Table 2.

Means (standard deviations) of neutral zone stiffness (NZS) and elastic zone stiffness (EZS) of upper (T1/T4), middle (T4/T8), and lower (T8/T12) thoracic segments for all modes of bending for intact rib cage and no rib cage conditions of human thoracic spines with 400 N follower loads under ±5 N·m dynamic moments (*p<0.05; †p<0.1)

		Lateral Bending		Flexion/Extension		Axial Rotation
Segment	Condition	NZS	EZS	NZS	EZS	NZS	EZS
Upper (T1/T4)	Intact Ribs	5.66	6.85	1.05	2.29	2.94	3.28
		(3.84)	(2.09)	(0.62)	(1.75)	(4.42)	(3.60)
	No Ribs	3.12	4.70†	1.29	2.12	0.51*	1.35
		(3.04)	(1.58)	(1.09)	(1.31)	(0.31)	(0.59)
Middle (T4/T8)	Intact Ribs	8.87	8.30	3.27	4.74	2.04	4.51
		(4.46)	(5.50)	(3.91)	(4.10)	(2.49)	(6.13)
	No Ribs	5.45	4.48†	1.95†	3.36	0.42	1.08
		(3.63)	(3.53)	(2.25)	(2.17)	(0.14)	(0.27)
Lower (T8/T12)	Intact Ribs	3.10	2.87	1.79	2.97	0.59	2.31
		(1.25)	(4.72)	(1.72)	(2.23)	(0.29)	(2.89)
	No Ribs	2.68	1.50	0.89	1.39†	0.48*	1.02
		(2.38)	(0.80)	(0.35)	(0.35)	(0.29)	(0.33)