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.

Modified pedicle subtraction osteotomy for osteoporotic vertebral compression fractures: a retrospective study of 104 patients.

BACKGROUND: Osteoporotic vertebral compression fractures (OVCF) caused by osteoporosis is a common clinical fracture type. There are many surgical treatment options for OVCF, but there is a lack of comparison among different options. Therefore, we counted a total of 104 cases of OVCF operations with different surgical plans, followed up the patients, and compared the surgical outcome indications before, after and during the follow-up. METHOD: 104 patients who underwent posterior osteotomy (Modified PSO, SPO, PSO, VCR) and kyphosis correction surgery at our hospital between April 2006 and August 2021 with a minimum follow-up period of 24 months were included. All cases were injuries induced by a fall incurred while standing or lifting heavy objects without high-energy trauma. The mean CT value was 71 HU, which was below 110 HU, indicating severe osteoporosis. The indications for surgery included gait disturbance due to severe pain with pseudarthrosis, increased kyphotic angle, and progressive neurological symptoms. Pre- and postoperative CL, TLK, TK, PrTK, TKmax, GK, LL, PI, SS, PT, SVA, TPA, were investigated radiologically. Additionally, We evaluated estimated blood loss, surgical time and perioperative symptom. RESULT: The results show, after operation, TLK (37.32 ± 10.61° vs. 11.01 ± 8.06°, P < 0.001), TK (35.42 ± 17.64° vs. 25.62 ± 12.24°, P < 0.001), TKmax (49.71 ± 16.32° vs. 24.12 ± 13.34°, P < 0.001), SVA (44.91 ± 48.67 vs. 23.52 ± 30.21, P = 0.013), CL (20.23 ± 13.21° vs. 11.45 ± 9.85°, P = 0.024) and TPA (27.44 ± 12.76° vs. 13.91 ± 9.24°, P = 0.009) were improved significantly in modified Pedicle subtraction osteotomy (mPSO) after operation. During follow-up, TLK (37.32 ± 10.61° vs. 13.88 ± 10.02°, P < 0.001) and TKmax (49.71 ± 16.32° vs. 24.12 ± 13.34°, P < 0.001) were improved significantly in Modified PSO group. In additon, estimated blood loss (790.0 ± 552.2 ml vs. 987.0 ± 638.5 ml, P = 0.038), time of operation (244.1 ± 63.0 min vs. 292.4 ± 87.6 min, P = 0.025) were favorable in Modified PSO group compared to control group. CONCLUSION: To conclude, mPSO could acquire a favorable degree of kyphosis correction as well as fewer follow-up complications. Compared with other surgical methods, it also has the advantages of less surgical trauma and shorter operation time. It can be an effective solution for the treatment of OVCF.

A new mathematical model for evaluating surface changes in the mid-abdominal sagittal plane after two-level pedicle reduction osteotomy in patients with ankylosing spondylitis.

BACKGROUND: The purpose of this study was to create a mathematical model to precalculate the acreage change in the abdominal median sagittal plane (ac-AMSP) of patients with ankylosing spondylitis (AS) for whom two-level pedicle subtraction osteotomy (PSO) was planned. METHODS: A single-centre retrospective review of prospectively collected data was conducted among 11 adults with AS. Acreage of the abdominal median sagittal plane (a-AMSP) was performed. The distances and angles between the osteotomy apexes, anterosuperior edge of T12, xiphoid process, superior edge of the pubis, and anterosuperior corner of the sacrum were measured on preoperative thoracolumbar computed tomography. A mathematical model was created using basic trigonometric functions in accordance with the abdominal parameters. Planned osteotomized vertebra angles (POVAs) were substituted into the mathematical model, and the predictive ac-AMSP (P-AC) was obtained. A paired sample t test was performed to determine the differences between the P-AC and actual ac-AMSP (A-AC) and between the predictive acreage change rate (P-CR) and actual acreage change rate (A-CR). RESULTS: The mean age and GK were 44.4 ± 8.99 years and 102.9° ± 19.17°, respectively. No significant difference exists between A-CR and P-CR via mathematical modeling (p > 0.05). No statistically significant difference existed between POVA and actual osteotomized vertebra angles (AOVA) (p > 0.05). A statistically significant difference was observed between preoperative and postoperative measurements of LL, SVA, and GK variables (p < 0.001). CONCLUSIONS: The novel mathematical model was reliable in predicting the ac-AMSP in AS patients undergoing two-level PSO.

