Distal junctional kyphosis in patients with Scheuermann's disease: a retrospective radiographic analysis

To investigate the relationship between preoperative and postoperative spinopelvic alignment and occurrence of DJK/DJF. This was a retrospective observational cohort study. The sample included 40 patients who underwent posterior correction of SK from January 2006 to December 2014. Correlation analysis between the preoperative and postoperative spinopelvic alignment parameters and development of DJK over the course of the study period were studied. Whole spine X-rays obtained before surgery, 3 months after surgery and at the latest follow-up were analyzed. The following parameters were measured: maximum of thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lower instrumented vertebra (LIV) and LIV plumb line. Development of DJK was considered as the primary end point of the study. The patient population was split into a control and DJK group, with 34 patients and 6 patients, respectively. Statistic analysis was performed using unpaired t test for normal contribution and Mann-Whitney test for skew distributed values. The significance level was set to 0.05. DJK occurred in 15% (n = 6) over the study period. There was a significantly lower postoperative TK for the group with DJK (42.4 +/- 5.3 vs 49.8 +/- 6.7, p = 0.015). LIV plumb line showed higher negative values in the DJK group (-43.6 +/- 25.1 vs -2.2 +/- 17.8, p = 0.0435). Furthermore, postoperative LL changes were lower for the DJK group (33.84 +/- 13.86% vs 31.77 +/- 14.05, p < 0.0001.) The age of the patients who developed DJK was also significantly lower than that of the control group (16.8 +/- 1.7 vs 19.6 +/- 4.9, p = 0.0024.) SK patients who developed DJK appeared to have a significantly higher degree of TK correction and more negative LIV plumb line. In addition, there may be a higher risk for DJK in patients undergoing corrective surgery at a younger age.