US health care giant Johnson & Johnson is in talks to buy US-Swiss medical-equipment maker Synthes in a deal that could be valued at around $20 billion, The Wall Street Journal reported. Citing unnamed \"people familiar with the matter,\" the newspaper said that if the two sides reached a deal, it would rank as one of the biggest health-care takeovers in recent years. It is unclear just how far the talks have progressed, The Journal said. One person, the paper noted, cautioned that the talks were fragile and could fall apart at any time. Shares of Synthes rose 6.2 percent Friday as speculation about a sale of the company mounted, the report pointed out. But these stock movements could also undo the transaction, The Journal said.