Bone microarchitectural alterations associated with spinal cord injury: Relation to sex hormones, metabolic factors, and loading

Abstract

Context: People living with spinal cord injury (SCI) are at high risk for bone fractures. Neural, hormonal and metabolic contributors to bone microarchitectural alterations are incompletely understood.

Objective: To determine the relationship of physical, metabolic and endocrine characteristics with bone microarchitecture, characterized using high-resolution peripheral quantitative computed tomography (HRpQCT) in SCI.

Design: Cross-sectional analyses of bone properties in people with SCI.

Participants: Twenty adults with SCI and paraplegia (12) or motor incomplete quadriplegia (8).

Outcome measures: Distal tibia and radius HRpQCT parameters, including density, microstructure and strength by microfinite element anaysis (μFEA); sex hormones; metabolic and inflammatory markers.

Results: The mean age of the participants with SCI was 41.5 ± 10.3 years, BMI 25.7 ± 6.2 kg/m², time since injury 10.4 ± 9.0 years. Participants with SCI had significantly lower median total (Z score - 3.3), trabecular (-2.93), and cortical vBMD (-1.87), and Failure Load by μFEA (-2.48) at the tibia than controls. However, radius vBMD, aBMD and microarchitecture were similar in participants with SCI and un-injured controls. Unexpectedly, C-Reactive Protein (CRP) was positively associated with tibial trabecular vBMD (β = 0.77, p = 0.02), thickness (β = 0.52, p = 0.04) and number (β = 0.92, p = 0.02). At the radius, estradiol level was positively associated with total vBMD (β = 0.59, p = 0.01), trabecular thickness (β = 0.43, p = 0.04), cortical thickness (β = 0.63, p = 0.01) and cortical porosity (β = 0.74 p = 0.04).

Conclusions: Radius vBMD and microarchitecture is preserved but tibial total, cortical and trabecular vBMD, and estimated bone strength are markedly lower and bone microarchitectural parameters substantially degraded in people with SCI. The alterations in bone microarchitecture in people with SCI are likely multifactorial, however marked degradation of bone microarchitecture in tibia but not radius suggests that unloading is an important contributor of site-specific alterations of bone microarchitecture after SCI. Fracture prevention in SCI should focus on strategies to safely increase bone loading.

Clinicaltrials: gov registration #: (NCT03576001).

Keywords: Bone loss; Bone microarchitecture; Male osteoporosis; Osteoporosis; Spinal cord injury; Unloading.