There have been several cases of some metal-on-metal (MoM) hip replacements wearing off sooner than expected, medical expert says. Those who usually undergo MoM hip replacements are those suffering from damaged hips caused by a fracture or caused by arthritis.  Instead of relieving a person from those pains, their situation worsens, causing them to file a lawsuit against DePuy Orthopaedics, a unit of Johnson & Johnson, However it seems that the victims of the defective DePuy hip implants may ...