Finite element analysis comparing a PEEK posterior fixation device versus pedicle screws for lumbar fusion

Table 3 Range of motion with three models at four operated segments at a pure moment of 7.5 Nm

Motion	Lumbar level	Implant location	ROM (°)			Difference in ROM (°)
Motion	Lumbar level	Implant location	Intact spine	CPPF	PSS	PSS versus intact spine	CPPF versus intact spine	CPPF versus PSS
Flexion	L4–L5	L4–L5	9.0	0.2	0.2	− 8.8	− 8.8	0.0
	L5–S1	L5–S1	9.2	0.8	0.7	− 8.5	− 8.4	0.1
	L4–S1	L4–L5	9.0	0.3	0.2	− 8.8	− 8.7	0.1
	L4–S1	L5–S1	9.2	0.9	0.4	− 8.8	− 8.3	0.5
Extension	L4–L5	L4–L5	− 3.5	− 0.4	− 0.3	3.2	3.1	− 0.1
	L5–S1	L5–S1	− 6.0	− 0.7	− 0.6	5.4	5.3	− 0.1
	L4–S1	L4–L5	− 3.5	− 0.2	− 0.2	3.3	3.3	0.0
	L4–S1	L5–S1	− 6.0	− 0.4	− 0.4	5.6	5.6	0.0
Lateral bending	L4–L5	L4–L5	4.5	0.9	0.8	− 3.7	− 3.6	0.1
	L5–S1	L5–S1	3.2	0.8	0.6	− 2.6	− 2.4	0.2
	L4–S1	L4–L5	4.5	0.9	0.6	− 3.9	− 3.6	0.3
	L4–S1	L5–S1	3.2	0.7	0.1	− 3.1	− 2.5	0.6
Torsion	L4–L5	L4–L5	2.1	0.4	0.9	− 1.2	− 1.7	− 0.5
	L5–S1	L5–S1	2.6	0.6	0.9	− 1.7	− 2.0	− 0.3
	L4–S1	L4–L5	2.1	0.3	0.6	− 1.5	− 1.8	− 0.3
	L4–S1	L5–S1	2.6	0.5	0.4	− 2.2	− 2.1	0.1

CPPF—cortico-pedicular fixation, PSS—pedicle screw system, ROM—range of motion

ISSN: 1749-799X