Domino connector for thoracic pedicle subtraction osteotomy reduction: surgical technique and patient series.

PURPOSE: Different techniques have been previously described to close the pedicle subtraction osteotomy (PSO) site for correction of sagittal malalignment; the use of a side-to-side domino connector as a correction tool in the thoracic spine has not been specifically studied. METHODS: Twenty adult patients who underwent single-level thoracic PSO from T1 to T12 were included and retrospectively reviewed (two centers). Preoperative and postoperative full-body X-rays, perioperative data, clinical data and complications were recorded with a minimum 2 years of follow-up. Surgical technique and the nuances in using the domino connector were described in detail. RESULTS: Patients had a mean age of 40y; 40% were female. Two different techniques involving the domino were applied for closure of the PSO site depending on the type of kyphosis (smooth vs. angular deformity). Both techniques provided significant correction of the local kyphosis (from 48° to 18°) with reciprocal reduction of compensatory cervical lordosis (from 37.6° to 18.6°, p < 0.01) in upper thoracic PSO or lumbar lordosis (from 74.5° to 46.6°, p < 0.01) in lower thoracic PSO. Four patients presented postoperative complications that resolved (hemothorax, GI bleeding), and two patients presented transient neurological deficit. Oswestry Disability Index score improved in the majority of the patients (from 32.7 to 22.5, p < 0.05). There were no pseudarthroses, symptomatic instrumentation breakage, or surgical site infection. CONCLUSION: Use of a side-to-side domino connector in combination with two different rod cantilever techniques is effective for the reduction of thoracic pedicle subtraction osteotomy achieving satisfactory radiological and clinical outcome.

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.

Comparison of staged lateral lumbar interbody fusion combined two-stage posterior screw fixation and two osteotomy strategies for adult degeneration scoliosis: a retrospective comparative study.

AIMS: The commonly used treatments of adult degeneration scoliosis (ADS) were posterior long segment screw fixation with osteotomies. Recently, lateral lumbar intervertebral fusion combined two-stage posterior screw fixation (LLIF + PSF) as a new strategy without osteotomy. Herein, this study aimed to compare the clinical and radiological outcomes among LLIF + PSF and pedicle subtraction osteotomy (PSO), posterior column osteotomies (PCO). METHODS: Totals of 139 ADS patients underwent operation with 2 years longer follow-up visit between January 2013 and January 2018 in Ningbo No.6 Hospital were enrolled into this study. 58 patients were included in PSO group, 45 in PCO group and 36 in LLIF + PSF group, The clinical and radiological data were reviewed from medical records. Baseline characteristic, perioperative radiological data (sagittal vertical axis (SVA), coronal balance (CB), Cobb angle of Mian curve (MC), Lumbar lordosis (LL), pelvic tilt (PT) and pelvic incidence-lumbar lordosis mismatch (PI-LL)), clinical outcomes (VAS of back and leg, Oswestry disability index (ODI) and Scoliosis Research Society 22-question Questionnaire (SRS-22)) and complications were evaluated and compared. RESULT: There were no significantly difference in baseline characteristics, preoperative radiological parameters and clinical outcomes among three groups. LLIF + PSF group was significantly shorter in operation time than other two groups (P < 0.05), whereas significant longer hospital stay was observed in LLIF + PSF group (P < 0.05). As for radiological parameters, LLIF + PSF group had significantly improvement in SVA, CB, MC, LL and PI-LL (P < 0.05). Moreover, LLIF + PSF group achieved significantly less correction loss in SVA, CB and PT than PSO and PCO group (1.5 ± 0.7 VS 2.0 ± 0.9 VS 2.2 ± 0.8, P < 0.05; 1.0 ± 0.4 VS 1.3 ± 0.5 VS 1.1 ± 0.7, P < 0.05 and 4.2 ± 2.8 VS 7.2 ± 3.1 VS 6.0 ± 2.8, P < 0.05). Significantly recovery in VAS of back and leg, ODI score and SRS-22 were found among all groups, however, LLIF + PSF shown significant better clinical therapy maintain at follow-up visit than other two groups (P < 0.05). There were no significantly difference in complications among groups (P = 0.66). CONCLUSION: Lateral lumbar interbody fusion combined two-stage posterior screw fixation (LLIF + PSF) can achieve comparable clinical therapy for adult degeneration scoliosis as osteotomy strategies. However, furthermore more studies need be taken for verifying the effect of LLIF + PSF in the future.

