Radiologic and clinical outcomes comparison between single- and two-level pedicle subtraction osteotomies in correcting ankylosing spondylitis kyphosis

An effective strategy for treatment of severe kyphosis secondary to ankylosing spondylitis: one-level modified osteotomy combined with shoulders lifting correction method

BACKGROUND

Severe kyphosis is a common condition in patients with advanced ankylosing spondylitis (AS). Although two-level osteotomy may serve as a potential alternative, it is often associated with increased blood loss and elevated surgical risks. To date, the optimal treatment for the challenging condition remains unclear. This study aims to introduce an effective strategy for the treatment of severe kyphosis secondary to AS, using one-level modified osteotomy combined with shoulders lifting correction method.

METHODS

Seventy AS kyphosis who were treated with the strategy from 2012 to 2022, were reviewed retrospectively. All patients were followed up for a minimum duration of 2 years. Spinal and pelvic parameters were measured, including pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), lumber lordosis (LL), PI and LL mismatch (PI-LL), thoracic kyphosis, global kyphosis (GK), T1 pelvic angle (TPA), sagittal vertical axis (SVA), osteotomized vertebral angle (OVA), and chin-brow vertical angle (CBVA). Parameters of local osteotomized complex were measured and calculated, including the height of osteotomized complex and the length of spinal cord shortening. Clinical outcome was evaluated using Scoliosis Research Society-22 and Oswestry Disability Index scores.

RESULTS

Seventy patients with average age of 39.8 years were followed-up for 29.3 months. Average operation time was 373.5 min, and average blood loss was 751.0 ml. Postoperatively, sagittal balance was successfully restored. GK decreased from 90.6° to 35.6°, LL decreased from 8.0° to -35.1°, TPA decreased from 56.8° to 27.8°, and SVA decreased from 24.4 cm to 8.7 cm (P < 0.05). A harmonious and matched spinopelvic alignment was achieved. PT decreased from 37.2° to 26.3°, PI-LL decreased from 54.1° to 10.2°, and SS increased from 9.2° to 19.7°(P < 0.05). Horizontal vision was obtained with postoperative CBVA of 8.8°. Average OVA correction was up to 47.3°, and the spinal cord was shortened by 24.3 mm, with a shortening rate of 36.0%. All patients demonstrated a favorable clinical outcome. No permanent nerve damage, screw loosening, rod breakage and main vascular injury were observed. One case required revision surgery due to screw cap loosening and delayed union. Solid bone fusion was achieved in all other patients.

CONCLUSIONS

One-level modified osteotomy combined with shoulders lifting correction method is a safe and effective strategy for the treatment of severe AS kyphosis. This strategy offers a promising alternative for managing severe AS kyphosis, and may be particularly well-suited for individuals with concurrent osteoporosis.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Multilevel Pedicle Subtraction Osteotomy for Correction of Thoracolumbar Kyphosis in Ankylosing Spondylitis: Clinical Effect and Biomechanical Evaluation

OBJECTIVE

To compare the clinical outcomes and biomechanical characteristics of 1-, 2-, and 3-level pedicle subtraction osteotomy (PSO), and establish selection criteria based on preoperative radiographic parameters.

METHODS

Patients undergone PSO to treat ankylosing spondylitis from February 2009 to May 2019 in Sun Yat-sen Memorial Hospital of Sun Yat-sen University were enrolled. According to the quantity of osteotomy performed, the participants were divided into group A (1-level PSO, n = 24), group B (2-level PSO, n = 19), and group C (3-level PSO, n = 11). Clinical outcomes were assessed before surgery and at the final follow-up. Comparisons of the radiographic parameters and quality-of-life indicators were performed among and within these groups, and the selection criteria were established by regression. Finite element analysis was conducted to compare the biomechanical characteristics of the spine treated with different quantity of osteotomies under different working conditions.

RESULTS

Three-level PSO improved the sagittal parameters more significantly, but resulted in longer operative time and greater blood loss (p < 0.05). Greater stress was found in the proximal screws and proximal junction area of the vertebra in the model simulating 1-level PSO. Larger stress of screws and vertebra was observed at the distal end in the model simulating 3-level PSO.

CONCLUSION

Multilevel PSO works better for larger deformity correction than single-level PSO by allowing greater sagittal parameter correction and obtaining a better distribution of stress in the hardware construct, although with longer operation time and greater blood loss. Three-level osteotomy is recommended for the patients with preoperative of global kyphosis > 85.95°, T1 pelvic angle > 62.3°, sagittal vertical alignment > 299.55 mm, and pelvic tilt+ chin-brow vertical angle > 109.6°.

Long-term outcome evaluation in ankylosing spondylitis with high-angle thoracolumbar kyphotic deformity corrected by one-stage single-level pedicle subtraction osteotomy augmented with Ponte osteotomy: A case series

INTRODUCTION AND IMPORTANCE

A high-angle thoracolumbar kyphotic deformity (TLKD) may complicate surgical rectification of AS patients since one-stage two-level pedicle subtraction osteotomy (PSO), which provides high-angular correction, leads to excessive blood loss, neurological deficits and fixation failures. This case series presents the long-term results of one-stage single level PSO with Ponte osteotomy (PO) in the treatment of AS patients with high-angle TLKD.

CASE PRESENTATION

This case series presents two AS patients with high kyphotic angles (KAs) of 86.1o. We collected data retrospectively from our institution's database between 2019 and 2023. A sagittal axis imbalance was the only complaint initially, no neurological deficits or other problems. A PSO augmented by PO was performed with a decompression laminectomy. Intraoperative monitoring (IOM) during reduction was used to observe neurological deficits. Blood loss at the highest rate was 1000 cc. It corrected 57.8o of KA postoperatively without neurological deficits. We found consistent results over 36 months.

CLINICAL DISCUSSION

A thorough analytical approach may help diagnose AS. One-stage single-level PSO may correct high-angle TLKD in AS patients effectively. To achieve greater angular correction, PO, a less risky osteotomy, must be added. Decompression laminectomy is vital before osteotomy and IOM is crucial during reduction to prevent nerve injury. Even with two osteotomies, there was less blood loss than previously reported. These impressive long-term results call for further research.

CONCLUSION

Combined PSO and PO with IOM efficiently magnifies the angular correction without postoperative neurological deficits or excessive blood loss in AS patients with high-angle TLKD.

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.

Staged osteotomy in lateral position for the treatment of severe kyphotic deformity secondary to ankylosing spondylitis: a retrospective study

BACKGROUND

Patients with severe kyphotic deformity (Cobb > 100°) secondary to ankylosing spondylitis (AS) occasionally cannot undergo corrective surgery in the prone position. Osteotomy in the lateral position might provide a possible solution. In this study, we aim to evaluate the clinical efficacy and safety of staged osteotomy in the lateral position for the treatment of AS-related severe kyphosis with a minimum of 2-year follow-up.

