Verification of pure moment testing in a multi–degree of freedom spine testing apparatus

Amy M. Fuller; Jennifer M. Chui; Daniel J. Cook; Matthew S. Yeager; David A. Gladowski; Boyle C. Cheng

doi:10.1016/j.ijsp.2011.12.001

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Fig. 1
Diagram depicting all constructs used for experiments, with shaded vertebra indicating an instrumented or fixed body. (A) In group A 3 constructs were used to test the pure moment assumption. (B) In group B 8 constructs were used to test for degradation due to testing order and change in orientation.
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Fig. 2
ROM in degrees for group A, testing the pure moment assumption, in 3 modes of loading: flexion-extension, lateral bending, and axial torsion.
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Fig. 3
ROM in degrees for group B in 3 modes of loading—flexion-extension, lateral bending, and axial torsion—at (A) L1-L2 and (B) L2-L3. Group B testing was performed to observe degradation of specimens over 8 treatments and change in orientation of specimens.

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Table 1

Calculated P values from group B testing, indicating increase in ROM over 8 treatments

	B1		B2		B3		B4		B5		B6		B7		B8

Treatment	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3	L1-2	L2-3
Flexion-extension
B1			>.999	>.999	>.999	>.999	.275	>.999	.144	.898	.006^*	.211	.039^*	.369	<.001^*	.135
B2	>.999	>.999			>.999	>.999	>.999	.437	.178	.284	.035^*	.037^*	.217	.088	.005^*	.056
B3	>.999	>.999	>.999	>.999			>.999	>.999	.025^*	>.999	.017^*	.044^*	.037^*	.066	.074	.047^*
B4	.275	>.999	>.999	.437	>.999	>.999			>.999	>.999	.011^*	.012^*	.207	.068	.041^*	.041^*
B5	.144	.898	.178	.284	.025^*	>.999	>.999	>.999			.791	.013^*	>.999	.039^*	.413	.03^*
B6	.006^*	.221	.035^*	.037^*	.017^*	.044^*	.011^*	.012^*	.791	.13			>.999	>.999	>.999	.113
B7	.039^*	.369	.217	.088	.037^*	.066	.207	.068	>.999	.039^*	>.999	>.999			>.999	.189
B8	<.001^*	.135	.005^*	.056	.074	.047^*	.041^*	.041^*	.413	.03^*	>.999	.113	>.999	.189
Lateral bending
B1			>.999	>.999	>.999	>.999	>.999	>.999	.742	.727	.134	.329	.169	.289	.094	.162
B2	>.999	>.999			>.999	>.999	>.999	>.999	>.999	>.999	>.999	>.999	>.999	>.999	>.999	.608
B3	>.999	>.999	>.999	>.999			>.999	>.999	.667	.134	.049^*	.006^*	.114	.007^*	.08	.014^*
B4	>.999	>.999	>.999	>.999	>.999	>.999			.808	.322	.013^*	.036^*	.049^*	.027^*	.06	.033^*
B5	.742	.727	>.999	>.999	.667	.134	.808	.322			.809	.72	.864	.086	.061	.013^*
B6	.134	.329	>.999	>.999	.049^*	.006^*	.013^*	.036^*	.809	.72			>.999	>.999	.562	.215
B7	.169	.289	>.999	>.999	.114	.007^*	.049^*	.027^*	.864	.086	>.999	>.999			.573	.095
B8	.094	.162	>.999	.608	.08	.014^*	.06	.033^*	.061	.013^*	.562	.215	.573	.095
Axial torsion
B1			>.999	>.999	>.999	>.999	.57	.791	.348	.687	.059	.1111	.059	.126	.08	.391
B2	>.999	>.999			>.999	>.999	>.999	>.999	>.999	>.999	>.999	.006^*	>.999	>.999	>.999	>.999
B3	>.999	>.999	>.999	>.999			.703	>.999	.424	.239	.115	.07	.102	.011^*	.1	.227
B4	.57	.791	>.999	>.999	.703	>.999			.432	>.999	.206	.021^*	.15	.06	.106	.311
B5	.348	.687	>.999	>.999	.424	.239	.432	>.999			.516		.386	.012^*	.125	.255
B6	.059	.111	>.999	>.999	.115	.006^*	.206	.07	.516	.021^*		.535	>.999	.535	.5	>.999
B7	.059	.126	>.999	>.999	.102	.011^*	.15	.06	.386	.012^*	>.999				.964	>.999
B8	.08	.391	>.999	>.999	.1	.227	.106	.311	.125	.255	.5	>.999	.964	>.999