Nearly half of surgeons who earned more than $1 million from companies that make orthopedic devices did not disclose it when they published medical journal articles, U.S. researchers said on Monday.

A cross-check of records from five orthopedic device makers found major gaps in reporting of compensation provided to medical journals, the researchers reported in the Archives of Internal Medicine.

The findings raise troubling questions about undisclosed payments or royalties and other fees from medical device companies that could lead to biased scientific conclusions, said David Rothman of the Institute on Medicine as a Profession, a think tank based at Columbia University in New York.

Members of Congress including Senator Charles Grassley, an Iowa Republican, have been pushing to limit the influence drugmakers have over the practice of medicine in the United States after investigations revealed that Harvard University psychiatrist Dr. Joseph Biederman and others failed to fully disclose payments from drug companies.

Rothman's team used a public database to check the accuracy of surgeons' financial disclosure statements.

They focused on five companies: Biomet; DePuy Orthopedics, a unit of Johnson & Johnson; Smith & Nephew; Stryker and Zimmer.

These companies made a total of 1,654 payments that amounted to $248 million in 2007 for consulting, honoraria or other payments for services, the team reported.

The analysis also showed that payments to 41 orthopedic surgeons ranged from just over $1 million to $8.8 million.

Out of 95 published articles, fewer than half disclosed a financial relationship between the researcher and company, and none hinted at the size of the payments.

Nearly all of the articles were directly related to a device, such as a hip implant, made by the company, the team said.

Medicine