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.

Determining the vertebra for pedicle subtraction osteotomy in surgical correction for ankylosing spondylitis with thoracolumbar kyphosis.

OBJECTIVE: This study aimed to provide a method for determining the apical vertebra for pedicle subtraction osteotomy (PSO) in corrective surgery for patients with ankylosing spondylitis (AS) with thoracolumbar kyphosis (TLK). METHODS: The medical records of AS patients with TLK who underwent PSO between May 2009 and August 2022 were retrospectively reviewed, and 235 patients were included in the study. Using the proposed method, choosing the vertebra based on Kim's apex (KA), which is defined as the farthest vertebra from a line drawn from the center of the T10 vertebral body to the midpoint of the S1 upper endplate, the authors analyzed 229 patients with apices at T12, L1, or L2 (excluding L3 because of the small sample size, n = 6). They divided all patients into two groups. Group A (n = 144) underwent PSO at the KA vertebra, while group B (n = 85) underwent PSO at a different level. Demographic and radiological data, including sagittal spinopelvic parameters of the entire spine, were collected. An additional analysis was performed on patients with the same KA vertebra. RESULTS: The vertebra distributions of patients based on KA were T12 (28 [12.2%]), L1 (119 [52.0%]), and L2 (82 [35.8%]). The corrections of sagittal vertical axis (SVA; 101.0 ± 48.5 mm vs 82.0 ± 53.8 mm, p = 0.010), global kyphosis (GK; 31.6° ± 10.0° vs 26.4° ± 10.5°, p = 0.005), and TLK (29.4° ± 10.2° vs 24.2° ± 12.9°, p = 0.012) in group A were significantly greater than those in group B, and there was no difference in the corrections of thoracic kyphosis (TK), lumbar lordosis, and pelvic incidence between the two groups. On further analysis, group A showed greater correction in TK (26.2° ± 13.7° vs 0.1° ± 8.1°, p = 0.013) for patients with T12 as the KA; greater improvements in SVA (101.5 ± 44.2 mm vs 73.4 ± 48.7 mm, p = 0.020), GK (30.6° ± 11.0° vs 25.0° ± 10.4°, p = 0.046), and TLK (32.6° ± 7.8° vs 26.7° ± 9.9°, p = 0.012) for those with L1 as the KA; and significant correction in TLK (30.0° ± 6.3° vs 4.3° ± 19.5°, p = 0.008) for patients with L2 as the KA, compared with group B. CONCLUSIONS: PSO at the apical vertebra provides a greater degree of correction of sagittal imbalance. The proposed method, selecting the vertebra based on KA, is easily reproducible for determining the apex level in AS patients with TLK.

Restoring L4-S1 Lordosis Shape in Severe Sagittal Deformity: Impact of Correction Techniques on Alignment and Complication Profile.

BACKGROUND: Severe sagittal plane deformity with loss of L4-S1 lordosis is disabling and can be improved through various surgical techniques. However, data are limited on the differing ability of anterior lumbar interbody fusion (ALIF), pedicle subtraction osteotomy (PSO), and transforaminal lumbar interbody fusion (TLIF) to achieve alignment goals in severely malaligned patients. METHODS: Severe adult spinal deformity patients with preoperative PI-LL >20°, L4-S1 lordosis <30°, and full body radiographs and PROMs at baseline and 6-week postoperative visit were included. Patients were grouped into ALIF (1-2 level ALIF at L4-S1), PSO (L4/L5 PSO), and TLIF (1-2 level TLIF at L4-S1). Comparative analyses were performed on demographics, radiographic spinopelvic parameters, complications, and PROMs. RESULTS: Among the 96 included patients, 40 underwent ALIF, 27 underwent PSO, and 29 underwent TLIF. At baseline, cohorts had comparable age, sex, race, Edmonton frailty scores, and radiographic spinopelvic parameters (P > 0.05). However, PSO was performed more often in revision cases (P < 0.001). Following surgery, L4-S1 lordosis correction (P = 0.001) was comparable among ALIF and PSO patients and caudal lordotic apex migration (P = 0.044) was highest among ALIF patients. PSO patients had higher intraoperative estimated blood loss (P < 0.001) and motor deficits (P = 0.049), and in-hospital ICU admission (P = 0.022) and blood products given (P = 0.004), but were otherwise comparable in terms of length of stay, blood transfusion given, and postoperative admission to rehab. Likewise, 90-day postoperative complication profiles and 6-week PROMs were comparable as well. CONCLUSIONS: ALIF can restore L4-S1 sagittal alignment as powerfully as PSO, with fewer intraoperative and in-hospital complications. When feasible, ALIF is a suitable alternative to PSO and likely superior to TLIF for correcting L4-S1 lordosis among patients with severe sagittal malalignment.

