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Influence of lumbar sagittal profile on pelvic orientation and pelvic motion during postural changes in patients with ankylosing spondylitis–related thoracolumbar kyphosis following pedicle subtraction osteotomy

Yao Li, Bang-ping Qian, Yong Qiu, Shi-zhou Zhao, Xiao-lin Zhong, and Bin Wang

OBJECTIVE

The objective of this study was to investigate the impact of the lumbar sagittal profile on pelvic orientation and pelvic motion during postural changes in patients with ankylosing spondylitis (AS) and thoracolumbar kyphosis and to evaluate the potential risk of prosthetic dislocation after total hip arthroplasty (THA) following pedicle subtraction osteotomy (PSO).

METHODS

Seventy-two patients with AS-related thoracolumbar kyphosis following spinal osteotomy were retrospectively reviewed, and 21 healthy volunteers were recruited as a control group. Pre- and postoperative 2D full-body images in standing and sitting positions were obtained to evaluate the anterior pelvic plane angle (APPA), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), proximal femur angle (PFA), and femoroacetabular flexion during postural changes. Patients with AS were categorized in either a lordotic or kyphotic group based on the lumbar sagittal profile.

RESULTS

Significant increases in the SS and decreases in the APPA, PT, and LL were observed postoperatively in both the standing and sitting positions (p < 0.001 for all). Significantly higher APPA, PT, LL, and ΔPT, and lower SS, ΔSS, and ΔSS+ΔPFA were observed in the kyphotic group (p < 0.05). After undergoing PSO, ΔPT and ΔSS significantly decreased while femoroacetabular flexion significantly increased in both AS groups (p < 0.05), and no significant difference was present between the two groups (p > 0.05). Bath Ankylosing Spondylitis Radiology Hip Index scores in the kyphotic group were significantly worse than those in the lordotic group pre- and postoperatively (p < 0.05). No significant difference in parameters concerning pelvic motion (ΔAPPA, ΔPT, and ΔSS) was found when PSO was performed in the thoracolumbar or lumbar spine.

CONCLUSIONS

Lumbar sagittal profiles greatly affect pelvic orientation and pelvic motion in AS. When THA is performed before PSO, AS patients with lumbar kyphosis are at higher risk of anterior prosthetic dislocation, while those with lordotic lumbar sagittal profiles are at higher risk of posterior dislocation. PSO should be performed prior to THA. After PSO, further decreased pelvic motion indicated a potential risk of posterior prosthetic dislocation after sequential THA, whereas theoretically patients with preoperative lumbar kyphosis are at higher risk of THA dislocation. The site where PSO was performed (thoracolumbar or lumbar spine) does not influence the risk of THA dislocation.

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Variation patterns of cervical alignment in ankylosing spondylitis–related thoracolumbar kyphosis following pedicle subtraction osteotomy in the sitting position: an EOS-based investigation

Shi-zhou Zhao, Bang-ping Qian, Ji-chen Huang, Mu Qiao, Bin Wang, and Yong Qiu

OBJECTIVE

Both unchanged upper cervical lordosis combined with decreased lower cervical lordosis and decreased upper cervical lordosis combined with decreased lower cervical lordosis have been reported to occur after correction surgery for adult spinal deformity. However, variations in cervical alignment after correction surgery in patients with ankylosing spondylitis (AS) have not been investigated. The current study aimed to investigate the variations in cervical alignment following the correction surgery in AS patients with thoracolumbar kyphosis.

METHODS

Patients with AS who underwent pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis from June 2016 to June 2019 with a minimum of 1-year follow-up were reviewed. Patients were grouped according to the presence (ossified group) and absence (non-ossified group) of total ossification of the anterior longitudinal ligament (ALL) in the lower cervical spine. Radiographic parameters, including thoracolumbar, craniocervical, and global radiographic parameters, were measured on lateral sitting EOS images.

RESULTS

Thirty-two patients (27 males and 5 females) with a mean follow-up of 1.5 years were identified. There were 21 patients in the non-ossified group and 11 patients in the ossified group. After PSO, both groups showed a decrease in the occiput–C7 angle (p < 0.001 for both). In the non-ossified group, the C2–7 angle decreased significantly (p < 0.001), while the occiput–C2 angle remained unchanged (p = 0.570). In the ossified group, the occiput–C2 angle decreased significantly (p < 0.001), while C2–7 angle remained unchanged (p = 0.311). In addition, the change in occiput–C2 was correlated with the osteotomy angle in the ossified group (R = 0.776, p = 0.005).

CONCLUSIONS

The variation patterns of cervical alignment following correction surgery for AS-related thoracolumbar kyphosis were different based on patients with or without total ossification of ALL in the lower cervical spine. When planning PSO for patients in the ossified group, restoration of the physiological upper cervical lordosis angle could be achieved by adjusting the osteotomy angle.

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Variation patterns of cervical alignment in ankylosing spondylitis–related thoracolumbar kyphosis following pedicle subtraction osteotomy in the sitting position: an EOS-based investigation

Shi-zhou Zhao, Bang-ping Qian, Ji-chen Huang, Mu Qiao, Bin Wang, and Yong Qiu

OBJECTIVE

Both unchanged upper cervical lordosis combined with decreased lower cervical lordosis and decreased upper cervical lordosis combined with decreased lower cervical lordosis have been reported to occur after correction surgery for adult spinal deformity. However, variations in cervical alignment after correction surgery in patients with ankylosing spondylitis (AS) have not been investigated. The current study aimed to investigate the variations in cervical alignment following the correction surgery in AS patients with thoracolumbar kyphosis.

