A hip replacement prosthesis can fail for various reasons. A redo operation is known as revision hip replacement.

Hip replacement is a good reliable operation, but some hip prostheses fail over time. Failure rate is approximately 5% over the first 10 years of implantation. Statistically speaking, the 3 most common reasons for failure of a hip replacement prosthesis are

1. Infection
2. Dislocation
3. Adverse reaction to a metal-on-metal prosthesis: pseudotumors, local tissue damage, cobalt poisoning, etc.

Revision of a hip prosthesis is not a trivial operation.

Depending on the particular problem being addressed, either parts or the entire prosthesis may have to be removed. Certain prostheses are notoriously difficult to remove: the femur typically has to be osteotomized to allow removal of the stem. Recovery, as a consequence is slower as well.

All the risks of regular hip replacement surgery apply: a patient undergoing revision surgery is presumably aware of such risks. However, both the rate of complications, and the severity, are increased compared to a regular hip replacement.