Canal Bone Ratio for Predicting Bone Mineral Density in Lumbar Degenerative Diseases

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Figure 1
Method for measuring canal bone ratio (CBR). This figure illustrates the measurement of CBR using the femoral shaft, with an inner diameter of 15.7 mm and an outer diameter of 28.3 mm. The calculated CBR is 0.554 (CBR = inner diameter/outer diameter).
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Figure 2
Correlation graphs between (A) CBR and low T score and (B) CBR and age. Although a correlation was observed between CBR and T score (r = −0.361, P < 0.001), there was no correlation between CBR and age (r = 0.164, P = 0.100). Abbreviation: CBR, canal bone ratio.
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Figure 3
ROC curve for osteoporosis in patients with lumbar degenerative disease. The results of the ROC curve analysis and the AUC of CBR-7 for the proximal femora are shown. Abbreviations: AUC, area under the curve; CBR, canal bone ratio; ROC, receiver operating characteristic.

Table 1

Baseline characteristics of patients (N = 102).

Characteristic	Value
Age, y, mean (SD)	73.3 (7.6)
Sex, men/women, n	49/53
Height, cm, mean (SD)	157.2 (8.8)
Body weight, kg, mean (SD)	60.0 (12.7)
BMI, mean (SD)	24.2 (3.8)
Indications, n (%)
LCS+ (LDS)	88 (86)
Degenerative lumbar scoliosis	9 (9)
Foraminal stenosis	4 (4)
Lumbar disc herniation	1 (1)
Lumbar BMD, mean (SD)	0.978 (0.227)
Lumbar YAM BMD, %, mean (SD)	99.6 (22.8)
Lumbar spine T score, mean (SD)	0 (2.0)
Femoral neck BMD, mean (SD)	0.652 (0.143)
Femoral neck YAM BMD, %, mean (SD)	82.2 (17.9)
Femoral neck T score, mean (SD)	−1.6 (1.6)
Low T score, mean (SD)	−1.7 (1.5)
Low YAM BMD, %, mean (SD)	81.3 (17.3)
T score, n (%)
Normal (>−1.0)	30 (29)
Osteopenia (<−1.0, >−2.5)	40 (39)
Osteoporosis (<−2.5)	32 (31)
Inner diameter of the femoral shaft, mean (SD)	14.1 (2.0)
Outer diameter of the femoral shaft, mean (SD)	28.7 (2.4)
CBR, mean (SD)	0.491 (0.058)

Abbreviations: BMD, bone mineral density; BMI, body mass index; CBR, canal bone ratio; LCS, lumbar canal stenosis; LDS, lumbar degenerative spondylolisthesis; YAM, young adult mean.
Note: Lower values of the 2 measured BMD sites signified “low T score” and “low YAM BMD.”

Table 2

Spearman product-moment correlation matrix between HU at L1−L4 and VBQ scores.

Abbreviations: CBR, canal bone ratio; HU, Hounsfield units; VBQ, vertebral body quality.
*P < 0.05 indicates significant differences.

Table 3

Spearman product-moment correlation matrix between lumbar T score, femoral neck T score, low T score, and HU values.

Table 4

Comparison of clinical outcomes in osteoporotic vs nonosteoporotic patients.

Characteristic	Nonosteoporosis (n = 70)	Osteoporosis (n = 32)	P
Age, y, mean (SD)	72.1 (8.0)	76.1 (5.6)	0.011^{^a}
Sex, men/women, n	43/27	6/26	<0.001^{^a}
Height, cm, mean (SD)	159.6 (8.5)	151.9 (7.2)	<0.001^{^a}
Body weight, kg, mean (SD)	63.8 (12.6)	51.9 (8.4)	<0.001^{^a}
BMI, mean (SD)	24.9 (3.7)	22.5 (3.3)	0.002^{^a}
Tobacco use, n (%)	13 (19)	3 (9)	0.194
Steroid use, n (%)	4 (6)	6 (19)	0.092
Indications, n (%)
LCS+ (LDS)	61 (87)	27 (84)	0.362
Degenerative lumbar scoliosis	7 (10)	2 (6)
Foraminal stenosis	1 (1)	3 (9)
Lumbar disc herniation	1 (1)	0 (0)
Lumbar BMD, mean (SD)	1.059 (0.213)	0.800(0.134)	<0.001^{^a}
Lumbar YAM BMD, %, mean (SD)	107.8 (21.5)	81.5 (13.1)	<0.001^{^a}
Lumbar spine T score, mean (SD)	0.7 (1.9)	−1.6 (1.1)	<0.001^{^a}
Femoral neck BMD, mean (SD)	0.717 (0.119)	0.509 (0.065)	<0.001^{^a}
Femoral neck YAM BMD, %, mean (SD)	90.5 (14.9)	64.1 (7.6)	<0.001^{^a}
Femoral neck T score, mean (SD)	−0.9 (1.3)	−3.2 (0.6)	<0.001^{^a}
Low YAM BMD, %, mean (SD)	89.3 (14.4)	63.7 (7.1)	<0.001^{^a}
Low T score, mean (SD)	−0.9 (1.3)	−3.2 (0.6)	<0.001^{^a}
Inner diameter of the femoral shaft, mean (SD)	13.9 (2.0)	14.5 (1.9)	0.200
Outer diameter of the femoral shaft, mean (SD)	29.2 (2.3)	27.7 (2.4)	0.005^{^a}
CBR, mean (SD)	0.477 (0.056)	0.521 (0.050)	<0.001^{^a}

Abbreviations: BMD, bone mineral density; BMI, body mass index; CBR, canal bone ratio; LCS, lumbar canal stenosis; LDS, lumbar degenerative spondylolisthesis; YAM, young adult mean.
Note: Data presented as mean (SD) or number of patients (%).
↵a Statistically significant.