Coronal deformity in ankylosing spondylitis with concomitant thoracolumbar kyphosis: patterns, manifestations and surgical strategies.

PURPOSE: To evaluate different patterns of coronal deformity secondary to ankylosing spondylitis (AS), to propose relevant treatment strategies, and to assess efficacy of asymmetrical pedicle subtraction osteotomy (APSO). METHODS: Coronal deformity was defined as coronal Cobb angle over 20º or coronal balance distance (CBD) more than 3 cm. 65 consecutive AS patients with concomitant coronal and sagittal deformity who underwent PSO were included. The average follow-up time was 40.4 months. Radiographic evaluation included coronal Cobb angle and CBD. Furthermore, sagittal parameters were used to assess magnitude and maintenance of kyphosis correction. RESULTS: Based on curve characteristics, coronal deformity caused by AS included four different radiologic patterns: Pattern I: lumbar scoliosis; Pattern II: C-shaped thoracolumbar curve; Pattern III: trunk shift without major curve; Pattern IV: proximal thoracic scoliosis. APSO was performed for patients in Pattern I to III while conventional PSO was applied for patients in Pattern IV. Significant improvement in all the sagittal parameters were noted in 65 patients without obvious correction loss at the last follow-up. Besides, significant and sustained correction of coronal mal-alignment was identified in 59 APSO-treated patients. Rod fracture occurred in four cases and revision surgery was performed for one case. CONCLUSION: According to radiologic manifestations, coronal deformity caused by AS could be categorized into four patterns. APSO proved to be a feasible and effective procedure for correction of Pattern I to III patients. Coronal deformity pattern, apex location, sagittal profile of lumbar spine and preoperative hip function should be considered for osteotomy level selection in APSO.

Risk factors of hip joint structural changes following pedicle subtraction osteotomy for ankylosing spondylitis-related thoracolumbar kyphosis: a minimum two-year observation.

PURPOSE: To determine the clinical- and surgical-related factors of hip joint structural changes in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis who underwent PSO. METHODS: Hip involvement was assessed by the Bath Ankylosing Spondylitis Radiology Hip Index (BASRI-h) and defined by a score of at least 2. 52 patients with BASRI-h scores maintained and 78 patients with BASRI-h scores increased during follow-up were retrospectively reviewed. Clinical data were recorded. Radiological assessment was performed preoperatively, postoperatively, and at the final follow-up. RESULTS: No significant difference existed in age, gender and follow-up time between the groups, but earlier onset of AS, longer disease and kyphotic duration, and worse Bath Ankylosing Spondylitis Functional Index (BASFI) scores at the final follow-up were observed in patients with BASRI-h scores increased (P < 0.05). Besides, global kyphosis (GK), T1-pelvic angle (TPA), pelvic tilt (PT) and anterior pelvic plane angle (APPA) were always larger in patients with BASRI-h scores increased, accompanied with more sacral fixation (P < 0.05). Multivariate logistics regression showed that earlier onset of AS, longer kyphotic duration, larger preoperative GK, sacral fixation and larger APPA during follow-up were independent risk factors. CONCLUSION: Earlier onset of AS and longer kyphotic duration were the clinical risk factors of hip joint structural changes in AS patients following PSO, while larger preoperative GK, sacral fixation in PSO and larger APPA during follow-up were the surgical-related factors. Surgeons should inform patients with risk factors of the possibility for severe hip joint structural changes after PSO.

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.

Does the thoracolumbar kyphosis secondary to ankylosing spondylitis affect the iliac trajectory of S2AI screw?

BACKGROUND: The study aimed to evaluate the influence of thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) on parameters of S2AI trajectory and to compare the ideal S2AI trajectory with those of the non-deformity patients with AS, sagittal deformity patients without AS, and the normal population reported in literatures. METHODS: Sagittal parameters including global kyphosis (GK), pelvic tilt (PT) and sacral slope (SS) were measured. Besides, according to the simulated ideal S2AI trajectory on the CT images, trajectory parameters were measured including Sag angle, Tsv angle, Max-length, Sacral distance and Iliac width. Starting-point parameters were also measured including PSIS distance, Skin distance, Iliac wing and S2 midline. RESULTS: Ninety-four AS-related thoracolumbar kyphosis patients were included. After adjusting the age and gender, twenty non-deformity patients with AS and 20 sagittal deformity patients without AS were selected to compare with patients with AS-related thoracolumbar kyphosis, respectively. Sag angle in deformity patients with AS was smaller than other two groups (P < 0.001). No difference was found in Tsv angle and Sacral distance between AS patients with and without deformity. However, these two parameters were shown significant differences between deformity patients with AS and without AS. In deformity patients with AS, no significant differences were found in all parameters between genders Furthermore, there were strong correlations between PT and the bilateral Sag angle (P < 0.001). CONCLUSIONS: The thoracolumbar kyphosis secondary to AS affects the Sag angle of the ideal S2AI trajectory which was approximately 20° smaller than that in non-deformity patients with AS, sagittal deformity patients without AS, and the normal population. Additionally, the Tsv angle and the Sacral distance in AS patients with thoracolumbar kyphosis were about 10° and 10 mm larger than those in sagittal deformity patients without AS, and the normal population reported in literatures.