Health-related quality of life 2 years after pedicle subtraction osteotomy for sagittal imbalance: a single-center experience of 65 patients.

PURPOSE: Pedicle subtraction osteotomy (PSO) as an invasive procedure with high reoperation and complication rates in an often elderly population has often been questioned. The purpose of our study was to evaluate the impact of PSO for sagittal imbalance (SI) on patient-reported outcomes including self-reported satisfaction and health-related quality of life 2 years postoperatively. METHODS: Consecutive patients who underwent correction of their spinal deformity by thoracolumbar PSO were assessed using self-reporting questionnaires 2 years postoperatively. Outcome was measured by visual analogue scale (VAS) for back and leg pain, Oswestry Disability Index (ODI), and EQ-5D scores. Additionally, a Patient Satisfaction Index (PSI) rated in four grades (A: very satisfied to D: not satisfied), walking range, and the Timed Up and Go (TUG) Test were evaluated. RESULTS: Sixty-five patients were included, and each parameter was assessed preoperatively and 24 months postoperatively. The intervention led to significant improvements in back pain (8.1 ± 1.2 vs. 2.9 ± 1.9; p < 0.001), as well as ODI scores (57.7 ± 13.9 vs. 32.6 ± 18.9; p < 0.001), walking range (589 ± 1676 m vs. 3265 ± 3405 m; p < 0.001), and TUG (19.2 s vs. 9.7 s; p < 0.05). 90.7% of patients (n = 59/65) reported a PSI grade "A" or "B" 24 months postoperatively. CONCLUSION: Patient satisfaction 24 months after PSO for SI is high. Quality of life improved significantly by restoring sagittal balance.

Geometric analysis of pedicle subtraction osteotomy (PSO) for Kyphosis correction: anterior lengthening may occur at the osteotomized body as well as at the discs above and below.

OBJECTIVE: To validate the authors kyphosis correction formula for pedicle subtraction osteotomy (PSO) cases. Additionally, to use the formula to evaluate the safety of PSO by determining if there is anterior lengthening. METHODS: Twenty-two patients with primarily kyphosis corrected by PSO and with clear landmarks on preoperative and postoperative x-rays were selected. Several anatomical lines and angle measurements were utilized as depicted previously in the Vertebral Column Resection formula (see below). Two approximations were calculated: the geometric approximation (G) = (tanG°*2 + 1)*15° and the rough approximation (R) which is about the same amount of actual shortening (x), if parallel length (y) ≥ 40; twice of x, if y < 40. For each patient, the change of segmental kyphosis angle (K°) was measured and compared with G° and R°, and the correlation between each value was analyzed. RESULTS: The absolute Mean ± SE for K - G and K - R was 2.33° ± 0.34 and 6.09° ± 0.58, respectively. K - G is < 3° (p = 0.03). K - R is < 8° (p = 0.001). In other words, K was close to G and R and thus can be predicted by these approximations. Average posterior shortening, anterior shortening, and kyphosis correction at each level were 20.8 ± 2.0 mm, - 3.64 ± 1.5 mm (which equates to anterior lengthening), and 31.05° ± 2.0, respectively. Anterior lengthening occurred in 13 cases (in 4 cases, both at the body as well as at the disc above and below.) The correlation between posterior and anterior shortening was 0.03 (p = 0.88). There were 3 cage insertion cases: 1 had anterior lengthening, while 2 had anterior shortening even with the cage. CONCLUSION: This study validated the geometric and rough approximations originally used in PVCR patients, for PSO patients. Additionally, this study found that anterior lengthening may occur in PSOs usually at the discs, but occasionally at the osteotomized body.

