Survival Analysis of Posterior Short Fusion in Thoracolumbar Fracture: Significance of Load-Sharing Score and Bone Mineral Density-Changseop / 대한척추외과학회지

STUDY DESIGN: A retrospective study. OBJECTIVES: To evaluate the fixation survival rate and the radiologic prognostic factors of posterior short fusion in thoracolumbar fracture. SUMMARY OF BACKGROUND DATA: Posterior short fusion has the advantage of saving motion segments in spite of high fixation failure rate. The high load-sharing score is well known as a cause of fixation failure, but the effect of osteopenia is not evaluated. MATERIALS AND METHODS: Authors evaluated 27 patients treated surgically with posterior short fusion using pedicle screws as thoracolumbar fractures from 1995 to 1999. The median follow-up was 20.5 months (6-54). The survivorship using Kaplan-Meier method and the radiologic prognostic factors were evaluated. RESULTS: The sagittal index was preoperatively 16.7 dgree (+/-7.9 SD), immediate postoperatively 6.9 dgree (+/-4.6), and at last follow-up 10.6 dgree (+/-6.9). The fixation failures were detected in 4 patients, and the failure time was ranged from 6 months to 11(median 7.5). The overall survival rate was 82.3% at the last follow-up. The significant prognostic variables were load-sharing score, Jikei grade, compression percent and age in uni-variate analysis, but the load-sharing score and Jikei grade were significant prog-nostic factors in multivariate analysis. CONCLUSIONS: In decision to perform posterior short fusion, the load-sharing score and evidence of osteopenia should be consid-ered as a prognostic factors to avoid fixation failure in thoracolumbar fracture.

The Sagittal Balance and Compensatory Mechanisms in Lumbar Spinal Stenosis / 대한척추외과학회지

PURPOSE: To evaluate the sagittal alignment and the main factors contributing to sagittal compensatory mechanism in lumbar stenosis. MATERIALS AND METHODS: 63 patients of spinal stenosis surgically treated were evaluated using 14x36 inch standing lateral films. The global sagittal balance was measured with C7 plumb line and hip flexion angle. The thoracic kyphosis, lumbar lordo-sis and pelvic tilting angle were compared to each of normal korean values to find out main factors participating in compensatory mechanism. At last follow-up, at least 6 months after surgery, the changes of sagittal parameters and global balance were evaluated according to the correction amount of pathologic segments angle to understand the compensatory mechanism and its contributing factors. RESULTS: The C7 plumb line was +3.04 cm(/0.91 SD), thoracic kyphosis 30.0dgree(/12.1), lumbar lordosis 43.1dgree(/14.7) and pelvic tilting angle 21.7dgree(/8.2). All patients except 8 showed global compensation state. The differences compared to normal korean values were 10 dgree of pelvic tilting angle and 2dgreeof thoracic kyphosis. Pelvic tilting angle was more contributing factor of compensatory mechanism than thoracic kyphosis. At last follow up, 14 patients surgically corrected 5dgreeor more showed significant posterior shift of C7 plumb line and increased lumbar lordosis(p<0.05). 11 patients aggravated 5dgree or more showed significant increase of adjacent segment angle to participate in compensatory mechanism(p<0.05). CONCLUSION: Most lumbar spinal stenosis patients showed compensated sagittal balance state. Adjacent segments and pelvic tilting were thought as main contributing factors of compensation mechanism.