Hounsfield units in assessing bone mineral density in ankylosing spondylitis patients with cervical fracture-dislocation

Table 1 Demographics and clinical data of 51 ankylosing spondylitis patients with cervical spine fracture-dislocation

Feature	Male, n = 44	Female, n = 7	Total, n = 51
Age (years)	55.14	59.57	55.4
Injury level
C1/2	5 (11.36)	0 (0)	5 (9.80)
C2/3	2 (4.55)	0 (0)	2 (3.92)
C3/4	2 (4.55)	0 (0)	2 (3.92)
C4/5	5 (11.36)	1 (14.28)	6 (11.76)
C5/6	13 (29.54)	3 (42.86)	16 (31.37)
C6/7	17 (38.64)	3 (42.86)	20 (39.23)
ASIA grade
A	2 (4.55)	1 (14.28)	3 (5.88)
B	5 (11.36)	2 (28.58)	7 (13.73)
C	14 (31.82)	3 (42.86)	17 (33.33)
D	23 (52.27)	1 (14.28)	24 (47.06)

Data are n (%). ASIA: American Spinal Injury Association.

Table 2 Hounsfield units from three levels of sagittal plane reconstruction images of two readers

Segment	Reader 1-Housfield units			Reader 2-Housfield units
	Right	Middle	Left	Right	Middle	Left
C2	337	296	334	336	297	334
C3	266	228	261	266	229	260
C4	250	215	249	253	215	250
C5	233	198	226	235	198	225
C6	218	181	214	217	182	215
C7	201	173	196	202	174	196
Average	251	215	247	252	216	247

Table 3 Reliability and agreement of Hounsfield units

Segment	Readers 1-Housfield units	Readers 2-Housfield units		ICC
C2	322.83	322.10		0.96
C3	252.23	251.55		0.94
C4	238.95	239.57		0.96
C5	219.60	218.47		0.91
C6	204.49	205.02		0.99
C7	190.20	190.41		0.98
Average	238.05	237.85		0.93

ICC: Interclass correlation coefficient.

Table 4 Hounsfield unit thresholds for osteopenia and osteoporosis

Bone mineral Density	T-value	HU
Normal	-1 or greater	≤ 274.33
Osteopenia	-1 to -2.5	228.08-274.33
Osteoporosis	-2.5 or less	≤ 228.08

HU: Hounsfield unit.