Domino connector is an efficient tool to improve lumbar lordosis correction angle after pedicle subtraction osteotomy for adult spinal deformity.

PURPOSE: To compare the radiological outcomes and complications of adult spinal deformity patients who underwent a pedicle subtraction osteotomy (PSO) below L2 but categorized according to their construct where either a domino connector was applied for osteotomy correction or not. METHODS: Retrospective review of a prospective, multicenter adult spinal deformity database (5 sites). Inclusion criteria were adult patients who underwent PSO between L3 and L5 with a minimum follow-up of 2 years. Among 1243 patients in the database, 79 met the inclusion criteria, 41 in the no-domino (ND) group and 38 in the domino (D) group. The domino technique consisted of using 2 parallel rods connected by a domino on one side of the PSO in order to achieve gradual and controlled compression at the osteotomy site. Demographic data, operative parameters, spinopelvic parameters and complications were collected. RESULTS: Demographic data and operative parameters were globally similar between both groups, and they showed a comparable preoperative sagittal malalignment. Segmental lordosis improved by 22° and 31° (p < 0.05) and L1S1 lordosis improved by 23° and 32° (p < 0.05) in the ND and D group, respectively. The use of multiple rods was similar between the groups (58% vs. 57%). Also, mechanical complications rate was globally similar between both groups with no statistically significant difference (22% vs. 28.9%). CONCLUSION: Domino connector is a safe, powerful and efficient tool for pedicle subtraction osteotomy site closure. It improved the lumbar lordosis correction angle with an acceptable rate of complications.

Biomechanical comparison of multi-rod constructs by satellite rod configurations (in-line vs. lateral) and screw types (monoaxial vs. polyaxial) spanning a lumbar pedicle subtraction osteotomy (PSO): is there an optimal configuration?

PURPOSE: Multi-rod constructs are used commonly to stabilize pedicle subtraction osteotomies (PSO). This study aimed to evaluate biomechanical properties of different satellite rod configurations and effects of screw-type spanning a PSO. METHODS: A validated 3D spinopelvic finite element model with a L3 PSO (30°) was used to evaluate 5 models: (1) Control (T10-pelvis + 2 rods); (2) lateral satellite rods connected via offsets to monoaxial screws (LatSat-Mono) or (3) polyaxial screws (LatSat-Poly); (4) in-line satellite rods connected to monoaxial screws (InSat-Mono) or (4) polyaxial screws (InSat-Poly). Global and PSO range of motions (ROM) were recorded. Rods' von Mises stresses and PSO forces were recorded and the percent differences from Control were calculated. RESULTS: All satellite rods (save InSat-Mono) increased PSO ROM and decreased primary rods' von Mises stresses at the PSO. Lateral rods increased PSO forces (LatSat-Mono:347.1 N; LatSat-Poly:348.6 N; Control:336 N) and had relatively lower stresses, while in-line rods decreased PSO forces (InSat-Mono:280.1 N; InSat-Poly:330.7 N) and had relatively higher stresses. Relative to polyaxial screws, monoaxial screws further decreased PSO ROM, increased satellite rods' stresses, and decreased PSO forces for in-line rods, but did not change PSO forces for lateral rods. CONCLUSION: Multi-rod constructs using in-line and lateral satellite rods across a PSO reduced primary rods' stresses. Subtle differences in biomechanics suggest lateral satellite rods, irrespective of screw type, increase PSO forces and lower rod stresses compared to in-line satellite rods, which had a high degree of posterior instrumentation stress shielding and lower PSO forces. Clinical studies are warranted to determine if these findings influence clinical outcomes.

