Background/Purpose

The three-dimensional evaluation of bone by HR-pQCT has the advantage to provide assessment to not only bone density, but also to a noninvasive evaluation of bone structure and bone strength. Information about changes in bone microarchitecture in juvenile-onset SLE (JoSLE) with and without fractures is lacking and they may improve future strategies of therapy and prediction of fracture risk in these patients. The objective of this study was, therefore, to analyze bone microarchitecture in JoSLE with and without vertebral fractures(VF).  

Methods

Twelve consecutive JoSLE female patients with VF according to Vertebral fracture assessment (VFA) by dual-energy X-ray absorptiometry (DXA)  were selected and compared to 44 female JoSLE patients without VF. Demographic, anthropometric, clinical and laboratory data were recorded by interview and electronic chart review. Bone microarchitecture was evaluated by High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT) at the distal radius.

Results

Patients with and without VF had comparable age (18.0±2.73 vs. 18.5±3.35 years, p=0.0636), BMI (23.03±4.39 vs. 23.15±3.45 kg/m², p=0.927), disease duration (58.25 ± 45.03 vs. 71.39 ± 48.57 months, p=0.403), SLEDAI (4.14±4.04 vs. 4.73±5.92, p=0.744), CG cumulative dose (8602.71±8484.15 vs. 6291.54±6737.18 mg, p=0.454), current GC dose (16.04±14.44 vs. 15.97±19.75 mg/day, p=0.990), maximum GC dose (34.17±26.53 vs. 29.20±31.35 mg/day, p=0.466) and 25-hydroxyvitamin D (22.25 ± 6.93 vs. 23.38 ± 6.90 ng/ml, p=0.610). In spite of these comparable parameters, Table 1 illustrates significant differences in HR-pQCT in distal radius findings in the two groups of patients analyzed. Patients with vertebral fractures had reduced density parameters, particularly related to D100 (p=0.011) and D trab (p=0.024), suggesting a predominant trabecular bone involvement. Structural evaluation in patients with VF revealed a significant reduction in BV/TV (p=0.023) and Tb.Th (p=0.033), both parameters  associated with trabecular organization. Finally, a significant decrease in apparent modulus was observed in patients with VF (p=0.018) indicating a bone strength impairment of VF group.

Table 1:Density and Structural parameters of distal radius assessed HR-pQCT in JoSLE patients with and without vertebral fractures

 

HR-pQCT	Vertebral Fractures   (n=12)	No Vertebral Fractures (n=44)	P
Density Parameters
D 100, mg HA/ccm	229.45 ± 42.09	275.93 ± 56.87	0.011*
D trab, mg HA/ccm	136.96 ± 30.84	163.17 ± 35.45	0.024*
D comp, mg HA/ccm	742.83 ± 87.41	787.67 ± 105.88	0.122
Structural Parameters
BV/TV	0.114 ± 0.03	0.136 ± 0.03	0.023*
Tb.N, 1/mm	1.986 ± 0.31	2.123 ± 0.28	0.165
Tb.Th, mm	0.057 ± 0.01	0.064 ± 0.01	0.033*
Th.Sp, mm	0.461 ± 0.11	0.416 ± 0.07	0.129
Ct.Th, mm	0.428 ± 0.17	0.520 ± 0.22	0.189
Biomechanical Properties
Stiffness, kN/mm	61599.99 ± 34636.81	61814.79 ± 13493.61	0.071
Estimated Failure Load, N	3196.70 ± 2345.13	3005.52 ± 619.73	0.059
Apparent Modulus, N/mm²	1236.36 ± 334.85	1523.70 ± 367.14	0.018*

D100=average bone density; Dtrab=trabecular bone density; Dcomp=compact bone density; HA=hydroxyapatite; BV/TV=trabecular bone volume to tissue volume; Tb.N=trabecular number; Tb.Th=trabecular thickness; Tb.Sp=trabecular separation; Ct.Th=cortical thickness

Conclusion

The novel identification by a non-invasive technique (HRpQCT) that JoSLE patients with vertebral fractures have trabecular bone alterations with a significant reduction in bone strength opens a new perspective to define in future prospective studies the utility of this method for fracture prediction in this disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/trabecular-bone-impairment-assessed-by-hr-pqct-in-juvenile-onset-systemic-lupus-erythematous-with-vertebral-fractures/