| Background and objectivesOsteoporosis, leading to an increased risk of fracture, poor posture and reduced functional ability is a significant global public health issue which has affected more than200million people and is expected to substantially increase by2050throughout the world. In the year2005, approximately$19billion was spent in osteoporosis related fractures, and by the year2025, the cost is estimated to reach$25.3billion (National Osteoporosis Foundation). The most common clinical manifestation of osteoporotic fractures are vertebral fractures, with older female patients being the most severely affected due to the compromised resistance of bone as a consequence of decreased bone mineral, reduced bone quality and destructive micro architecture resulting from post-menopause.In addition to the above bone characteristic, more attention has been drawn into studies involving functional impairment including curvature deformity, balance disorder and the change of trunk mobility. Such abnormal posture and spinal mobility is demonstrated to cause significant functional impairments in activities of daily living. A series of studies by Miyakoshi et al. suggested lumbar kyphosis as a negative predictor of quality of life (QOL) and spinal mobility as a positive predictor and most important factor relating QOL. In addition, lumbar spinal mobility was proven to be the most important factor to QOL in patients with postmenopausal osteoporosis. Conversely for middle-aged and elderly males, sagittal balance, lumbar lordosis angle, and spinal range of motion were also proved to be related to QOL. On the other hand, studies have shown that thoracic hyperkyphosis is independently associated with decreased mobility, which is accompanied by a slower gait, a poor balance, and greater body sway, in turn correlated with an increased tendency to falls. Moreover it was reported that trunk deformities and spinal mobility also induce chronic back pain, increase vertebral fractures risk, reduce gait and stair-climbing function due to a decrease in lung function, and increase mortality rates, decreasing QOL and life satisfaction. Therefore, rehabilitation intervention which has showed to influence a reduction in kyphosis may be an effective way to improve daily living functionality and QOL.However an explanation to abnormal posture, spinal mobility and balance is multiplex and multifactorial. The proportion of older persons with the worst degrees of kyphosis who have vertebral fractures is only36-37%. Other causes impacting hyperkyphosis include postural changes, muscular weakness, degenerative disc disease and some genetic predisposition. Consequently, there still exist some controversies which are not yet fully understood. Although lumbar lordosis tends to decrease with age in most research studies other reports are inconsistent, reporting an increase or no change in curvature, whereas Takahashi et al. showed that11.9%of the participants had a decreased lumbar lordosis, and4.7%exhibiting an increased lumbar curvature. While studies have demonstrated thoracic hyperkyphosis as an independent predictor of balance and QOL, lumbar kyphosis has been shown to affect spinal inclination and postural balance, presenting an additional risk factor for a tendency to falls. Most notably, abnormal posture and spinal mobility should be studied as an overall alignment pattern including the thoracic and lumbar regions of the spine. A same angular change in a similar segment of different persons may have a different effect on the global spine due to the compensatory and interactive relationship among separate segments of the spine in the process of senescence. Thus, it is important and meaningful to focus more attention on changes and relationships between different global spine curvature types. Meanwhile a difference has been reported in the shape of the sagittal spinal curvature between Japan and the United States. With one of the biggest populations in the world, a large elderly population and increasing longevity, osteoporosis has become a significant burden on society and healthcare systems in China. An understanding of the changes of spinal deformity and functional impairment in the Chinese population would be useful in the planning of public health strategies in this region. However, there are very few articles reporting spinal functional impairment and alignment of Chinese people. Thus, the objective of this study was to provide further evidence about the change of trunk mobility and the relationship between spinal curvature and balance disorder, especially for the different type of global spine deformity in a Chinese population.Materials and methods1.450osteoporotic volunteers were recruited for this study. Spinal range of motion and global curvature were evaluated noninvasively using the Spinal-Mouse(?) system and sagittal postural deformities characterized.2. Seven female human thoracic (T7) and seven lumbar (L4) vertebrae were obtained from seven female frozen, unembalmed human cadavers. For the vertebrae, the spinous processes first were removed, and then the vertebral body was cut along the sagittal plane with a low-speed diamond saw under constant deionized water irrigation to minimize the undesired mineral formation on the surface of the specimen. The embedded samples were metallographically polished to produce the smooth surfaces needed for nanoindentation testing.3. Anteroposterior and lateral radiographs of326women spine were obtained at baseline and after6years. The osteoporotic vertebral fracture, thoracic kyphosis and lumbar lordosis were measured.Result1. We found a new spine postural alignment consisting of an increased thoracic kyphosis and decreased lumbar lordosis which we classified as our modified round back. We did not find any of Satoh’s type5classification on our population. Type2sagittal alignment was the most common spinal deformity (38.44%). In standing, thoracic kyphosis angles in types2(58.34°) and3(58.03°) were the largest and lumbar lordosis angles in types4(13.95°) and5(-8.61°) were the smallest. The range of flexion (ROF) and range of flexion-extension (ROFE) of types2and3were usually greater than types4and5, with type1being the largest.2. All experiments were performed using the TI-950Hysitron. A total of1120indentations were produced in this study. Basic modulus and hardness results were0.32±0.06GPa and8.02±1.31GPa. There was no statistically different between them.3.326patients were included. A significant increase in thoracic curvature was found in the subgroup with thoracic fractures as compared to the subgroups with thoracolumbar or lumbar fractures. No lumbar curvature differences were found. A significant increase in thoracic curvature was apparent6years into the study. A moderate increase in lumbar curvature was found after6years, although the difference was not statistically significant.Conclusion1. The present study classified and compared for the first time the mobility, curvature and balance in a Chinese population based on the entire spine alignment and found types4and5to present the worst balance and mobility. This study included a new spine postural alignment classification that should be considered in future population studies.2. This study demonstrates that the nanoindentation method may offer a valuable tool for gaining insight into the elastic properties of bone tissue at the micro-structure level. However, uncertainties in the measurement of bone tissue by nanoindentation, including the influences of elastic anisotropy, need to be addressed further.3. Thoracic compression fractures significantly increase thoracic kyphosis as compared to dorsolumbar and lumbar fractures. Thoracic kyphosis worsens over time in patients with prevalent vertebral fractures. These data invite an evaluation of techniques capable of providing early correction of alignment disorders, such as widespread use of bracing or kyphoplasty. |
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