Effects of Long-Duration Spaceflight on Vertebral Strength and Risk of Spine Fracture

Abstract

Although the negative impact of long-duration spaceflight on spine BMD has been reported, its impact on vertebral strength and risk of vertebral fracture remains unknown. This study examined 17 crewmembers with long-duration service on the International Space Station in whom computed tomography (CT) scans of the lumbar spine (L 1 and L 2 ) were collected preflight, immediately postflight and 1 to 4 years after return to Earth. We assessed vertebral strength via CT-based finite element analysis (CT-FEA) and spinal loading during different activities via subject-specific musculoskeletal models. Six months of spaceflight reduced vertebral strength by 6.1% (−2.3%, −8.7%) (median [interquartile range]) compared to preflight (p < 0.05), with 65% of subjects experiencing deficits of greater than 5%, and strengths were not recovered up to 4 years after the mission. This decline in vertebral strength exceeded (p < 0.05) the 2.2% (−1.3%, −6.0%) decline in lumbar spine DXA-BMD. Further, the subject-specific changes in vertebral strength were not correlated with the changes in DXA-BMD. Although spinal loading increased slightly postflight, the ratio of vertebral compressive load to vertebral strength for typical daily activities remained well below a value of 1.0, indicating a low risk of vertebral fracture despite the loss in vertebral strength. However, for more strenuous activity, the postflight load-to-strength ratios ranged from 0.3 to 0.7, indicating a moderate risk of vertebral fracture in some individuals. Our findings suggest persistent deficits in vertebral strength following long-duration spaceflight, and although risk of vertebral fracture remains low for typical activities, the risk of vertebral fracture is notable in some crewmembers for strenuous exercise requiring maximal effort.

Microgravity-Related Changes in Bone Density and Treatment Options: A Systematic Review

“…Earlier studies demonstrated a reduction in BMD of 0.5–1.5% per month in space [ 6 , 7 ]. This finding was supported by Burkhart et al, who reported a monthly reduction of 0.5–1% in BMD on the ISS in humans [ 43 ]. However, Bilancio et al reported only a 0.9–1.4% decrease in total BMD after 6 months on the ISS in humans [ 42 ].…”

“…BMD was decreased in humans by 0.9% after 6 months [ 42 ] and 1% per month in space [ 43 ]. The decrease in BMD in animals was 18–35.7% after 1 month [ 45 , 46 ].…”

Musculoskeletal research in human space flight – unmet needs for the success of crewed deep space exploration

“…The longer exploration space missions will bring new challenges to musculoskeletal health. One of the first steps to be taken in the coming years is to understand whether the musculoskeletal adaptations observed on missions of several months 3 , 19 – 22 can be extrapolated to space missions of more than twelve months. Recent studies that examined bone health during the recovery phase suggest that bone atrophy and functional decline persist well beyond return from space 20 , 22 .…”

Rückenschmerzen und erhöhtes Bandscheibenvorfallrisiko bei Astronauten während und nach Raumfahrtmissionen

“…In einer kürzlich durchgeführten Studie wurde eine 11-prozentige Verringerung der Lendenlordose unmittelbar nach der Rückkehr von einer langen ISS-Mission festgestellt 38 . Nachuntersuchungen, durchgeführt nach einem und 2 Jahren, zeigten eine Normalisierung der Wirbelsäulenverkrümmung zu ihrem Zustand vor der Mission 38 . Ebenso wurde eine abgeflachte Lordose nach einer Bettruhestudie festgestellt, die zudem zeigte, dass die obere Lendenwirbelsäule lordotischer wurde 39 .…”

“…Eine Erklärung dafür könnte die Abflachung der Wirbelsäule sein. In einer kürzlich durchgeführten Studie wurde eine 11-prozentige Verringerung der Lendenlordose unmittelbar nach der Rückkehr von einer langen ISS-Mission festgestellt [38]. Nachuntersuchungen, durchgeführt nach einem und 2 Jahren, zeigten eine Normalisierung der Wirbelsäulenverkrümmung zu ihrem Zustand vor der Mission [38].…”