METHODS

In total, 23 patients who underwent staged osteotomy in the lateral position from October 2015 to June 2017 were analyzed. In the first stage of surgery, all but one patient underwent a single-level Ponte osteotomy, which was followed by a pedicle subtraction osteotomy in the second stage. Mean follow-up was 30.8 ± 4.6 months. Global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), osteotomized vertebra intervertebral angle (OVI), chin-brow vertical angle (CBVA), Oswestry Disability Index (ODI) score and Scoliosis Research Society-22 Patient Questionnaire (SRS-22) were all compared pre- and postoperation.

RESULTS

All kyphosis parameters were significantly improved (all P < 0.05). GK was corrected from 115.0 ± 13.4° to 46.5 ± 9.0° postoperatively, with a mean correction of 68.5°. SVA was improved from 21.2 ± 5.1 cm to 5.1 ± 1.8 cm postoperatively. After surgery, CBVA was adjusted from 64.1 ± 23.2° to 5.7 ± 10.6° and OVI was changed from 9.0 ± 2.7° to - 20.1 ± 5.6°. Both the ODI and SRS-22 showed substantial improvements (all P < 0.05). Four patients with mild complications were observed perioperatively.

CONCLUSION

In AS patients with severe kyphosis, satisfactory correction can be safely achieved with staged osteotomy in the lateral position, which can not only correct the sagittal imbalance of the spine with acceptable complications but also facilitate the placement of the intraoperative position.

Comparison of One-Level Osteotomy and Two-Level Osteotomy for Thoracolumbar Kyphotic Deformity in Ankylosing Spondylitis: A Systematic Review and Meta-Analysis

BACKGROUND

One- and two-level osteotomies have been used to treat thoracolumbar kyphosis in patients with ankylosing spondylitis (AS). However, the effectiveness and safety of the 2 methods have not been systematically compared, and few studies have reported on which method might be more suitable for treating AS.

METHODS

We performed a systematic literature search. All comparative studies of one- and two-level osteotomy for the treatment of thoracolumbar kyphosis caused by AS were included. Efficacy was determined by the radiographic outcomes, including global kyphosis, sagittal vertical axis, and lumbar lordosis and the Oswestry disability index. The complication rates were used to assess the safety. We analyzed the data using Review Manager software.

RESULTS

A total of 10 studies were included and used for the meta-analysis. We pooled the studies according to the type of data they had reported to evaluate the radiographic correction and incidence of complications. We found that two-level osteotomy provided advantages compared with one-level osteotomy for spinal correction, including global kyphosis and lumbar lordosis. However, the correction was dependent on the degree of preoperative kyphosis. In addition, we found no differences between the 2 groups in the correction of the sagittal vertical axis or improvement in the Oswestry disability index. However, we did find differences in the incidence of neural complications, dural tear, and operative site infection.

CONCLUSIONS

Our findings have shown that one-level osteotomy is safer than two-level osteotomy. For AS patients with nonsevere kyphosis, one-level osteotomy will be sufficient for spinal sequence correction and maintenance of balance, and two-level osteotomy will not be needed. For AS patients with severe kyphosis, two-level osteotomy can be recommended for better orthopedic effects; however, a careful surgical technique is required.

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

STUDY DESIGN

Retrospective study.

OBJECTIVES

To analyze the change in acetabular anteversion (AA) after lumbar pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis who have already undergone total hip arthroplasty (THA).

METHODS

AS patients with thoracolumbar kyphosis following lumbar PSO from January 2005 to January 2020 were retrospectively reviewed. Only the patients performed with THA prior to the PSO were included. AA was measured on the full-length standing posterior-anterior radiographs using the ellipse method.

RESULTS

Twenty patients (34 hips) with a mean age of 36.8 years (range, 22 to 63 years) were included. After lumbar PSO, AA was reduced from 18.59° to 5.85° (P < 0.001). Postoperative change in AA was correlated with the spinal deformity correction. Additionally, the change in AA postoperatively was correlated with pelvic incidence (PI) (R = 0.346, P = 0.045). Although the postoperative change in sagittal vertical axis (SVA) was larger in the patients after L2 or L3 PSO (153.97 mm vs 70.03 mm, P = 0.006), no difference was found in the postoperative change in AA (12.83° vs 10.96°, P = 0.540) compared with the patients following L1 PSO.

CONCLUSIONS

AA was significantly decreased following lumbar PSO and the postoperative change in AA was correlated with the magnitude of spinal deformity correction. Notably, the effect of osteotomy level on the postoperative change in AA was limited in the AS patients underwent 1-level PSO.

Multilevel non-contiguous thoracic pedicle subtraction osteotomy for fixed rounded hyperkyphotic deformity of the thoraco-lumbar junction with anterior bony fusion: technical note

BACKGROUND

Fixed severe hyperkyphotic deformities spread over more than five vertebral levels represent a therapeutic challenge, especially when the deformity apex is located at the thoraco-lumbar junction, thus requiring a huge amount of correction. The aim of this article is to describe an innovative all-posterior corrective technique based on multilevel non-contiguous thoracic pedicle subtraction ostoeotomy (PSO).

MATERIALS AND METHODS

A retrospective review of three patients with fixed severe thoracic hyperkyphosis (a deformity angle of over 70°) with a thoraco-lumbar apex (between T11 and L1) treated by simultaneous two-level thoracic PSO and thoraco-lumbar posterior fusion was performed. Radiographic and clinical records were evaluated pre-operatively, post-operatively and at last follow-up (after a minimum of 2 years). Each variable was presented as mean ± SD (standard deviation). Statistical analyses were performed using paired t-tests (P value < 0.05 was considered significant).

RESULTS

The mean local deformity angle decreased by 75% (from 81.3° ± 2.1° to 20.7° ± 1.4°, p < 0.001), the post-operative thoracic kyphosis decreased by 46% (from 61.4° ± 2.4° to 33.2° ± 0.9°, p < 0.001) and the sagittal vertical axis decreased by 73% (from 14.7 cm ± 0.8 cm to 3.9 cm ± 0.3 cm, p < 0.001). No differences were observed in the radiological results between post-operative values and those at the final follow-up. The average Oswestry Disability Index (ODI) score reduced from 65.7 ± 1.8 pre-operatively to 17.3 ± 1.7 at last follow-up (p < 0.001). No neurological, mechanical nor infective complication occurred.

