to five years in prison.