Utility of Natural Sitting Lateral Radiograph in the Diagnosis of Segmental Instability for Patients with Degenerative Lumbar Spondylolisthesis.

BACKGROUND: Segmental instability in patients with degenerative lumbar spondylolisthesis is an indication for surgical intervention. The most common method to evaluate segmental mobility is lumbar standing flexion-extension radiographs. Meanwhile, other simple radiographs, such as standing upright radiograph, a supine sagittal magnetic resonance imaging (MRI) or supine lateral radiograph, or a slump or natural sitting lateral radiograph, have been reported to diagnose segmental instability. However, those common posture radiographs have not been well characterized in one group of patients. Therefore, we measured slip percentage in a group of patients with degenerative lumbar spondylolisthesis using radiographs of patients in standing upright, natural sitting, standing flexion, and standing extension positions as well as supine MRI. QUESTIONS/PURPOSES: We asked: (1) Does the natural sitting radiograph have a larger slip percentage than the standing upright or standing flexion radiograph? (2) Does the supine sagittal MRI reveal a lower slip percentage than the standing extension radiograph? (3) Does the combination of the natural sitting radiograph and the supine sagittal MRI have a higher translational range of motion (ROM) and positive detection rate of translational instability than traditional flexion-extension mobility using translational instability criteria of greater than or equal to 8%? METHODS: We retrospectively performed a study of 62 patients (18 men and 44 women) with symptomatic degenerative lumbar spondylolisthesis at L4 who planned to undergo a surgical intervention at our institution between September 2018 and June 2019. Each patient underwent radiography in the standing upright, standing flexion, standing extension, and natural sitting positions, as well as MRI in the supine position. The slip percentage was measured three times by single observer on these five radiographs using Meyerding's technique (intraclass correlation coefficient 0.88 [95% CI 0.86 to 0.90]). Translational ROM was calculated by absolute values of difference between two radiograph positions. Based on the results of comparison of slip percentage and translational ROM, we developed the diagnostic algorithm to evaluate segmental instability. Also, the positive rate of translational instability using our diagnostic algorithms was compared with traditional flexion-extension radiographs. RESULTS: The natural sitting radiograph revealed a larger mean slip percentage than the standing upright radiograph (21% ± 7.4% versus 17.7% ± 8.2%; p < 0.001) and the standing flexion radiograph (21% ±7.4% versus 18% ± 8.4%; p = 0.002). The supine sagittal MRI revealed a lower slip percentage than the standing extension radiograph (95% CI 0.49% to 2.8%; p = 0.006). The combination of natural sitting radiograph and the supine sagittal MRI had higher translational ROM than the standing flexion and extension radiographs (10% ± 4.8% versus 5.4% ± 3.7%; p < 0.001). More patients were diagnosed with translational instability using the combination of natural sitting radiograph and supine sagittal MRI than the standing flexion and extension radiographs (61% [38 of 62] versus 19% [12 of 62]; odds ratio 3.9; p < 0.001). CONCLUSION: Our results indicate that a sitting radiograph reveals high slip percentage, and supine sagittal MRI demonstrated a reduction in anterolisthesis. The combination of natural sitting and supine sagittal MRI was suitable to the traditional flexion-extension modality for assessing translational instability in patients with degenerative lumbar spondylolisthesis. LEVEL OF EVIDENCE: Level III, diagnostic study.

Failure patterns and related risk factors of sagittal reconstruction following pedicle subtraction osteotomy in patients with ankylosing spondylitis and thoracolumbar kyphosis.

