Hello colleagues -
At the risk of annoying, if not flat out
infuriating, any more of the group of clinicians and researchers who prefer
camaraderie to accuracy and relevance, I realize that in the US, the term
anteversion (directed forward) is commonly used to describe femoral antetorsion
(twisted about the longitudinal axis, such that the longitudinal head and neck
bisection is directed anteriorly when the posterior border of the condyles (the
transcondylar axis) is aligned on the frontal plane).
However, terms
anteversion and antetorsion are NOT synonymous. You change the femoral head and
neck anteversion angle with every change in femoral rotation position. Hip
lateral rotation increases the head and neck anteversion angle relative to both
the acetabulum (which is also anteverted) and to the frontal plane, for example,
while the torsional geometry of the femur remains unchanged.
Whoever it
was that identified a twisted femur - that leaves the head and neck bisection
directed anteriorly (anteverted) when the posterior border of the condyles (the
transcondylar axis) was lying on the table (the frontal plane) - as femoral
anteversion (what if the femoral head were heavy enough to drop to the table
instead?) created a LOAD of havoc and confusion. This mess is evidently not a
problem for European clinicians who do not use the term anteversion to describe
antetorsion unless they come to the US to present a paper on the subject.
My
best source on this issue is Dietrich Tonnis et al (1987)
Congenital
Dysplasia and Dislocation of the Hip In Children And Adults.
New York:
Springer-Verlag. In the second chapter, he states that in the western
hemisphere, anteversion is used inaccurately lieu of antetorsion.
In
order to facilitate your mental processing, I suggest you get some aluminum
foil, get 2 marker pens and a drum stick or something that could be used for the
femoral shaft. Use the foil to wrap the marker pens onto each end of the stick
at 90-degrees to it, add a small foil bulb for the femoral head to one
end, and regard the other end as the condyles and knee axis.
What's
the point of niggling over nomenclature in this case?
The magnitude of
femoral antetorsion normally diminishes from birth - when the mean approaches 40
degrees - through adulthood - when the mean rests between 15 and 20
degrees.(
Shands AR, Steele MK. (1958) Torsion of the femur: a follow-up
report on the use of the Dunlap method for its determination. J Bone Joint Surg.
40-A(4):803-816.; Tonnis D, Heinecke A. (1991) Diminished femoral antetorsion
syndrome: a cause of pain and osteoarthritis. J Pediatr Orthop.
11(4):419-431) At age 3 or 4 years, nondisabled children who
have a normal femoral antetorsion of about 30 degrees walk with their knee axes
aligned on or very near the frontal plane, and the patellae in midline at the
midstance and midswing phases of gait. They therefore use about 30 degrees of
femoral head and neck anteversion relative to the frontal plane at those same
moments of the gait cycle. Adults with 16 degrees of femoral antetorsion use 16
degrees of anteversion by comparison.
Researchers who implement 3-D
skeletal modeling techniques to visualize normal and pathologic musculoskeletal
alignment in gait might not bring this distinction to their computerized
visualizations.
If a child with increased femoral antetorsion (common to
many with cerebral palsy, for example), shows medially-rotated knee axes in
gait, the unwitting clinician who wishes to improve the appearance of the gait
pattern by applying lateral rotation straps or cables might place the femoral
head and neck in excessive anteversion, and risk the load-bearing status of the
hip joint. However, since children normally use more functional femoral
head and neck anteversion than adults, the femur could be safely so positioned
as long as the head and neck align within 10 degrees of the reported normal mean
for the child's age. (
Shands and Steele's norms fall near the middle of the
span of reported norms in the collective graph that appears in Tonnis et al
(1991). So they are like a median for the reported means, and I use them as a
clinical guide. Furthermore, the authors state that 80% of their findings fell
within 10 degrees of the means.)
Furthermore, if the rotation angle
of the knee axis is known via computerized kinematic analysis, and the femoral
torsion status is known, then the functional angle of the femoral head and neck
could be calculated and compared with the norms reported by Shands and Steele.
Perhaps most children with pathologic gait related to increased femoral
antetorsion use a relatively normal femoral head and neck anteversion angle
which would preserve the load-bearing function of the more proximal joint, and
display the consequences of the torsional deviation at the (secondary) knee
joint.
I would appreciate hearing from anyone out there who either
shares this concern over our deteriorating nomenclature, finds this particular
information in any way useful, or would like to offer a different point of
view.
Thanks for your time.
Beverly Cusick, PT,
MS
PS: I've also addressed this aspect of LE skeletal development
in my courses on developmental biomechanics, on my website, and in the opening
monograph for the home study on Physical Therapy in Pediatrics, published in
2000 by the APTA's Orthopedic Section. (Info also available on my website:
www.gaitways.com . The home study package is still available, but I do not think
they are conducting a course on it anymore.)
=========================================
Beverly Cusick, MS,
PT
[log in to unmask]http://www.gaitways.com
