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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Because the disc and facets work together to constrain spinal kinematics, changes in the instant axis of rotation associated with disc degeneration or disc replacement may adversely influence risk for facet overloading and arthritis. The relationships between L5/S1 segmental kinematics and facet forces are not well defined, since previous studies have separated investigations of spinal motion and facet force. The goal of this cadaveric biomechanical study was to report and correlate a measure of intervertebral kinematics (the centrode, or the path of the instant axis of rotation) and the facet forces at the L5/S1 motion segment while under a physiologic combination of compression and anterior shear loading. ⋯ Overall, the facet force was increased on the ipsilateral side of bending (P=0.002). The IAR positions demonstrate that the L5 vertebral body primarily rotates forward during flexion (IAR close to vertebral body center) and rotates/translates backward during extension (IAR at or below the L5/S1 intervertebral disc). In lateral bending, the IAR obliquity demonstrated coupling with axial torsion due to resistance of the ipsilateral facet.
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Comparative Study
Detailed pathological changes of human lumbar facet joints L1-L5 in elderly individuals.
Facet joints play an important role in intervertebral load transmission and are crucial for rotational kinematics. Clinically, the role of facet joints as a possible source of low back pain is seen as controversial and at present is not sufficiently investigated. In this study, human lumbar facet (zygapopyhysial) joints from donors with advanced age were analyzed macroscopically, for degenerative changes. ⋯ In conclusion, most margins of the articular facets are subject to degenerative changes in the lumbar spine of elderly persons, the topographical pattern being different in superior and inferior facets. This observation can be explained by the segmental motion patterns during extension/flexion movements of the facets. Sometimes, due to the marginal extension, it is obvious that not all changes can be assessed by CT or MRI.
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Comparative Study
Subdental synchondrosis and anatomy of the axis in aging: a histomorphometric study on 30 autopsy cases.
During skeletal development the two ossification centers of the odontoid process are separated from the corpus of the axis by a subdental synchondrosis. This synchondrosis is thought to close and disappear spontaneously in adolescence although this has never been studied in detail. The basis of the dens is of clinical relevance as type II dens fractures are located here. ⋯ Histologically a cartilaginous matrix composition of the subdental synchondrosis persisted throughout all groups. The trabecular microarchitecture demonstrated a significant reduction of bone volume and trabecular number as well as an increased trabecular separation within the basis of the dens as compared to the corpus or the dens of C2. This histomorphometric data regarding a poor integration of the synchondrosis into the trabecular network and the reduced bone mass within the basis of the dens might offer a previously underestimated explanation for the occurrence of type II dens fractures and their association with pseudoarthrosis, respectively.
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Atlantoaxial (C1-C2) facet joint osteoarthitis is a distinct clinical syndrome that often goes unrecognized. Severe pain resistant to conservative treatment that is corroborated by the radiographic findings represents the indication for surgery. The aim of this study was to retrospectively examine the long-term outcome [after an average 6.5 years (SD 4.0)] of C1-2 fusion for osteoarthritis of the atlantoaxial segment in 35 consecutive patients [25 male, 10 female; aged 62 (SD 15) years]. ⋯ The average score on the NPDS (0-100) was 34 (SD 27), representing 'mild' neck problems, and the average pain intensity (0-5 VAS) was 1.5 (SD 1.5). Eighty-five percent of the patients declared that they would make the same decision again to undergo surgery. In conclusion, in a group of patients with a painful and debilitating degenerative disorder of C1-2, posterior transarticular atlantoaxial fusion proved to be an effective treatment with a low rate of serious complications.