IT was a long, fruitful medical marriage that is fast becoming an angry public divorce, one that offers a rare look at a clash between a top-shelf consultant and his corporate patron over patient safety.

For years, Dr. Richard A. Berger designed surgical tools and artificial joints for Zimmer Holdings, trained hundreds of doctors to use its products and talked it up wherever he went. In return, Zimmer, an orthopedic implant maker, helped enrich Dr. Berger, portraying him as a master surgeon and paying him more than $8 million over a decade.

Those days are gone. Dr. Berger started complaining to Zimmer a while back that one of its artificial-knee models was failing prematurely, and he went public recently with a study that he says proves it. Zimmer told him that the problem was not the artificial knee, but his technique, and pointed to data overseas indicating that the knee was safe.

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