A Hybrid Uniplanar Pedicle Screw System with a New Intermediate Screw for Minimally Invasive Spinal Fixation: A Finite Element Analysis
Table 5
Maximum von Mises stress (MPa) on the screw and rod of the construct under different types of loading.
Screw position/rod
Flexion
Extension
6-MAPS
6-UPPS
6-PAPS
4-MAPS/ 2-NIS
4-UPPS/ 2-NIS
4-PAPS/ 2-NIS
6-MAPS
6-UPPS
6-PAPS
4-MAPS/ 2-NIS
4-UPPS/ 2-NIS
4-PAPS/ 2-NIS
Upper
188.03
138.04
96.627
202.93
145.23
96.439
107.68
66.724
126.17
127.42
75.025
124.17
Intermediate
96.809
78.74
83.935
55.664
58.019
61.909
75.384
38.466
49.169
18.843
20.919
48.863
Lower
166.75
108.1
100.74
152.28
107.65
118.27
127.32
187.86
206.74
135.73
192.08
195.52
Rod
109.66
71.177
58.335
119.11
95.562
86.133
116.23
76.532
55.825
113.85
81.163
68.775
Screw position/rod
Right lateral bending
Right axial rotation
6-MAPS
6-UPPS
6-PAPS
4-MAPS/ 2-NIS
4-UPPS/ 2-NIS
4-PAPS/ 2-NIS
6-MAPS
6-UPPS
6-PAPS
4-MAPS/ 2-NIS
4-UPPS/ 2-NIS
4-PAPS/ 2-NIS
Upper
224.7
148.89
218.58
244.2
161.27
144.66
361.95
301.43
28.544
367.55
296.67
56.743
Intermediate
103.91
62.373
58.86
41.66
42.455
61.692
310.21
263.81
66.087
119.46
170.4
256.62
Lower
182.93
205.77
272.05
166.83
211.47
272.7
289.38
190.43
79.318
277.75
187.06
105.01
Rod
180.69
126.13
74.584
179.06
136.06
88.923
132.01
111.46
62.264
147.51
146.31
225.1
6-MAPS: six monoaxial pedicle screw fixation; 6-PAPS: six polyaxial pedicle screw fixation; 6-UPPS: six uniplanar pedicle screw fixation; 4-MAPS/2-NIS: four monoaxial pedicle screw fixation with two new intermediate screws; 4-PAPS/2-NIS: four polyaxial pedicle screw fixation with two new intermediate screws; 4-UPPS/2-NIS: four uniplanar pedicle screw fixation with two new intermediate screws. The maximum von Mises stress of the entire construct under loading was shown as italics.