Radiographic outcomes and complications after L4 or L5 pedicle subtraction osteotomy for fixed sagittal malalignment in 102 adult spinal deformity patients with a minimum 2-year follow-up.

PURPOSE: The objective of this retrospective study was to provide the radiographic outcomes and complications for pedicle subtraction osteotomy (PSO) performed at the low lumbar spine, i.e., L4 or L5 for ASD patients with fixed sagittal malalignment. METHODS: ASD patients who underwent L4 or L5 PSO with a minimum 2-year follow-up were included. Preoperative and postoperative radiographs, and complications were collected. Radiographic analysis included lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), thoracic kyphosis (TK), sagittal vertical axis (SVA), spinal lordosis (SL) ratio and global tilt (GT) on standing long-cassette radiographs. RESULTS: A total of 102 patients from 2 spinal centers were analyzed. 66 patients underwent PSO at L4 and 36 patients at L5. From preoperatively to the final follow-up, significant improvements occurred in LL (from - 31° to - 52°), SVA (from 13 to 5 cm), and GT (from 44° to 27°) (all, p < 0.05). 12 patients had transient neurological deficits, and 8 patients had persistent neurological deficit. 23 patients underwent revision for PJK (2), pseudarthrosis (10), neurological deficit (2), epidural hematoma (1), or deep surgical site infection (8). No PJK was observed in any of the patients with L5 PSO. CONCLUSIONS: PSO at the level of L4 or L5 remains a challenging technique but with an acceptable rate of complications and revisions. It enables correction of fixed sagittal malalignment in ASD patients with a globally satisfactory outcome. In comparison with L4 PSO, L5 PSO patients did not show PJK as a mechanical complication. Distal lumbar PSO at the level of L5 may represent one of the factors that may help preventing the proximal junctional kyphosis complication.

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.

Adult spinal deformity surgery: posterior three-column osteotomies vs anterior lordotic cages with posterior fusion. Complications, clinical and radiological results. A systematic review of the literature.

PURPOSE: The aim of our study is to analyse mid- to long-term severe adult spinal deformity (ASD) surgery outcomes by comparing three-column osteotomies (3CO) and multiple anterior interbody fusion cages (AC). MATERIALS AND METHODS: The PRISMA flowchart was used to systematically review the literature. Only articles with a minimum 24-month follow-up were examined, and 11 articles were included. The following radiological parameters were observed: pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), sagittal vertical axis (SVA), Cobb angle and T1-sacrum plumbline. Clinical outcome was assessed using the visual analogue scale (VAS) and Oswestry disability index (ODI) scores. The main complications were analysed, and the two groups were compared. RESULTS: Except for age, the two populations were homogeneous. Both techniques had the same number of posterior instrumented levels (7.4 ± 1.7). The AC group had a mean 3 ± 1.4 interbody fusions per patient. In the PSO group, all patients had 1 3CO and 89.8% of the osteotomies were performed at L2 or L3 vertebrae. No difference was observed between the two groups in terms of clinical outcomes. Both techniques were effective in sagittal parameters restoration with a final PI-LL mismatch = 4.4°. The PSO group had a statistically higher rate of intraoperative blood loss (p = 0.036), major complications, pseudoarthrosis and dural tears (p < 0.001). CONCLUSION: Both PSO and multiple AC are effective in treating ASD. Multiple AC seems more suitable when treating older patients because of a lower intraoperative blood loss, lower rate of major complications and fewer number of revision surgeries.

Quantitative determining of pre-operative osteotomy plan for severe spinal deformity: an analysis of 131 consecutive Yang's A type cases from single center.

