Dear Doctors: When a femur is broken and an 18-inch rod is inserted to stabilize the bone during healing, then removed about a year later, does the bone marrow ever regrow back into the femur? Or will it remain a hollow cavity forever? I appreciate any information you can provide.
Dear Reader: The procedure you are asking about is called intramedullary femoral nailing. For those who are not familiar, this is a surgical process. The purpose is to stabilize a broken thigh bone during healing. The word "intramedullary" means "within the marrow cavity." This is the hollow center of the bone that contains bone marrow. The word "femoral" refers to the femur, or thigh bone. And the wince-inducing term "nailing" refers to the long metal implant, known as a nail, that gets inserted into the marrow cavity in this procedure.
To understand why this type of surgery is necessary, we should begin with the femur. It is the largest and strongest bone in the body. The femur carries much of our body weight. It is subject to constant rotational forces as we walk, bend, turn, kneel and stretch. When a femur breaks, the powerful thigh muscles could keep pulling a broken femur apart as it tries to heal. Doctors can insert a nail or rod into the bone to help prevent this. In addition, the implant makes it possible to bear weight on the injured limb sooner than other forms of treatment would allow.
In most cases, an intramedullary nail is left in place once the femur has fully healed. But it can be removed if needed. For example, if the implant site gets infected, if bone growth around the implant causes problems, or if the implant causes pain or discomfort, the implant can be removed. Intramedullary nails are more likely to be removed in children, who have years of growth ahead of them. Removing the implant is a surgical procedure, done under anesthesia. The surgeon extracts the nail through its original insertion site. How soon a patient can bear weight on the leg after removal depends on the original injury, the condition of the bone and the type of implant used.
Removal of the implant leaves an open space within the medullary canal. And that brings us to bone marrow. This is a specialized tissue that occurs in two different forms. Red marrow contains stem cells that give rise to red and white blood cells, as well as platelets. Yellow marrow is a mostly fatty tissue with little blood-forming activity. As we age, yellow marrow gradually replaces red marrow in the long bones, including the femur.
Most blood cell production actually takes place in the marrow in the pelvis, spine, ribs and sternum. That means having or removing an intramedullary nail doesn't significantly reduce the body's ability to produce blood cells. Over time, the medullary canal will heal and the bone will rebuild. Marrow can fill the open space, although perhaps not to exactly the way it was before surgery.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