Importance of the lumbar paraspinal muscles on the maintenance of global sagittal alignment after lumbar pedicle subtraction osteotomy.

OBJECTIVE: There are limited data about the influence of the lumbar paraspinal muscles on the maintenance of sagittal alignment after pedicle subtraction osteotomy (PSO) and the risk factors for sagittal realignment failure. The authors aimed to investigate the influence of preoperative lumbar paraspinal muscle quality on the postoperative maintenance of sagittal alignment after lumbar PSO. METHODS: Patients who underwent lumbar PSO with preoperative lumbar MRI and pre- and postoperative whole-spine radiography in the standing position were included. Spinopelvic measurements included pelvic incidence, sacral slope, pelvic tilt, L1-S1 lordosis, T4-12 thoracic kyphosis, spinosacral angle, C7-S1 sagittal vertical axis (SVA), T1 pelvic angle, and mismatch between pelvic incidence and L1-S1 lordosis. Validated custom software was used to calculate the percent fat infiltration (FI) of the psoas major, as well as the erector spinae and multifidus (MF). A multivariable linear mixed model was applied to further examine the association between MF FI and the postoperative progression of SVA over time, accounting for repeated measures over time that were adjusted for age, sex, BMI, and length of follow-up. RESULTS: Seventy-seven patients were recruited. The authors' results demonstrated significant correlations between MF FI and the maintenance of corrected sagittal alignment after PSO. After adjustment for the aforementioned parameters, the model showed that the MF FI was significantly associated with the postoperative progression of positive SVA over time. A 1% increase from the preoperatively assessed total MF FI was correlated with an increase of 0.92 mm in SVA postoperatively (95% CI 0.42-1.41, p < 0.0001). CONCLUSIONS: This study included a large patient cohort with midterm follow-up after PSO and emphasized the importance of the lumbar paraspinal muscles in the maintenance of sagittal alignment correction. Surgeons should assess the quality of the MF preoperatively in patients undergoing PSO to identify patients with severe FI, as they may be at higher risk for sagittal decompensation.

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.

Complications and outcomes after three-column osteotomy: a 5-year follow-up.

