| 摘要 |
This rod comprises a first cylindrical part, being a lumbosacral part (6), which is rigid in all directions, a second part, being a dorsal part (7), which is rigid in a frontal plane, in order to prevent scoliosis, and flexible in a sagittal plane, and a dorsolumbar transition zone (8) connecting the lumbar and dorsal parts and profiled in a progressive manner so that its thickness in the sagittal plane diminishes progressively and its width in the frontal plane increases progressively: this profile is such that the second moment of area of the transition zone remains substantially constant over its entire length. The profile, thus defined, of the transition zone has the aim of avoiding, to a great extent, the risks of breaking due to the fatigue in this zone, resulting from the various movements of the patient in a chair, in particular the flexion/extension movements in a sagittal plane, promoted by the rectangular profile of the dorsal part of the rod.
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