OBJECTIVE: The aim of this study was to analyze the specific patterns and risk factors of sagittal reconstruction failure in ankylosing spondylitis (AS)-related thoracolumbar kyphosis after pedicle subtraction osteotomy (PSO). METHODS: A retrospective study was performed in patients with AS and thoracolumbar kyphosis after lumbar PSO with a minimum follow-up of 2 years. Patients were classified as having successful realignment (group A), inadequate correction immediately postoperatively (group B), and sagittal decompensation during follow-up (group C) according to the immediately postoperative and latest follow-up sagittal vertical axis (SVA). Radiographic parameters and clinical outcomes were collected. Pelvic tilt (PT) was used to assess the magnitude of pelvic backward rotation. Hip structural damage and ossification of the anterior longitudinal ligament (ALL) at the proximal junction, PSO level, and distal junction were also evaluated on radiographs. RESULTS: Overall, 109 patients with a mean age of 35.3 years were included. Patients in both group B (n = 16) and group C (n = 13) were older than those in group A (n = 80) (mean ages 43.6 vs 32.9 years, p < 0.011; and 39.2 vs 32.9 years, p = 0.018; respectively). Age (OR 1.102, p = 0.011), and preoperative PT (OR 1.171, p = 0.041) and SVA (OR 1.041, p = 0.016) were identified as independent risk factors of inadequate correction. Additionally, a higher distribution of patients with adequate ALL ossification at the PSO level was found in group B than in group A (37.5% vs 22.5%, p = 0.003). Age (OR 1.101, p = 0.011) and preoperative SVA (OR 1.013, p = 0.020) were identified as independent risk factors of sagittal decompensation. Furthermore, compared with group A, group C showed a higher distribution of patients with severe hip structural damage (15.4% vs 0, p = 0.018) and higher incidences of rod fracture (RF) (38.5% vs 8.8%, p = 0.011) and pseudarthrosis (15.4% vs 0, p = 0.018). Additionally, the incidence of RF (19.6% vs 6.9%, p = 0.045) and changes in the proximal junctional angle (0.5° vs 2.2°, p = 0.027) and the distal junctional angle (0.3° vs 2.2°, p = 0.019) were lower during follow-up in patients with adequate ALL ossification than in those without adequate ossification. CONCLUSIONS: Sagittal reconstruction failure in patients with AS could be attributed to inadequate correction immediately after surgery (14.7%) and sagittal decompensation during follow-up (11.9%). Adequate ALL ossification was a risk factor of inadequate correction. However, adequate ALL ossification could decrease the development of RF and relieve the junctional kyphotic change during follow-up. Older age and greater baseline SVA were independent risk factors for both inadequate correction and sagittal decompensation.

Can fusion to S1 maintain favorable surgical outcomes following one-level pedicle subtraction osteotomy in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis?

PURPOSE: To compare the surgical outcomes between ankylosing spondylitis (AS)-related thoracolumbar kyphosis patients with the lowest instrumented vertebra (LIV) at S1 or above following one-level pedicle subtraction osteotomy (PSO). METHODS: One hundred and two AS patients undergoing one-level PSO with a minimum of 2-year follow-up were included. Twenty-two patients were in group S1 (LIV at S1), and eighty were in group non-S1 (LIV above S1). Radiographic parameters including lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI), and sagittal vertical axis (SVA) were measured. Oswestry Disability Index (ODI) and visual analog scale (VAS) were applied for clinical assessment. RESULTS: In both S1 and non-S1 groups, the radiographic parameters and clinical outcomes were significantly improved after surgery (P < 0.05). Patients undergoing distal fusion to S1 had significantly larger preoperative PI-LL mismatch, SVA, and smaller preoperative LL and SS compared to those in group non-S1 (P < 0.05). No significant difference was found between the two groups regarding preoperative and final follow-up ODI and VAS (P > 0.05), as well as the improvement in ODI and VAS (P > 0.05). The incidence of overall complications and each type of complication including the implant failure was similar between group S1 and non-S1 (P > 0.05). CONCLUSION: Selecting S1 as the LIV without pelvic fixation following one-level PSO in thoracolumbar kyphosis caused by AS could achieve satisfactory surgical outcomes and might not increase the complications. Patients with relatively severe sagittal imbalance, loss of LL, PI-LL mismatch, and small SS might be the potential candidates for distal fusion to S1 following one-level PSO.

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.

Quantitative evaluation of the relationship between COMP promoter methylation and the susceptibility and curve progression of adolescent idiopathic scoliosis.

PURPOSE: The cartilage oligomeric matrix protein (COMP) was reported to be down-regulated in adolescent idiopathic scoliosis (AIS). The purposes of the study were to evaluate the roles of COMP promoter methylation on the abnormal gene expression and the epigenetic phenotype in AIS. METHODS: DNA samples of 50 AIS patients and 50 healthy controls were analyzed. Five CpG sites of COMP gene were amplified and sequenced using the polymerase chain reaction (PCR) and the pyrophosphate sequencing technology, while the COMP gene expression was evaluated using real-time PCR. Comparisons were analyzed with the Chi-square test and independent t test. Pearson coefficients of correlation were used to evaluate the association between gene methylation and clinical phenotypes. RESULTS: The average COMP gene promoter methylation of the AIS and control groups was 12.26 ± 2.36 and 8.76 ± 1.94 (p < 0.0001), and correspondingly the relative expression of COMP gene expression was 0.52 ± 0.12 and 1.16 ± 0.52 (p < 0.001), respectively. The correlation analysis showed significantly negative correlation between methylation level and gene expression (p < 0.0001). The comparison analysis between AIS patients with positive and negative methylation showed significant difference in chronological age (p < 0.001) and Cobb angle of main curve (p = 0.011). The methylation level of the COMP promoters was significantly correlated with Cobb angle of main curve and age (p < 0.0001) among the five CpG sites. CONCLUSIONS: AIS patients had significantly high COMP promoter methylation and low gene expression. Positive and high COMP promoter methylation was correlated with young age and high Cobb angle of main curve. Therefore, COMP gene promoter methylation may provide significant prognostic information in predicting the susceptibility and curve progression of AIS.

