European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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Harvesting autogenous bone grafts of the iliac crest carries complications and lengthens operative times. Allografts are preferred to avoid these problems. Fusion after using allogenic bone grafts has been well studied, by examining trabeculations and remodelling on anteroposterior and lateral radiographs. ⋯ Fresh-frozen femoral or tibial allografts worked effectively to maintain correction after trauma when combined with anterior instrumentation. CT examinations with sagittal and coronal reconstructions were more effective for evaluation of fusion compared with anteroposterior and lateral radiographs. The high fusion rate and the low morbidity achieved using allografts in this way supports the exclusive use of allografts in the anterior thoracic and lumbar spine in the future.
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The lumbar spine is of primary importance in gait and its development is influenced by the upright posture adopted in human locomotion. However, little is known about the kinematic behavior of the lumbar spine during walking. The aim of this study was to examine (1) lumbar spine kinematics during walking, (2) the effect of walking velocity on lumbar motion patterns and (3) the coupling characteristics of rotation and bending. ⋯ Coupling of rotation and bending during walking was individually variable and dependent on walking velocity. Moreover, the smoothness of the bending-rotation path varied with walking velocity. A simplified envelope of lumbar coupling characteristics during walking is presented, and the existence of an individually variable walking speed that is characterized by a more harmonic lumbar contribution is hypothesized.
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Some patients with scoliosis have a relatively short vertebral canal. This poses the question of whether a short spinal cord may sometimes cause scoliosis. The present paper presents two observations that may support this concept. ⋯ The study confirms that the vertebral canal and the intervertebral foraminae retain their original orientation. The spinal cord is eccentric in the canal towards the concavity of the curve; the major component of rotation occurs anterior to the vertebral canal and the axis of this rotation seems to be at the site of the spinal cord. These observations do not establish that a short spinal cord will result in scoliosis, but the results are compatible with this hypothesis, and that impairment of spinal cord growth factors may sometimes be responsible for scoliosis.
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Bone fragments in the spinal canal after thoracolumbar spine injuries causing spinal canal narrowing is a frequent phenomenon. Efforts to remove such fragments are often considered. The purpose of the present study was to evaluate the effects of surgery on spinal canal dimensions, as well as the subsequent effect of natural remodelling, previously described by other authors. ⋯ The study shows that canal enlargement during surgery is caused by indirect effects when the spine is distracted and put into lordosis. Remodelling will occur if there is residual narrowing. Acute intervention into the spinal canal, as well as subsequent surgery because of residual bone, should be avoided.
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The aim of the current study is twofold: first, to compare load sharing in compression between an intact and a surgically repaired lumbar spine motion segment L3/4 using a biomechanically validated finite element approach; second, to analyse the influence of bone mineral density on load sharing. Six cadaveric human lumbar spine segments (three segments L2/3 and three segments L4/5) were taken from fresh human cadavers. The intact segments were tested under axial compression of 600 N, first without preload and then following instrumented stabilisation. ⋯ Using 10 MPa--representing soft, osteoporotic bone--this percentage decreased, but it increased using 100 MPa in both the intact and the altered segment. Thus, it is concluded that reconstruction of both the disc and the posterior elements with the implants used in the study recreates the ability of the spine to act as a load-sharing construction in compression. The similarity in load sharing between normal and instrumented spines appears to depend on assumed bone density, and it may also depend on applied load and loading history.