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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Vertebroplasty and kyphoplasty are routine treatments for compression fractures of vertebral bodies. A wedge-shaped compression fracture shifts the centre of gravity of the upper body anteriorly and generally, this shift can be compensated in the spine and in the hips. However, it is still unclear how a wedge-shaped compression fracture of a vertebra increases forces in the trunk muscle and the intradiscal pressure in the adjacent discs. ⋯ The advantages of kyphoplasty found in this study will be apparent only if nearly full fracture reduction is achieved. Otherwise, differences between kyphoplasty and vertebroplasty become small or vanish. Our results suggest that vertebral body fractures in the adjacent vertebrae after vertebroplasty or kyphoplasty are not induced by the elevated stiffness of the treated vertebra, but instead the anterior shift of the upper body is the dominating factor.
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Intervertebral discs have a primarily mechanical role in transmitting loads through the spine. The disc is subjected to a combination of elastic, viscous and osmotic forces; previous 3D models of the disc have typically neglected osmotic forces. The fibril-reinforced poroviscoelastic swelling model, which our group has recently developed, is used to compute the interplay of osmotic, viscous and elastic forces in an intervertebral disc under axial compressive load. ⋯ Fiber stresses were highest on the most outward bulging on the posterior-lateral side. The osmotic forces resulted in tensile hoop stresses, which were higher than typical values in a non-osmotic disc. The computed axial stress profiles reproduced the main features of the stress profiles, in particular the characteristic posterior and anterior stress which were observed experimentally.
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Randomized Controlled Trial
Results of complete hemivertebra excision followed by circumferential fusion and anterior or posterior instrumentation in patients with type-IA formation defect.
To evaluate the results of surgical treatment in patients with unlocked full-segmented hemivertebra treated by excision. Twenty-six patients with a mean age of 12.4+/-1.7 years were included in the study. The mean duration of follow-up was 47.8+/-21.9 months. ⋯ Circumferential fusion could be achieved in all cases. No neurological complication developed, the only complication was delayed wound healing. In view of these data, it is concluded that these techniques can be safely used for this patient group at low thoracic, thoracolumbar, and lumbar levels of vertebral column with high correction rates.
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Intervertebral disc structures are exposed to wide ranges of intradiscal hydrostatic pressure during different loading exercises and are at their minimum during lying or relaxed sitting and at maximum during lifting weights with a round back. We hypothesize that these different loading magnitudes influence the intervertebral disc (IVD) by alteration of disc matrix turnover depending on their magnitudes. Therefore the aim of this study was to assess changes in gene expression of human nucleus cells after the application of low hydrostatic pressure (0.25 MPa) and high hydrostatic pressure (2.5 MPa). ⋯ These results suggest that hydrostatic pressure as one of the physiological stimuli of the IVD may influence matrix turnover in a magnitude dependent way. Low hydrostatic pressure (0.25 MPa) has quite small influences with a tendency to anabolic effects, whereas high hydrostatic pressure (2.5 MPa) tends to decrease the matrix protein expression with a tendency to increase some matrix-turnover enzymes. Therefore, hydrostatic pressure may regulate disc matrix turnover in a dose-dependent way.
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It is generally advised that the graft inserted in adult cervical spine should be pre-loaded with a compressive force or that the screws are inserted in a divergent orientation, in order to maximise compression and the chance of graft incorporation (Truumees et al. in Spine 28:1097-1102, 2003). However, there is little evidence that a compressive force is maintained once the force applicator has been removed, or that the divergent screws enhance compression. This study compared the maintenance of applied pre-load force, across cervical spine graft, between standard anterior plating technique with pre-load and divergent screws and a novel plate technique, which allows its application prior to removal of the force applicator. ⋯ Here, 77+/-10% of the applied pre-load was maintained. The difference between the plates is significant (P<0.001). Conclusions are as follows: (1) Applied pre-load is not maintained across a graft once the force applicator is removed. (2) Divergent screws with a plate do not compress graft and rather tend to offload it. (3) Compressive force may be maintained if the plate is applied prior to the force applicator removal.