Abstract
ObjectiveThis study aimed to describe the changes in spinopelvic sagittal alignment in the sitting position after posterior lumbar fusion, and to identify the factors influencing unfused adjacent segment lordosis.MethodsConsecutive patients with lumbar degenerative disease who underwent posterior lumbar interbody fusion between December 2010 and April 2012 were recruited. Lateral full spine radiographs were obtained in the standing, erect sitting, and natural sitting positions. Spinopelvic parameters were measured preoperatively and at the final follow-up.ResultsThe data of 63 patients were analyzed in this study. The average age was 61.6 ± 11.0 years. When changing from standing to sitting at the final follow-up, all spinopelvic sagittal parameters with the exceptions of pelvic incidence and thoracic kyphosis were significantly altered. The most noticeable changes occurred in the natural sitting position, with the spine slumped toward achieving a C-shaped sagittal profile. Multiple linear regression analysis revealed that when changing to a natural sitting position, age and fusion levels reflected the changes in lumbar lordosis (ΔLL), age and lumbosacral fusion reflected the changes in upper residual lordosis (ΔURL).ConclusionThe most noticeable changes in spinopelvic sagittal alignment occurred in the natural sitting position after lumbar fusion. Age, fusion levels, and lumbosacral fusion significantly influenced the differences in LL and URL between the standing and natural sitting position. These characteristics should be fully considered when planning spinal realignment surgery and investigating the etiological factors of junctional complications.
Highlights
Due to the changes induced by modern lifestyles, people are spending increasingly more time in the sitting position, with many spending more time sitting than standing
Previous studies have investigated the basic changes occurring in the lumbar and pelvic regions when moving from the standing to sitting position in healthy subjects, which can be summarized as a straightened curve in the lumbar region and pelvic retroversion [1,2,3,4,5]
The results indicated that in the sitting position, the curvature of lumbar lordosis (LL) decreased by 50% and pelvic tilt (PT) increased by 25%, which can be summarized as a straightened curve in the lumbar region, pelvic retroversion, and forward displacement of sagittal balance [1,2,3,4,5, 11]
Summary
Due to the changes induced by modern lifestyles, people are spending increasingly more time in the sitting position, with many spending more time sitting than standing. It is important to understand the effects of the sitting position on changes in lumbar alignment and pelvic compensation. Restoring sagittal balance is an important goal of surgical treatment for patients with lumbar degenerative disease, but the ideal reference values for surgical planning are predominantly based on standing radiograph results [8, 9]. The spinopelvic sagittal alignment and sagittal balance in the sitting position after lumbar fusion have not been well discussed, and the changes in the sagittal alignment of unfused adjacent segments are unclear
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