Ms. Butler criticized the health care staff at the Metropolitan Detention Center, the federal jail in Brooklyn where Mr. DiFiore is being held. They were late in giving him his insulin shot on Monday, she said. They have given him compression socks for the swelling, but they have not helped. He was supposed to have regular CT scans, and those were not being performed. He still needed a full work-up on his kidneys, and on his eyes.

That criticism made the end of the proceeding all the stranger. After sentencing Mr. DiFiore, Judge Ross offered to recommend a transfer to a medical facility run by the Bureau of Prisons. His lawyers declined.

“To have him moved to a different facility would be counterproductive because of the stress that that takes,” one of the lawyers, Steve Zissou, said, requesting that Mr. DiFiore be kept at the Metropolitan Detention Center.

The sentence was in the range sought by prosecutors — 21 to 27 months.

“He’s getting these illicit earnings off of other people’s backs,” Alicyn L. Cooley, an assistant United States attorney, said.

The charge, of conspiracy to collect unlawful debt, stemmed from a 2013 dispute over a loan. A man affiliated with the Bonanno crime family, for which Mr. DiFiore was the “street boss,” had lent money to a carwash employee who was affiliated with the Gambino crime family. But the Bonanno affiliate did not have clearance from his higher-ups to make the loan, and the loan was not being repaid.

Bonanno members intervened, including Vincent Asaro, 80, who is scheduled to go on trial this fall in Brooklyn in connection with the 1978 Lufthansa heist, among other offenses. “Stab him today,” Mr. Asaro told a friend about the Bonanno affiliate. “Today!”

The Bonannos resolved it by getting a $30,000 payment. Mr. Asaro figured $10,000 for himself, $10,000 for his son, $6,000 for the friend and $4,000 for Mr. DiFiore, though Mr. Asaro said he had taken Mr. DiFiore’s portion.