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
-
Deformity planning for sagittal plane corrective osteotomies of the spine in ankylosing spondylitis.
Ankylosing spondylitis (AS) may lead to a severe fixed thoracolumbar kyphotic deformity (TLKD) of the spine. In a few patients, the TLKD is so extreme that a corrective osteotomy of the spine may be considered. Several authors have reported the results of patients treated by a lumbar osteotomy, but there is no consensus on the level of the osteotomy and on the exact degree of correction required. ⋯ In one patient, the achieved correction of the deformity proved to correct the sagittal spinal balance and the pelvic sacral endplate angle. In the other patient, the achieved correction was not sufficient. It is concluded that adequate deformity planning for sagittal plane corrective osteotomies of the spine in AS is essential for reliable prediction of the effect of a lumbar osteotomy on the correction of the spine.
-
Anterior instrumentation for the correction of scoliotic curves has recently been gaining in popularity. The problems of high mortality and morbidity that were associated with the employment of anterior instrumentation in the first years it was used have now been overcome. Efforts are now being concentrated on increasing the correction rates in the frontal plane and decreasing the kyphotic effect in the sagittal plane. ⋯ In view of these findings, it was determined that CDH instrumentation achieves significant correction rates in the frontal and sagittal planes, particularly in single flexible lumbar, thoracolumbar and thoracic rigid curves. It was found that the kyphotic effect was minimized with a double rod system. Significant clinical and radiological corrections were achieved in balance values, without any imbalance and decompensation problems.
-
Psoas muscle (PM) function with regard to the lumbar spine (LS) is disputed. Electromyographic studies attribute to the PM a possible role as stabilizer. Anatomical textbooks describe the PM as an LS flexor, but not a stabilizer. ⋯ Conversely, any increase of lordosis of the strip brought about by vertical downward pushing of its top, will be stabilized by tightening the pulling string in the same specific direction. As this direction corresponded with the psoas orientation, the experiments show that the PM probably functions as a stabilizer of the lordotic LS in an upright stance by adapting the state of contraction of each of its fascicles to the momentary degree of lordosis imposed by factors outside the LS, such as general posture, general muscle activity and weight bearing. The presence of multiple PM fascicles, all of about equal length, and attaching to all LS levels, facilitates this function.
-
A high rate of pseudarthrosis and a high overall rate of implant migration requiring surgical revision has been reported following posterior lumbar interbody fusion using BAK threaded cages. The high rate of both pseudarthrosis and implant migration may be due to poor fixation of the implant. The purpose of this study was to analyse the motion of threaded cages in posterior lumbar interbody fusion. ⋯ Motion of the implants was not seen in compression. In torsion, a rolling motion was noted, with a range of motion of 10.6 degrees around the central axis of the implant when left/right torsion (25 Nm) was applied. The way the implants move within the segment may be due to their special shape: the thread of the implants can not prevent the BAK cages rolling within the disc space.
-
Comparative Study
Three-dimensional motion analysis with Synex. Comparative biomechanical test series with a new vertebral body replacement for the thoracolumbar spine.
The authors present a new implant for vertebral body replacement in the thoracic and lumbar spine. Synex is a titanium implant designated for reconstruction of the anterior column in injury, post-traumatic kyphosis or tumour of the thoracolumbar spine and must be supplemented by a stabilizing implant. After positioning, the implant is distracted in situ, thus ensuring best contact with adjacent end-plates and three-dimensional (3D) stability, and minimizing the possibility of secondary dislocation or loss of correction. ⋯ The increased biomechanical stability demonstrated for Synex suggests that a more rigid construction would also be achieved in vivo. When using MOSS in combination with posterior stabilization, the induction of intervertebral compression via the posterior fixator is recommended. This surgical step was not necessary with Synex.