CONCLUSIONS

The presented technique, although technically demanding, proved to be a safe and effective alternative for the management of fixed severe thoraco-lumbar junction hyperkyphotic deformities.

LEVEL OF EVIDENCE

IV TRIAL REGISTRATION Retrospectively registered.

Does the Level of Pedicle Subtraction Osteotomy Affect the Surgical Outcomes in Ankylosing Spondylitis-Related Thoracolumbar Kyphosis With the Same Curve Pattern?

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the effect of pedicle subtraction osteotomy (PSO) level on the surgical outcomes in ankylosing spondylitis-related thoracolumbar kyphosis with the same curve pattern.

METHODS

ankylosing spondylitis (AS) patients with thoracolumbar kyphosis, who underwent 1-level lumbar PSO between March 2006 and June 2017, were retrospectively reviewed. Criteria for curve-matched thoracolumbar kyphosis were: (1) have same level of preoperative apex (pre-apex); (2) have similar global kyphosis (GK, the angle between the superior/inferior endplate of the maximally tilted upper and lower end vertebra) (the difference of GK less than 15˚). The radiographic parameters measured were sagittal vertical axis (SVA, the horizontal distance between the C7 plumb line and the posterosuperior corner of the S1), GK, thoracic kyphosis (TK, the angle between the T5 superior endplate and the T12 inferior endplate), lumbar lordosis (LL, the angle between the L1 and S1 superior endplate), sacral slope (SS, the angle between the sacral endplate and the horizontal line), pelvic tilt (PT, the angle between the vertical and the line joining the midpoint of the sacral plate and hip axis), and pelvic incidence (PI, the angle between the line vertical to the superior margin of S1 and the line connecting the sacral plate midpoint with the hip joint axis). All of these parameters and health-related quality of life (HRQoL, evaluated by preoperative and the last follow-up questionnaires including ODI and VAS) scores were collected before surgery and at the last follow-up. According to their osteotomy level, patients were devided into 2 sub-groups (L1 group and L2 group), and differences of these mentioned parameters between 2 groups were compared.

RESULTS

26 curve-matched patients were recruited with a mean follow-up of 37.2 months. All patients improved significantly after surgery in HRQoL scores (VAS 1.6 vs 5.4, P < 0.001; ODI 11.9 vs 26.4, P < 0.001). Except for TK and PI, those radiographic parameters were also observed to be significantly changed after surgery. Compared to L2 group, PSO at L1 may have larger correction of TK (ΔTK -6.8 vs -0.3°, P = 0.164), PI (ΔPI -7.4 vs -0.7°, P = 0.364) and smaller correction of SVA (ΔSVA -105.3 vs -128.5 mm, P = 0.096), LL (ΔLL -31.1 vs -43.0°, P = 0.307) and SS (ΔSS 6.9 vs 12.2°, P = 0.279) but had no statistical significance.

CONCLUSION

The results of this investigation showed that in AS-related thoracolumbar kyphosis patients with the same curve pattern, the different levels of osteotomy had little effect on the improvement of surgical outcomes. However, osteotomy at L2 is more likely to obtain a larger correction of SVA compared to osteotomy at L1.

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

Background

This study aimed to determine preoperative predictors for sagittal imbalance in kyphosis secondary to ankylosing spondylitis (AS) after one-level three-column osteotomy.

Methods

A total of 55 patients with AS who underwent one-level three-column osteotomy were enrolled. The patients were divided into two groups according to sagittal vertical axis (SVA) value at the final follow-up (group A: SVA > 5 cm; group B: SVA ≤ 5 cm). The radiographic measures included global kyphosis, lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), sacral slope, T1 pelvic angle (TPA), SVA, osteotomized vertebral angle and PI and LL mismatch (PI − LL). Postoperative clinical outcomes were evaluated using Scoliosis Research Society-22 questionnaire (SRS-22) and Oswestry Disability Index (ODI).

Results

Fifty-five AS patients had an average follow-up of 30.6 ± 10.2 months (range 24–84 months). Group A had larger preoperative and postoperative LL, PT, PI − LL, TPA and SVA values compared with group B (P < 0.05), and no significant differences were found in ODI and SRS-22 scores between the two groups (P > 0.05). Preoperative LL, PT, PI − LL, TPA, and SVA values were positively correlated with the follow-up SVA value (P < 0.05). Among them, TPA > 40.9°, PI − LL > 32.5° and SVA > 13.7 cm were the top three predictors with the best accuracy to predict sagittal imbalance. Immediate postoperative SVA value of ≤ 7.4 cm was a key factor in reducing the risk of sagittal imbalance during follow-up.

Conclusions

Preoperative TPA > 40.9°, PI − LL > 32.5° and SVA > 13.7 cm could predict sagittal imbalance in AS kyphosis after one-level three-column osteotomy, and additional osteotomies were recommended for this condition. Immediate postoperative SVA ≤ 7.4 cm was an optimal indicator for preventing sagittal imbalance.

Level of evidence

IV.

Pedicle subtraction osteotomy for the corrective surgery of ankylosing spondylitis with thoracolumbar kyphosis: experience with 38 patients

OBJECTIVE

To evaluate the sagittal parameters and clinical outcome of pedicle subtraction osteotomy (PSO) for the treatment of ankylosing spondylitis (AS) combined with thoracolumbar kyphosis.

METHODS

The clinical data of 38 patients with AS combined with thoracolumbar kyphosis who underwent PSO were enrolled and divided into the lumbar lordosis group and the lumbar kyphosis group according to the preoperative sagittal morphology. They were subdivided into the lumbar lordosis T12 group, lordosis L1 group, kyphosis L2 group, and kyphosis L3 group. The spine sagittal parameters were compared between the preoperative and the postoperative. Outcome evaluation was performed by the Japanese Orthopedic Association (JOA) score, visual analogue scale (VAS), and the Oswestry Disability Index (ODI).

RESULTS

A total of 38 patients with AS combined with thoracolumbar kyphosis were successfully treated by PSO, with a mean follow-up time of 26.9 ± 11.9 months. There were 30 males and 8 females with a mean age of 41.6 ± 7.1 years. Twenty patients consisted in the lumbar lordosis group and 18 patients in the lumbar kyphosis group. GK, SVA, and CBVA were improved significantly (P < 0.05) at the final follow-up between the lumbar lordosis T12 group and the L1 group. Patients in the lumbar kyphosis L2 group and L3 group all received satisfactory, including LL, GK, and SVA (P < 0.05). There was no statistically significant difference in the preoperative TK, GK, SVA, PT, and PI between the lumbar lordosis and lumbar kyphosis groups (P > 0.05). Postoperative complications occurred in three cases.

