Multiobjective Optimization Design of Spinal Pedicle Screws Using Neural Networks and Genetic Algorithm: Mathematical Models and Mechanical Validation
Table 2
Structures and results of FE analyses and mechanical tests of four commercially available pedicle screws and the optimal design. Values were expressed as mean (standard deviation).
Mechanical properties
Synthes type
A-Spine type
Moss Miami type
Viper type
Optimal design
BP (mm)
0
0
40
cylindrical
0
CD (mm)
2.76
4
4.61
4.4
3.8
PRR (mm)
0.22
0.1
3
3
0.4
P (mm)
2
2
2.95
2.87
3.3
PHA (°)
0
0
31.35
29.93
5
TW (mm)
0.1
0.1
0.2
0.33
0.1
Maximum tensile stress (MPa)
1220
628
1268
1766
422
Total reaction force (N)
40.25
40.77
33.53
34.04
39.1
Fatigue life (103 cycles)
13.77 (4.62)
46.53 (15.9)
8.52 (1.35)
—
>1000
Pullout strength, 0.32 g/cm3 (N)
2148 (144)
2068 (117)
1598 (56)
1553 (84)
2009 (74)
Pullout strength, 0.16 g/cm3 (N)
1015 (74)
951 (48)
705 (48)
662 (63)
825 (52)
Cyclic loading tests of Viper type screws were not completed because the screws yielded quickly during the tests.
