Sir Paul McCartney's estranged wife Heather Mills is facing a hip operation, according to reports. It appears undergoing serious surgery could be the latest struggle for the former model, who lost a leg when she was hit by a motorbike in 1993. A metal plate was inserted in her leg, but is now causing problems for Mills. A source tells British newspaper the Daily Mirror, "It separated after a screw came out. "Two weeks ago the joint moved and is out of line - it's not stable. She could face a serious operation." The former Beatle and Mills attended a settlement meeting before a judge at London's Royal Courts Of Justice last Thursday (11Oct07), but failed to agree on the terms of their divorce despite eight hours of talks.