CONCLUSION

PSO was a practical method for the treatment of patients with AS combined with thoracolumbar kyphosis. PSO at L3 was recommended to be selected for the lumbar kyphosis to obtain greater SVA correction. CBVA of single-segment PSO may be significantly lower than the two-segment PSO in the management of patients with kyphosis of lower CBVA.

Multilevel Pedicle Subtraction Osteotomy for Correction of Severe Rigid Adult Spinal Deformities: A Case Series, Indications, Considerations, and Literature Review

BACKGROUND

Rigid and ankylosed thoracolumbar spinal deformities require three-column osteotomy (3CO) to achieve adequate correction. For severe and multiregional deformities, multilevel 3CO is required but its use and outcomes are rarely reported.

OBJECTIVE

To describe the use of multilevel pedicle subtraction osteotomy (PSO) in adult spinal deformity (ASD) patients with severe, rigid, and ankylosed multiregional deformity.

METHODS

Retrospective review of 5 ASD patients who underwent multilevel PSO for the correction of severe fixed deformity and review the literature regarding the use of multilevel PSO.

RESULTS

Five patients presented with spinal imbalance secondary to regional and multiregional spinal deformities involving the thoracolumbar spine. All patients underwent a single-stage two-level noncontiguous PSO, and 2 of the patients underwent a staged third PSO to treat deformity involving a separate spinal region. Significant radiographic correction was achieved with normalization of spinal alignment and parameters. Two-level PSO was able to provide greater than 80 degrees of sagittal plane correction in both the lumbar and thoracic spine. Two patients experienced new postoperative weakness which recovered to preoperative baseline at 3 to 6 mo follow-up. At most recent follow-up, 4 of the 5 patients gained significant pain relief and had improved functionality.

CONCLUSION

Noncontiguous multilevel PSO is a formidable surgical technique. Additional risk (compared to single-level 3CO) comes in the form of greater blood loss and higher risk for postoperative weakness. Nonetheless, multilevel PSO is feasible and effective for correcting severe multiplanar and multiregional ASD, and patients gain significant benefits in increased functionality and pain relief.

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.

The Sagittal Parameters and Efficacy of Pedicle Subtraction Osteotomy in Patients with Ankylosing Spondylitis and Kyphosis Under Different Lumbar Sagittal Morphologies

OBJECTIVE

This study aimed to compare the changes in sagittal parameters and the efficacy of pedicle subtraction osteotomy (PSO) in patients with ankylosing spondylitis (AS) and kyphosis under different lumbar sagittal morphologies and to explore the effect of sagittal morphology on the selection of PSO levels.

METHODS

A total of 24 patients with AS and thoracolumbar kyphosis (TK) who were admitted to the First Affiliated Hospital of Xinjiang Medical University between 2008 and 2019 were enrolled in this study. They were divided into two groups: a lumbar lordosis group (n = 14) and a lumbar kyphosis group (n = 10). Changes in sagittal parameters, lumbar Japanese Orthopaedic Association (JOA) scores, and visual analog scale (VAS) scores for lumbar pain before and after operation were compared between the two groups to evaluate postoperative efficacy.

RESULTS

The preoperative lumbar lordosis (LL) was -29.29 ± 5.40 (lordosis) and 13.50 ± 3.65 (kyphosis) (P < 0.01), and the preoperative sagittal vertical axis (SVA) was 171.35 ± 25.46 (lordosis) and 223.58 ± 21.87 (kyphosis) (P < 0.01). Preoperative global kyphosis (GK) was 75.71 ± 5.26 (lordosis) and 86.30 ± 10.32 (kyphosis) (P < 0.05). All patients in the lordosis group underwent PSO surgery at the twelfth thoracic vertebra (T12) or the first lumbar spinal vertebra (L1), while all patients in the kyphosis group underwent the surgery at the second or third lumbar spinal vertebra (L2 or L3). The differences in postoperative GK, LL, and SVA between the two groups were not significant (P > 0.05). The JOA scores of the two groups increased from 13.00 ± 0.83 (lordosis) and 11.30 ± 0.93 (kyphosis) before surgery to 21.00 ± 0.67 and 19.70 ± 0.60 after surgery (P < 0.05).

CONCLUSION

Preoperative lumbar sagittal morphology needs to be considered when selecting the optimal osteotomy plane. An osteotomy can achieve the greatest success in patients with lumbar kyphosis at L2/L3; for patients with lumbar lordosis, it can achieve satisfactory outcomes at T12/L1.

One-level mini-open pedicle subtraction osteotomy for treating spinal kyphosis in patients with ankylosing spondylitis

BACKGROUND

To report a mini-open pedicle subtraction osteotomy (PSO) technique, to summarize the 2-year follow-up results of 25 patients, and to describe a modified operating table which allows the osteotomy to be closed in a more controllable manner.

METHODS

We retrospectively reviewed the records of patients with AS who received one-level mini-open PSO between July 2015 and January 2018. The 25 patients with complete medical records and 2-year radiographic follow-up were included in the analysis. Estimated blood loss, operation time, incision length, complications, bed rest period, and length of hospitalization were extracted from the medical records and recorded.

RESULTS

The mean age of the 25 patients (22 males and 3 females) was 39.5 years. The average global kyphosis(GK) decreased from 70.2° before surgery to 22.3° after surgery; the average C7- sagittal vertical axis (C7-SVA) decreased from 15.5 cm before surgery to 5.1 cm after surgery; the average pelvic incidence(PT) decreased from 37.8° before surgery to 22.5° after surgery. The average length of the incision was 10.2 cm. The average surgical time was 263.0 min, the average estimated blood loss was 840.0 ml, and the average time to mobilization was 4.1 days.

CONCLUSIONS

The current report shows that one-level PSO can be performed through an incision of about 10 cm. The one-level mini-open PSO could be superior to traditional PSO surgery with respect to cosmetic outcomes. Further comparative studies are necessary to evaluate the current and conventional techniques.

Protection of L1 nerve roots by pre-relieve tension in parallel endplate osteotomy for severe rigid thoracolumbar spine deformity

BACKGROUND

This is a retrospective study of the use of parallel endplate osteotomy (PEO) for correction of severe rigid thoracolumbar spine deformity.

METHODS

From July 2016 to January 2019, 12 patients with severe rigid thoracolumbar spine deformity underwent PEO on T12 or L1 vertebrae were studied.

