Radiological morphology variances of osteotomized vertebra-disc complex following pedicle subtraction osteotomy for ankylosing spondylitis with thoracolumbar kyphosis: the incidence, mechanisms, and prognosis

Orientation of Osteotomized Vertebrae in 2-Level Pedicle Subtraction Osteotomy Plays a Crucial Role in the Remodeling of Harmonious Sagittal Curve for Severe Thoracolumbar Kyphotic Deformity Caused by Ankylosing Spondylitis

BACKGROUND

Few studies reported the remodeling of harmonious sagittal curve after 2-level pedicle subtraction osteotomy (PSO) for severe thoracolumbar kyphosis in ankylosing spondylitis (AS).

OBJECTIVE

To investigate how the orientation of osteotomized vertebrae (OV) affects the remodeling of harmonious sagittal curve in patients with AS undergoing 2-level PSO.

METHODS

Twenty-six patients treated with 2-level PSO were reviewed. Plumb lines of thoracic apex and lumbar apex, the superior/inferior endplate angle of OV, and OV tilt were measured. Patients with AS were grouped based on the postoperative lumbar lordotic apex (LLA, L3 or L4 vs L5 or others).

RESULTS

The level of thoracic kyphotic apex was positively correlated with that of superior OV postoperatively. Larger sacral slope, L1-L3 lordotic angle, and plumb lines of lumbar apex could be obtained in patients with LLA at L3 or L4, accompanied with larger superior endplate angle of OV and OV tilt of inferior OV ( P < .05). Besides, larger lumbar lordotic angle (LL) was observed in these patients (marginally significant, P = .057). For patients with relocated LLA at L5 or others, lower pelvic incidence was observed, accompanied with significant loss of correction ( P < .05) and worse Visual Analog Scale scores (marginally significant, P = .054) during follow-up.

CONCLUSION

Ventrally leaning inferior OV combined with dorsally leaning superior OV contributed to the most harmonious sagittal curve defined as thoracic kyphotic apex at T8 or above and LLA at L3 or L4. Sagittal curve with LLA at L5 could be acceptable in patients with more severe kyphosis, especially those with low pelvic incidence.

Remodeling morphology of the subluxated osteotomy vertebra in closing-opening wedge osteotomy in ankylosing spondylitis: would the anterior bony beak blunt?

INTRODUCTION

To investigate the remodeling morphology of subluxated osteotomy vertebra in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis after single-level closing-opening wedge osteotomy (COWO).

MATERIALS AND METHODS

Standing lateral radiographs were taken to evaluate sagittal parameters including lumbar lordosis (LL), C7 sagittal vertical axis (SVA), global kyphosis (GK), sacral slope (SS), and pelvic tilt (PT). Radiographic parameters of the osteotomy vertebra included osteotomized vertebra angle (OVA), sagittal translation (ST), anterior height (AH), posterior height (PH), and middle height (MH) of the osteotomy vertebrae. Furthermore, lateral projection area of the vertebral body was also measured to evaluate the remodeling of the osteotomy vertebrae.

RESULTS

Sixty AS patients who underwent single-level lumbar COWO with a minimal 2-year follow-up were included. The cohort consisted of 54 males and 6 females with an average age of 36.6 years. All patients were divided into two groups according to the development of vertebral subluxation (VS): 15 in VS group (ST ≥ 5 mm), 45 in non-VS group (ST < 5 mm). There was significant difference in the correction of GK, SVA, and the loss of correction of SVA between AS patients with and without VS. Significant difference in vertebra-related parameters regarding AH and OVA was found between VS group and non-VS group (P < 0.05).

CONCLUSIONS

After COWO, new bone formation narrowing the gap and adaptive resorption of the anterior bony beak at the osteotomy level during follow-up was surprisingly favorable. However, the ability of spinal canal remodeling is limited in patients complicated with VS.

Posterior Three-column Osteotomy for Treatment of Congenital Kyphosis with Multiple Thoracolumbar/lumbar (TL/L) Anterior Unsegmented Vertebrae (AUVs): A Comparison between Patients with Increasing Number of AUVs

BACKGROUND

Three-column osteotomy (3-CO) is sometimes challenging when confronting many anterior unsegmented vertebrae in congenital kyphosis (CK-AUVs).

