Thursday, January 08, 2009

Stacking bones Male Comparison to Female

A major constraint that most fitting systems don't concern is the comparison of the male and female pelves.  This is a major constraint, as it attaches to the lower vertebrae column and their can even be abnormal spinal curvatures (scoliosis, kyphosis, lordosis). 

Because most of the stress of the vertebral column occurs in the lumbar region, these are the sturdiest of the vertebrae.  Their size does vary from person to person (male to female). However, a bone that articulates with L5, the sacrum (a 5 fused vertebrae) that lies within pelvic girdle is of great concern.  The sacrum is slightly concave anteriorly and forms the posterior border of the pelvis.  It also has a couple of articular process(s) that lie superior and lateral and allow for movement with the inferior articular process of the next upper vertebrae.

This important antomic landmark articulates with centrum of 5th lumbar.  Why?  The presence of the discs and their construction of the vertebral column prevent shock to the head and allow for flexibility in the movement of the body trunk much needed for balance sports.  Don't measure this complex system or have the wrong saddle shape tilt that is too far forward or backwards or has the wrong tilt and you will cause problems.  And as we know, you don't use the shape of a male hip and turn around and use that info for a female hip.

Although bones of males are usually larger and heavier and have more prominent bone markings, the bones of the male and female skeletons are very similar when looking from the outside only.  But truth is, there are many difference!

The outstanding exception to this often generalization is pelvic structure.  So striking are the differences between male and female pelves that a "trained anatomist" can immediately determine the sex of the skeleton during a casual examination of the pelvis.


                                                      Female                Male

General structure        Tilted forward, shallow,                     
Less tilt, narrow, and deep, for
and functional               broad pelvis                                        males heavier build & stronger mm

Bone thickness             Less, lighter, thiner                          Greater, heavier, thicker

Acetabula                     Smaller; farther apart                           Larger; closer

Pubic angle/arch        Broader (over 90-degree)                     Angle more acute (less than 90)

Anterior view             Mini Mouse look                                     Micky Mouse look

Sacrum                       Wider, shorter, sacral accentuated       Narrow, sacral more ventral

Coccyx                        More movable; straighter                      Less movable; curves ventrally

Lateral view            Coccyx points more posteriorly               Coccyx more tucked

Pelvic inlet              Wider oval side-to-side                              Narrow, heart shaped

Pelvic outlet          Wider; ischial tuberosities shorter,          Narrower; tuberosities longer
                                 father apart, and everted                            sharper, and point more medially

The ability to bear weight is more important here than exceptional mobility and flexibility. The combined weight of the upper body rests on the bony pelvis (specifically, where the hip bones meet the sacrum).

In both sexes, the sacroiliac joint, because of the pressure it must bear, is often a site of lower back problems.  The dimensions of these regions may better be determined by palpation, more accurately.  

The iliac crest terminates in the anterior superior spine ASIS (the origin site of many thigh flexor muscles) and the posterior superior spine, to which many muscles extending the thigh attach.  

The ischium is the "sit-down" bone, forming the most inferior and posterior portion of the coxal bone.  The most outstanding marking on the ischium is the ischial tuberosity, which receives the weight of the body when sitting on a saddle of choice.

Two other anatomical features are the lesser and greater sciatic notches, which allow passage of nerves and blood vessels to and from the leg.

Then you have the thigh.  The femur is the sole bone of the thigh and is the heaviest, strongest bone in the body.  The head of the multi shape thigh articulates with the acetabulum of the hip bone.  The femur inclines medially as it runs downward to the lower leg bones; in most cases: this brings the knees in line with the body's  center of gravity or maximum weight.

I think you get the point.  Without taking true palpations or more costly X-rays measurements of the many landmarks that lie within the body i.e. hip , you are only providing a basic observation of movement.  Think the many muscles that attach here!

Bottom line!  If you don't get the front end of the car aligned by a professional who takes measurements of the hard parts, you are going to wear the tires out faster!!!

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