BACKGROUND: Three-column spinal osteotomies (3-CO) are powerful techniques used to correct spinal deformity. These surgeries are associated with an elevated risk of complications. While outcomes have been reported in the literature with 2 years follow-up, longer-term outcomes of three-column osteotomies remain understudied. OBJECTIVES: This study aims to examine patient reported outcomes and complications for three-column osteotomies at 5 years. STUDY DESIGN: Retrospective review of a prospectively collected spinal deformity cases database. PATIENT SAMPLE: All consecutive adult patients at a single spine surgery center treated with either a pedicle subtraction osteotomy (PSO) or vertebral column resection (VCR) for spinal deformity, and with a minimum 5-year follow-up were included. OUTCOME MEASURES: Visual-analog scale (VAS) for back pain score (0 to 10), Oswestry Disability Index (ODI) score (0 to 100), number of complications, revision rate, sagittal balance, lumbar lordosis at preoperative and at 5-year visit. METHODS: Data was extracted from a prospectively collected spinal deformity surgery database continuously updated since 2002 with data from operative reports, patients' medical visit notes and patients' self-reported VAS and ODI questionnaires completed at each office visit. Radiographic measurements were performed on standing full-length spine radiographs taken at pre-op and 5-year visits. Descriptive statistics, comparison of means and proportions among groups, and a logistic regression analysis were conducted using the statistical software package SPSS version 28. Statistical significance was set at p<.05. RESULTS: Of 127 consecutive adult patients with minimum of 5-year follow-up undergoing a 3-CO posterior spinal surgery for spinal deformity were identified and included in the study, 79 (62%) were treated with PSO, and 48 (38%) with VCR. Both PSO and VCR groups demonstrated significant improvements in VAS (PSO pre-op: 6.7, 5-year: 4.6, p<.001; VCR pre-op: 7.1, 5-year: 5.2, p<.001), and ODI (PSO pre-op: 52.9, 5-year: 45.4, p<.001; VCR pre-op: 57.5, 5-year 43.0, p<.001) that were maintained at 5 years. Major and minor complications occurring within 5 years were not statistically different between the PSO and VCR groups (major: 59.5% vs 56.3%, p=.85; minor: 45.6% vs 37.5%, p=.46). The rate of revision surgery within 5 years was 39.4% overall. Of the fifty patients requiring revision, 37.5% were for nonunion, 27.1% instrumentation failure, 14.6% proximal junctional kyphosis (PJK), 12.5% vertebral fracture, 6.3% motor weakness, and 2.1% infection. Improvements in lumbar lordosis were maintained at 5 years in both the PSO (29.9° vs 47.2°, p<.001) and VCR (34.6° vs 48.5°, p<.001) groups while sagittal balance maintained significant improvement in the VCR group (9.5 cm vs 6.3 cm, p=.008) but not the PSO (11.4 cm vs 9.3 cm, p=.065). CONCLUSION: Patients undergoing three-column osteotomies had a major complication rate of 57.5% and a minor complication rate of 42.5% after 5 years. Improvements in lumbar lordosis were maintained at 5-year follow-up, but sagittal balance was only maintained in the VCR group. Despite these radiographic findings, both VCR and PSO groups maintained significant clinical improvements in both VAS and ODI scores at 5-year follow up.

Clinical and radiologic outcomes of posterior column extension, pedicle subtraction, and vertebral column resection osteotomies in adult chin on chest deformity: A systematic review.

Background: Chin-on-chest deformity is a rare and severely disabling condition characterized by kyphotic deformity in the cervicothoracic spine. To treat this deformity, various osteotomy techniques were described. Methods: A comprehensive literature search of biomedical databases including MEDLINE (via PubMed), Scopus (via Elsevier), Embase (via Elsevier), and Cochrane Library in English from 1/1/1990 to 3/31/2022 was conducted using a combination of text and Medical Subject Headings (MeSH). Results: The final analysis included 16 studies. All the studies were assigned a level of evidence of four. Except for two articles, all of the articles were non-comparative studies. A total of 288 patients were included in this review. Of the 288 patients, 107 underwent posterior column extension osteotomy (PCEO), 108 underwent pedicle subtraction osteotomy (PSO), and 33 underwent vertebral column resection osteotomy (VCRO). The most common osteotomy level in fifteen of the studies was C7/T1. The studies included in this review described several techniques for cervical sagittal balance correction. The range of preoperative and postoperative visual analogue scale (VAS) scores was 5.5-8.6 to 1.7-4.91, respectively. The range of preoperative and postoperative neck disability index (NDI) was 34.2-65.4 to 22.1-51.3, respectively. The most common complications were upper extremity paresthesia and hand numbness through the C8 dermatome distribution. Conclusions: Corrective osteotomies provide satisfactory results in patients with chin-on-chest deformity; however, the quality of the included studies limits the evidence.

