Detailed Analysis of the Central Osteodensitometry Data from Cosmonauts Participating in the Mir and ISS Programs

Abstract

This paper analyzes results of osteodensitometric surveys of cosmonauts (participants of the Mir and ISS programs) carried out in the Laboratory of Osteology of the Institute of Biomedical Problems. The data array including 122 pre-flight and 74 post-flight surveys of 57 cosmonauts aged 30 to 60 years was investigated. Flight duration ranged from 73 to 438 days. Changes in osteodensitometry were considered selectively for individual vertebrae of the lumbar spine (L1–L4) and areas of the proximal femur differing in structure and metabolic activity. For the first time, we analyzed auxiliary and estimate indicators, such as the projection area (PA) of the investigated region and the mass fraction of its constituents. It was found that the decrease in bone mineral density (BMD) in the lumbar region L1–L4 in cosmonauts after long flights is mainly due to the lower vertebrae L3–L4, which carry a large functional load under conditions of earth gravity. BMD losses in the proximal femoral epiphysis are the same in regions with different bone structure and function. No significant differences were found in the pre- and post-flight (7–14 days after) values of the projection area of the lumbar spine, indicating no significant anatomical changes. The expected increase in the height of the lumbar segment L1–L4 in zero gravity due to intervertebral discs on the 7–14th day after the flight is not observed.