Correlative factors for adjacent segment degeneration after lumbar spinal fusion

English Keywords:Lumbar fusion  Adjacent segment degeneration  Pelvic incidence

English Abstract:

  【Abstract】 Objectives: To explore risk factors associating with adjacent segmental degenerations after lumbar fusion surgery. Methods: A retrospective analysis was performed on 109 cases of lumbar stenosis undergoing lumbar posterior decompression, pedicle screw fixation and fusion in orthopedic department of Peking University Third Hospital from January 2009 to January 2011. These cases included 39 males and 70 females with ages ranging from 24 to 79 years(average, 54 years). All of them were followed up by a 2- to 4-year(average, 3.4 years) outpatient questionnaire. Measurement included peroperative angles of fusion segment(FA), proximal and distal adjacent angles of fusion segments(PA, DA), lumbar lordosis(LL), sacral slope(SS), pelvic incidence(PI) in pre-operation, and slip distance（SD） between fusion and non-fusion segments. Adjacent segment rdiograpfic degeneration was defined as adjacent segmental slip of 3mm or more on standing X-ray at post-operative 24 months. All patients were categorized into degenerative group(group A) and non-degenerative group(group B). Gender, age, bone mineral density, number of fusion segments were also recorded. The comparative results between two groups were analyzed by t-test and χ2 -test. Risk factors of adjacent segment radiographic degeneration were analyzed by using Logistic regression. Results: There were 18 cases(16.5%) in group A and 91 cases(83.5%) in group B developing ASD, and all ASD occurred at proximal adjacent segments. Preoperative results were as follows: LL for group A and B was 29.8°±12.5° and 32.4°±11.2°; SS for group A and B was 31.5°±12.1° and 37.4°±13.4°; FA for group A and B was 18.3°±9.0° and 14.8°±10.5°; PA for group A and B was 6.8°±3.2° and 7.2°±5.2°, which all showed significant differences between two groups(P＜0.05). PI of group A(42.3°±9.8°) was significantly lower than that of group B(49.9°±9.8°)(P＜0.05). Gender, age, bone mineral density, number of fusion segments and DA were not associated with ASD(P＞0.05). Logistic regression analysis showed significant correlation with PI and incidence of ASD(P＜0.05), but no correlation between SS, LL, FA, PA and incidence of ASD（P＞0.05）. Conclusions: Of the risk factors inducing ASD, low PI may be one of the important factors.