RESULTS

Following PEO at T12 or L1, the mean kyphosis and scoliosis correction rates reached 77.0 ± 8.9% and 75.5 ± 8.0%, respectively and the intraoperative estimated blood loss was 1950 ± 1050 mL, and the mean operative time was 6.98 ± 4.02 h. The SF-36 scores of physical function, role-physical, bodily pain, general health, vitality, social function, role-emotional and mental health changed from 63 ± 28, 50 ± 25, 50 ± 30, 34 ± 19, 53 ± 28, 45 ± 30, 30 ± 36 and 54 ± 18 at baseline to 83 ± 18, 69 ± 19, 72 ± 12, 66 ± 21, 75 ± 15, 72 ± 22, 66 ± 34 and 76 ± 12 at 1 year postoperatively, 83 ± 8, 68 ± 32, 83 ± 17, 73 ± 17, 82 ± 18, 76 ± 26, 70 ± 37 and 88 ± 12 at 18 months postoperatively, 86 ± 6, 83 ± 33, 90 ± 16, 81 ± 16, 89 ± 14, 88 ± 25, 83 ± 17 and 94 ± 10 at 24 months postoperatively, respectively (P < 0.01). Three patients had symptoms of L1 nerve root injury, as reflected by lower limb weakness and inner thigh numbness on knee extension and hip flexion, which was further confirmed by electromyography.

CONCLUSIONS

PEO is easier to operate, and the spinal cord and nerve root are under direct vision and can effectively and safely correct severe rigid thoracolumbar spine deformity with satisfactory clinical results. However, it is important to identify, separate and protect L1 nerve roots during surgery in cases where patients have symptoms of back pain, muscle weakness and leg numbness on the convex side after surgery.

Combined percutaneous and open instrumentation for thoracolumbar kyphosis correction by two-level pedicle subtraction osteotomy in ankylosing spondylitis

BACKGROUND

A long global thoracolumbar kyphosis is common in ankylosing spondylitis. Surgical correction of fixed sagittal malalignment by pedicle subtraction osteotomy (PSO) might improve disability and quality of life (QoL). Two-level osteotomies represent major procedures with a risk of hemorrhage. Combined open and minimal invasive surgery has not been described and might be considered.

CASE PRESENTATION

A 30-year-old female with ankylosing spondylitis was treated by golimumab and teriparatide. The treatment was stopped during pregnancy which led to vertebral compression fractures and kyphosis of 50° between T11 and L3. A PSO was planned at the kyphotic apex L2. The second PSO was planned at L4 according to the pelvic incidence of 56°, matching with a spinopelvic alignment Roussouly type 3. A derived full balance integrated method was used to calculate the amount of correction. During the first stage surgery, an open approach was performed from L1 to pelvis and combined with percutaneous cement-augmented instrumentation in already fused segments T5-T12, thus reducing perioperative morbidity. A stepwise approach including L2 PSO closure with temporary rods and L4 PSO with final instrumentation was used. Blood loss was estimated around 1100 ml. The patient was able to walk on the second day after surgery. A secondary anterior fusion with LLI cages from L2 to L5 and an ALIF at L5-S1 were performed because of high non-ossified intervertebral disks to reduce the risk for nonunion and rod fractures. At 2-year follow-up, the patient's QoL had significantly improved and full spine radiographs showed stable normalized sagittal parameters.

CONCLUSION

The combined open and percutaneous approach was feasible and might be considered as an alternative option to conventional open surgery when planning major deformity correction in ankylosing spondylitis.

Does relocation of the apex after osteotomy affect surgical and clinical outcomes in patients with ankylosing spondylitis and thoracolumbar kyphosis?

OBJECTIVE

Relocation of the apex is often found in patients with ankylosing spondylitis (AS)-associated thoracolumbar/lumbar kyphosis after corrective surgery. This study evaluates the influence of different postoperative apex locations on surgical and clinical outcomes of osteotomy for patients with AS and thoracolumbar kyphosis.

METHODS

Sixty-two patients with a mean age of 34.6 ± 9.7 years (range 17-59 years) and a minimum of 2 years of follow-up, who underwent 1-level lumbar pedicle subtraction osteotomy for AS-related thoracolumbar kyphosis, were enrolled in the study, as well as 62 age-matched healthy individuals. Patients were divided into 2 groups according to the postoperative location of the apex (group 1, T8 or above; group 2, T9 or below). Demographic data, radiographic measurements (including 3 postoperative apex-related parameters), and clinical outcomes were compared between the 2 groups preoperatively, postoperatively, and at the last follow-up. Furthermore, a subgroup analysis was performed among patients with a postoperative apex located at T6-11 and postoperatively the entire AS cohort was compared with normal controls regarding the apex location of the thoracic spine.

RESULTS

In the majority of the enrolled patients, the apex location changed from T12-L2 preoperatively to T6-9 postoperatively. The sagittal vertical axis (SVA) differed significantly both postoperatively (25.7 vs 59.0 mm, p = 0.001) and at the last follow-up (34.6 vs 59.9 mm, p = 0.003) between the 2 groups, and the patients in group 1 had significantly smaller horizontal distance between the C7-vertical line and the apex (DCA) than the patients in group 2 (67.5 vs 103.7 mm, p = 0.001). Subgroup analysis demonstrated similar results, showing that the patients with a postoperative apex located at T8 or above had an average SVA < 47 mm. Notably, a significant correlation was found between postoperative SVA and DCA (r = 0.642, p = 0.001). Patients who underwent an osteotomy at L3 had limited apex relocation but larger SVA correction than those at L1 or L2. However, no significant difference was found in health-related quality of life between the 2 groups.

CONCLUSIONS

AS patients with an apex located at T8 or above after surgery tended to have better SVA correction (within 47 mm) than those who had a more caudally located apical vertebra. For ideal postoperative apex relocation, a higher (closer to or at the preoperative apex) level of osteotomy is more likely to obtain the surgical goal.

The relationship between global spinal alignment and pelvic orientation from standing to sitting following pedicle subtraction osteotomy in ankylosing spondylitis patients with thoracolumbar kyphosis

INTRODUCTION

To investigate the relationship between the spinal sagittal alignment and arc of pelvic motion from standing to sitting in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis following pedicle subtraction osteotomy (PSO).

MATERIALS AND METHODS

AS patients who underwent PSO for thoracolumbar kyphosis from January 2016 to July 2018 were recruited. EOS standing and sitting images were obtained pre- and postoperatively. Radiographic parameters were measured on the sagittal radiographs, including lumbar lordosis, thoracic kyphosis, pelvic incidence, pelvic tilt, sacral slope, sagittal vertical axis (SVA), spinosacral angle, anterior pelvic plane angle (APPA) and knee flexion angle.

