Spontaneous correction of sagittal spinopelvic malalignment after decompression surgery without corrective fusion procedure for lumbar spinal stenosis and its impact on clinical outcomes: A systematic review

Abstract

BackgroundThe impact of a positive sagittal vertical axis (SVA) on the surgical outcome for lumbar spinal stenosis (LSS) remains unclear, because sagittal imbalance in LSS may partly result from the tendency of patients to lean forward to reduce symptoms. Such an abnormality could be normalized by decompression surgery alone without corrective fusion. As this spontaneous correction is not well known, some surgeons perform only neural decompression in patients with positive SVA and decreased lumbar lordosis (LL), unless flatback-related symptoms are present, whereas other surgeons add corrective fusion to restore spinopelvic alignment. We systematically reviewed previous studies on this issue. MethodsPubMed, Cochrane Library, and Embase were searched for English articles on the relationship between SVA and decompression surgery for LSS. The rates of spontaneous correction in spinopelvic parameters and the impact of SVA on clinical outcomes were analyzed. ResultsThe rate of spontaneous SVA correction from >40–50 mm to normal values following decompression surgery alone varied from 25% to 73%. Overall, the spinopelvic parameters tended to improve postoperatively, with statistically significant changes in some series. Postoperative residual sagittal imbalance, rather than preoperative imbalance, more consistently showed a negative impact on clinical outcomes, but not on leg symptoms. For predicting postoperative sagittal imbalance, 2 studies identified the cutoff of >20° for preoperative PI-LL mismatch. Another study suggested SVA >80 mm as a useful value for this purpose. ConclusionIn LSS treated with decompression surgery alone, postoperative rather than preoperative sagittal imbalance more consistently affects clinical outcomes, particularly low back pain. This is probably because decompression usually partly improves preoperative spinopelvic sagittal malalignment. Thus, LSS, if associated with preoperative PI-LL mismatch <20° and SVA <80 mm, may not require additional corrective fusion procedures.