Can pelvic tilt be restored by spinal osteotomy in ankylosing spondylitis patients with thoracolumbar kyphosis? A minimum follow-up of 2 years

Abstract

BackgroundDefining the postoperative pelvic tilt (PT) individually can help to reconstruct sagittal balance. However, the postoperative actual PT is hardly restored to theoretical value. Some cases with theoretical postoperative PT was overcorrected and still did not have normal horizontal visual field after surgery. The objective of this study is to describe the pelvic tilt change after spinal osteotomy in ankylosing spondylitis (AS) kyphotic deformity and evaluate the effect on clinical outcomes.MethodsTwenty-three AS patients including 21 men and two women with thoracolumbar kyphosis, who underwent spinal osteotomy from 2013 to 2015 in our center, were retrospectively reviewed. A series of parameters including sacral slop (SS), pelvic incidence (PI), PT, and sagittal vertical axis (SVA) measured on preoperative and postoperative standing radiographs were analyzed. The theoretical postoperative PT (tPT) was calculated by the formula tPT = 0.37 × PI − 7. The radiographic measurements were compared before surgery, 2 weeks and at least 2 years postoperatively. Clinical outcomes were performed with the Oswestry disability index and Scoliosis Research Society-22 surveys.ResultsMean age of the patients (2 women, 21 men) was 39.8 ± 9.1 years. Mean follow-up was 27.4 ± 3.8 months, at least 24 months. After spinal osteotomy, SS and SVA were corrected from 11.9° ± 11.2° and 18.0 ± 7.6 mm preoperatively to 25.8° ± 8.1° and 9.6 ± 6.3 mm postoperatively, respectively (p < 0.001). PT reduced from 37.6° ± 12.1° to 21.8° ± 9.8° postoperatively (p < 0.001). The tPT was different from postoperative actual PT significantly (p < 0.001). The clinical evaluations were not correlated with postoperative PT.ConclusionThe abnormal PT is corrected by spinal osteotomy but is hard to restore to theoretical normal value. PT is a helpful parameter in making surgery plan. But pursuing postoperative PT being totally equal to tPT is undesirable and even may cause for overcorrection.

Does the Change of Acetabular Anteversion Result From Lumbar Pedicle Subtraction Osteotomy in Ankylosing Spondylitis-Related Kyphosis After Primary Total Hip Arthroplasty?

“…24 Except for the significant decrease in PT in the AS patients with less baseline SVA or C7 tilt, compensated pelvic backward rotation remained to maintain the sagittal balance (C7 tilt ¼ 0) after PSO. 24,25 Thus, more caudal PSO level would mainly result in the restoration of SVA. The greater decrease in PT or AA might not occur in AS patients following PSO with more caudal osteotomy level (Figures 3, 4).…”

“…23 Since the restricted magnitude of deformity correction achieved by 1-level PSO, ideal spinopelvic sagittal alignment might not be achieved in the most AS patients with thoracolumbar kyphosis. 24 Except for the significant decrease in PT in the AS patients with less baseline SVA or C7 tilt, compensated pelvic backward rotation remained to maintain the sagittal balance (C7 tilt ¼ 0) after PSO. 24,25 Thus, more caudal PSO level would mainly result in the restoration of SVA.…”

Preoperative prediction of sagittal imbalance in kyphosis secondary to ankylosing spondylitis after one-level three-column osteotomy

“…As the pelvis was rotated backward to compensate sagittal imbalance preoperatively, the posteriorly rotated pelvis could have some degree of anterior rotation postoperatively in the absence of hip stiffness. Of note, the pelvis forward rotation could not be accomplished immediately after surgery, because AS with severe pelvic retroversion was usually complicated with hip joint contracture caused by ligament tension, which could be gradually corrected to a certain extent with rehabilitation exercises [ 4 , 20 , 21 ]. In addition, AS patients were still accustomed to the preoperative anterior center of gravity; thus, they kept flexing the trunk while standing until they got used to the new center of gravity after a period of time.…”

Preoperative prediction of sagittal imbalance in kyphosis secondary to ankylosing spondylitis after one-level three-column osteotomy

“…As the pelvis rotated backward to compensate sagittal imbalance preoperatively, the backward rotated pelvis could anteriorly rotate to some extent postoperatively provided the hip joints were not ankylosed. Of note, the pelvis rotation anteriorly could not be accomplished immediately after surgery because the AS with severe pelvic retroversion usually complicated with the contracture of hip joints for the tense ligaments, which could be gradually corrected to a certain extent with rehabilitation exercise [4,19,20]. Second, the patients with AS were still accustomed to the preoperative anterior center of gravity; thus, they kept on exing the trunk when standing until they got used to the new center of mass after a period.…”