Abstract
BackgroundIn the literature, ‘below and lateral to the superior S1 facet’ is defined as the basic technique for screw introduction. Until a recently published modification, no analysis for alternative starting point has been proposed nor evaluated, although some surgeons claim to use some modifications. In this study, we analyse the data from anatomical and radiological studies for optimal starting point in transpedicular S1 screw placement.MethodsA Medline search for key word combination: sacrum, anatomy, pedicle, screws and bone density resulted in 26 publications relevant to the topic. After a review of literature, two articles were chosen, as those including the appropriate set of data. The data retrieved from the articles is used for the analysis. The spatial relation of S1 facet, pedicles and vertebral body with cortical thickness and bone density in normal, osteopenic and osteoporotic sacrum is analysed.ResultsPresented data advocates for more medial placement of the screws due to higher bone density and lower bone loss in osteoporosis. Medial shift of the starting point does not increase the risk of spinal canal perforation. Osteoarthritic changes within the facet can augment the posterior supporting point for screw. The facet angular orientation is similar to convergent screw trajectory.ConclusionsModified technique for S1 screw placement takes advantage of latest anatomical and clinical data. In our opinion, technique modification improves the reproducibility and may increase stability and the screws within the posterior cortex of the S1 vertebra. Further biomechanical and clinical study should be performed to prove its superiority to classical technique.
Highlights
In the literature, ‘below and lateral to the superior S1 facet’ is defined as the basic technique for screw introduction
One of the theories which justifies the above is the biomechanical analysis, making junction of mobile lumbar spine and immobile sacrum responsible for acceleration of degenerative process. Another factor aggravating the local biomechanics is spatial configuration, causing shear forces, whose effects are best seen in spondylolisthesis [1]
The first one published by Arman et al in 2009 deals with sacral anatomy, focusing on spine surgery application [18]
Summary
In the literature, ‘below and lateral to the superior S1 facet’ is defined as the basic technique for screw introduction. Until a recently published modification, no analysis for alternative starting point has been proposed nor evaluated, some surgeons claim to use some modifications. We analyse the data from anatomical and radiological studies for optimal starting point in transpedicular S1 screw placement. One of the theories which justifies the above is the biomechanical analysis, making junction of mobile lumbar spine and immobile sacrum responsible for acceleration of degenerative process. Another factor aggravating the local biomechanics is spatial configuration, causing shear forces, whose effects are best seen in spondylolisthesis [1]
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