The mechanisms underlying the variety of preoperative directionalities of shoulder tilting in adolescent idiopathic scoliosis patients with double thoracic curve.

PURPOSE: Preoperative directionality of shoulder tilting seems to be independent of the radiographic features of proximal thoracic (PT) curve in adolescent idiopathic scoliosis (AIS) patients. To date, no study had investigated the mechanisms underlying the variety of preoperative directionalities of shoulder tilting in AIS patients. The purpose of this study was to evaluate the differences of radiographic features between Lenke type 2 (double thoracic curve) AIS patients with different preoperative directionalities of shoulder tilting. METHODS: A total of 130 Lenke type 2 AIS patients were included in this study and were divided into two groups according to the value of radiographic shoulder height (RSH). There were 78 cases (71 females and 7 males) with RSH less than 0 cm in Group A and 52 cases (44 females and 8 males) with RSH equal to or more than 0 cm in Group B. Preoperative standing anteroposterior X-ray films of the spine were obtained in all these subjects and were analyzed with respect to the following parameters: T1 tilt, PT Cobb angle, main thoracic (MT) Cobb angle, the apical level of PT curve, the apical level of MT curve, and RSH. These parameters were compared between these two groups and the correlations between RSH and the other parameters were analyzed in all of these subjects. RESULTS: No significant difference was found between these two groups with respect to PT Cobb angle or the apical level of PT curve (P > 0.05). The apical level of MT curve was significantly more proximal in Group A compared with Group B (P < 0.05). The MT Cobb angle was significantly larger in Group A compared with Group B (P < 0.05). Both the T1 tilt and the PT Cobb angle/MT Cobb angle ratio in Group A were significantly smaller than those in Group B (P < 0.05). The RSH was positively associated with T1 tilt, the apical level of MT curve, and the PT Cobb angle/MT Cobb angle ratio, but was negatively associated with MT Cobb angle (P < 0.05). CONCLUSION: The directionality of shoulder tilting is diverse in Lenke type 2 AIS patients. The preoperative directionality of shoulder mainly depends on the profile of MT curve rather than that of PT curve. The RSH should be carefully evaluated before making a surgical plan in these patients.

The clinical relevance of the presence of bridging syndesmophytes on kyphosis correction and maintenance following pedicle subtraction osteotomy for thoracolumbar kyphotic deformity in ankylosing spondylitis: a comparative cohort study.

BACKGROUND: The presence of bridging syndesmophytes (BS) in spinal osteotomy region serves traditionally as one critical determinant for selection of osteotomy techniques. While nowadays the proportion of kyphotic ankylosing spondylitis (AS) patients receiving pedicle subtraction osteotomy (PSO) with yet mobile neighboring disc has seen a substantial increase. Literatures investigating the clinical relevance of the presence of BS on kyphosis correction and maintenance following PSO are scarce. METHODS: A total of 71 thoracolumbar kyphotic AS patients treated with single-level PSO at our hospital between September 2010 and August 2014 were retrospectively reviewed, 32 of whom were stratified into the BS group (BG). The operative corrections of multiple spino-pelvic sagittal parameters were assessed. Comparison of the contribution of adjacent disc wedging to total correction per PSO segment was made between the BS and non-BS groups (NBG). The correction loss were also evaluated and compared with a minimum 2-year follow-up. RESULTS: A significantly younger age (30.97 ± 8.28 vs. 40.31 ± 8.44 yrs., p < 0.001), smaller pelvic incidence (PI) (43.03 ± 10.60 vs. 49.36 ± 9.75°, p = 0.011), greater wedging index of osteotomized vertebra (1.17 ± 0.16 vs. 1.09 ± 0.08, p = 0.011) and larger local kyphosis (19.59 ± 10.84 vs. 13.56 ± 8.50°, p = 0.013) was observed in NBG preoperatively. Patients in BG and NBG accomplished comparable amount of kyphosis correction per PSO segment (40.22 ± 7.09 vs. 43.85 ± 8.71°, p = 0.062). However, the contribution of adjacent disc wedging to total correction per PSO was significantly larger in NBG [8.10 ± 6.19 (18.5%) vs. 1.09 ± 2.88° (2.7%), p < 0.001]. By ultimate follow-up, the global kyphosis (18.26 ± 10.97 vs. 21.51 ± 10.89°, p < 0.05) and thoracic kyphosis (37.95 ± 11.87 vs. 42.87 ± 11.56°, p < 0.05) deteriorated significantly in the NBG but not BG, so was further pelvic retroversion as represented by increased pelvic tilt (19.46 ± 8.13 vs. 23.44 ± 8.19°, p < 0.05) and decreased sacral slope (23.02 ± 9.12 vs. 18.62 ± 10.10°, p < 0.05). Loss of corrections concerning contribution of adjacent disc wedging was also larger in NBG (1.41 ± 3.27 vs. 0.22 ± 1.49°, p < 0.05). CONCLUSIONS: Our study might suggest that the evaluation and treatment methods of kyphotic AS patients needed to be fine-tuned with appropriate subgrouping by the presence of syndesmophytes with bamboo sign as they were potentially distinct groups with different PI, contributor of lordosing capability and prognosis that might require separate analysis.

