From The Gait Guys
Gait, Running or Biomechanical problems ? Today we talk of Torsions and Versions….
(excerpted from the forthcoming second edition of our book)
We’ve all heard of, and probably have used, the terms torsion or version especially in the vernacular of antetorsion or anteversion and retrotorsion and retroversion. We (including authors and researchers) often like to use these terms interchangeably. Technically speaking, we have all been wrong.
Believe it or not, there was actually a group of folks in 1979 called the Subcommittee on Torsional Deformity and Pediatric Orthopedic Society whose mission was to set people straight on the differences between torsionand version. Version is actually the normal difference in angulation of the proximal and distal portions of a long bone. Torsion is said to be present when this measurement falls outside 2 standard deviations of the normal version.
Versions are present in utero and are considered part of the developmental process. For example, the femur has approximately 30 degrees of anteversion at birth (ie the femoral condyles are rotated 30 degrees medial to the plane of the femur head). During the normal developmental process, the femur “untwists” at a rate as slow as 1-3 degrees per year to approximately a 20 degree by age 6, leading to a “normal” angle of 8-12 degrees of anteversion. Of course this can occur slower or faster or to a greater or lesser degree as well resulting in a torsion, which may or may not have symptomatic sequela later in life. Regardless, these torsions are very important transverse plane deformities from a gait biomechanists point of view in regards to resultant compensations which occur in the lower kinetic chain and more proximally.
These versions and torsions can affect any long bone, but most important to us, the femur and tibia. Of interesting note, there is a 2:1 preponderance of left sided deformities believed to be due to most babies being carried on their backs on the left side of the mother in utero, causing the left leg to overlie the right in an externally rotated and abducted position.
Now maybe you will think twice about the position of the feet of a newborn when placing them on their stomach, as this posturing will effect their development over time and potentially contribute to adult torsional deformity! How’s the sleeping position of your child? Do they consistently sleep on one side? Is their thigh drawn up and internally rotated with a compensatory external rotation of the foot relative to the tibia? Wow, and you thought as long as you fed them well and didn’t let them watch too much TV that all would be OK!
Torsions and Versions…. They are not just for breakfast anymore…
Yes, we ARE a little twisted……Ivo and Shawn
JC Physiotherapy addition:
There are functional demands which govern positioning of these structures:
- Hip ROM is huge and often a leg sum of torsions and versions results in IR will toe in.
- The person also will preferentially want to track their foot straight this competes with 1, and can have an IR or ER bias.
- The 3 rockers of the foot. These are essential for balance and I would predict this would add strength to point 2.
NB: What people do not have (in ROM), they will try to create.