A Hybrid Uniplanar Pedicle Screw System with a New Intermediate Screw for Minimally Invasive Spinal Fixation: A Finite Element Analysis

Table 4

Range of motion (ROM) (°) of T12-L2 and maximum displacement (mm) of T12 after six types of the pedicle screw fixation under different types of loading.

Fixation types	ROM of T12-L2				Maximum displacement of T12
	Flexion	Extension	RLB	RAR	Flexion	Extension	RLB	RAR
6-MAPS	3.89	1.86	4.34	2.35	2.31	0.71	1.93	1.96
6-UPPS	3.88	2.89	5.15	2.53	2.28	0.74	2.06	2.29
6-PAPS	3.94	3.64	6.06	3.5	2.32	0.89	2.31	3.55
4-MAPS/2-NIS	3.84	2.22	4.35	2.37	2.28	0.73	1.94	1.98
4-UPPS/2-NIS	3.96	2.79	5.27	2.52	2.33	0.78	2.11	2.28
4-PAPS/2-NIS	3.94	3.19	5.98	2.58	2.32	0.84	2.28	2.62

RLB: right lateral bending; RAR: right axial rotation; 6-MAPS: six monoaxial pedicle screw fixation; 6-PAPS: six polyaxial pedicle screw fixation; 6-UPPS: six uniplanar pedicle screws 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.