A group of patients exposed to hydraulic fluid on surgical instruments at two Duke University hospitals contends in legal filings that the university used flawed studies to claim the 2004 incident caused no extra harm.

And even though some patients were eventually ruled out as having been operated on with the tainted surgical tools, the court filings state, the university did not notify them they were clear until earlier this year - five years after the situation came to light.

In the intervening years, some patients sued. Ronald Buchanan's lawsuit was dismissed earlier this year when Duke provided evidence he wasn't exposed, and now Duke is suing him to recover legal expenses.

Buchanan is fighting that battle on grounds that Duke led him to believe he had been exposed to the fluid for five years and "now seeks to punish him further by taxing him with the defense costs in this litigation," according to the documents.

Buchanan's claim and the charges about the faulty studies were made in two court filings in Durham County Superior Court.

Duke spokesman Doug Stokke said he could not comment on active litigation. The lawyer for the patients in both actions, G. Henry Temple Jr. of Raleigh, also declined to comment.

Temple represents 14 patients who were among more than 3,600 originally identified as having been potentially exposed to the hydraulic fluid in November and December 2004 at Durham Regional and Duke Raleigh, which are owned by Duke University Health System.

Greasy instruments

The exposure resulted when repair crews at Duke Raleigh drained elevator fluid into discarded detergent barrels. The barrels were inadvertently picked up by thedetergent supplier and mistakenly returned to the hospitals as washing fluid for the machines that clean surgical instruments.

For more than a month, doctors and nurses at thehospitals complained about greasy instruments.

After the mistake was discovered, Duke commissioned a study to determine how toxic the instruments were and another study to track whether patients had extra complications as a result of their exposures.

The studies found little harm. The toxicology report indicated that only tiny amounts of hydraulic fluid remained on the instruments, and the patient study reported that people suffered no problems beyond what would normally be expected after surgeries.

The group of 14 patients is challenging those results.

They contend some of the instruments provided by Duke for toxicology tests were clean, including some dated a month before the industrial fluid was delivered, so results were skewed to show smaller amounts of the grease.

Similarly, the legal filing contends, at least 1,000 patients studied as part of the analysis of harm had not been exposed to the fluid, possibly diminishing the rate of complications that occurred.

The patient study, the plaintiffs allege in their court filing, was used "to support and promote an untenable conclusion: that patients exposed to hydraulic fluid actually had fewer adverse outcomes, in every category, than patients who had not been exposed - a virtual statistical impossibility."

The lawsuit involving this group of 14 patients is one of several that resulted from the incident. Previous cases settled without trials, and the participants agreed to keep the details secret.