The femoral anteversion refers to the normal rotation of the femoral neck in relation to the femoral shaft. It is a normal anatomical occurrence when it occurs within the normal range. However, in some persons, for one reason or other the femoral anteversion value or the rotaion of the neck with respect to rest of the femur is more than the normal range.
This is called increased or exaggerated femoral anteversion and can lead to various problems as we would discuss below.
Many articles refer both as ‘femoral anteversion’ only but to avoid confusion, it is best to have clarity of the issue.
Anteversion and Retroversion
Before we move further on, it is better to understand what is anteversion and retroversion of an organ.
Anteversion and Retroversion describe the relative rotation of an organ or part of it.
Anteversion means rotated forwards (towards the front of the body)
Retroversion means rotated backward (towards the back of the body)
The version is in comparison to a reference position.
For example, the normal uterus is typically slightly anteverted but in certain cases, it may be retroverted.
In musculoskeletal science, the terms are important in hip and shoulder.
For example, in the hip, the neck of the femur is anteverted slightly. An increase anteversion or retroversion can cause problems in the alignment and gait.
The normal humeral head has 30º of retroversion to the frontal axis of the elbow joint. The femoral head has 12 to 15º of anteversion to the line connecting posterior aspect of both femoral condyles
The acetabulum in a similar manner is slightly anteverted.
Knowing the right version is important in designing of arthroplasty implants and placement during surgery.
Thus the femoral neck is normally anteverted with respect to the rest of the femur [see the diagram]. It is considered abnormal only if it is significantly different from the average value of a patient of the same age.
Femoral Anteversion or Hip Anteversion
The Femur neck is normally anteverted with respect to the rest of the femur [see the diagram]. It is considered abnormal only if it is significantly different from the average value of a patient of the same age.
It is defined as the angle between an imaginary transverse line that runs medially to laterally through the knee joint and an imaginary transverse line passing through the center of the femoral head and neck.
Normal femoral anteversion in adults is 15 and 20 degrees from the frontal plane of the body.
The term medial femoral torsion is also used to describe femoral neck anteversion and is thought to result from medial or internal rotation of the limb bud in early intrauterine life.
The anteverted femur is the most common cause of children walking with their toes inward (in-toeing) in children older than 3 years of age.
With an abnormal anteverted femur, a parent might notice that his or her child is walking with the toes turned inward. A child might also trip or fall more commonly than normal children. The child rarely has pain.
Abnormal femoral anteversion is a developmental abnormality. The normal child is born with 31-40 degrees of femoral anteversion. This gradually decreases to 10 to 15 degrees at adolescence and generally improves with further growth.
Therefore, no treatment is necessary if the value is within this normal range.
Otherwise, the child may be considered for femoral derotation osteotomy.
Change in Femoral Anteversion Angle with Age
- Newborn – 31 degrees
- 5 years – 26 degrees
- 9 years – 21 degrees
- 16 years – 15 degrees by 16 years of age.
How to Measure?
Most femoral torsion problems are evaluated with computerized tomography. This involves 3 images or scans—2 proximal and 1 distal. One image defines the location of the center of the femoral head, the second image defines the base of the femoral neck, and the third image defines the distal femoral condylar axis.
The angle in the transverse plane between the intersection of the plane of the neck and the condylar plane defines the angle of anteversion.
- Children with an in-toeing or out-toeing gait have an increased or decreased femoral neck anteversion angle respectively
- Decreased femoral neck anteversion is thought to be a factor in developing slipped capital femoral epiphysis though more studies are required on this topic.
- Patients who had decreased femoral neck anteversion angle angles also were more likely to have osteoarthritis of the hip.
- An increase or decrease in the femoral anteversion may alter the hip’s congruity and place abnormal stress on the acetabular labrum and could lead to injury.
Femoral Retroversion or Retroversion of Hip
When the femoral neck angle is less than the average range [ 15-20 degrees], it is called femoral retroversion or hip retroversion.
If the anteversion is less than the normal average or the inclination of the femoral neck is in opposite direction. Femoral neck retroversion is present when the head and neck of the femur are angled less than the average anteversion angle along the frontal plane of the body.
In some cases, the femoral head and neck may even be angled backward from the frontal plane of the body.