Heterogeneity in microstructural deterioration following spinal cord injury

Ghasem-Zadeh, Ali<sup>1,2</sup>; Galea, Mary P.<sup>1,3</sup>; Nunn, Andrew<sup>1,3</sup>; Panisset, Maya<sup>1,3</sup>; Wang, Xiao-Fang<sup>1,2</sup>; Iuliano, Sandra<sup>1,2</sup>; Boyd, Steven K.<sup>4</sup>; Forwood, Mark R.<sup>5</sup>; Seeman, Ego<sup>1,2</sup>

Affiliations

¹Depts of Medicine and Endocrinology, Austin Health, The University of Melbourne, Melbourne, Australia

²Dept of Endocrinology, Austin Health, The University of Melbourne, Melbourne, Australia

³Depts of Medicine and Victorian Spinal Cord Service, Austin Health, The University of Melbourne, Melbourne, Australia

⁴McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, AB, Canada

⁵School of Medical Science and Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia

Abstract and keywords

Background Modelling and remodelling adapt bone morphology to accommodate strains commonly encountered during loading. If strains exceed a threshold threatening fracture, modelling-based bone formation increases bone volume reducing these strains. If unloading reduces strains below a threshold that inhibits resorption, increased remodelling-based bone resorption reduces bone volume restoring strains, but at the price of compromised bone volume and microstructure. As weight-bearing regions are adapted to greater strains, we hypothesized that microstructural deterioration will be more severe than at regions commonly adapted to low strains following spinal cord injury.

Methods: We quantified distal tibial, fibula and radius volumetric bone mineral density (vBMD) using high-resolution peripheral quantitative computed tomography in 31 men, mean age 43.5 years (range 23.5‐75.0), 12 with tetraplegia and 19 with paraplegia of 0.7 to 18.6 years duration, and 102 healthy age- and sex-matched controls. Differences in morphology relative to controls were expressed as standardized deviation (SD) scores (mean ± SD). Standardized between-region differences in vBMD were expressed as SDs (95% confidence intervals, CI).

Results: Relative to controls, men with tetraplegia had deficits in total vBMD of −1.72 ± 1.38 SD at the distal tibia (p < 0.001) and − 0.68 ± 0.69 SD at distal fibula (p = 0.041), but not at the distal radius, despite paralysis. Deficits in men with paraplegia were −2.14 ± 1.50 SD (p < 0.001) at the distal tibia and −0.83 ± 0.98 SD (p = 0.005) at the distal fibula while distal radial total vBMD was 0.23 ± 1.02 (p = 0.371), not significantly increased, despite upper limb mobility. Comparing regions, in men with tetraplegia, distal tibial total vBMD was 1.04 SD (95%CI 0.07, 2.01) lower than at the distal fibula (p = 0.037) and 1.51 SD (95%CI 0.45, 2.57) lower than at the distal radius (p = 0.007); the latter two sites did not differ from each other. Results were similar in men with paraplegia, but total vBMD at the distal fibula was 1.06 SD (95%CI 0.35, 1.77) lower than at the distal radius (p = 0.004).

Conclusion: Microarchitectural deterioration following spinal cord injury is heterogeneous, perhaps partly because strain thresholds regulating the cellular activity of mechano-transduction are region specific.

Keywords: Cortical -bone; HR-pQCT; Microstructure; Paralysis; Spinal -cord -injury; Trabecular bone; Unloading; Weight-bearing

Links

DOI: 10.1016/j.bone.2020.115778

PubMed: 33253932

WoS: 000601336000006

History

Received: 2020-08-19

Revised: 2020-11-25

Accepted: 2020-11-25

Online: 2020-11-28

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Cited By (2)

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2021	Stürznickel J, Schmidt FN, Schäfer HS, Beil FT, Frosch K-H, Schlickewei C, Amling M, Barg A, Rolvien T. Bone microarchitecture of the distal fibula assessed by HR-pQCT. Bone. October 2021;151:116057.
2023	Abdelrahman S, Purcell M, Rantalainen T, Coupaud S, Ireland A. Regional and temporal variation in bone loss during the first year following spinal cord injury. Bone. June 2023;171:116726.