One-level Pedicle Subtraction Osteotomy Research Articles

Application of vertebral body compression osteotomy in pedicle subtraction osteotomy on ankylosing spondylitis kyphosis: Finite element analysis and retrospective study.

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease, with pathological characteristics of bone erosion, inflammation of attachment point, and bone ankylosis. Due to the ossified intervertebral disc and ligament, pedicle subtraction osteotomy (PSO) is one of the mainstream surgeries of AS-related thoracolumbar kyphosis, but the large amount of blood loss and high risk of instrumental instability limit its clinical application. The purpose of our study is to propose a new transpedicular vertebral body compression osteotomy (VBCO) in PSO to reduce blood loss and improve stability. A retrospective analysis was performed on patients with AS-related thoracolumbar kyphosis who underwent one-level PSO in our hospital from February 2009 to May 2019.A total of 31 patients were included in this study; 6 received VBCO and 25 received eggshell vertebral body osteotomy. We collected demographic data containing gender and age at diagnosis. Surgical data contained operation time, estimated blood loss (EBL), and complications. Radiographic data contained pre-operative and follow-up sagittal parameters including chin brow-vertical angle (CBVA), global kyphosis (GK), thoracic kyphosis (TK), and lumbar lordosis (LL). A typical case with L2-PSO was used to establish a finite element model. The mechanical characteristics of the internal fixation device, vertebral body, and osteotomy plane of the two osteotomy models were analyzed under different working conditions. The VBCO could provide comparable restoring of CBVA, GK, TK, and LL in the eggshell osteotomy procedure (all p > 0.05). The VBCO significantly reduced EBL compared to those with eggshell osteotomy [800.0ml (500.0-1,439.5 ml) vs. 1,455.5 ml (1,410.5-1,497.8 ml), p = 0.033]. Compared with the eggshell osteotomy, VBCO showed better mechanical property. For the intra-pedicular screw fixation, the VBCO group had a more average distributed and lower stress condition on both nails and connecting rod. VBCO had a flattened osteotomy plane than the pitted osteotomy plane of the eggshell group, showing a lower and more average distributed maximum stress and displacement of osteotomy plane. In our study, we introduced VBCO as an improved method in PSO, with advantages in reducing blood loss and providing greater stability. Further investigation should focus on clinical research and biomechanical analysis for the application of VBCO.

Clinical Results of Utilizing the Satellite Rod Technique in Treating Ankylosing Spondylitis Kyphosis

ObjectiveAccording to the literature, there are no clinical reports documenting the use of the satellite rod technique in the treatment of ankylosing spondylitis kyphosis. The purpose of this retrospective study was to compare the clinical outcome of patients with ankylosing spondylitis kyphosis who adopted satellite rods versus those who did not.MethodsPatients with ankylosing spondylitis kyphosis who underwent one or two‐level pedicle subtraction osteotomy (PSO) were reviewed, and total of 119 patients (112 males and seven females, average age 39.89 ± 6.61 years) were eligible and included in this present study. Anterior–posterior and lateral full‐length spine X‐ray films were performed preoperatively and at the two‐year follow‐up visit. Global kyphosis (GK), lumbar lordosis (LL), thoracolumbar kyphosis (TLK), thoracic kyphosis (TK), and osteotomy angle (OA) were measured. The complications of every group of patients were collected. Pre‐ and postoperative health‐related quality of life instruments, including the Bath Ankylosing Spondylitis Functional Index (Basfi) and Scoliosis Research Society outcomes instrument‐22 (SRS‐22), were recorded. The patients were divided into three groups based on features of their osteotomy including PSO levels and whether the satellite rod technique was applied. Patients who underwent one‐level PSO without the satellite rod technique were categorized in the one‐level group. Patients who underwent one‐level PSO with the satellite rod technique were classified in the satellite rod group. Patients who underwent two‐level PSO without the satellite rod technique were included in the two‐level group. The paired sample t test was used to compare pre‐ and postoperative parameters. One‐way ANOVA was performed for multiple group comparisons.ResultsThe average follow‐up time is 29.31 ± 3.66 months. The patients' GK were significantly improved from 46.84 ± 20.37 degree to 3.31 ± 15.09 degree. OS achieved through each osteotomy segment of one‐level group (39.78 ± 12.29 degree) and satellite rods group (42.23 ± 9.82 degree), was larger than that of two‐level group (34.73 ± 7.54 and 28.85 ± 7.26 degree). There was no significant difference between the one‐level group and the satellite rod group in achieving the OS. Thirteen patients experienced different complications (10.92%). Three patients experienced rod fracture in the one‐level group. There was no rod fracture or screw failure in the satellite rod group or the two‐level group.ConclusionThe satellite rod technique is also recommended for patients who undergo PSO osteotomy to correct ankylosing spondylitis kyphosis deformities.

