Summary
Increasing the holding strength by giving bone cement under
pressure through holes between threads of cannulated screw in
femoral neck fractures.
Reshad Mecid oglu Zeynalov
Femoral neck fractures are one of the most common fracture
types in elderly patients. Dedicated screws were designed or
augmented with different materials to increase the holding power at
the femoral head for better fixation.
In our study 48 human femoral heads divided into two groups
after measuring bone mineral densities by Q-CT. In the control group
7 mm cannulated screws and in the study group 7 mm cannulated
screws with holes between the threads augmented by cement
(PMMA) were used. Pull out, maximum extraction torque and cut
out strength values were compared after mating these groups by
similar bone mineral densities. In the pull out group maximum
holding strength (N) was measured after applying 0,5 mm/sec.
axial pull out force by Instron testing. In the cut out group load
applied using 5 N followed by 2 mm/min. axial loading force after
fixing the femoral heads to the Instron testing. The procedure
was continued until at least 5 mm displacement occured. In the
maximum extraction torque group 4°/sec. torque force was applied in
reverse direction by torquemeter. During the extraction highest
torque was determined. The difference between all three subgroups
was significant(pull out, p<0,011; cut out, p<0,05; extraction torque,
p<0,0001).
The designed screw augmented by PMMA has found to be
worth in this experimental study to be further studied in the clinical
application of the femoral neck fractures.