OBJECTIVE

To compare the surgical outcomes of single level 3-CO and the associated complications between CK with increasing number of AUVs.

METHODS

25 consecutive operated patients with CK-AUVs at a mean age of 16.2±10.3 years were retrospectively reviewed. They were stratified into two groups according to the number of AUVs: 3-AUVs group and ≥4 AUVs group. The osteotomy types, surgical outcomes and the related complications were analyzed and compared between the two groups.

RESULTS

13 and 12 patients were recruited in the 3-AUVs group and the ≥4 AUVs group, respectively. The ratio of Pedicle Subtraction Osteotomy, Grade IV osteotomy, Vertebra Column Resection and Vertebral Column Decancellation were 15.4%, 38.5%, 46.1% and 0% for 3-AUVs group and 8.3%, 0%, 83.3% and 8.3% for ≥4 AUVs group, respectively. Preoperative focal kyphosis was significantly higher in the ≥4 AUVs group (82.9±28° vs.59.7±9.4°, p=0.010), which was remarkably corrected in both groups postoperatively. While ≥4 AUVs group had a significantly higher remaining kyphosis (33.6±13.4° vs. 15.1±9.1°, p<0.001) with a significantly lower correction rate (61.2±13.6% vs. 75.0±15.6%, p=0.001). The complication rate was significantly higher in ≥4 AUVs group than 3-AUVs group (8/12 vs. 1/13, p=0.004), mainly involving vertebral subluxation and proximal junctional kyphosis.

CONCLUSIONS

Posterior single-level grade Ⅲ-Ⅴ 3-CO can achieve satisfactory kyphosis correction in CK with 3 AUVs. Decreasing kyphosis correction and increasing surgery-related complications are prone to develop when treating CK with ≥4 AUVs.

When Can One-level Pedicle Subtraction Osteotomy Obtain Satisfied Outcomes for Severe Thoracolumbar Kyphosis with Global Kyphosis ≥80° in Ankylosing Spondylitis: A Comparison with Two-level Pedicle Subtraction Osteotomy

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to make a thorough comparison of clinical and radiographic outcomes between ankylosing spondylitis (AS) patients with severe kyphosis who underwent one- or two-level pedicle subtraction osteotomy (PSO) and to determine the indications of one-level PSO.

SUMMARY OF BACKGROUND DATA

Traditionally, one-level PSO was considered being able to obtain 35° to 40° correction. However, in our practice, one-level PSO might achieve satisfied clinical and radiographic outcomes in AS patients with severe thoracolumbar kyphosis defined as global kyphosis (GK) ≥80°.

METHODS

Fifty-five AS-related severe thoracolumbar kyphosis patients undergoing one- or two-level PSO from January 2007 to November 2016 were reviewed. The radiographic parameters included thoracic kyphosis (TK), lumbar lordosis (LL), GK, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), and femoral obliquity angle (FOA). Clinical outcomes were evaluated by Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS).

RESULTS

The mean follow-up period was 39.7 ± 20.2 months (range, 24-120 months). Patients who underwent one-level PSO have significantly smaller preoperative GK, SVA, FOA, and larger preoperative LL and SS compared to those who underwent two-level PSO (P < 0.05). The optimal cutoff points of preoperative radiographic parameters for selecting one-level PSO were: GK <94°, SVA <18.0 cm, and LL <18°. No significant difference was observed between the two groups with regard to preoperative ODI and VAS (P > 0.05), and the improvement of ODI and VAS (P > 0.05). Significantly more operative time, blood loss, and fusion levels were found in two-level PSO group (P < 0.05).

CONCLUSION

One-level PSO might be appropriate for selected severe AS-related kyphosis patients with GK <94°, SVA <18.0 cm, and LL <18°. This finding might be beneficial for surgical decision-making in performing one-level PSO, a relatively less risky procedure, to reconstruct the ideal sagittal alignment in AS patients with severe thoracolumbar kyphosis.Level of Evidence: 2.