‘‘In situ’’ fusion or reduction in high-grade high dysplastic developmental spondylolisthesis (HDSS)

Purpose To assess if the evaluation of the spino-pelvic balance can be effective in the surgical decision making of the high-grade high dysplastic developmental spondylolisthesis (HDDS). Methods Sixteen patients affected with high-grade HDDS (6 treated with ‘‘in situ’’ fusion, and 10 with reduction and fusion) were retrospectively evaluated. A clinical and radiological assessment of the deformity correction was carried out, with a minimum follow-up of 2 years. The differences between the pre- and postoperative measures were statistically analyzed using a two-tailed, paired t test. Results The six patients treated with ‘‘in situ’’ fusion showed no statistically significant change at the last followup relative to pelvic tilt (PT), sacral slope (SS), and grade, while the 10 patients treated with reduction showed significant changes: PT significantly decreased following surgery, while SS and grade significantly increased. Conclusions The analysis of the spino-pelvic sagittal balance allows to identify two types of HDDS: the balanced deformities, which do not need reduction, and the unbalanced deformities, in which correction is needed.