One\u2010level mini\u2010open pedicle subtraction osteotomy for treating spinal kyphosis in patients with ankylosing spondylitis

BackgroundTo 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.MethodsWe 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.ResultsThe 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.ConclusionsThe 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.

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

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). 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. 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). 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.

Two-Level Osteotomy for the Corrective Surgery of Severe Kyphosis From Ankylosing Spondylitis: A Retrospective Series.

Retrospective study. To describe the treatment results of patients with severe ankylosing spondylitis (AS) kyphosis who underwent two-level osteotomy and correction surgery. The best solution for the fixed kyphotic deformity of AS is corrective osteotomy. Many osteotomy options are available: pedicle subtraction osteotomy (PSO), Smith-Peterson osteotomy (SPO), and vertical column resection (VCR). These procedures all provide multiplanar deformity correction. Nevertheless, when the AS deformity is severe, an additional osteotomy site to get more correction, achieve more ideal, and smooth curvature of the spine than single osteotomy. From May, 2008 to August, 2016, 19 patients of severe AS kyphosis underwent two-level spinal osteotomy and correction surgery. The patients had an average kyphosis angle greater than 90°. The radiological features and clinical evaluation, including Oswestry Disability Index (ODI), visual analog scale (VAS), and Scoliosis Research Society (SRS)-22 components were assessed before surgery and at follow-up. The patients underwent either one-level PSO combined with one-level SPO (n = 9) or two-level PSO (n = 10). The height was increased after surgery in all patients (P < 0.05). The median follow-up was 24 months. The kyphosis angle improved from 92.0 ± 16.6° to 30.0 ± 17.2°. The chin-brow vertical angle improved from 37.6 ± 19.2° to -0.6 ± 2.5°. The sacral slope improved from 3.9 ± 11.8° to 21.7 ± 7.4°. Sagittal imbalance improved from 241.4 ± 115.3 mm to 74.6 ± 48.5 mm (P < 0.05). Lumbar lordosis improved from -3.9 ± 20.8° to 29.4 ± 14.1° (all P < 0.05). There were significant improvements in the ODI, VAS, and all components of SRS-22 (all P < 0.05). All patients with pseudarthrosis (n = 5) underwent PSO + SPO and achieved satisfactory results. Six complications were observed perioperatively, but without permanent sequelae. Two-level osteotomy and correction procedure can achieve satisfactory results in severe AS kyphosis. PSO + SPO could be a good option for patients with pseudarthrosis because of relatively easier and faster operation. 4.

What is the optimal postoperative sagittal alignment in ankylosing spondylitis patients with thoracolumbar kyphosis following one-level pedicle subtraction osteotomy?

