West Chester medical device manufacturer Synthes Inc. and its Norian Corp. subsidiary formally pleaded guilty today to charges that they illegally experimented with a spinal bone cement on patients and will pay fines totaling $23.2 million.

Synthes also agreed to sell Norian and enter a corporate integrity agreement, according to an agreement reached with the U.S. Attorney's Office and the Department of Health and Human Services.

Norian tested the cement from 2002 to 2004 on 200 patients without approval from the Food and Drug Administration. Three of the patients died on the operating table.

Prosecutors say the companies sought profits over patient safety.

Norian pleaded guilty today to conspiracy to impede federal safety standards, a felony, and 110 related misdemeanors. Synthes pleaded guilty to the misdemeanor of shipping a mislabeled product.

Four executives from Pennsylvania have pleaded guilty to charges in the case and are awaiting sentencing.

Norian would be excluded from participating in Medicare and other government-funded health care programs if it remained a Synthes subsidiary. According to its agreement with the government, Synthes has to sell Norian by May 24.

Contact staff writer Andrew Maykuth at 215-854-2947 or amaykuth@phillynews.com.