WASHINGTON (AP) ¿ Federal health officials say an implant from Zimmer Holdings Inc. appears to be effective in treating spinal problems, but questions remain about whether company payments to doctors influenced the device's trial data.

Zimmer has asked the Food and Drug Administration to approve its titanium Dynesys implant to re-stabilize the spine. The FDA posted its review of the first-of-a-kind device Monday, ahead of a panel meeting to discuss the device on Wednesday.

Agency reviewers said a Zimmer study of the device met its goal, showing results at least as good as the company's older Silhouette implant. Patients implanted with Dynesys showed a 52 percent treatment success rate, compared with 40 percent for Silhouette.

However, the FDA raised questions about whether company payments to physicians conducting the trial may have influenced the results.

Most patients in the trial were treated by surgeons who had received consulting payments from Warsaw, Ind.-based Zimmer. More than half of the patients in the trial were treated at medical centers that reported more than $100,000 in payments from the company, according to FDA's review.

The FDA said one analysis of the company's results showed a positive relationship between financial payments and clinical success for the device.

"However, all correlations were far from being statistically significant," the agency said, in documents posted online. "Therefore, there is only a trend which suggests the possibility of bias from compensation."

A spokesman for Zimmer had no immediate comment Monday evening.

The FDA will ask its panel of outside panel of orthopedic specialists to weigh in on the company's study and whether additional data is needed.

The agency is not required to follow the group's advice, though it usually does.

Shares of Zimmer Holdings Inc. fell 4 cents Monday in after-hours trading to $52.73, having closed earlier up 20 cents at $52.77.

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