The femoral neck is a bone segment crucial for human movement and hip joint stability. Its structure facilitates the hip’s wide range of motion, enabling activities like walking and running. It also transmits significant forces between the torso and lower limbs, supporting body weight.
Understanding Its Structure
The femoral neck is a flattened, pyramidal process connecting the spherical femoral head to the femoral shaft. It extends upward, inward, and slightly forward from the thigh bone. It articulates with the acetabulum, a cup-shaped socket in the pelvis, forming the ball-and-socket hip joint.
Its angulation includes two primary angles. The angle of inclination, between the neck and femoral shaft, typically ranges from 120 to 135 degrees in adults, averaging 125-126 degrees. This angle varies with age and sex. The angle of torsion (femoral anteversion) describes the femoral neck’s forward twist relative to the knee’s axis, usually 10 to 20 degrees. These angles are important for hip biomechanics.
The femoral neck consists of two bone tissue types: compact and cancellous. The outer layer is dense compact bone, providing strength and protection. Inside, cancellous (spongy) bone forms a network of interconnected trabeculae. These trabeculae are arranged along stress lines, allowing the bone to bear weight and absorb shock.
Its Role in Movement and Stability
The femoral neck’s angulation and robust structure are crucial for the hip joint’s extensive range of motion. Its connection to the acetabulum enables multi-directional movement, including flexion, extension, rotation, and abduction, allowing for diverse physical activities.
It also functions as a weight-bearing component, transmitting forces from the upper body through the pelvis to the legs. The internal arrangement of cancellous bone helps distribute loads, reducing stress on the bone. It acts as a lever arm for the powerful hip muscles. These muscles attach to the femur and, with the neck’s support, generate force for walking, running, jumping, and maintaining balance.
Common Conditions Affecting the Femoral Neck
The femoral neck is susceptible to injuries and conditions due to its anatomical position and load-bearing function. Fractures are common, often categorized by their location relative to the hip joint capsule. Intracapsular fractures occur within the joint capsule, potentially compromising blood supply to the femoral head. These include subcapital, transcervical, and basicervical types.
Intracapsular fractures, common in older individuals with reduced bone density, are classified by the Garden system based on displacement. A displaced fracture can kink or tear blood vessels supplying the femoral head, increasing complication risk. Stress fractures result from repetitive loading rather than a single traumatic event. They are frequently seen in athletes or military personnel and can be classified as tension-side or compression-side depending on crack location.
Avascular necrosis (AVN), or osteonecrosis, is a condition affecting the femoral head and neck. It occurs when blood supply to the bone is disrupted, leading to bone cell death. This can complicate displaced femoral neck fractures, as blood vessels run along the neck. Without adequate blood flow, bone structure weakens and may collapse, causing pain and joint dysfunction.
Identifying and Managing Femoral Neck Issues
Diagnosis of femoral neck issues typically begins with a physical examination and imaging studies. X-rays are often the initial diagnostic tool for fractures. However, subtle or early-stage stress fractures might not be visible on plain X-rays. In such cases, magnetic resonance imaging (MRI) is a sensitive method for detecting occult fractures, bone marrow edema, and early avascular necrosis. Computed tomography (CT) scans provide detailed cross-sectional images, assisting in complex fracture assessment and surgical planning.
Treatment for femoral neck conditions varies depending on the type, severity, and patient’s overall health. For femoral neck fractures, surgical intervention is often necessary. Options include internal fixation (screws or pins to stabilize the bone), particularly for non-displaced fractures or younger patients. For displaced fractures, especially in older individuals, hip replacement surgery (hemiarthroplasty or total hip arthroplasty) may be performed.
Non-surgical management may be considered for less severe conditions, such as some stress fractures, or for patients unable to undergo surgery due to other medical conditions. This typically involves rest, activity modification, pain management, and physical therapy to restore strength and mobility. Early mobilization is encouraged to prevent complications from prolonged immobility.