Association between braced curve behavior by pubertal growth peak and bracing effectiveness in female idiopathic scoliosis: a longitudinal cohort study.

BACKGROUND: Pre-pubertal idiopathic scoliosis (IS) is associated with high risk of bracing ineffectiveness. Integrated multidimensional maturity assessments are useful but complex to predict the high-risk occurrence of curve progression. This study is designed to provide a simple screening method for brace effectiveness by determining whether or not the braced curve behavior at growth spurt, being defined as variations in Cobb angle velocity (AV) at peak height velocity (PHV), can be a new factor predictive of brace outcome prescribed before PHV. METHODS: This is a retrospective study of a series of 35 IS girls with simplified skeletal maturity score no more than 3 at initiation of bracing treatment and followed up through the growth spurt until brace weaning or surgery. Serial Cobb angle and maturity indicators involving height velocity, Risser sign, triradiate cartilage, simplified skeletal maturity score and distal radius and ulna classification were assessed and patients were stratified into either a positive or negative category based on a positive or negative value of AV at PHV. Comparisons were made between the positive and negative AV groups, as well as the failed and successful bracing groups, using independent sample T test and crosstab analysis. Logistic regression analysis was used to identify the predictive factors of failed brace treatment. RESULTS: Brace treatment prescribed before PHV was found to have an overall failure rate of 57.1% and a surgical rate of 45.7%. Negative AV at PHV accounting for 54.3% of the recruited patients were associated with lower brace failure rate (36.8% vs. 81.2%, p = 0.016) and surgical rate (21.1% vs. 75.0%, p = 0.002). Patients in the failed bracing group showed higher ratio of thoracic curve (80.0% vs. 26.7%,p = 0.002) and higher AV at growth peak (2.3 ± 9.1 vs. -6.5 ± 11.4°/yrs., p = 0.016). The logistic regression analysis revealed that positive AV at PHV (OR = 9.268, 95% CI = 1.279-67.137, p = 0.028) and thoracic curve type (OR = 13.391, 95% CI = 2.006-89.412, p = 0.007) were strong predictive factors of ineffective brace treatment initiated before PHV. CONCLUSIONS: Sustained curve correction following bracing despite early onset and rapid pubertal growth was strongly predictive of effective brace control of scoliosis.

Can acetabular orientation be restored by lumbar pedicle subtraction osteotomy in ankylosing spondylitis patients with thoracolumbar kyphosis?

PURPOSE: To evaluate whether acetabular orientation (abduction and anteversion) can be restored by lumbar pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis. MATERIALS AND METHODS: A total of 33 consecutive AS patients with thoracolumbar kyphosis undergoing one-level lumbar PSO were retrospectively reviewed. Radiographical measurements included sagittal vertical axis, global kyphosis, thoracic kyphosis, local kyphosis, lumbar lordosis, pelvic incidence, sacral slope, and pelvic tilt. Acetabular abduction and anteversion were measured on CT scans of the pelvis before and after lumbar PSO. The preoperative and postoperative parameters were compared by the paired samples t test. Pearson's correlation analysis was conducted to determine the correlations between the changes in acetabular abduction and anteversion and the changes in sagittal spinopelvic parameters. RESULTS: After lumbar PSO, sagittal vertical axis, global kyphosis, and pelvic tilt were corrected from 15.7 ± 6.7 cm, 66.8° ± 17.5°, and 38.6° ± 9.0° to 2.9 ± 4.9 cm, 21.3° ± 8.2°, and 23.2° ± 8.2°, respectively (p < 0.001). Of note, acetabular abduction and anteversion decreased from 59.6° ± 4.6° to 31.4° ± 6.5° before surgery to 51.4° ± 6.5° and 20.2° ± 4.4° after surgery, respectively (p < 0.001). Moreover, the changes in acetabular abduction and anteversion were observed significantly correlated with the change in pelvic tilt (r = 0.527, p = 0.002; r = 0.586, p < 0.001). CONCLUSION: Abnormal acetabular abduction and anteversion could be corrected by lumbar PSO in AS patients with thoracolumbar kyphosis. Consequently, a relatively normal acetabular orientation could be achieved after lumbar PSO, which might decrease the potential risk of dislocation in AS patients with spine and hip deformities requiring subsequent THR surgery.