RESULTS

Thirty-six patients were enrolled. From standing to sitting, APPA was increased by a mean of 14.7° (P < 0.001) and 3.0° (P = 0.083) before and after surgery, respectively. The increase in APPA from standing to sitting was correlated with the standing SVA (R = 0.592, P < 0.001) preoperatively. After PSO, the change in APPA was correlated with the change in SSA in both the standing and sitting position (R = 0.381, P = 0.022 and R = 0.667, P < 0.001, respectively). The APPA from standing to sitting was decreased in 11 patients with standing C7 plumb line posterior to the femoral head postoperatively.

CONCLUSIONS

In AS patients, pelvic orientation was adjusted by the global spinal alignment. When planning total hip arthroplasty for AS patients, global spinal alignment should be considered to improve the joint stability.

Comparison of 2 Surgeries in Correction of Severe Kyphotic Deformity Caused by Ankylosing Spondylitis: Vertebral Column Decancellation and Pedicle Subtraction Osteotomy

OBJECTIVE

To compare the treatment results between 1-level vertebral column decancellation (VCD) and pedicle subtraction osteotomy (PSO) for correcting severe kyphotic deformity in ankylosing spondylitis (AS). VCD and PSO have been used to correct AS-related kyphotic deformity, but the differences on correcting results between VCD and PSO are not clear.

METHODS

Between 2013 and 2015, 57 patients underwent 1-level spinal osteotomy (VCD: n = 30; PSO: n = 27) for correcting kyphotic deformity. Sagittal parameters, fusion results, surgical information, and clinical outcomes were documented and compared. All data were obtained before and 1 week after surgery, 6 months after surgery, and at final follow-up (at least 2 years).

RESULTS

VCD provided significantly greater osteotomy angle (50.8° ± 9.7°) than PSO (38.5° ± 6.1°). In the VCD group, the change of the anterior column was 5.0 ± 1.3 mm, which was larger than the PSO group. The middle column was shortened by 9.9 ± 2.0 mm and 19.1 ± 3.3 mm in the VCD group and PSO group, respectively. There was no significant difference in operating time and blood loss between the 2 groups. All cases had solid fusion. Between the 2 groups, Scoliosis Research Society Outcomes Instrument-22 scores were similar at the final follow-up. No major acute complications occurred in both groups.

CONCLUSIONS

VCD is a safe and effective method in treating rigid kyphotic deformity secondary to AS. VCD provides a larger correction angle in one segment and preserves more height of osteotomized vertebrae than PSO.

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

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.

Does solid fusion eliminate rod fracture after pedicle subtraction osteotomy in ankylosing spondylitis-related thoracolumbar kyphosis?

BACKGROUND CONTEXT

Rod fracture (RF) has a negative impact on the surgical outcome of patients with ankylosing spondylitis (AS) after lumbar pedicle subtraction osteotomy (PSO). However, there is a paucity of published studies analyzing the risk factors for RF in PSO-treated patients with AS with thoracolumbar kyphosis.

PURPOSE

The objective of this study was to investigate the risk factors for RF after PSO for thoracolumbar kyphosis secondary to AS.

STUDY DESIGN/SETTING

This is a retrospective single-center study.

PATIENT SAMPLE

Patients with AS who underwent PSO for thoracolumbar kyphosis between January 2002 and December 2016 were included.

OUTCOME MEASURES

Demographic data, including age, sex, body mass index, and smoking status, were summarized. The surgical data analyzed included the levels of osteotomy, the fusion levels, the upper instrumented vertebra, the lower instrumented vertebra, the osteotomy site, the rod material, the rod diameter, and the rod contour angle (RCA). Radiographic parameters included the sagittal vertical axis, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. Radiographic parameters were measured at baseline, immediately after the operation, and at the final follow-up. Adequate ossification of the anterior longitudinal ligament (ALL) at the PSO level was defined by a total bony bridge. Adequate ossification of the ALL was also measured at baseline, immediately after the operation, and at the final follow-up.

METHODS

Patients with a minimum of 2 years' follow-up or patients who developed RF were enrolled in the study. Recruited patients were divided into the RF group and the no-RF group based on whether they developed RF. Patient demographics, operative data, radiographic parameters, and adequate ossification of the ALL were analyzed to determine the risk factors for RF. For patients with RF, the fusion status at the PSO level, the time course to the development of RF, the site of RF, and the corresponding solution were also recorded.

RESULTS

Rod fracture occurred in 11 (8.9%) of the 123 recruited patients. Solid fusion at the PSO level was found in all patients in the RF group. The average duration to the onset of RF was 31.4 months (range, 12-68 months). All RFs occurred at or immediately adjacent to the PSO level. The RCA was greater in the RF group than in the no-RF group (27.8° vs 22.9°, p=.031). A greater proportion of patients with a rod diameter of 5.50 mm were found in the RF group than in the no-RF group (100.0% vs 68.8%, p=.033). There was a larger proportion of patients with adequate ossification of the ALL at the final follow-up visit in the no-RF group than in the RF group (67.0% vs 27.3%, p=.018). Multivariate analyses demonstrated that the RCA (odds ratio, 1.174; 95% confidence interval, 1.018-1.354; p=.028) and adequate ossification of the ALL at the final follow-up visit (odds ratio, 0.079; 95% confidence interval, 0.014-0.465; p=.005) were independent factors for RF. Notably, revision surgery was performed among six patients, whereas conservative treatment was used for the remaining five patients.

CONCLUSIONS

In patients with AS after PSO for thoracolumbar kyphosis with solid fusion at the PSO level, the incidence of RF was 8.9%. Rod diameter was identified as a risk factor for RF. Furthermore, the RCA was identified as an independent risk factor for RF. In contrast, adequate ossification of the ALL around the PSO level at the final follow-up visit was identified as an independent protective factor for RF.

Does the preoperative lumbar sagittal profile affect the selection of osteotomy level in pedicle subtraction osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis?

OBJECTIVE

To investigate the different preoperative lumbar sagittal profiles of ankylosing spondylitis (AS) patients and the selection of osteotomy level for one-level pedicle subtraction osteotomy (PSO) for the correction of thoracolumbar kyphosis.

PATIENTS AND METHODS

Seventy-one consecutive AS patients with an average age of 35.3 years and a mean follow-up time of 35.9 months who underwent one-level PSO for thoracolumbar kyphosis were divided into 2 groups based on their preoperative lumbar sagittal profiles as follows: group A, lordotic lumbar sagittal profiles; and group B, kyphotic lumbar sagittal profiles. The following radiological parameters were measured and compared: chin-brow vertical angle (CBVA), global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). Clinical evaluation included Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS). Perioperative and mid-term complications were reviewed.

