Two-Level Osteotomy for Correcting Severe Ankylosing Spondylitis Kyphosis: Radiologic Outcomes of Different Osteotomy Position-Selection Strategy for Different Type of Patients

Abstract

Objective: To report on the radiologic outcomes of different osteotomy position-selection strategies for a two-level osteotomy for correcting severe ankylosing spondylitis kyphosis.

Methods: From July 2009 to September 2016, a total of 46 patients in our department with severe ankylosing spondylitis kyphosis who underwent two-level pedicle subtraction osteotomy (PSO) were studied. Pre- and postoperative relevant parameters were recorded. The patients were divided into two types and further separated into four groups. The lumbar lordotic angle of Type I patients was larger than or equal to 0°. The lumbar lordotic angle of Type II patients was less than 0°. The patients of Group I belonging to Type I underwent superior spinal osteotomy at the L1 vertebra. The patients of Group II belonging to Type I underwent superior spinal osteotomy at the T12 vertebra. The patients of Group III belonging to Type II underwent superior spinal osteotomy at the L1 vertebra. The patients of Group IV belonging to Type II underwent superior spinal osteotomy at the T12 vertebra.

Results: Analysis of preoperative data showed that the lumbar lordosis (LL) of Group I and II patients was significantly larger than those of Group III and IV. Postoperative data analysis showed that there was significant difference among the four groups in the postoperative LL and TK. The LL of Group II and III patients was smaller than that of Group I patients, and was larger than that of Group IV patients. Group II and Group III patients had more moderate LL and better physiological curvature than those in Group I and Group IV. There were no significant differences between Group II and Group III patients in postoperative LL, thoracolumbar kyphosis, thoracic kyphosis, and global kyphosis. And, likewise, there were no significant differences among the four groups in cervical 7 sacrum angle (C7SA).

Conclusion: Two-level osteotomy was effective for correcting severe ankylosing spondylitis kyphosis. In patients with LL greater than or equal to 0°, it would be better if the second or superior spinal osteotomy was performed at T12 rather than at L1 for restoring the sagittal balance. In patients with LL smaller than 0°, it would be more satisfactory to perform two-level osteotomy at lumbar vertebras for correcting sagittal imbalance.

Level of evidence: Level III.

Keywords: Ankylosing spondylitis; Kyphosis; Osteotomy.