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Objective To explore the effect of sagittal alignment of pedical screws and medium-term efficacy on surgical reduction in patients with lumbar spondylolisthesis that receive posterior short segment reduction and internal fixation system, and to provide theories for the clinical treatment.Methods Retrospectively analyzing the data of patients with moderate to severe spondylolisthesis from July 2005 to June 2009 in the 1st Chenzhou hospital, and screening 77 Patients aged from 27 to 66, including 34 males and 43 females. The recruited cases was conducted with the following inclusion criteria: (1) A diagnosis of degree or aboveⅡaccording to the classification of Marchetli Bartolozzi in 1994 and Meyerding. (2)Meeting for Posterior operative reduction. (3)Short segment was used as the internal fixation.(4) Imaging data integrity, X-ray were required anteroposterior and lateral view in standing position of lumbar. And subjects with any previous and Severe adhesion,degree underⅡ, osteoporosis or internal fixation did not with short segment fixation were excluded from the study. All patients must shooting X-ray before and after operation. According to the reset results, patients were divided into two groups: reset rate≥90% were called completely reset group, 50%<reset rate<90% called incomplete reduction group, each group contain 41 and 36 cases individually. there was no significant difference between the two groups in sex, age, course of disease, surgical and other general.Measuring sagittal alignment before operation and during the follow-up, such as: 1. Antedor slippage rate, 2. Reset rate, 3. Slip displacementh, 4. Lumbar slip angle, 5. Screw tail height difference, 6 Screw angle,7,Screw longer, 8. Loss of reduction rate,9.Screw breakage rate, 10.Bone graft not fusion rate. Order clinical effects score was calculated according to Oswestry barrier score system before and after surgery. Sagittal alignment and ODI between two groups make t test or pair t test, Pearsonχ2 test were used for analyzing the relationship between reset results and sagittal parameter. All data are dealing with SPSS 16.0.Results No significant differences was found in AsR, SD, LSA and ODI between completely reset group and incomplete reduction group(sP﹥0.05), and no significant difference was found in ODI in two groups at pre-operative and the early and mid-term of postoperative(P﹥0.05); compared with pre-operative, significant differences was found in AsR, SD, ODI between two groups at postoperative(P﹤0.05); Significant differences was found in LRR, SBR, nFR between two groups at mid-term of postoperative(P﹤0.05); parameters of set screw is correlated with reset results, and reduction is better when SA≥LSA or StHD≥SD(P﹤0.05).Conclusion 1. Reset results of moderate to severe spondylolisthesis has impact on imaging effects but not on medium-term clinical effects.2. Within a certain range, sagittal screws angles and height difference of sagittal screw tail has some affect on operative reduction with moderate to severe spondylolisthesis.
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