What is the femur, and how can it get injured?

anatomy of the femur

If you can stand up, thank your femurs. These two bones—one in each leg—are the longest and strongest bones in the human body. They support the weight of your body as you walk, run, and jump. At one end, each femur has a rounded joint called a ball joint that slots into the hip socket, allowing your legs to swivel. At the other end is the knee, where the femur meets the kneecap, tibia, and fibula. Most of the bone is the femoral shaft, the long, sturdy column that supports your leg.

The femur is often called the thighbone, because it runs through the body under the thigh.

How can the femur break?

While it’s not easy to break such a sturdy bone, it’s certainly possible, especially when the forces of a high-speed crash are involved.

How the bone breaks will differ depending on the forces involved. A comparatively low force (perhaps as a result of a lower-speed accident or a strike from a smaller vehicle) can cause a stable fracture, in which the bone is cracked but not out of place. A higher force might cause a displaced fracture, which means that the two ends of the broken bone are separated from each other. A very high-speed accident or a crushing injury could cause a communited fracture, in which the bone is shattered into three or more pieces.

A transverse fracture happens when the bone is broken horizontally and displaced. When the bone breaks at an angle, the fracture is said to be oblique. An oblique fracture may start out as stable, but if the break is not treated quickly it can become displaced, potentially causing more serious complications. A bone that is acted on in by a twisting force may crack in a spiral-shaped pattern, called a spiral fracture.

When the broken end of a bone protrudes through the skin, the fracture is said to be open or compound. Immediate treatment is needed for these type of fractures because the open wound can become infected, spreading pathogens deep into the body. A doctor treating this type of fracture must also take special care with the torn skin, muscles, and other soft tissues surrounding the bone.

A closed fracture involves a bone that has not broken through the skin, although nearby muscles and blood vessels may still be pierced or torn. In some severe closed fractures, the edges of the broken bone may be seen “tenting” the skin.

The femur can also fracture above and below the shaft. A fracture in the upper quarter of the femur, where it slots into the pelvis, is called a hip fracture. An intracapsular fracture happens within the soft tissue envelope of the hip joint, at the “neck” of the bone. These fractures can be dangerous because they may cut off blood supply to the bone. An intertrochanteric fracture can happen between the neck of the femur and a feature called the lesser trochanter. A subtrochanteric happens below this area but above the shaft of the femur.

The area below the shaft is called the distal femur. Fractures in this area can affect the function of the knee. While a fracture in the distal femur may create pain and swelling in the knee, some patients feel pain further up in the thigh.

How can a femoral fracture be treated?

Treatment for a femoral fracture depends on where exactly the bone has broken. Because this bone is so long and so important for any weightbearing activity, healing the bone may require reinforcing it or temporarily taking weight off of it.

After a severe break, surgery may be necessary for drawing the broken ends of the bone together and holding them together while they heal. In a femoral shaft fracture, a surgeon may use a technique called external fixation in which metal screws or pins anchored in the bone are attached to a bar on the outside of the body. While this type of surgery is easy to form, it’s an unpleasant long-term solution, and is usually done to stabilize a patient until a more permanent surgery can take place. The most popular procedure for surgically treating a femoral shaft fracture is called intramedullary nailing: a metal rod is passed all the way through the bone in the marrow canal and fixed in place with screws. This stabilizes the bone as it heals. When smaller fragments are involved in a fracture, metal plates and screws can be used to hold them in place.

It’s very rare for a femoral shaft fracture to heal cleanly without surgery. Young children, whose bones are still in the process of rapidly growing, may be treated with a cast.

If the femur is fractured at the hip, the surgical procedure will be different. Some types of fractures are small and stable enough that a surgeon may not feel the need to operate. A surgeon may also elect not to perform surgery on a hip fracture if they are concerned that their patient is too ill to undergo anesthesia.

Hip surgeries are intricate and delicate procedures. Multiple screws may be necessary to hold the fractured pieces of the hip in place. A surgeon may also need to perform procedures to fix damaged cartilage and restore the blood supply to prevent avascular necrosis, a condition in which the tissue of the bone dies because its blood supply is severed.

In severe cases, a surgeon may need to perform a hip replacement to fix a severely injured femur. A total hip replacement involves removing the entire hip socket and ball joint and replacing them with an artificial implant. A hemiarthroplasty leaves the hip socket and replaces only the ball of the hip.

Sources:

 "Femur Shaft Fractures (Broken Thighbone)-OrthoInfo - AAOS." Femur Shaft Fractures (Broken Thighbone)-OrthoInfo - AAOS. N.p., n.d. Web. 10 June 2016.