METHODS

Patients with AS who underwent pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis from June 2016 to June 2019 with a minimum of 1-year follow-up were reviewed. Patients were grouped according to the presence (ossified group) and absence (non-ossified group) of total ossification of the anterior longitudinal ligament (ALL) in the lower cervical spine. Radiographic parameters, including thoracolumbar, craniocervical, and global radiographic parameters, were measured on lateral sitting EOS images.

RESULTS

Thirty-two patients (27 males and 5 females) with a mean follow-up of 1.5 years were identified. There were 21 patients in the non-ossified group and 11 patients in the ossified group. After PSO, both groups showed a decrease in the occiput–C7 angle (p < 0.001 for both). In the non-ossified group, the C2–7 angle decreased significantly (p < 0.001), while the occiput–C2 angle remained unchanged (p = 0.570). In the ossified group, the occiput–C2 angle decreased significantly (p < 0.001), while C2–7 angle remained unchanged (p = 0.311). In addition, the change in occiput–C2 was correlated with the osteotomy angle in the ossified group (R = 0.776, p = 0.005).

CONCLUSIONS

The variation patterns of cervical alignment following correction surgery for AS-related thoracolumbar kyphosis were different based on patients with or without total ossification of ALL in the lower cervical spine. When planning PSO for patients in the ossified group, restoration of the physiological upper cervical lordosis angle could be achieved by adjusting the osteotomy angle.

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

Shi-Zhou Zhao, Bang-Ping Qian, Ji-Chen Huang, Mu Qiao, Bin Wang, and Yong Qiu

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.

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Complications of spinal osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis in 342 patients: incidence and risk factors

Bang-ping Qian, Ji-chen Huang, Yong Qiu, Bin Wang, Yang Yu, Ze-zhang Zhu, Sai-hu Mao, and Jun Jiang

OBJECTIVE

To describe the incidence of complications in spinal osteotomy for thoracolumbar kyphosis caused by ankylosing spondylitis (AS) and to investigate the risk factors for these complications.

METHODS

From April 2000 to July 2017, 342 consecutive AS patients with a mean age (± SD) of 35.4 ± 9.8 years (range 17–71 years) undergoing spinal osteotomy were enrolled. Patients with complications within the 1st postoperative year were identified. Demographic, radiological, and surgical data were compared between patients with and without complications. The complications were classified into intraoperative and postoperative complications.

RESULTS

A total of 310 consecutive pedicle subtraction osteotomy (PSO) and 37 multiple Smith-Petersen osteotomy (SPO) procedures were performed in 342 patients. Overall, 47 complications were identified in 47 patients (13.7%), including 31 intraoperative complications and 16 postoperative complications. Patients with complications were older than those without (p = 0.006). A significant difference was observed in preoperative global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), and the correction of these radiographic parameters between patients with and without complications (p < 0.05). Two-level PSO (p = 0.022) and an increased number of instrumented vertebrae (p = 0.019) were significantly associated with an increased risk of complications.

CONCLUSIONS

The overall incidence of complications was 13.7%. Age; preoperative GK, LL, and SVA; the correction of GK, LL, and SVA; 2-level PSO; and number of instrumented vertebrae were risk factors. Therefore, the potential risk of extensive surgeries with large correction and long fusion in older AS patients with severe GK should be seriously considered in surgical decision-making.

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

Zhuo-jie Liu, Bang-ping Qian, Yong Qiu, Sai-hu Mao, Jun Jiang, and Bin Wang

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.

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How does sagittal spinopelvic alignment of lumbar multisegmental spondylolysis differ from monosegmental spondylolysis?

Qing-shuang Zhou, MM, Xu Sun, Xi Chen, Liang Xu, Bang-ping Qian, Ze-zhang Zhu, Bin Wang, and Yong Qiu

OBJECTIVE

The aim of this study was to investigate sagittal alignment and compensatory mechanisms in patients with monosegmental spondylolysis (mono_lysis) and multisegmental spondylolysis (multi_lysis).

METHODS

A total of 453 adult patients treated for symptomatic low-grade spondylolytic spondylolisthesis were retrospectively studied at a single center. Patients were divided into 2 subgroups, the mono_lysis group and the multi_lysis group, based on the number of spondylolysis segments. A total of 158 asymptomatic healthy volunteers were enrolled in this study as the control group. Radiographic parameters measured on standing sagittal radiographs and the ratios of L4–S1 segmental lordosis (SL) to lumbar lordosis (L4–S1 SL/LL) and pelvic tilt to pelvic incidence (PT/PI) were compared between all experimental groups.

RESULTS

There were 51 patients (11.3%) with a diagnosis of multi_lysis in the spondylolysis group. When compared with the control group, the spondylolysis group exhibited larger PI (p < 0.001), PT (p < 0.001), LL (p < 0.001), and L4–S1 SL (p = 0.025) and a smaller L4–S1 SL/LL ratio (p < 0.001). When analyzing the specific spondylolysis subgroups, there were no significant differences in PI, but the multi_lysis group had a higher L5 incidence (p = 0.004), PT (p = 0.018), and PT/PI ratio (p = 0.039). The multi_lysis group also had a smaller L4–S1 SL/LL ratio (p = 0.012) and greater sagittal vertical axis (p < 0.001).

CONCLUSIONS

A high-PI spinopelvic pattern was involved in the development of spondylolytic spondylolisthesis, and a larger L5 incidence might be associated with the occurrence of consecutive multi_lysis. Unlike patients with mono_lysis, individuals with multi_lysis were characterized by an anterior trunk, insufficiency of L4–S1 SL, and pelvic retroversion.