Bone Mineral Density at the Distal Femur and Proximal Tibia and Related Factors During the First Year of Spinal Cord Injury

Figures & data

Table 1 Demographic and Clinical Data of SCI Patients

Cases (n)	36
Gender (M/F)	26/10
Age (years)	37.0±10.3
Postinjury duration (months)	2 (0.98, 4.45)
Cause of SCI (traumatic/non-traumatic)	31/5
Type of paralysis (paraplegia/quadriplegia)	30/6
Injury severity (complete/incomplete)	20/16
BMI (kg/m^2)	22.96±3.67
DF BMD (g/cm^2)	0.816±0.155
PT BMD (g/cm^2)	0.800±0.159
Femoral neck BMD (g/cm^2)	0.752±0.110
Total hip BMD (g/cm^2)	0.904±0.149
Ca (mmol/L)	2.34±0.12
P (mmol/L)	1.41±0.20
ALP (IU/L)	81.10 (62.48, 125.78)
25OHD (ng/mL)	14.28±6.18
Number/Percentage of 25OHD deficiency	32/88.89%
CTX (ng/mL)	1.056±0.357
PINP (ng/mL)	106.10 (85.58, 145.75)
OC (ng/mL)	19.38±6.88
PTH (ng/mL)	20.79 (16.85, 26.63)

Abbreviations: SCI, spinal cord injury; BMI, body mass index; DF, distal femur; PT, proximal tibia; BMD, bone mineral density; ALP, alkaline phosphatase; 25OHD, 25-hydroxyvitamin D; CTX, collagen type-I C-terminal telopeptide; PINP, N-terminal propeptide of type-I procollagen; OC, osteocalcin; PTH, parathyroid hormone.

Table 2 Z-Score of Femoral Neck and Total Hip in SCI Patients

	6 w PI (n=15)	6 w–3 m PI (n=10)	3–12 m PI (n=11)	All SCI (n=36)
Z-score of femoral neck	−0.620±0.948	−0.660±0.802	−1.245±0.474	−0.822±0.819
Z-score of total hip	−0.220±0.998	−0.330±0.779	−1.300±0.867	−0.581±1.003

Abbreviations: SCI, spinal cord injury; PI, post-injury; 6 w, 6 weeks; 6 w–3 m, 6 weeks to 3 months; 3–12 m, 3–12 months.

Figure 1 Comparison of BMDs at the DF, PT, and hip between SCI patients and healthy controls. (A) Comparison of BMDs between All SCI patients (n=36) and the controls; (B) Comparison of BMDs between SCI patients within 6 weeks post-injury (n=15) and the controls; (C) Comparison of BMDs between SCI patients during 6 weeks–3months post-injury (n=10) and the controls; (D) Comparison of BMDs between SCI patients during 3–12months post-injury (n=11) and the controls. *P<0.05, **P<0.01, ***P<0.001, independent sample t-test.

Abbreviations: BMD, bone mineral density; DF, distal femur; PT, proximal tibia; SCI, spinal cord injury.

Table 3 Longitudinal Comparison of BMDs at the DF, PT, and Hip in Eight SCI Patients

	DF BMD (g/cm^2)	PT BMD (g/cm^2)	Femoral Neck BMD (g/cm^2)	Total Hip BMD (g/cm^2)
Baseline	0.851±0.114	0.824±0.128	0.719±0.083	0.876±0.126
After six months	0.754±0.147	0.735±0.178	0.692±0.077	0.796±0.136
Reduction (%)	11.40	10.80	3.76	9.13
t	2.569	3.234	1.242	1.968
P	0.042	0.018	0.261	0.097

Abbreviations: DF, distal femur; PT, proximal tibia; BMD, bone mineral density.

Table 4 Correlations Between Clinical Indicators and BMDs at the DF and PT

	DF BMD		PT BMD
	r	P	r	P
Age	−0.457	0.005	−0.503	0.002
Time post-injury	−0.24	0.158	0.236	0.167
BMI	0.025	0.884	0.238	0.162
Ca	0.256	0.150	0.091	0.616
P	0.293	0.098	0.290	0.102
ALP	0.404	0.020	0.305	0.084
25OHD	0.397	0.040	0.132	0.510
OC	0.156	0.428	−0.023	0.907
CTX	0.287	0.139	0.23	0.238
PINP	0.401	0.034	0.423	0.025
PTH	−0.449	0.017	−0.285	0.141
Femoral neck BMD	0.638	<0.001	0.706	<0.001
Total hip BMD	0.547	0.001	0.631	<0.001

Abbreviations: BMI, body mass index; DF, distal femur; PT, proximal tibia; BMD, bone mineral density; ALP, alkaline phosphatase; 25OHD, 25-hydroxyvitamin D; CTX, collagen type-I C-terminal telopeptide; PINP, N-terminal propeptide of type-I procollagen; OC, osteocalcin; PTH, parathyroid hormone.

Table 5 Multiple Linear Regression Analysis of BMDs at the DF and PT

	Variable	Regression Coefficient	Standard Error	Standard Regression Coefficient	t	P
DF BMD	Age	−0.006	0.003	−0.363	−2.242	0.036
	25OHD	0.011	0.004	0.422	2.444	0.022
PT BMD	Age	−0.008	0.003	−0.436	−2.551	0.019
	Gender	−0.179	0.075	−0.474	−2.385	0.027

Abbreviations: DF, distal femur; PT, proximal tibia; BMD, bone mineral density; 25OHD, 25-hydroxyvitamin D.

Table 6 Comparison of BMD Between Complete Lesion and Incomplete Lesion Groups

Injury Severity	DF BMD (g/cm^2)	PT BMD (g/cm^2)	Femoral Neck BMD (g/cm^2)	Total Hip BMD (g/cm^2)
Complete (n=20)	0.856±0.144	0.835±0.141	0.781±0.122	0.926±0.151
Incomplete (n=16)	0.759±0.157	0.757±0.175	0.709±0.088	0.877±0.145
t	1.933	1.469	1.996	0.988
P	0.062	0.151	0.054	0.330

Abbreviations: DF, distal femur; PT, proximal tibia; BMD, bone mineral density.