The patterns of loss of correction after posterior wedge osteotomy in ankylosing spondylitis-related thoracolumbar kyphosis: a minimum of five-year follow-up.

BACKGROUND: Short-term studies have demonstrated good surgical outcomes after pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) patients, but there is a paucity of literature focused on middle-term results, especially regarding patterns of loss of correction. The objective of this study is to assess the durability of surgical outcomes and the patterns of loss of correction in thoracolumbar kyphosis secondary to AS following lumbar PSO with over 5-year follow-up. METHODS: We performed a retrospective review of 155 consecutive AS patients undergoing lumbar PSO from January 2001 to December 2011. Twenty-four patients were included with an average follow-up of 6.9 years (range, 5-15 years). Radiographical evaluations included global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis, spinal-sacral angle, kyphosis of proximal non-fused segments (KPNS), angle of fused segments (AFS), osteotomized vertebra angle (OVA), distal intervertebral disc wedging (DIDW) and proximal junctional angle. Meanwhile, clinical outcomes were assessed by the Oswestry disability index (ODI) and Numerical rating scale (NRS). RESULTS: The average correction per PSO segment was 34.9°. Significant improvement in sagittal parameters were found postoperatively, and no obvious deterioration was noticed during the follow-up. Mild loss of correction in GK (2.82°) and LL (3.77°) were observed at the final follow-up (P < 0.05). The KPNS and DIDW increased from 26° and -5.0° postoperatively to 30° and -2.2° at the final follow-up (P < 0.05), respectively. In contrast, no significant diminishment was identified in OVA and AFS (P > 0.05). The ODI and NRS improved significantly from 20.6 and 6.6 preoperatively to 5.9 and 2.3 at the final follow-up (P < 0.05). CONCLUSIONS: PSO is an effective procedure for treating AS-related thoracolumbar kyphosis and can maintain sustained surgical outcomes during the middle-term follow-up. The loss of correction was mainly attributable to non-instrumented segments without fully ossified bridging syndesmophyte in the thoracolumbar region instead of instrumented levels.

Full fusion of proximal thoracic curve helps to prevent postoperative cervical tilt in Lenke type 2 adolescent idiopathic scoliosis patients with right-elevated shoulder.

BACKGROUND: To date, no study had reported the phenomenon of deteriorated postoperative cervical tilt in Lenke type 2 adolescent idiopathic scoliosis patients. The purpose of this study is to evaluate the cervical tilt in Lenke type 2 adolescent idiopathic scoliosis patients with right-elevated shoulder treated by either full fusion or partial/non fusion of the proximal thoracic curve. METHODS: A total of 30 Lenke type 2 AIS patients with preoperative right-elevated shoulder underwent posterior spinal instrumentation from 2009 to 2011 were included in this study. All the subjects were divided into 2 groups according to the selection of upper instrumented vertebra. There were 14 cases proximally fused to T1 or T2 (Group A) and 16 cases proximally fused to T3 or below (Group B). Both standing anteroposterior and sagittal X-ray films of the spine obtained preoperatively, one week after the operation, and at a minimum of two-year follow-up were analyzed with respect to the following parameters: cervical tilt, T1 tilt, proximal thoracic Cobb angle, main thoracic Cobb angle, apical vertebral translation of proximal thoracic curve, apical vertebral translation of main thoracic curve, radiographic shoulder height, cervical lordosis, proximal thoracic kyphosis and main thoracic kyphosis. RESULTS: Most (83.3%) of the patients in these two groups gained satisfactory shoulder balance after surgery. However, the cervical tilt significantly improved in group A (p < 0.001) but deteriorated in group B (p < 0.001). In group A, the decrease of cervical tilt significantly positively correlated with that of T1 tilt (p < 0.001). In group B, the increase of cervical tilt significantly positively correlated with both the increase of T1 tilt (p < 0.001) and the increase of apical vertebral translation of proximal thoracic curve (p < 0.05). CONCLUSIONS: Lenke type 2 AIS patients with right-elevated shoulder gain improved shoulder but deteriorated cervical tilt after partial/non fusion of proximal thoracic curve. Full fusion of proximal thoracic curve helps to prevent the residual cervical tilt in these patients.

Quality of life and correlation with clinical and radiographic variables in patients with ankylosing spondylitis: a retrospective case series study.

