[Proportions of the femur and humerus in relation to bone length].
[Proportions of the femur and humerus in relation to bone length]. [Article in German]. Rother P, Krüger G, Schramek G. Taking as a starting point the known fact. Posts about humerus written by Mike Taylor and Matt Wedel. Rather than try to summarize the good bit, I'll just quote it. Based on that figure, the consistent relationship between humeral and femoral shaft circumference in. The direction of the nutrient canal in relation to the end of the diaphysis still later the arteries of the radius, ulna and femurchange their direction, so that in the The text-books of anatomy generally quote either 1Wrard's(8) or Humphry's.
Since humans and chimps share a, relatively, recent common ancestor presumably some evolution has occured in limb proportions. We can look at the postcranial skeletons of a few hominids to determine a rough time line.
Evolution of Human Limb Proportions: Part One | Afarensis: Anthropology, Evolution, and Science
Australopithecus afarensis, for example, has a humerofemoral index of about 84 largely attributed to a smaller femur and a brachial index of about 91 larger radius relative to humerus. In Homo erectus, on the other hand the humerofemoral index is approximately 73 and the brachial index is 79 or roughly the same as in modern humans.Beautiful quotes about relationships - Love - Relationships - Life - Problems
So, during the course of human evolution there have been changes in forearm proportions and in femur length. For quite a while this was interpreted as an example of gradualism in hominin evolution. Then, the fly in the ointment was found.
The fly being OH OH62 was found in by a team led by Donald Johanson in and has been referred to H. In people today, the upper arm bone humerus is considerably shorter than the upper leg bone femur. In modern apes, the humerus and femur are nearly identical in length.
Paleoanthropologists can quantify this difference using a measure called the humerofemoral index, which is defined as the length of the humerus divided by the length of the femur times If the humerus and the femur are nearly equal in length, the index equals If the femur is much longer than the humerus, then the index is a lower number.
So, the shaft of the femur in resting stance on one foot is not expected to be vertical. Just to get everybody confused, we say that the tibia is in valgus relative to the femur.
It's wrong, but we say it anyway - wink wink. Valgus means that as you go distally from the reference joint, the bone deviates away from the body midline.
I can Identify the similarities between the humerus and femur. - Jessica's Skeletal portfolio
Actually the tibia is dead parallel to that midline and it is the femur approaching it. Relative to the femoral neck, the femur shaft is in varus approaches the body midline as we go down. The back of the femur at the top is deeper relative to the neck than the front. Looking at the back of the right femur we see the deep ridge that goes from greater to lesser trochanter. The greater is the handle for upward pulling hip abductors gluteus medius and minimus. The lesser is the handle for the psoas tendon.
Sitting behind the femoral head, the flexion action of the psoas is also an outward rotation force as the lesser trochanter is pulled forward and upward - spinning and raising the femur.
If the psoas is short and prevents the hip from extending, then the lesser trochanter at that point becomes an unusual fulcrum in that it is not only not the femoral head but it is also posterior. Pressure on the head of trying to extend the leg against this fulcrum presses the femoral hear forward and upward. A psoas contracture can - via leg momentum - act as a fulcrum to have the socket pull a hip prosthesis up and out dislodging it and spinning it forward.
That same force in repetitive deformation produces a steeper femoral neck valgus and nudges the head forward anteversion. The sweep of short red arrows indicates that an important bundle of blood vessels sneaks up the back of the neck on its outer surface to enter the femoral head.
This is an important inflow of blood to the femoral head.