Thigh numbness after a total hip replacement (THR) can occur when the surgery is done from the front of the thigh. This approach is called an anterior THR. When two small incisions are made instead of one long one, it's referred to as a minimally invasive (MI) approach.
There is a nerve to the leg along the front of the thigh that branches into several divisions. The exact location of the nerve and its branches isn't always easy to predict. This means the surgeon can't always avoid cutting it when making more than one incision. Every effort is made to keep this from happening but sometimes it's unavoidable.
Some patients develop thigh numbness weeks or months after the operation. This can occur when scar tissue presses on the nerve or even wraps around the nerve. Over time and with the proper stretching exercises, this problem can go away.