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. Forces that are acting at the hip joint during
walking produces stresses in the proximal femur as a result of combined effect
of the axial & bending and tortional loads. In the normal situation the
proximal femur is loaded(   )
. so this loads making the medial cortex is compressed and the lateral cortex
is under tension . The majority of the compressive stresses in the femur are
the greatest in the medial cortex 1- 3 
inches  below the lesser
trochanter . i. e the subtrochanteric region is considered one of the most
stressed region in the body . tensile stresses of it about 25%  and less occurrence at the lateral cortex
slight  proximally(   ) .

As a result of fracture ,and the associated subsequent
unbalanced muscle pull that leads to displacement of the fracture , hence this displacement
will result in some difficulty in neutralization of that
fracture .the insertion of the iliopsoas to the lesser trochanter leads to
flexion and external rotation of the proximal fragment and the insertion of the
short adductor muscles  to the greater
trochanter leads to abduction of the proximal fragment of the fracture. distal
fragment always displaced medially  as a
result of the pull of the adductor magnus muscle. further more the presence of
comminution of the medial cortex leads to damage to this stressed area(     ) .

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Cephalomedullary nails are getting the ability to
provide necessary bending and tortional stability to withstand the displacement
of the fracture fragments. And also its load sharing devices and has getting
the advantage of the short lever arm , thus decreasing the tensile strain which
are working on this implant(   )

The hip screw of the proximal nailing providing
rotational stability of the head –neck fragments .the distal screw control the
rotation of the distal fragment . a biomechanical analysis by TENCER(  )   etal on
different implants used for the subtrochanteric fracture find that the bending
stress ,torsional stress , load to axial failure are superior in
cephalomedullary nails  than other
implants . another  biomechanical
analysis by PAUL R . T KUZYK(  )   etal in
2009 , on reverse oblique trochanteric 
fractures and he find that the cephalomedullary devices stiffer and had
greater load to failure than the 135 degrees and 95 degrees implants such as
DHS (Dynamic hip screw) ,especially in cases when there is a gap between the
bony fragments . indirect reduction of the fracture and the preservation of the
fracture haematoma with minimal soft tissue dissection thus decreasing the
amount of blood loss and resultant decrease in the overall morbidity .






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