Multiple three-column osteotomies successfully correcting cervicothoracic kyphosis in the setting of ankylosing spondylitis: illustrative case.

BACKGROUND: Ankylosing spondylitis (AS) is an autoimmune spondylarthritis often associated with rigid kyphoscoliosis. The authors describe a surgical approach that employs multilevel three-column osteotomies for the restoration of normal global alignment. OBSERVATIONS: A 48-year-old male with a past medical history of AS presented to the clinic with a stooped-over posture: his chin-brow vertical angle (CBVA) was 58.0°; T1 slope (T1S), 97.8°; thoracic kyphosis (TK; T1-12), 94.2°; proximal TK (T1-5), 50.8°; distal TK (T5-12), 43.5°; and sagittal vertical axis (SVA), 22.6 cm. A two-stage procedure was planned. During stage 1, instrumentation was placed from C5 to T10, followed by a T3 vertebral column resection. During stage 2, bilateral pedicle screws were placed from T11 to the pelvis. An L3 pedicle subtraction osteotomy (PSO) was completed and was followed by a T7 PSO. Postoperatively, the patient had significant postural improvement: CBVA was 29.3°; T1S, 57.8°; TK, 77.3°; proximal TK, 33.5°; distal TK, 43.8°; and SVA, 15 cm. At 6 years postoperatively, the patient continued to do well and was without evidence of construct breakdown. LESSONS: The authors propose that multilevel three-column osteotomies, if optimally located, successfully correct spinal malalignment associated with AS.

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.

The Predictors of Incidental Durotomy in Patients Undergoing Pedicle Subtraction Osteotomy for the Correction of Adult Spinal Deformity.

Background: Pedicle subtraction osteotomy (PSO) is a powerful tool for sagittal plane correction in patients with rigid adult spinal deformity (ASD); however, it is associated with high intraoperative blood loss and the increased risk of durotomy. The objective of the present study was to identify intraoperative techniques and baseline patient factors capable of predicting intraoperative durotomy. Methods: A tri-institutional database was retrospectively queried for all patients who underwent PSO for ASD. Data on baseline comorbidities, surgical history, surgeon characteristics and intraoperative maneuvers were gathered. PSO aggressiveness was defined as conventional (Schwab 3 PSO) or an extended PSO (Schwab type 4). The primary outcome of the study was the occurrence of durotomy intraoperatively. Univariable analyses were performed with Mann-Whitney U tests, Chi-squared analyses, and Fisher's exact tests. Statistical significance was defined by p < 0.05. Results: One hundred and sixteen patients were identified (mean age 61.9 ± 12.6 yr; 44.8% male), of whom 51 (44.0%) experienced intraoperative durotomy. There were no significant differences in baseline comorbidities between those who did and did not experience durotomy, with the exception that baseline weight and body mass index were higher in patients who did not suffer durotomy. Prior surgery (OR 2.73; 95% CI [1.13, 6.58]; p = 0.03) and, more specifically, prior decompression at the PSO level (OR 4.23; 95% CI [1.92, 9.34]; p < 0.001) was predictive of durotomy. A comparison of surgeon training showed no statistically significant difference in durotomy rate between fellowship and non-fellowship trained surgeons, or between orthopedic surgeons and neurosurgeons. The PSO level, PSO aggressiveness, the presence of stenosis at the PSO level, nor the surgical instrument used predicted the odds of durotomy occurrence. Those experiencing durotomy had similar hospitalization durations, rates of reoperation and rates of nonroutine discharge. Conclusions: In this large multisite series, a history of prior decompression at the PSO level was associated with a four-fold increase in intraoperative durotomy risk. Notably the use of extended (versus) standard PSO, surgical technique, nor baseline patient characteristics predicted durotomy. Durotomies occurred in 44% of patients and may prolong operative times. Additional prospective investigations are merited.

