The Upper Instrumented Vertebra Horizontalization: An Essential Factor Predicting the Spontaneous Correction of Compensatory Curve After Lumbosacral Hemivertebra Resection and Short Fusion.

<bold>Study Design: </bold>A retrospective study.<bold>Objective: </bold>To determine the significance of postoperative upper instrumented vertebra (UIV) horizontalization on the evolution of proximal compensatory curve after hemivertebra resection and short fusion in young patients with lumbosacral hemivertebra (LSHV).<bold>Summary Of Background Data: </bold>Postoperative compensatory curve progression (CCP) is an undesired complication in patients undergoing spinal fusion. Posterior-only hemivertebra resection and short fusion has gradually become a preferred treatment for young patients with LSHV. Postoperative UIV horizontalization might play an important role in the behavior of compensatory curve after surgery.<bold>Methods: </bold>This study reviewed a consecutive series of patients undergoing posterior-only LSHV resection and short fusion from August 2006 to June 2016. The radiographic parameters were measured at preoperation, immediately postoperation, and the last follow-up. Based on the immediately postoperative UIV tilt, patients were divided into horizontal group (UIV tilt < 5°) and inclined group (UIV tilt ≥5°). Postoperative CCP was defined as the Cobb angle of compensatory curve increased more than 10° than the immediately postoperative value.<bold>Results: </bold>Forty-eight patients (8.1 ± 3.4 yrs) were recruited. Seventeen patients with immediately postoperative UIV tilt more than or equal to 5° constituted the inclined group, while the other 31 patients were in horizontal group. The two groups had similar age, fusion levels, preoperative spinal curvatures, and sagittal profiles. Compared with horizontal group, patients in inclined group had greater CBD (20.7 ± 14.8 mm vs. 13.2 ± 9.9 mm, P = 0.041) and greater Cobb angle of compensatory curve (17.7 ± 8.2° vs. 9.1 ± 5.3°, P < 0.001) at the last follow-up. Thirteen patients of inclined group experienced postoperative CCP, which was more prevalent than that in horizontal group (76.5% vs. 9.7%, P < 0.001).<bold>Conclusion: </bold>Horizontalizing the UIV can reduce the risk of postoperative CCP in LSHV patients undergoing posterior-only hemivertebra resection and short fusion.<bold>Level Of Evidence: </bold>3. [ABSTRACT FROM AUTHOR]