Have you ever really tried to fit a square peg in a round hole? It can be done if the hole is big enough. If not, you could break the peg. This is a bit like the problem doctors face when putting a straight stem into a curved bone during a total hip replacement procedure.
The thighbone (femur) is straight at first, but then curves slightly as it gets closer to the knee. Doctors use X-rays before the operation to see the size and shape of the femur. This helps them choose the right implant for each patient.
A big concern is that fractures at the tip of the implant aren’t always visible during the operation. They probably occur when the implant is put in place down the shaft of the femur. X-rays are taken in the operating room after the stem is in. Finding a fracture during the operation can prevent a second surgery later.
Doctors at the Mount Sinai Hospital in Toronto, Canada, are studying the problem of bone fractures at the tip of uncemented long-stem hip implants. From their findings, they make several suggestions. These apply to patients who have had a failed first hip replacement and are now getting a second implant: