The femur, or thigh bone, is the longest and strongest bone in the human body. The femoral neck is the narrow segment connecting the spherical femoral head, which forms the hip joint, to the main shaft of the femur. A femur neck fracture is a break in this specific area, located entirely within the joint capsule. This type of fracture is considered a serious injury requiring immediate medical attention and usually surgical intervention.
Defining the Injury and Primary Causes
A femur neck fracture involves a break in the bone segment immediately below the ball of the hip joint. The mechanism of injury differs significantly based on patient age and bone health. The vast majority of these fractures occur in older adults, typically resulting from low-impact trauma such as a simple fall. This vulnerability is driven by osteoporosis, a condition characterized by decreased bone mineral density.
Advanced age and female gender are the most recognized risk factors for this type of fragility fracture. In younger individuals, the fracture is usually due to high-impact trauma, such as motor vehicle collisions or falls from a significant height, which generates the massive force required to break a healthy bone.
Understanding Fracture Classification
Accurate classification of a femur neck fracture directly determines the appropriate treatment approach. The most commonly used system is the Garden classification, which assesses the degree of fracture displacement. Fractures are broadly categorized as either non-displaced (stable, Garden Types I and II) or displaced (unstable, Garden Types III and IV).
Non-displaced fractures mean the bone fragments are still correctly aligned or minimally impacted. Displaced fractures mean the fragments have shifted significantly and are no longer in contact. The distinction is important due to the risk of avascular necrosis (AVN). The femoral head receives its blood supply from vessels running along the neck of the femur.
When a fracture is displaced, these blood vessels are often torn, interrupting blood flow. This creates a high risk of AVN, where the bone tissue in the femoral head dies from a lack of oxygen and nutrients. Displaced fractures carry an AVN risk as high as 30% to 45%, compared to less than 10% for non-displaced fractures. This loss of circulation is compounded by the fracture’s intracapsular location, where joint fluid inhibits the formation of a healing clot. Therefore, treatment for displaced fractures often involves replacing the damaged femoral head entirely.
Surgical Treatment Options
Surgery is the standard treatment for nearly all femur neck fractures to restore function and prevent complications. The choice among the three main surgical options depends on the fracture classification, the patient’s age, and their pre-injury activity level. The primary goal is to mobilize the patient quickly to avoid complications associated with prolonged bed rest.
Internal Fixation
Internal fixation, known as osteosynthesis, is the preferred method for non-displaced fractures in patients of any age, and for displaced fractures in younger patients. This procedure uses specialized metal screws, pins, or a sliding hip screw to hold the fractured bone fragments together while they heal naturally. This approach preserves the patient’s native hip joint and is favored when there is a reasonable chance of successful bone union and an intact blood supply.
For younger patients with displaced fractures, surgeons prioritize internal fixation to attempt to save the femoral head, despite the elevated risk of AVN. These procedures ideally need to be performed rapidly, often within 6 to 24 hours of the injury, to maximize the chance of preserving blood flow.
Hemiarthroplasty
Hemiarthroplasty, or partial hip replacement, is the most common treatment for displaced fractures in older, less active patients, particularly those over 65 years old. In this procedure, the fractured femoral head and neck are removed and replaced with a prosthetic implant. This implant typically consists of a metal stem inserted into the femur with a ball component that articulates with the patient’s native hip socket (acetabulum).
This replacement avoids the high risk of non-union and avascular necrosis associated with fixing a displaced fracture in an elderly patient with poor bone quality. Hemiarthroplasty is a less complex operation than a total hip replacement and provides a reliable solution for patients with lower functional demands.
Total Hip Arthroplasty
Total Hip Arthroplasty (THA), or total hip replacement, replaces both the femoral head and the hip socket with prosthetic components. This option is generally reserved for active elderly patients with displaced fractures who have high functional expectations. It is also the treatment of choice if the patient has pre-existing degenerative arthritis in the hip joint.
THA offers superior long-term functional outcomes and less risk of future revision surgery compared to hemiarthroplasty. However, it is a more extensive operation and carries a slightly increased risk of dislocation immediately post-operatively.
Recovery and Long-Term Outlook
The recovery process begins immediately after surgery. Early mobilization, often starting on the first day post-operation, is a focus to prevent complications such as pneumonia and blood clots. Physical therapy (PT) is a necessary component, initially focusing on pain management and gentle range-of-motion exercises.
The full rehabilitation duration can vary significantly, ranging from three to twelve months before a patient returns to their pre-injury mobility. Weight-bearing restrictions are initially imposed and gradually lifted, a process that can take up to twelve weeks depending on the surgery type. PT progresses to strengthening the surrounding muscles, improving balance, and gait retraining to ensure safe, independent walking.
Despite successful surgery, specific long-term complications remain a concern. Non-union, the failure of the fracture to heal, occurs in up to 25% of displaced fractures treated with internal fixation. Avascular necrosis, if not avoided, will require a conversion to a hip replacement later on. Preventive measures are important for the at-risk population, focusing on reducing the risk of falls. Strategies include home safety modifications, balance training, and medical management of underlying osteoporosis.