PURPOSE: This study aimed to quantify osteotomy protocol for severe spinal deformity correction based on pre-operative demographic, clinical and radiologic parameters. METHODS: A total of 131 Yang's A type severe spinal deformity patients were included. All patients received one of following osteotomies: Ponte/2 (Ponte osteotomy/Grade 2 osteotomy, n = 30), PSO/3 (pedicle subtraction osteotomy/Grade 3 osteotomy, n = 19), BDBO/4 (bone-disc-bone osteotomy/Grade 4 osteotomy, n = 26), SVCR/5 (single-level vertebral column resection/Grade 5 osteotomy, n = 38) and MVCR/6 (multilevel vertebral column resection/Grade 6 osteotomy, n = 18). Demographic, clinical and radiologic characteristics were compared among groups. RESULTS: Tukey's test identified 6 significant variables between paired groups: age for MVCR/6 versus Ponte/2 + PSO/3 + BDBO/4 + SVCR/5 groups; bending Cobb angle for Ponte/2 versus MVCR/6; sagittal deformity angular ratio (S-DAR) for Ponte/2 + PSO/3 versus BDBO/3 + SVCR/5 versus MVCR/6; pre-operative scoliosis for Ponte/2 versus SVCR/5; total-DAR (T-DAR) and pre-operative kyphosis for Ponte/2 + PSO/3 versus BDBO/4 + SVCR/5 + MVCR/6. Receiver Operating Characteristic (ROC) analysis showed the Area under the Curve (AUC) for the 6 variables ranged from 0.69 to 0.839. Multivariate k-means clustering analysis showed that Ponte/2 + PSO/3, BDBO/4 + SVCR/5, and MVCR/6 were three comparatively significant clusters, which could be discriminated by pre-operative kyphosis, T-DAR, age and S-DAR. CONCLUSION: This study showed that osteotomy plan of severe spinal deformity could be determined as follows: Firstly, Ponte/2 + PSO/3 and BDBO/4 + SVCR/5 + MVCR/6 groups can be divided by either T-DAR (cutoff = 28) or the Cobb angle of pre-operative maximum kyphosis (cutoff = 100). Secondly, Ponte/2 + PSO/3 group could be further dichotomized into Ponte/2 and PSO/3 by age (cutoff = 18). Finally, BDBO/4 + SVCR/5 + MVCR/6 group could be divided into BDBO/4 + SVCR/5 and MVCR/6 groups by S-DAR (cutoff = 20).

The effect of pedicle subtraction osteotomy for the correction of severe Scheuermann thoracolumbar kyphosis on sagittal spinopelvic alignment.

PURPOSE: To analyze how pedicle subtraction osteotomy (PSO) treatment of severe Scheuermann thoracolumbar kyphosis (STLK) using pedicle screw instrumentation affects sagittal spinopelvic parameters. BACKGROUND: The medical literature on the post-surgical effects of treatments such as Ponte osteotomy is limited, but suggests few effects on spinopelvic profiles. Currently, there is no research regarding changes in sagittal spinopelvic alignment upon PSO treatment in STLK patients. METHODS: We performed a retrospective study on 11 patients with severe STLK. These patients underwent posterior-only correction surgeries with PSO and pedicle screw instrumentation between 2012 to 2017 in a single institute. Patients were measured for the following spinopelvic parameters: global kyphosis (GK), thoracic kyphosis (TK), thoracolumbar kyphosis (TL), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tile (PT), sacral slope (SS), and administered a Scoliosis Research Society-22 questionnaire (SRS-22) pre-operation, post-operation and at final follow-up. RESULTS: GK improved from a median of 74.1° to 40.0° after surgery, achieving a correction rate of 48.8% with a median correction loss of 0.8°. TK, TL and LL all showed significant difference (P < 0.05) and SVA improved 22.7 (11.6, 30.9) mm post operation. No significant difference was found in pelvic parameters (PI, PT, SS, all P < 0.05). The absolute value of LL- PI significantly improved from a median of 26.5° pre-operation to 6.1° at the final follow-up. 72.7% in this series showed an evident trend of thoracic and lumbar apices migrating closer to ideal physiological segments after surgery. Self-reported scores of pain, self-image, and mental health from SRS-22 revealed significant improvement at final follow-up (all P < 0.05). CONCLUSIONS: PSO treatment of severe STLK with pedicle screw instrumentation can improve spine alignment and help obtain a proper alignment of the spine and the pelvis.