RESULTS

There were 28 patients in group A and 43 in group B. The preoperative LL was -21.0° in group A and 2.3° in group B (P < 0.05). The preoperative SVA was 122.5 mm in group A and 184.3 mm in group B (P < 0.05). All the patients in group A (100%) underwent PSO at L1/L2, while 90% of group B patients underwent PSO at L2/L3, with no significant difference of postoperative GK, LL and SVA between the 2 groups (P > 0.05). No obvious loss of correction was observed in either group at the final follow-up. The correction of LL and SVA showed a strong but not statistically significant increasing trend as the PSO level descended from L1 to L3 (P > 0.05). The postoperative ODI was significantly lower in patients underwent PSO at L1 or L2 (P < 0.05).

CONCLUSIONS

Patients in group B had significantly worse preoperative sagittal alignments compared to group A. The distribution of osteotomy levels varied between the 2 groups due to the different lumbar profiles; however, satisfactory correction was achieved in both groups. The preoperative lumbar profiles need to be considered in selecting the optimal osteotomy level. Patients with kyphotic lumbar profiles are suitable candidates for PSO at L2/L3, while L1/L2 PSO is appropriate for patients with lordotic lumbar profiles.

The Safe Correction Angle of Osteotomy at T12 and L1 for Ankylosing Spondylitis Kyphosis: Patients With 2-level Osteotomy

STUDY DESIGN

This is a retrospective clinical study.

OBJECTIVE

To investigate the correction angle and safety of the spinal osteotomy at the T12 or L1 vertebra.

SUMMARY OF BACKGROUND DATE

Monosegment subtraction osteotomy cannot effectively correct severe kyphosis in ankylosing spondylitis (AS), generally 2-level spinal osteotomy was taken for achieving expected correction. According to literature, the T12 or L1 were usually taken as the upper spinal osteotomy vertebra. Because of the canalis vertebralis at the T12 and L1 were spinal cord and medullary cone, so the spinal osteotomy at the T12 or L1 vertebra were more dangerous than at lower level. The correction angle and safety of the spinal osteotomy at the T12 or L1 vertebra have not yet been reported.

MATERIALS AND METHODS

From July 2009 to 2014, 33 patients in our department with severe AS kyphosis underwent 2-level pedicle subtraction osteotomy were studied. Preoperative and postoperative relevant parameters and complications were recorded.

RESULTS

The upper spinal osteotomy was taken at the T12 vertebra for 10 patients. The upper spinal osteotomy was taken at the L1 vertebra for 23 patients. The mean amount of correction of T12 and L1 was 26.230 and 27.952 degrees, respectively. All patients could walk with orthophoria and lie horizontally postoperatively. No deadly vascular and neurological lesion occurred.

CONCLUSIONS

Performing pedicle subtraction osteotomy at T12 and L1 can safely achieve a mean correction of 26.230 and 27.952 degrees, respectively. Two-level osteotomy was safely and advocated for correcting severe AS kyphosis.

LEVEL OF EVIDENCE

Level III.

Analysis of Sagittal Parameters in Patients Undergoing One- or Two-Level Closing Wedge Osteotomy for Correcting Thoracolumbar Kyphosis Secondary to Ankylosing Spondylitis

STUDY DESIGN

Retrospective analysis of clinical records.

OBJECTIVE

To assess and compare the improvement in sagittal balance after one- or two-level closing wedge osteotomy for correcting thoracolumbar kyphosis secondary to ankylosing spondylitis (AS).

SUMMARY OF BACKGROUND DATA

Closing wedge osteotomy represents a common approach to correct kyphosis in AS. Although several reports have described the outcomes of one- or two-level closing wedge osteotomy in terms of sagittal parameters, data comparing the outcomes of these procedures are scarce.

METHODS

Between January 2010 and December 2014, 22 patients with AS underwent closing wedge osteotomy (one-level, 12 patients; two-level, 10 patients) for correcting thoracolumbar kyphosis (mean follow-up, 24.8 months; range, 12-60 months). Preoperative and postoperative chin-brow vertical angle, and the sagittal parameters of the vertebral osteotomy segment were documented and compared. Perioperative and postoperative complications were also recorded.

RESULTS

The chin-brow vertical angle improved significantly, from 55.0° ± 27.3° to 4.7° ± 4.9° and from 38.2° ± 14.9° to 3.2° ± 5.4° in the one-level and two-level groups, respectively. The total correction (thoracic kyphosis and lumbar lordosis) was 32.8° ± 18.2° and 53.7° ± 9.4° in the one-level and two-level groups, respectively. No death, complete paralysis, or vascular complications occurred during the procedure, but cerebrospinal fluid leak was noted in one and two patients from the one-level and two-level groups, respectively. A distal pedicle screw adjacent to the osteotomy segment became loose during surgery in one patient (one-level group). Postoperatively, no transient neurological deficit, infection, delay union, or loosening or breaking of the internal fixation devices was observed. Osteotomy site fusion was achieved in all patients, and the Oswestry Disability Index scores improved significantly.

CONCLUSION

Closing wedge osteotomy is effective and safe for correcting thoracolumbar kyphosis in patients with AS. Significant correction and improvement in all sagittal parameters were noted in both groups, but two-level closing wedge osteotomy provided better correction.

LEVEL OF EVIDENCE

3.

Does the position of conus medullaris change with increased thoracolumbar kyphosis in ankylosing spondylitis patients?

To date, only a few reports described the potential factors influencing the position of conus medullaris. One previous study revealed no significant change of conus locations in patients with idiopathic scoliosis; however, the effect of ankylosing spondylitis (AS)-related thoracolumbar kyphosis on conus position remains unexplored. Therefore, we aimed to investigate the variation of conus medullaris terminations in patients with thoracolumbar kyphosis secondary to AS when compared with normal subjects, and evaluated the relationship between conus positions and the magnitude of kyphosis. In this study, MR images of 96 AS patients with thoracolumbar kyphosis, including 86 males and 10 females with an average of 34.6 years (range, 17-65 years), and 100 age-matched normal controls were reviewed to determine the conus terminations in relation to spinal levels. Sagittal parameters of the AS group measured on radiograph included: global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), and thoracolumbar junction (TLJ). Finally, conus tips located at the mean level of the lower 3rd of L1 in both groups, there was no significant difference of the conus distributions between AS and control group (P = 0.49). In addition, conus medullaris displayed similar positions in AS patients among various apical region groups (P = 0.88), and no significant difference was found when AS population was stratified into GK ranges of 30° (P = 0.173). Also, no remarkable correlation of the conus positions with GK (r = -0.15, P = 0.15), TK (r = -0.10, P = 0.34), LL (r = -0.10, P = 0.32), and TLJ (r = -0.06, P = 0.54) was identified. This study showed the conus terminations displayed a wide range of distributions in AS patients with thoracolumbar kyphosis, which was similar to normal subjects. Moreover, the conus located at a relatively fixed position and would not be affected by the change of kyphosis magnitude, which is an important knowledge that surgeons should acquire in surgical correction of the deformity in these patients.

