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Intervertebral Disk
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
The facet joints are the left and right articulations of the superior and inferior facets (articular processes) of adjacent vertebrae. They are synovial joints covered by hyaline cartilage. In the lumbar spine, these joints are vertically oriented and therefore restrict rotation. Because of their orientation, they are particularly important load-bearing structures in rotation and shear, but they are also loaded in compression. Farfan’s studies indicate that they contribute about 40% to the torsional resistance of a motion segment (3), which is about the same as that from the disk. Hutton et al. (4) found the load sharing to be similar when shear loads were applied, that is, disk 40% and facet joints 40%. The amount of compressive load being transmitted through the facet joints depends on whether the spine is in flexion or extension. Theoretically, more load is transmitted through the facet joints in extension. Lorenz et al. (S) found the facets to carry about 25 % of the compressive load in a neutral position.
Standing and Sitting at Work
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
Excessive loading of the facet joints stresses the soft tissues around the joint and causes low back pain. For these reasons, excessive lumbar lordosis should be avoided when standing. Extrapolating from this, any workspace or task factors that require workers to arch the back greater than they would normally do should be designed out. However, there is evidence to show that hyperextension of the lumbar spine can be beneficial in temporarily relieving the load on the intervertebral discs (Magnusson et al., 1996c), and so there are grounds for recommending that short periods of lumbar hyperextension be introduced to relieve disc compression in standing tasks, particularly if forward flexion is also required. Sustained hyperextension in the upright position should be avoided.
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
Facet syndrome or facet joint arthritis is one of the major etiologies of low back pain for which surgical intervention might be applied [55,56]. Lumbar facets or zygapophyseal joints are synovial arthroses richly innervated with nerve endings from the medial branch of the posterior primary ramus [57]. Current treatment options include facet joint block or medial branch block for short-term pain relief and facet joint denervation for long-term pain relief by radiofrequency or cryotherapy. The results of facet joint denervation or rhizotomy have been variable, with many patients requiring repeated procedures or experiencing inadequate pain relief. Some authors have reported laser facet denervation techniques [56,58,59]. The patient is placed prone on the radiolucent table. Under fluoroscopic guidance or endoscopic visualization, the Ho:YAG straight-firing laser probe is directed at the medial branch or the dorsal ramus, the nerve that gives rise to the articular branches at each level. Each facet joint is innervated from above and below the segments. The laser probe can be also directed to the facet joint itself. The target points are the lower, middle, and upper portions of the facet joint. The total irradiation energy at one facet is about 500–600 J. Laser has the advantage of coagulating a relatively larger area in the vicinity of the probe tip compared with a radiofrequency probe. Laser facet denervation can be applicable and efficient for patients who failed to be relieved by block or radiofrequency facet rhizotomy.