What is the Difference Between Intracapsular and Extracapsular Fracture of Neck of Femur

The key difference between intracapsular and extracapsular fracture of neck of femur is that intracapsular fracture of the neck of the femur occurs proximal to the point at which the hip joint capsule connects to the femur, while extracapsular fracture of the neck of the femur occurs distal to the point at which hip joint capsule connects to the femur.

The femur is the largest, thickest, and strongest bone in the human body. There are two femurs; the left femur and the right femur. The proximal ends of the femurs articulate with the tibia, forming knee joints. Heads of the femurs articulate with acetabulum forming hip joints. The femur provides attachment points for muscles that exert their forces on the hip and knee joints. The neck of the femur is one part of the femur, which is a flattened pyramidal process of bone. It connects the femoral head and femoral shaft. Structurally, it is the weakest part of the femur. The neck of femur fractures, also known as femoral neck fractures, are very common in the elderly population. They are a type of hip fracture. There are two types of neck of femur fractures;  they are intracapsular and extracapsular fractures.

CONTENTS

1. Overview and Key Difference
2. What is an Intracapsular Fracture of Neck of Femur
3. What is an Extracapsular Fracture of Neck of Femur
4. Similarities – Intracapsular and Extracapsular Fracture of Neck of Femur
5. Intracapsular vs Extracapsular Fracture of Neck of Femur in Tabular Form
6. Summary – Intracapsular vs Extracapsular Fracture of Neck of Femur

What is an Intracapsular Fracture of Neck of Femur?

Intracapsular fracture of neck of the femur occurs proximal to the point at which the hip joint capsule is attached to the femur. This means intracapsular fracture of the neck of the femur occurs within the capsule of the hip joint. The clinical presentation may include a fall followed by pain in the groin, limited ability to weight bear, limited range of movement, and external rotation with shortening of the length of the limb in displaced fractures. Intracapsular fracture of the neck of the femur may be caused by high-energy trauma such as road traffic accidents and falls from a standing height.

An intracapsular fracture can be diagnosed through plain X-ray, MRI pelvis, CT pelvis, and technetium bones scan. Furthermore, treatment options for this condition may include internal fixation via 3 to 4 parallel partially threaded cancellous screws, replacement of the femoral head (hemiarthroplasty), and total hip replacement.

What is an Extracapsular Fracture of Neck of Femur?

Extracapsular fracture of neck of femur occurs distal to the point at which the hip joint capsule is attached to the femur. This means extracapsular fracture of the neck of the femur occurs out of the capsule of the hip joint. This type of fracture is below the intertrochanteric line. Moreover, extracapsular fracture of the neck of the femur includes intertrochanteric and subtrochanteric fractures. As the joint capsule is not damaged in this fracture type, the blood supply to the fracture site is adequate. Ultimately, this leads to better fracture healing and an improved prognosis.

The clinical presentation of extracapsular fracture of the neck of the femur may include pain in the groin that radiates down to the thigh, inability to bear weight, reduced range of hip movement, the shortening of the affected limb, and bruising around the joint as the bone hematoma is not contained within the joint capsule. Extracapsular fractures of the neck of the femur can be caused by high-energy trauma, pathological fractures resulting from tumors or infections, osteopenia and osteoporosis due to reduced bone mineral density, corticosteroid usage, alcohol consumption, malnutrition, and stress fractures.

Extracapsular fracture of the neck of the femur can be diagnosed through plain radiography. Furthermore, treatment options for extracapsular fracture of the neck of the femur may include internal fixation with multiple pins (cannulated screws), intramedullary hip screw (IHMS), crossed screw nails, or compression with a dynamic screw and plate.

What are the Similarities Between Intracapsular and Extracapsular Fracture of Neck of Femur?

• Intracapsular and extracapsular fractures of the neck of the femur are two types of hip fractures.
• Both fracture types may have similar clinical presentations, such as pain in the groin that radiates down to the thigh, inability to bear weight, etc.
• Both fractures are common in older patients suffering from osteopenia and osteoporosis, and young people facing high-energy trauma.
• Both fractures can be diagnosed through imaging tests.
• They are predominantly treated by specific surgeries.

What is the Difference Between Intracapsular and Extracapsular Fracture of Neck of Femur?

Intracapsular fracture of the neck of the femur occurs proximal to the point at which the hip joint capsule is attached to the femur, while extracapsular fracture of the neck of the femur occurs distal to the point at which the hip joint capsule is attached to the femur. Thus, this is is the key difference between intracapsular and extracapsular fracture of neck of femur. Furthermore, in an intracapsular fracture of the neck of the femur, the joint capsule is damaged, and the blood supply to the fracture site is not sufficient. On the other hand, in the extracapsular fracture of the neck of the femur, the joint capsule is not damaged, and the blood supply to the fracture site is sufficient.

The below infographic presents the differences between intracapsular and extracapsular fracture of neck of femur in tabular form for side by side comparison.

Summary – Intracapsular vs Extracapsular Fracture of Neck of Femur

Hip fractures are breaks that occur in the top of the femur close to the hip joint. Intracapsular and extracapsular fractures of the neck of the femur are two different types of hip fractures. Intracapsular fracture of the neck of the femur occurs proximal to the point at which the hip joint capsule is attached to the femur, while extracapsular fracture of the neck of the femur occurs distal to the point at which the hip joint capsule is attached to the femur. So, this is the main difference between intracapsular and extracapsular fracture of neck of femur.

Reference:

1. Leyla Noury. “Fractured Neck of Femur: FNOF: Orthopaedics.” Geeky Medics, 26 Nov. 2022.
2. Gerard A Malanga, MD. “Femoral Neck Fracture.” Background, Etiology, Epidemiology, Medscape, 8 Feb. 2021.

Image Courtesy:

1. “Hip fracture classification” By Mikael Häggström (CC0) via Commons Wikimedia
2. “Neck of Femur fracture Right side in a 80 years old female patient” By Drvaram – Own work (CC BY-SA 4.0) via Commons Wikimedia