Abstract
ABSTRACT Objective To present a new principle for correction of the sagittal plane of the spine through the convergent or divergent placement of monoaxial pedicle screws in this plane, associated with compression or distraction, to provide lordotizing or kyphotizing leverage force. Method A statistical mechanical study of twenty-eight fixations in synthetic spine segments was performed. In fifteen pieces, pedicle screws were applied to the ends of the segments with positioning convergent to the center of the fixation. They were attached to the straight rods and subjected to compression force. The other thirteen segments were fixed with pedicle screws in a direction divergent to the center of the fixation, attached to the straight rods, and subjected to distraction force. Results To create kyphosis in the 15 synthetic segments of the spine, the mean pre-fixation Cobb angle was - 0.7° and the mean post-fixation angle was +15°. To create lordosis in the 13 segments, the mean pre-fixation Cobb angle was +1° and the mean post-fixation angle was +18°. The difference was confirmed by statistical mechanical tests and considered significant. However, there is no relevant difference between the mean angles for lordosis and kyphosis formation. Conclusions It was concluded that the correction of the sagittal plane of the spine by applying the new instrumentation method is efficient. A statistical mechanical test confirmed that the difference in Cobb degrees between pre- and post-fixation of the synthetic spine segments was considered significant in the creation of both kyphosis and lordosis. Level of evidence II C; Statistical mechanical study of synthetic spine segments.
Highlights
The literature refers to Scheuermann’s kyphosis as a structural pathology of the lumbar or thoracolumbar spine that affects 0.4 to 8.3% of the general population for which there are numerous diagnostic hypotheses.[1]Dickson confirmed that a loss of thoracic kyphosis may precede the development of deformity and vertebral rotation.[2]Winter and Nash reported that thoracic hypokyphosis was responsible for the reduction of pulmonary function in patients diagnosed with adolescent idiopathic scoliosis (AIS).[3,4]Even though spinal alignment has been assessed only in the coronal plane for many years, several publications highlight the importance of changes in the sagittal plane
A statistical mechanical test confirmed that the difference in Cobb degrees between pre- and post-fixation of the synthetic spine segments was considered significant in the creation of both kyphosis and lordosis
From what was confirmed in the statistical mechanical test, the difference in degrees between the pre- and post-fixation Cobb measurements of the synthetic spine segments was considered significant both for kyphosis and lordosis. (Table 1 and Figure 5)
Summary
The literature refers to Scheuermann’s kyphosis as a structural pathology of the lumbar or thoracolumbar spine that affects 0.4 to 8.3% of the general population for which there are numerous diagnostic hypotheses.[1]Dickson confirmed that a loss of thoracic kyphosis may precede the development of deformity and vertebral rotation.[2]Winter and Nash reported that thoracic hypokyphosis was responsible for the reduction of pulmonary function in patients diagnosed with adolescent idiopathic scoliosis (AIS).[3,4]Even though spinal alignment has been assessed only in the coronal plane for many years, several publications highlight the importance of changes in the sagittal plane. Dickson confirmed that a loss of thoracic kyphosis may precede the development of deformity and vertebral rotation.[2]. The authors highlight the relationship of the spine with changes in pelvic orientation and how they determine vertebral alignment as a whole.[5,6,7,8,9]. Pelvic Incidence (PI): The angle between the line perpendicular to the midpoint of the sacral plateau and a line that connects this point to the central axis of the femoral head, from 40° to 65o considered normal. Pelvic Tilt (PT): The angle between a line that connects the midpoint of the sacral plateau to the axis of the femoral head and a vertical line, perpendicular to the ground, from 10° to 25o considered normal.[10,11]
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