The femoral head may be twisted at birth.
Femoral torsion is common among neonates and may be either
- Internal (femoral anteversion): Knees pointing toward each other with toes in
- External (femoral retroversion): Knees pointing in opposite directions
At birth, internal torsion can be as much as 40° and still be normal. External torsion can also be prominent at birth and still be normal.
Femoral torsion is recognized by laying the child prone on the examining table. The hips are rotated externally and internally. Limitation of internal rotation indicates femoral anteversion, whereas limitation of external rotation indicates femoral retroversion.
Children with internal femoral torsion may regularly sit in the W position (ie, knees are together and feet are spread apart) or sleep prone with legs extended or flexed and internally rotated. These children probably assume this position because it is more comfortable. The W sitting position was thought to worsen torsion, but there is little evidence that the position should be discouraged or avoided. By adolescence, internal torsion tends to gradually decrease to about 15° without intervention. Orthopedic referral and treatment, which includes derotational osteotomy (in which the bone is broken, rotated into normal alignment, and casted), is reserved for children who have a neurologic deficit such as spina bifida or those in whom torsion interferes with ambulation.
External femoral torsion may occur if in utero forces result in an abduction or external rotation of the lower extremity. If external torsion is prominent at birth, a thorough evaluation (including x-rays or ultrasonography) for hip dislocation is indicated. External torsion typically corrects spontaneously, especially after children begin to stand and walk, but orthopedic referral is needed when excessive torsion persists after 8 years. Treatment of external torsion includes derotational osteotomy.