Trabecular bone microstructure is impaired in the proximal femur of human immunodeficiency virus-infected men with normal bone mineral density

Abstract

Background: There is evidence that human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) are independent risk factors for osteoporosis and fracture which is not solely explained by changes in bone mineral density. Thus, we hypothesized that the assessment of trabecular microstructure might play an important role for bone quality in this population and might explain the increased fracture risk. In this study, we have assessed bone microstructure in the proximal femur using high-resolution magnetic resonance imaging (MRI) as well as in the extremities using high resolution peripheral quantitative computed tomography (HR-pQCT) in HIV-infected men and healthy controls and compared these findings to those based on areal bone mineral density (aBMD) derived from dual X-ray absorptiometry (DXA) which is the standard clinical parameter for the diagnosis of osteoporosis.Methods: Eight HIV-infected men and 11 healthy age-matched controls were recruited and informed consent was obtained before each scan. High-resolution MRI of the proximal femur was performed using fully balanced steady state free precession (bSSFP) on a 3T system. Three volumes of interest at corresponding anatomic locations across all subjects were defined based on registrations of a common template. Four MR-based trabecular microstructural parameters were analyzed at each region: fuzzy bone volume fraction (f-BVF), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp). In addition, the distal radius and distal tibia were imaged with HR-pQCT. Four HR-pQCT-based microstructural parameters were analyzed: trabecular bone volume fraction (BV/TV), Tb.N, Tb.Th, and Tb.Sp. Total hip and spine aBMD were determined from DXA.Results: Microstructural bone parameters derived from MRI at the proximal femur and from HR-pQCT at the distal tibia showed significantly lower bone quality in HIV-infected patients compared to healthy controls. In contrast, DXA aBMD data showed no significant differences between HIV-infected patients and healthy controls. Conclusions:Our results suggest that high-resolution imaging is a powerful tool to assess trabecular bone microstructure and can be used to assess bone health in HIV-infected men who show no differences to healthy males by DXA aBMD. Advances in MRI technology have made microstructural imaging at the proximal femur possible. Further studies in larger patient cohorts are clearly warranted.Keywords: Human immunodeficiency virus (HIV); trabecular bone microstructure; high-resolution magnetic resonance imaging (MRI); high resolution peripheral quantitative computed tomography (HR-pQCT); dual X-ray absorptiometry (DXA); areal bone mineral density (aBMD)

MRI‐Based Quantitative Osteoporosis Imaging at the Spine and Femur

“…In vivo microstructural analysis of high-resolution MRI of the proximal femur has been clinically applied to postmenopausal women with osteoporosis, 47,71 long-term glucocorticoid users, 48 as well as human immunodeficiency virus-infected (HIV) men. 45 Patients with fractures had lower elastic modulus than the control group in all proximal femur regions but no differences in T-scores. 47 Another study investigated 60 postmenopausal women (30 with and 30 without fragility fractures) who did not have osteoporotic BMD in the proximal femur; however, the fracture group was found to have significantly impaired bone microstructure.…”

“…71 One study in eight HIV-infected men found significantly lower bone quality compared to healthy controls, but BMD did not show significant differences between HIV-infected patients and healthy controls. 45 These findings suggest that assessment of trabecular bone microarchitecture might play an important role in the context of bone quality in addition to BMD measurements.…”

“…Current state-of-the-art in vivo MRI acquisition at the proximal femur can achieve a spatial resolution of 234 μm in-plane and 500 μm slice thickness in a clinically feasible scan time. 43,45 Initially, mainly gradient-echo-based pulse sequences were used for high-resolution imaging of the proximal femur. [43][44][45][46][47][48] The advantage of this type of pulse sequence is the high SNR efficiency and, thus, a shorter scan time.…”

“…Since then, further progress has been made towards higher spatial resolution and better image quality. Current state‐of‐the‐art in vivo MRI acquisition at the proximal femur can achieve a spatial resolution of 234 μm in‐plane and 500 μm slice thickness in a clinically feasible scan time 43, 45 …”

Survey of MRI Usefulness for the Clinical Assessment of Bone Microstructure

“…A 72% diagnostic accuracy was computed [ 94 ]. Furthermore, a strong negative correlation was found between the pelvic bone marrow adipose tissue (BMAT) calculated in 56 healthy women using MRI and the corresponding DXA-based BMD (r = −0.646, p < 0.001) [ 95 ]. The negative correlation indicates that patients with decreased bone mineral density are characterized by an increased fat content in bone marrow [ 95 , 96 , 97 ].…”