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Astronauts have expressed an increased incidence of back pain during spaceflight and herniated intervertebral discs (IVD) have been diagnosed upon return of Skylab and Shuttle spaceflight participants. These conditions and symptoms may be from previous back injury, but the evidence of IVD injuries raises the concern that astronauts are at an increased risk of intervertebral disc damage during loading scenarios experienced during exploration missions (re-entry to a gravitational field and activities on planetary surfaces). To date, flight data related to potential back injuries have focused on spine elongation and the well-established effects of mechanical unloading on intervertebral discs. ==Causes and current studies== Sixty-eight percent of early astronauts, through 1991, who have flown in space have reported generalized back pain. The pain is considered most painful during early flight and lessens as the flight progresses. Possible causes of back pain in flight may be associated with: * the elongation of the vertebral column due to lowered gravitational forces * Core and back muscle weakness 〔 〕 including space-induced atrophy of back muscles * increased strain of proximal facet joint capsules 〔 〕 * fractured innervated vertebral end plates 〔 〕 * disc degeneration 〔 〕 * herniation of anulus fibrosus〔 〕 Regardless of the cause, astronauts may be at an increased risk of intervertebral disc injury or damage when the swollen discs are subjected to excessive forces or torques while working on planetary surfaces. Exploration missions on planetary surfaces may also introduce habitability issues that could induce excessive torsional stress, an established risk factor for herniation of anulus fibrosus. Currently, there is minimal in- and post-flight data that would characterize the changes in intervertebral discs in crewmembers to assess how these changes would predispose the discs to injury under re-loading. Herniated nucleus pulposus is known to occur in aviators exposed to high G-force environments and has occurred in astronauts after a mission. The relative risk rate of intervertebral disc damage has only recently been researched, but there is currently no evidence that links the origin of intervertebral disc damage with changes to the disc as a result of spaceflight. Based upon the intervertebral disc tissue analysis of unweighted animals, biochemical changes to the nucleus pulposus during spaceflight will affect the ability of the osmotic pressure and elasticity of the nucleus pulposus to resist compressive loading. Biochemical changes in the intervertebral discs of crewmembers after flight have not been identified, but there is in vitro research with bovine cartilage explants to use magnetic resonance technology to correlate changes in intervertebral disc proteoglycan content with the T1 rho relaxation of protons. This biomarker will enable non-invasive monitoring of proteoglycan content as a method of assessing the biochemical impact of weightlessness. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Intervertebral disc damage and spaceflight」の詳細全文を読む スポンサード リンク
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