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.

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.

L5 pedicle subtraction osteotomy maintains good radiological and clinical outcomes in elderly patients with a rigid kyphosis deformity: a more than 2-year follow-up report.

PURPOSE: L5 pedicle subtraction osteotomy (PSO) is a demanding technique; thus, PSOs are usually performed at the L3/L4 level to correct the lack of lumbar lordosis. Mid- to long-term improvements in clinical outcomes after L5 PSO are unknown. We aimed to determine the efficacy and safety of L5 PSO for rigid kyphosis deformities. METHODS: We retrospectively reviewed the records of 57 patients with a rigid kyphosis deformity (mean age: 68 years) who underwent extensive corrective surgery incorporating PSO with a > 2-year follow-up. Radiographic parameters, postoperative complication rates, and the Oswestry Disability Index (ODI) scores were compared in the L5, L4, and L1-3 PSO groups preoperatively and at 1, 2, and 5 years postoperatively. RESULTS: There were 12, 25, and 20 patients in the L5, L4, and L1-3 PSO groups, respectively. Significant between-group differences were found in preoperative L4-S1 lordosis (L5:L4:L1-3 PSO groups = - 8.9°:8.9°:16.2°, P < 0.001). The surgeries improved the postoperative spinopelvic alignment (similar in all groups). There was no significant between-group difference in the postoperative complication rate; no irreversible complications occurred. In the L5 PSO group, there was one case of a common iliac vein injury. The ODI scores improved postoperatively in all groups; this was maintained for 5 years postoperatively. CONCLUSION: L5 PSO for L4-5/L5 kyphosis deformities resulted in adequate correction and ODI improvement, which were maintained up to 5 years postoperatively. The surgical invasiveness, complication rates, and long-term prognosis associated with L5 PSO were similar to those of PSOs performed at other levels.

Effect of lumbar pedicle subtraction osteotomy level on lordosis distribution and shape.

PURPOSE: Little is known about the qualitative results (postoperative upper/lower lumbar arches distribution and lumbar apex or inflection point positioning) of lumbar pedicle subtraction osteotomies (L-PSO) depending on the level of L-PSO. METHODS: We conducted a retrospective analysis of prospectively collected data of adult deformity patients undergoing single-level L-PSO. We analyzed several variables in preoperative and postoperative sagittal radiographs: L-PSO level, Roussouly classification (R-type), inflection point (InfP), lumbar apex (LApex), spinopelvic parameters, lordosis distribution index (LDI = L4-S1/L1-S1), and number of levels in the lordosis (NVL). Comparisons between PSO levels were performed to determine lordosis distribution and sagittal shape using ANOVA test and Chi-squared statistics. RESULTS: A total of 126 patients were included in this study. L5-PSO mainly increased the lower lumbar arch, thereby increasing LDI. L4 increased upper/lower arches similarly. PSOs at and above L3 increased the upper lumbar arch, thereby decreasing LDI (P < 0.001). L4-PSO added 1 vertebra into the lordosis (NVL = + 1.2 ± 2.2). PSOs above L3 added 2 vertebrae into the lordosis (NVL = + 2.3 ± 1.4). Overall P = 0.007. PSOs above L4 shifted the LApex cranially in 70% of the cases (mean 1.12 levels) and the InfP in 85% of the cases (mean 2.4 levels). L5-PSO shifted the LApex caudally in 70% of the cases (mean - 1.1 levels) and the InfP in 50% of the cases (mean - 1.6 levels). Overall P < 0.006. The L-PSO level was not associated with a specific Roussouly-type P > 0.05. CONCLUSIONS: The level of L-PSO influenced upper/lower lumbar arches distribution, and lumbar apex and inflection point positioning. The correct level should be chosen based on the individual assessment of each patient.

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.