Effect of spinopelvic sagittal alignment on the development of adjacent segment degeneration after posterior lumbar fusion: investigation on cases with a minimum of 6 years of follow-up

English Keywords:Lumbar fusion  Spino-pelvic sagittal alignment  Adjacent segment degeneration

English Abstract:

  【Abstract】 Objectives: To investigate the effect of postoperative spino-pelvic sagittal alignment on the development of adjacent segment degeneration(ASD) after posterior lumbar fusion in a long-term follow-up. Methods: By retrieving the medical records from January 2002 to December 2006 in our hospital, 72 patients [33 males, 39 females; mean age 55.9±9.2 years(31-71 years) at surgery] were enrolled, with mean 86.8±7.5 months(72-120 months) follow-up after surgery. Preoperative and final follow-up radiographs and MRI images were evaluated. Pelvic incidence(PI), sacral slope(SS), pelvic tilt(PT), lumbar lordosis(LL), fusion lumbar lordosis and residual lumbar lordosis were examined on radiographical images by using PACS. ASD were evaluated on MRI and X-ray radiographs. 106 asymptomatic middle-aged and elderly volunteers were recruited as control to analyze the characteristics of spinopelvic sagittal alignment after posterior lumbar fusion in a long-term follow-up. The correlation between ASD and changes of sagittal alignment were analyzed. Results: At final follow-up, degenerative changes of adjacent segment were found in 50 cases (69.4%, 50/72). There was no significant difference in pelvic sagittal parameters(PI, PT and SS) among ASD, N-ASD and control group. LL at preoperation and at final follow-up in both ASD(32.6°±15.4°) and N-ASD(37.3°±12.0°) group was significantly less than that in control group(49.2°±9.1°)(P<0.05). Significant difference between N-ASD and ASD group on final follow-up radiographs were seen for LL (42.8°±10.5° vs 36.3°±14.0°, P<0.05). Among the 42 patients who received lumbar floating fusion, 31 patients had ASD at final follow-up. Among the 30 patients received lumbosacral fusion, 19 patients had ASD at final follow-up. There was no significant difference between these two groups in ASD(P=0.341). For patients with lumbosacral fusion, ASD was seen for postoperative longer fusion segments, less total and residual lumbar lordosis. Conclusions: (1)There is correlation between the postoperative long-term lumbar lordosis and development of ASD. Obtaining appropriate lumbar lordosis is important for preventing ASD. (2)Extended fusion to the sacrum does not independently enhance the risk of ASD. But for patients with lumbosacral fusion, longer fusion segments, less total and residual lumbar lordosis will increase the risk.