Femoral Neck Anteversion - Measurement, Significance, Variations, and Treatment

Introduction

The word ‘version’ in anatomy is used to refer to the angle or rotation of any part of the body like bone, organ, or other structures. Anteversion refers to any abnormal forward tilting or rotation of any body part. The femur is the long thigh bone connecting the knee joint to the hip joint. The forward rotation of the femur is known as the femur anteversion.

What Is Femoral Neck Anteversion?

Femoral neck anteversion (FNA) is a term used to describe the rotation of the femoral neck in relation to the femoral head. It is also known as the femoral version or femoral torsion. It refers to the angle between the axis of the femoral neck and the transcondylar axis of the femur.

What Is the Normal and Abnormal Femoral Neck Anteversion?

• Femoral neck anteversion (FNA) keeps changing throughout the growth of an individual.

• The normal femoral neck anteversion angle ranges from 8 to 15 degrees in adults. This range allows for proper alignment of the hip joint, stable gait, and efficient muscle function.

• During gestation, the femoral anteversion starts at 0 degrees and becomes 30 degrees during birth, which then changes as the individual grows to become 15 degrees in adulthood.

• Excessive anteversion can cause the hip to rotate too far inward, which causes abnormal gait. This can result in instability, muscle imbalances, and a predisposition to hip dislocation or subluxation.

• The opposite of anteversion is retroversion, in which the angle is less than 8 degrees. This can cause the hip to rotate outward, which may result in hip impingement.

How Is Femoral Neck Anteversion Measured?

Femoral neck anteversion can be measured using a variety of imaging techniques and clinical tests. Some of the commonly used methods are listed below.

• Imaging Techniques: X-rays, CT (computed tomography) scans, and MRI (magnetic resonance imaging) can be used to measure femoral neck anteversion. These imaging techniques provide a three-dimensional view of the hip joint and allow for accurate measurement of the angle.

• Clinical Tests: One of the commonly used clinical tests is called Craig's test. This test involves palpating the greater trochanter while the hip is passively rotated. The angle of the hip rotation is measured, and the femoral neck anteversion angle can be estimated based on this measurement.

• Ultrasound: A special ultrasound technique called Hip US (ultrasound) with measurement of femoral neck anteversion can also be used to measure femoral neck anteversion. This method is noninvasive and can be used in children and infants.

• Computed Tomography (CT) with 3D Reconstruction: This technique involves taking a CT scan of the hip and then reconstructing a 3D Image of the hip joint. This method is highly accurate and allows for precise measurement of the femoral neck anteversion.

What Is the Biomechanical Significance of Femoral Neck Anteversion?

The femoral neck anteversion has important biomechanical significance for the hip joint and the lower extremity as a whole.

• Joint Stability: The femoral neck anteversion angle plays a crucial role in determining the stability of the hip joint. If the angle is within the normal range, the hip joint is more stable and less prone to dislocation or subluxation. However, if the angle is too high or too low, it can lead to instability and an increased risk of injury.

• Gait and Movement: The femoral neck anteversion angle affects the mechanics of walking and other low extremity movements. In particular excessive anteversion can cause an in-toeing gait where the feet point inward, and retro version can cause an out-toeing gait where the feet point outward. These muscle imbalances can lead to muscle imbalances, joint pain, and reduced efficiency of movement.

• Joint Contact and Loading: The femoral neck anteversion angle affects the loading patterns within the hip joint. Abnormal angles can cause uneven pressure and loading on the hip joint, leading to wear and tear, degeneration, and the development of conditions such as hip osteoarthritis.

• Surgical Considerations: The femoral neck anteversion angle is an important consideration for orthopedic surgeons when planning surgical procedures involving the hip joint, such as hip arthroplasty or mastectomy. Thus angle affects the alignment of the hip joint, and improper alignment can lead to poor outcomes and complications.

What Causes Altered Femoral Neck Anteversion?

The exact cause of altered FNA is not always clear, and in some cases, it may be due to a combination of genetic, environmental, and developmental factors. Potential causes of altered FNA include:

• Congenital conditions like developmental dysplasia of the hip may result in altered FNA. This can occur due to the abnormal development of the hip joint during fetal development greatly childhood.

• Genetic factors may also play a role in altered FNA.

• Neuromuscular disorders like cerebral palsy or muscular dystrophy may cause imbalances and altered hip joint mechanics, leading to changes in femoral neck anteversion.

• Traumatic injuries to the hip joint or femur may cause changes in the femoral neck anteversion.

• Overuse injuries or repetitive stress to the hip joint.

• Idiopathic causes.

What Are the Consequences of Altered Femoral Neck Anteversion?

Alteredfemoral neck anteversion can have a range of consequences on a person's health, depending on the severity and underlying cause of the condition. Some of the potential consequences include

• Gait abnormalities.

• Pain in the hip, groin, thigh, or knee.

• Stiffness in the hip joint.

• Muscle weakness and overuse.

• Joint instability and dislocations.

• Joint degeneration.

• Hip impingement.

• Poor surgical outcomes.

• Functional limitations.

How Is Altered Femoral Neck Anteversion Treated?

The treatment for altered femoral neck anteversion depends on the severity of the condition, the underlying cause, and the presence or absence of symptoms. Some of the treatment options include:

• Observation: In some cases, the femoral neck anteversion may not cause any symptoms or functional limitations. In such cases, observation and regular monitoring may be sufficient.

• Physical Therapy: Physiotherapy can help address muscle imbalances and improve joint mechanics. This may include exercises to strengthen weak muscles and stretch tight ones, as well as gait training and functional activities.

• Orthotics: Orthotic devices, such as shoe inserts or braces, can help improve alignment and reduce symptoms in some cases.

• Surgery: In severe cases of altered FNA that cause significant joint instability, or functional limitations, surgery may be necessary. This may include procedures such as femoral mastectomy, hip arthroplasty, or soft tissue releases.

Conclusion

Altered femoral neck anteversion can have biomechanical, functional, and health consequences. An accurate diagnosis and appropriate management can help address the underlying causes and improve outcomes for individuals with altered femoral neck anteversion.