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 follow-up 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.