SIOUX FALLS, S.D. (AP) — Two doctors employed by Sanford Health are suing the company and one of its neurosurgeons, accusing them of defrauding the federal government and harming patients by performing unnecessary surgeries.

Dustin Bechtold and Bryan Wellman filed the lawsuit in 2016. The U.S. Attorney's Office for the District of South Dakota filed a motion to intervene in the case June 26 and a federal judge unsealed it June 27.

According to the complaint, Sanford Health has been buying medical devices from Medical Designs, a company owned by neurosurgeon Dr. Wilson Asfora. The suit said Asfora used those devices in spine surgeries at the hospital in violation of anti-kickback laws. The suit describes accounts of Asfora installing unnecessary screws and medical devices into his patients.

"One level was all that was medically necessary for this patient," according to a summary of one patient's fusion. "Dr. Asfora put in three additional cages, which this patient did not need, but which Dr. Asfora personally benefited from financially. Dr. Asfora never saw this patient prior to surgery. Three of these levels were off-label, medically unnecessary, and medically tainted by kickbacks."

The 111-page suit also said Sanford and Asfora billed Medicare and other federal programs for care that was never provided.

The suit said Sanford's leadership ignored complaints from doctors and intentionally covered up Asfora's surgical errors.

Sanford's chief medical officer Dr. Allison Suttle denied the allegations in a statement to the Argus Leader, calling the doctors' claims "baseless." She said Asfora is talented, provides excellent care and has saved hundreds of lives.

"The allegations in this lawsuit have been investigated and were found to have no merit," Suttle wrote. "Sanford Health is confident in the care provided to our patients and will continue to provide quality care."

In 2014, Sanford paid the federal government $625,000 in fines for violating anti-kickback rules, the Argus Leader reported.

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