BACKGROUND: Previously, many studies have evaluated quality of life (QoL) in patients with ankylosing spondylitis (AS), however, none of them specifically investigated the correlation between pain-related disability measured by Oswestry Disability Index (ODI) and QoL in AS patients. In addition, the correlation between global kyphosis (GK) in lateral plain radiographs and QoL in AS patients remains unclear up to now. Therefore, this study aimed to evaluate QoL and correlation with clinical and radiographic variables in AS patients, especially to figure out the relationship about the pain-specific disability measured by ODI, GK and QoL. METHODS: From January 2008 to November 2015, two hundred and forty-five consecutive patients with an average age of 36.2 ± 10.9 years (range, 17-66 years) satisfying the Modified New York Criteria for AS from a single institution were enrolled. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Metrology Index (BASMI) and Bath Ankylosing Spondylitis Global score (BAS-G) were applied to assess the disease activity, functional status, spinal mobility and overall feeling of AS patients, respectively. ODI was recorded to evaluate low back pain-related disability. QoL was evaluated by the Short Form-36 (SF-36). According to global kyphosis (GK) measured on standing lateral full-spine radiographs, the patients were divided into two groups: mild kyphotic group (GK < 70°,n = 176) and severe kyphotic group (GK ≥ 70°,n = 69). RESULTS: The scores of BASDAI, BASFI, BASMI and ODI had significant negative correlations with all SF-36 subscale scores (P < 0.01). BASFI and BASMI scores of severe kyphotic group were much higher than those of mild kyphotic group, respectively (P = 0.005 and P = 0.001, respectively) and the score of physical function (PF) subscale in severe kyphotic group was significantly higher than that in mild kyphotic group (P = 0.046) as well. Notably, the scores of ODI, BASFI and BASMI were the major predictors of PF subscale score of SF-36. CONCLUSIONS: Poor QoL is significantly correlated with high disease activity, poor functional status and decreased spinal mobility in AS. GK is significantly associated with functional status, spinal mobility and QoL in AS patients. ODI, BASFI and BASMI are the major predictors of PF subscale of SF-36.

Surgical overreduction and hyperlordotic fusion of C1-C2 joint are associated with cervical sagittal malalignment.

INTRODUCTION: Previous studies have shown that hyperlordotic C1-C2 fusion was related to postoperative subaxial kyphosis. However, most of the patients in these studies were complicated with rheumatoid arthritis (RA). Moreover, no studies have specifically evaluated the relationship between C1-C2 fusion angle and cervical sagittal vertical axis (cSVA), T1 slope or cranial tilt (CRT) after posterior C1-C2 fusion. This study aimed to investigate the cervical sagittal alignment in non-RA patients following posterior C1-C2 fusion and the correlation between C1-C2 fusion angle and postoperative cervical sagittal alignment. MATERIALS AND METHODS: From August 2004 to December 2015, twenty-eight consecutive patients with an average age of 39.2 years (range 6-70 years) who underwent posterior C1-C2 fusion from a single institution were enrolled. The mean follow-up period was 30.7 months (range 12-77 months). Angles of Oc-C1, C1-C2, C2-C3 and C2-C7, cSVA, T1 slope and CRT were measured in lateral cervical radiographs in neutral position before surgery and at the final follow-up. RESULTS: C1-C2 angle significantly increased from 13.6° ± 12.4° to 22.0° ± 8.1° at the final follow-up (P < 0.001). A significant decrease was found both in Oc-C1 and C2-C7 angles from pre-operation to the final follow-up (P < 0.001 and P = 0.011, respectively). Moreover, cSVA and CRT dramatically increased from pre-operation to the final follow-up (P < 0.001). C1-C2 fusion angle was significantly associated with Oc-C1, C2-C7 angle, cSVA and CRT at the final follow-up. A significant correlation was also observed between postoperative change of C1-C2 angle and that of Oc-C1, C2-C7 angle, cSVA and CRT. CONCLUSIONS: Apart from decreased subaxial lordosis, posterior C1-C2 fusion in hyperextension may also lead to kyphotic change of atlanto-occipital alignment and increased tilting forward of the cervical spine. Therefore, intraoperative overreduction of C1-C2 angle and hyperlordotic C1-C2 fusion should be avoided to maintain the physiologic cervical sagittal alignment.

Different potential risk of injury from thoracic pedicle screw insertion between left and right main-stem bronchus in Lenke 1 type adolescent idiopathic scoliosis.

