Femoral Antetorsion FAQ
What is femoral antetorsion?
What is femoral anteversion?
Is the femur the only bone that features antetorsion?
Why is femoral antetorsion relevant?
How can femoral antetorsion be quantified?
What is the best way to measure femoral antetorsion?
Does the converter also work with retrotorsion?
Who is responsible for this website?
References

What is femoral antetorsion?

The antetorsion of the femur is the angle between the femoral neck and the femoral condyles. In most persons, the orientation of the proximal and distal part of the femur is not parallel: The antetorsion angle is often positive (this is termed ‘antetorsion’), but can also be negative (this is termed ‘retrotorsion’).

What is femoral anteversion?

The term ‘anteversion’ is used interchangeably with ‘antetorsion’. Therefore, positive angles are termed ‘anteversion’ and negative values are termed ‘retroversion’.

Is the femur the only bone that features antetorsion?

No, other long bones in the human body also feature various amounts of antetorsion or retrotorsion, such as found in the tibia or the humerus.

Why is femoral antetorsion relevant?

There is a wide range of antetorsion values in both healthy individuals and patients with hip diseases. In some patients, an abnormal antetorsion is associated with a hip disease, while in other patients an abnormal antetorsion may have a limited or no association with a hip disease.
While it has been known for a long time that abnormal femoral antetorsion can be associated with diseases such as developmental dysplasia of the hip [Tönnis 1991], it has only recently been shown that abnormal femoral antetorsion can be a contributing factor in the development of femoroacetabular impingement (FAI)[Sutter 2012].

How can femoral antetorsion be quantified?

Quantification of normal and abnormal femoral antetorsion at clinical examination is not very reliable [Maier 2012]. While radiographs have been used previously to estimate femoral antetorsion, usually the measurements are now performed with computed tomography (CT), magnetic resonance imaging (MRI), or biplanar radiographs (EOS) [Sutter 2012, Rosskopf 2014]. There are various differences between different measurement techniques, so caution should be used when comparing antetorsion values obtained with different measurement techniques.

What is the best way to measure femoral antetorsion?

For anatomically correct measurements, the femoral antetorsion should be measured on strictly transverse images over the proximal and distal parts of the femur, as can be done on transverse CT or MRI images. However, many MRI protocols feature oblique images that are parallel to the femoral neck. Some authors perform measurements of femoral antetorsion by using these oblique images – however, in order to arrive at anatomically correct values, these measurements need to be converted as described in a recent paper [Sutter 2015]. This website provides an online calculator to perform this conversion.

Does the converter also work with retrotorsion?

The converter works both with positive and negative antetorsion values, so both antetorsion and retrotorsion values can be converted from the oblique method into the standard transverse values.

Who is responsible for this website?

This website is provided by Reto Sutter, M.D., a senior musculoskeletal radiologist at Balgrist University Hospital in Zurich/Switzerland and is based on one of his publications [Sutter 2015].

Dr. Sutter can be contacted via the Balgrist website.

References

Liu RW, Toogood P, Hart DE, Davy DT, Cooperman DR. The effect of varus and valgus osteotomies on femoral version. J Pediatr Orthop 2009;29:666-675. [ LINK ]

Maier C, Zingg P, Seifert B, Sutter R, Dora C. Femoral torsion: reliability and validity of the trochanteric prominence angle test. Hip Int 2012;22:534-538. [ LINK ]

Rosskopf AB, Ramseier LE, Sutter R, Pfirrmann CW, Buck FM. Femoral and tibial torsion measurement in children and adolescents: comparison of 3D models based on low-dose biplanar radiography and low-dose CT. AJR Am J Roentgenol. 2014;202(3):W285-91. [ LINK ]

Schneider B, Laubenberger J, Jemlich S, Groene K, Weber HM, Langer M. Measurement of femoral antetorsion and tibial torsion by magnetic resonance imaging. Br J Radiol 1997;70:575-579. [ LINK ]

Sutter R, Dietrich TJ, Zingg PO, Pfirrmann CW. Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology 2012;263:475-483. [ LINK ]

Sutter R, Dietrich TJ, Zingg PO, Pfirrmann CW. Assessment of Femoral Antetorsion with MRI: Comparison of Oblique Measurements to Standard Transverse Measurements. AJR Am J Roentgenol 2015;205:130-135. [ LINK ]

Sutter R, Pfirrmann CW. Update on Femoroacetabular Impingement: What Is New, and How Should We Assess It? Semin Musculoskelet Radiol. 2017;21(5):518-528. [ LINK ]

Tönnis D, Heinecke A. Diminished femoral antetorsion syndrome: a cause of pain and osteoarthritis. J Pediatr Orthop 1991;11:419-431. [ LINK ]

Tomczak RJ, Guenther KP, Rieber A, Mergo P, Ros PR, Brambs HJ. MR imaging measurement of the femoral antetorsional angle as a new technique: comparison with CT in children and adults. AJR 1997;168:791-794. [ LINK ]
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