Femur

The femur is the large upper leg bone that extends from the hip to the knee. It is the largest bone in the human body. Because of its significant size and strength, the femur plays a crucial anatomical role as a base for soft tissue attachment and for bearing weight. The femur is one of the body's long bones, which means that it is longer than it is wide. Being a long bone also means that the femur is composed of a hard outer surface called compact bone and a crisscrossed interior referred to as cancellous bone. Each end of the femur connects with a major joint. The proximal end of the femur, or the end that is closer to the center of the body, connects with the pelvis at the acetabulum to form the hip. The distal end of the femur, or the end farthest from the center of the body, forms the knee joint with the tibia and patella.

Background

Physicians and anatomists have studied the femur and the rest of the human skeleton since antiquity. In fact, it was the ancient Greek physician, surgeon, and philosopher Galen who first identified the femur as the largest bone in the body. Since that time, the work of various experts has revealed a great deal about the femur's unique structure and function.

The femur is arguably the most important bone in the lower body. Its size, strength, and structure are pivotal to a person's ability to stand and walk. The body of the femur, or the shaft, provides a great deal of weight-bearing strength without which the human frame could not support itself in an upright position. Beyond that, the femur has a number of different anatomical features that are critical to movement. The femoral head is one of those features. Located at the bone's proximal end, the femoral head is a smooth, cartilage-coated surface that is rounded and ball-like. It sits inside a pelvic cavity called the acetabulum to form the hip joint. The hip joint is stabilized through bony contact. It is also supported by the ligamentum teres femoris, a ligament that runs through the femoral head and connects to the surface of the acetabulum. The femoral head is connected to the shaft by the femoral neck, which also provides key structural support between the femur and the hip.

The shaft of the femur has two descending ridges called the linea aspera and the gluteal tuberosity. These ridges provide attachment sites for different muscles, including the gluteus maximus, the pectineus muscle, and others.

At the distal end of the shaft, there is a pair of round prominences called condyles. The condyles articulate with the tibia and provide attachment points for the key soft-tissue structures found in the knee. These include the menisci and the cruciate ligaments. The collateral ligaments connect with the femur through the medial and lateral epicondyles, which are situated just above the condyles. All of these structures work together with the femur, tibia, and fibula to make knee movement possible.

Overview

Aside from its simple weight-bearing functions, the femur primarily serves to facilitate a person's ability to walk. Much of this ability is based directly on the relationship between the femur and the acetabulum. One of the most important factors in this relationship is the angle of inclination, which is the angle of the femoral neck in relation to the shaft of the femur. This angle is greatest at birth, but gradually decreases as the weight load across the femoral increases during childhood and adolescence. In any event, the angle of inclination brings the femur away from the body and enables the swinging movement that makes walking as fluid and efficient as possible.

Abnormalities in the angle of inclination typically result in malalignments and other problems that can inhibit one's ability to walk or at least alter a person's gait. The two common abnormalities of this sort are coxa vara and coxa valga. In coxa vara, the position of the head and neck of the femur is decreased in relation to the shaft. In coxa valga, the position is increased. These abnormalities can be either congenital or acquired. Acquired abnormalities in the angle of inclination are usually the result of poor posture or injury. Coxa vara and coxa valga both typically lead to other physical abnormalities of the femur. Specifically, coxa vara and coxa valga change the angle between the femoral head and shaft and can affect the alignment of the lower limb.

Because of the femur's important role in weight-bearing and walking, injuries to the bone can be quite debilitating. Fractures are the most common injuries affecting the femur. Such fractures typically occur at the femoral head or the condyles. They may also occur in the shaft. Fractures of the femoral neck are most common in older patients who suffer from osteoporosis, a degenerative disease that causes bones to become brittle and weak over time. Other types of femoral fractures typically occur because of trauma such as falls, motor vehicle accidents, or gunshot wounds. Patients who suffer a femoral fracture often present with pain and swelling, an inability to stand or walk, and possible deformity of the injured leg. Treatment usually involves the use of splints and ambulatory aids like crutches or a walker. Casts are typically only used for young children. Severe fractures may also require surgery involving the placement of pins, screws, plates, or rods. Many femoral shaft fractures are treated with a procedure called intramedullary nailing, in which a metal rod is placed inside the hollow center of the bone to hold it in position during healing.

Femoral stress fractures are another common type of femur injury. Rather than a full break, these fractures are simply an incomplete crack in the bone. They are typically a result of the great forces and stresses that the femur regularly endures. When such forces become too strong or too repetitive, bone damage to the femur can occur. As this damage worsens over time, it can develop into a stress fracture. Femoral stress fractures usually result in thigh or knee pain that worsens with increased activity and improves with rest. Treatment generally requires a period of rest from weight-bearing activity until the pain subsides. Full recovery also often requires some form of physical therapy.

Bibliography

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