Spontaneous remodeling of spinal canal after sagittal translation in the osteotomy for thoracolumbar kyphosis in ankylosing spondylitis

English Keywords:Ankylosing spondylitis  Pedicle subtraction osteotomy  Sagittal translation  Spinal canal remodeling

English Abstract:

  【Abstract】 Objectives: To observe the transformation of spinal canal in patients with sagittal translation(ST) after osteotomy in ankylosing spondylitis(AS) kyphosis, and to investigate the spontaneous remodeling of spinal canal in these patients. Methods: Retrospective analysis was conducted on 16 patients with ST after the treatment of AS kyphosis through pedicle subtraction osteotomy(PSO) during January 2011 to December 2014 in our hospital, 14 males and 2 females, aged 28-55 years old(38.6±8.4 years old). Full-length free-standing spinal radiographs and computed tomography of ST level were available for all the patients before and after surgery, also at the final follow-up. Radiographic parameters including global kyphosis (GK), thoracolumbar kyphosis(TLK), lumbar lordosis(LL), sagittal vertical axis(SVA) and ST were measured. The change of ST and transformation of spinal canal after surgery and at the final follow-up were compared. The SRS scores before surgery and at the final follow-up were also collected. Results: The average follow-up time was 22.0 months, ranged from 12 to 36 months. There was no internal fixation failure during this period. The preoperative GK was 59.9°±21.0°, TLK was 38.0°±13.0°, LL was 7.4°±26.5°, SVA was 27.2±8.6mm. And the postoperative GK was 15.7°±2.1°, TLK was 5.6°±2.6°, LL was -36.1°±2.9°, SVA was 6.1±4.3mm. ST was 7.1±2.7mm after surgery while 1.2±1.0mm at the final follow-up, the difference was statistically significant(P<0.05). The rate of ST transformation was (84.9±9.7)%. 4 among 16 patients experienced neurological deficits(incidence of neurological deficits was 25%). The SRS scores before operation and at the final follow-up were 1.6±0.3 and 4.7±0.4 respectively(P<0.05). The remodeling of spinal canal occured in all the patients with different degrees. Conclusions: All patients with ST after PSO for AS kyphosis experience spontaneous remodeling of spinal canal, and ST decreases or even disappeares in different degrees.