BACKGROUND CONTEXTRadiographic realignment objectives for the surgical correction of adult spinal deformity (ASD) have been well-described. However, the optimal sagittal spinopelvic alignment after corrective osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) is still unknown so far. PURPOSETo comprehensively investigate the relationship between radiographic parameters and clinical outcomes measured by Oswestry Disability Index (ODI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in thoracolumbar kyphosis patients caused by AS following one-level pedicle subtraction osteotomy (PSO) and to determine the optimal sagittal alignment at a minimum of 2-year follow-up. STUDY DESIGNA retrospective review of consecutive AS patients from one institution (2006–2016). PATIENT SAMPLEOne hundred AS-related thoracolumbar kyphosis patients who underwent one-level PSO with a minimum of 2-year follow-up (range, 2–10 years). OUTCOME MEASURESSpinopelvic parameters at final follow-up (≥2 years) included thoracic kyphosis, lumbar lordosis, osteotomized vertebra angle, pelvic tilt (PT), sacral slope (SS), pelvic incidence, sagittal vertical axis, spinosacral angle (SSA), T1 pelvic angle (TPA), spinopelvic angle (SPA), and global kyphosis. Clinical outcomes at final follow-up (≥2 years) was evaluated by ODI and BASDAI, and ODI<20 was defined as good clinical outcome. METHODSPre- and postoperative radiographic and clinical outcomes were compared by paired samples t test. The correlation between the postoperative radiographic parameters and clinical outcomes was investigated by Pearson correlation analysis. Linear regression analysis was performed to construct predictive models of the clinically relevant radiographic parameters based on ODI scores and to determine the realignment goals. Multiple stepwise regression analysis was applied to figure out the major radiographic contributors of ODI score at the final follow-up. RESULTSIn total, 100 AS patients (92 males and 8 females) with a mean age of 34.7±9.5 years (range, 17–63 years) were followed up for 38.6±17.5 months (range, 24–120 months). At the final follow-up, PT and TPA were positively correlated with both ODI and BASDAI score (p<.05). Although SS, SSA, and SPA were negatively associated with the score of ODI (p<.05), and BASDAI was negatively related to SPA (p<.05). Predicting regression models of the clinically-relevant radiographic parameters were built based on the ODI score at the last follow-up. CONCLUSIONSBased on the regression models, the optimal sagittal alignment of AS patients satisfying good clinical outcome (ODI<20) at a minimum of 2-year follow-up was: PT<24°, SSA>108°, TPA<22°, and SPA>152°. Realizing the aforementioned realignment goals may contribute to satisfied clinical outcome for AS patients with thoracolumbar kyphosis undergoing one-level PSO.

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

ObjectiveTo 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 methodsSeventy-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. ResultsThere 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). ConclusionsPatients 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.

Mechanisms, Predisposing Factors, and Prognosis of Intraoperative Vertebral Subluxation During Pedicle Subtraction Osteotomy in Surgical Correction of Thoracolumbar Kyphosis Secondary to Ankylosing Spondylitis.

A retrospective study. To analyze the mechanisms, predisposing factors, and prognosis of the intraoperative vertebral subluxation (VS) during pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis secondary to ankylosing spondylitis (AS). VS is one of the most daunting challenges that surgeons encounter during PSO closure, especially in patients with AS with ankylosed and mostly osteoporotic spine. Unfortunately, there is a paucity of research designed to conceptualize the mechanisms, predisposing factors, and discuss the complication-avoidance strategies and prognosis. A retrospective single-center review was performed for a consecutive series of 153 patients with AS with rigid thoracolumbar kyphosis who underwent one-level PSO from April 2000 to December 2013. The incidence of the VS at the level of PSO during correction was analyzed and the potential causative factors were investigated. VS occurred in six patients with the incidence being 3.9% in this patient cohort. The predisposing factors were (1) early fracture of the anterior cortex of the osteotomized vertebra (OV); (2) excessive decancellation from vertebral body causing parallel collapse of the vertebral column with significant loss of the ability to create local lordosis; (3) improper manual osteoclasis due to insufficient decancellation of the OV; and (4) inappropriate application of cantilever technique and concomitant long instrumentation. The early surgical complication involved one patient with cerebrospinal fluid leakage at the osteotomized site, but no devastating neurological deficits. During follow-up, bone healing and adaptive vertebral remodeling with no rod breakage were observed for all these six patients. Intraoperative VS was a rare occurrence associated with inappropriate manual manipulation of osteotomy, gap closure, and rod insertion. Neurological complication was a potential risk, but could be well prevented with extensive laminectomy and emergency actions favoring partial subluxation reduction. Moreover, adaptive bone remodeling and fusion at the level of VS ensured the maintenance of kyphosis correction and avoidance of instrumentation failure. 4.