PURPOSE: The changed relative anatomic position of trachea with increased potential risk of injury from thoracic pedicle screw (TPS) has been reported in Lenke 1 type adolescent idiopathic scoliosis (AIS) patients. However, such change of main-stem bronchus has not been investigated. The purposes of this study were to evaluate the altered positions of both left and right main-stem bronchus in Lenke 1 type patients and to assess the potential risks of main-stem bronchus injuries from TPS screw insertion in these patients. METHODS: A total of 19 Lenke 1 type AIS patients and 15 normal teenagers were included. Axial computed tomography (CT) images at T5 level were obtained in all these subjects to evaluate the main-stem bronchus-vertebral distance (MVD, the closet distance between the main-stem bronchus and vertebral body) and main-stem bronchus-vertebral angle (MVA, defined as 0° when the main-stem bronchus was located directly lateral to the left and 180° when directly lateral to the right) on both left and right sides. The percentage of main-stem bronchus located adjacent to vertebrae and in the direction of screw passage was calculated to analyze potential risks of injuries from pedicle screw placement. RESULTS: Both the average left and right MVD were significantly smaller in AIS patients when compared with normal teenagers at T5 level (P < 0.05). Both the mean left and right MVA were lower in AIS patients than those in normal teenagers at T5 level (P < 0.05). All the AIS patients (100 %) had the right main-stem bronchus with high risk of injury from right TPS placement and only five AIS patients (26.3 %) had left main-stem bronchus with high risk of injury from left TPS placement at T5 level. No main-stem bronchus was found to be at risk of injury from TPS placement on both two sides in normal teenagers at this level. CONCLUSIONS: Both the right and left main-stem bronchus were located much closer to the vertebrae in Lenke 1 type AIS patients when compared with normal teenagers. However, the potential risk of injury of main-stem bronchus from TPS placement was higher on the right side than that on the left side.

Compensatory modulation for severe global sagittal imbalance: significance of cervical compensation on quality of life in thoracolumbar kyphosis secondary to ankylosing spondylitis.

PURPOSE: To investigate the cervical compensation pattern and to clarify relationships between cervical compensation and quality of life (QOL) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis. METHODS: A cross-sectional study of consecutive AS patients with thoracolumbar kyphosis was performed. Forty-four patients with hyperlordotic cervical spine were assigned to group A and sixteen with kyphotic cervical spine in group B. Sagittal parameters were measured and compared, including T1 slope, cervical lordosis (CL), cervical sagittal vertical axis (C-SVA), global SVA and global kyphosis (GK). Independent factors for cervical compensation were identified. To exclude confounding variables while comparing QOL between patients with hyperlordotic and kyphotic cervical spine, 31 patients were selected as group A-1, similar to 13 patients in group B-1 in the distribution of matching variables such as age, gender, course of disease, GK, global SVA and radiographic progression assessment for AS. The QOL was assessed by Neck Disability Index (NDI) and other indices. RESULTS: Mean C-SVA was significantly lower in group A than in group B, whereas mean T1 slope, global SVA and GK were significantly larger in group A. T1 slope (36.0 %) was the independent factor for CL. T1 slope was correlated with CL, GK and global SVA in group A. Group A-1 showed lower NDI score. CL (59.6 %) independently affects NDI. CONCLUSION: Notable cervical compensation exists in AS patients with thoracolumbar kyphosis. The cervical compensation responsive to global imbalance was mediated by T1 slope. AS patients with hyperlordotic cervical spine present with better QOL than patients with kyphotic cervical spine.

The potential risk of left subclavian artery injury from excessively long thoracic pedicle screws placed in the proximal thoracic regions of Lenke type 2 adolescent idiopathic scoliosis patients and normal teenagers: an anatomical study.

PURPOSE: The altered anatomic positions of important structures adjacent to the vertebrae in adolescent idiopathic scoliosis (AIS) patients have been comprehensively investigated by previous radiographic studies. However, no study has evaluated the altered position of left subclavian artery (SA) in these patients. The purpose of this study is to evaluate the altered position of left subclavian artery in AIS patients with a double thoracic curve pattern. METHODS: Nineteen Lenke type 2 AIS patients and thirteen normal teenagers were included in this study. Axial computed tomography images at T2 and T3 levels were obtained in all these subjects to evaluate the subclavian artery-vertebral angle (SAVA, defined as 0° when the artery was located directly lateral to the left and 180° when directly lateral to the right) and subclavian artery-vertebral distance (SAVD, the shortest distance between the artery and vertebral body). The percentage of left subclavian arteries at potential risk of injury from excessively long pedicle screws was calculated. RESULTS: The SAVA was significantly larger in AIS patients than that in normal teenagers at both T2 and T3 levels (P < 0.05) while the SAVD was significantly smaller in AIS patients compared with normal teenagers at both T2 and T3 levels (P < 0.05). The left SA was at potential risk of injury from excessively long left pedicle screws in 6 (31.6 %) AIS patients at T2 level and in 10 (52.6 %) patients at T3 level. The patients with risk of left SA injury had larger proximal thoracic (PT) and larger AVT of PT curve when compared with those without. No left SA was at potential risk of injury from excessively long left pedicle screws in normal teenagers. CONCLUSIONS: The left SA is located much closer to the vertebrae in the proximal thoracic curve of Lenke type 2 AIS patients when compared with normal teenagers. The spine surgeons should be aware of such altered position of left SA and choose appropriate pedicle length to avoid anterior cortical penetration in Lenke type 2 AIS patients.