The relationship between the extent of reduction and the change of spino-pelvic parameters in high dysplastic developmental spondylolisthesis

English Keywords:High dysplastic developmental spondylolisthesis  Reduction  Spino-pelvic alignment

English Abstract:

  【Abstract】 Objectives: To investigate the relationship between the extent of reduction and the change of spino-pelvic parameters in high dysplastic developmental spondylolisthesis(HDDS), so as to know about what extent of reduction could significantly improve postoperative spino-pelvic sagittal alignment. Methods: Thirty-five young patients of HDDS, aged 9 to 35 (14.9±5.9) years old and treated between March 2007 and April 2019 in our hospital were studied retrospectively, with an average follow-up time of (42.5±33.1) months (3-120 months). They were divided into four groups of <70°(7 cases), 70°-79.9°(8 cases), 80°-89.9°(4 cases) and ≥90° (16 cases) based on the final follow-up Dubousset lumbosacral angle(Dub-LSA), and were also divided into three groups of high-grade (grade Ⅲ and above) (5 cases), grade Ⅱ(6 cases), and grade Ⅰ(24 cases) based on the final follow-up Meyerding grade. Then, the preoperative and final follow-up spino-pelvic parameters of each group were compared to find out what extent of reduction could significantly improve these parameters and pelvic balance. Results: The slip percentage was [pre-operation (66.7±22.5)% (range 35%-100%) vs. final follow-up (18.9±20.9)% (range 0%-72%)]. The Dub-LSA was (pre-operation 61.9°±14.7° vs. final follow-up 82.1°±17.3°). The differences between preoperative and final follow-up parameters became more significant with the increase of Dub-LSA and the decrease of slippage. In the Dub-LSA ≥90° and the grade Ⅰ group, pelvic tilt(PT) and sacral slope(SS) were improved significantly, and the ratio of retroverted pelvis changing into balanced type was increased significantly. Dub-LSA ≥90° group: PT [pre-operation (36.4°±6.5°) vs. final follow-up (27.2°±4.9°), P<0.001], SS [pre-operation (33.5°±9.1°) vs. final follow-up (42.1°±9.3°), P<0.001], and the ratio of balanced pelvis [pre-operation 0%(0/16) vs. final follow-up 43.8% (7/16), P=0.007]. Grade Ⅰ group: PT [pre-operation (38.9°±8.6°) vs. final follow-up (30.6°±7.4°), P<0.001], SS [pre-operation (31.4°±11.5°) vs. final follow-up (41.2°±8.7°), P<0.001], and the ratio of balanced pelvis [pre-operation 0%(0/24) vs. final follow-up 29.2%(7/24), P=0.009]. Conclusions: Reduction of HDDS to Dub-LSA ≥90° and Meyerding grade Ⅰ could improve the spino-pelvic alignment significantly, and could convert part (43.8%) of the retroverted pelvis to balanced pelvis.