How to Calculate the Exact Angle for Two-level Osteotomy in Ankylosing Spondylitis?

STUDY DESIGN

A prospective case series study.

OBJECTIVE

To describe and assess a two-level osteotomy method for the management of severe thoracolumbar kyphosis (TLK) in patients with ankylosing spondylitis (AS).

SUMMARY OF BACKGROUND DATA

To achieve better postoperative outcomes in these patients, a sophisticated preoperative surgical plan is required. Most deformities are managed using a one-level osteotomy and a two-level osteotomy is seldomly reported. Till date, no study has described a two-level osteotomy for these cases.

METHODS

From January 2011 to December 2012, 10 consecutive patients with ankylosing spondylitis who underwent two-level spinal osteotomy were studied. Pre- and postoperative full-length free-standing radiographs, including the whole spine and pelvis, were available for all patients. Pre- and postoperative radiological parameters, including T5-S1 Cobb angles, TLK, lumbar lordosis, pelvic incidence, pelvic tilt, sacral slope, and sagittal vertical axis were measured. Health related quality of life , including Oswestry Disability Index and Scoliosis Research Society-22 surveys were administered before surgery and at 1-year follow up.

RESULTS

The preoperative and postoperative T5-S1 Cobb angles was 51.3° and -7.1°, respectively (P < 0.001). All patients demonstrated changes in postoperative radiographic parameters including decreased pelvic tilt (from 37.1° to 14.3°, P < 0.001), TLK (from 36.9° to 12.6°, P < 0.001), and sagittal vertical axis (from 21.4 cm to 7.1 cm, P < 0.001), increased lumbar lordosis (from -5.1° to -47.1°, P < 0.001), sacral slope (from 13.4° to 37.7°, P < 0.001), but no significant change in pelvic incidence. Health related quality of life scores at 1-year follow up were significantly improved compared to those before surgery.

CONCLUSION

This calculation of two-level osteotomy provides an accurate and reproducible method for ankylosing spondylitis correction. By which, we can obtain satisfactory radiological parameters and clinical outcomes.

LEVEL OF EVIDENCE

4.

Vertebral body or intervertebral disc wedging: which contributes more to thoracolumbar kyphosis in ankylosing spondylitis patients?: A retrospective study

Both vertebral body wedging and disc wedging are found in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis. However, their relative contribution to thoracolumbar kyphosis is not fully understood. The objective of this study was to compare different contributions of vertebral and disc wedging to the thoracolumbar kyphosis in AS patients, and to analyze the relationship between the apical vertebral wedging angle and thoracolumbar kyphosis.From October 2009 to October 2013, a total of 59 consecutive AS patients with thoracolumbar kyphosis with a mean age of 38.1 years were recruited in this study. Based on global kyphosis (GK), 26 patients with GK < 70° were assigned to group A, and the other 33 patients with GK ≥ 70° were included in group B. Each GK was divided into disc wedge angles and vertebral wedge angles. The wedging angle of each disc and vertebra comprising the thoracolumbar kyphosis was measured, and the proportion of the wedging angle to the GK was calculated accordingly. Intergroup and intragroup comparisons were subsequently performed to investigate the different contributions of disc and vertebra to the GK. The correlation between the apical vertebral wedging angle and GK was calculated by Pearson correlation analysis. The duration of disease and sex were also recorded in this study.With respect to the mean disease duration, significant difference was observed between the two groups (P < 0.01). The wedging angle and wedging percentage of discs were significantly higher than those of vertebrae in group A (34.8° ± 2.5° vs 26.7° ± 2.7°, P < 0.01 and 56.6% vs 43.4%, P < 0.01), whereas disc wedging and disc wedging percentage were significantly lower than vertebrae in group B (37.6° ± 7.0° vs 50.1° ± 5.1°, P < 0.01 and 42.7% vs 57.3%, P < 0.01). The wedging of vertebrae was significantly higher in group B than in group A (50.1° ± 5.1° vs 26.7° ± 2.7°, P < 0.01). Additionally, correlation analysis revealed a significant correlation between the apical vertebral wedging angle and GK (R = 0.850, P = 0.001).Various disc and vertebral wedging exist in thoracolumbar kyphosis secondary to AS. The discs wedging contributes more to the thoracolumbar kyphosis in patients with GK < 70° than vertebral wedging, whereas vertebral wedging is more conducive to the thoracolumbar kyphosis in patients with GK ≥ 70°, indicating different biomechanical pathogenesis in varied severity of thoracolumbar kyphosis secondary to AS.

Selection of Lowest Instrumented Vertebra for Thoracolumbar Kyphosis in Ankylosing Spondylitis

STUDY DESIGN

Retrospective study.

OBJECTIVE

To determine the optimal osteotomized vertebra (OV) and lowest instrumented vertebra (LIV) in ankylosing spondylitis (AS) kyphosis.

SUMMARY OF BACKGROUND DATA

Although most of AS kyphosis cases are treated by pedicle subtraction osteotomy (PSO), few studies have focused on the selection of the LIV relative to distal OV.

METHODS

We reviewed all AS kyphosis cases surgically treated at our institution between 2010 and 2013. Patients were divided into groups based on the relative position of LIV and distal OV: group OV+2, the LIV was the second vertebra below OV; group OV+3, the LIV was the third vertebra below OV; group OV+4, the LIV was the fourth vertebra below OV. The preoperative and 2-year postoperative radiographic parameters and clinical data of the former two groups were compared. In addition, if the LIV was S1, patients were included in group S1, and those remaining were included in group non-S1 (the LIV was L5 or above).

RESULTS

None of the patients presented fixation failure. Groups OV+2 and OV+3 had similar magnitudes of kyphosis (P > 0.05) and sagittal vertical axis corrections (P > 0.05) at the last follow-up. There was no difference in the incidence of proximal junctional kyphosis (PJK) between groups (P > 0.05). Between groups S1 and non-S1, the incidence of PJK and the magnitudes of kyphosis and sagittal vertical axis corrections were not significantly different (P > 0.05). The lumbosacral visual analogue scale and the incidence of pressure sores in group S1 were higher than in group non-S1 (P < 0.05).

CONCLUSION

When PSO is performed at the level of L2 or L3, the instrumentation can be limited to the two caudal vertebra that follow. Extending the fixation to more vertebra or to the sacrum does not appear to improve the stability of the instrumentation and the fusion rate, and it is not suitable to carry out PSO at L4.

LEVEL OF EVIDENCE

4.