Biomechanical Comparison between Isobar and Dynamic-Transitional Optima (DTO) Hybrid Lumbar Fixators: A Lumbosacral Finite Element and Intersegmental Motion Analysis

Table 1

Design effects of axial stiffness (S) versus maximal allowable displacement (MAD) on the Isobar performance (in terms of 100% intact degenerative model without instrumentation).

Performance	Design parameter		Flexion (%)			Extension (%)			Lateral bending (%)			Axial rotation (%)
			L2/3	L3/4	L5/S1	L2/3	L3L4	L5/S1	L2/3	L3/4	L5/S1	L2L3	L3L4	L5/S1
ROM	Axial stiffness (kN/mm)		57	-62	54	104	-72	41	40	-26	76	15	-8	-14
			↓			↓			↓			↓
			57	-59	53	101	-69	39	31	-18	76	15	-6	-12
	MAD (mm)		53	-51	52	92	-61	38	31	-17	75	15	-7	-11
			↑			↑			↑			↑
			57	-62	54	104	-69	41	40	-26	76	15	-8	-14
Disc stress	Axial stiffness (kN/mm)		51	-55	22	96	-65	22	34	-32	40	52	-37	13
			↓			↓			↓			↓
			49	-55	22	95	-65	22	22	-29	39	52	-35	13
	MAD (mm)		47	-49	52	84	-61	38	22	-27	35	48	-33	10
			↑			↑			↑			↑
			51	-55	54	96	-65	41	34	-32	40	52	-37	13