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

INTRODUCTION AND IMPORTANCE: A high-angle thoracolumbar kyphotic deformity (TLKD) may complicate surgical rectification of AS patients since one-stage two-level pedicle subtraction osteotomy (PSO), which provides high-angular correction, leads to excessive blood loss, neurological deficits and fixation failures. This case series presents the long-term results of one-stage single level PSO with Ponte osteotomy (PO) in the treatment of AS patients with high-angle TLKD. CASE PRESENTATION: This case series presents two AS patients with high kyphotic angles (KAs) of 86.1o. We collected data retrospectively from our institution's database between 2019 and 2023. A sagittal axis imbalance was the only complaint initially, no neurological deficits or other problems. A PSO augmented by PO was performed with a decompression laminectomy. Intraoperative monitoring (IOM) during reduction was used to observe neurological deficits. Blood loss at the highest rate was 1000 cc. It corrected 57.8o of KA postoperatively without neurological deficits. We found consistent results over 36 months. CLINICAL DISCUSSION: A thorough analytical approach may help diagnose AS. One-stage single-level PSO may correct high-angle TLKD in AS patients effectively. To achieve greater angular correction, PO, a less risky osteotomy, must be added. Decompression laminectomy is vital before osteotomy and IOM is crucial during reduction to prevent nerve injury. Even with two osteotomies, there was less blood loss than previously reported. These impressive long-term results call for further research. CONCLUSION: Combined PSO and PO with IOM efficiently magnifies the angular correction without postoperative neurological deficits or excessive blood loss in AS patients with high-angle TLKD.

A Femoral Neck Osteotomy for the Patients with Ankylosing Spondylitis and Thoracolumbar Kyphosis Combined with Hip Flexion Contracture.

OBJECTIVE: The surgical treatment of patients with ankylosing spondylitis and severe thoracolumbar kyphosis combined with hip flexion contracture is very difficult for all the surgeons. The femoral neck osteotomy (FNO) is the first step to break the ice. The evaluation of a new modified FNO method is very important to improve the curative effect. METHODS: Five male patients with nine bone-fused hips who underwent the new femoral neck osteotomy were included from October 2021 to March 2022. The FNO was designed that the saw blade was manipulated from the lateral femoral neck base to the inferior part of the femoral head, keeping Pauwels' angle less than 30° on the coronal plane. On the transverse plane, the angle between the saw blade and the coronal plane was more than 15°. On the sagittal plane, the saw blade cut through the femoral neck. They accepted pedicle subtraction osteotomy (PSO) after FNO according to the patient' recovery. Then, 2 weeks later, the patients underwent total hip arthroplasty (THA). The visual analogue scale (VAS), Harris hip score (HHS) and passive hip flexion-extension range of motion (ROM) were used to evaluate hip function. The data were analyzed by paired t-test. RESULTS: The average operation time and blood loss of FNO, the average interval between FNO and THA were collected. The average angle of the trunk and lower limb (ATL) was 36.33° ± 16.36° pre-FNO, 82.89° ± 13.51° post-FNO and 175.22° ± 3.42° post-THA. The average VAS scores were 0 pre-FNO, 5 ± 1.58 post-FNO and 2.6 ± 0.55 post-THA. The average HHS was 43.56 ± 1.59 preoperatively and 83.89 ± 2.21 postoperatively. The average hip extension ROM was 23.89° ± 12.69° pre-FNO, -22.67° ± 14.18° post-FNO and - 3.33° ± 2.50 post-THA°. The average hip flexion ROM was 23.89° ± 12.69° pre-FNO, 35.56° ± 12.11° post-FNO and 104.44° ± 5.27° post-THA. The differences among them were significant (p < 0.05). Only one hip (11.11%) displaced completely after FNO. CONCLUSION: A new modified FNO was developed, which can provide osteotomy with a certain degree of stability and greater ease for performing PSO and THA.

Biomechanical evaluation of multi-rod constructs to stabilize an S1 pedicle subtraction osteotomy (PSO): a finite element analysis.

PURPOSE: To develop and validate a finite element (FE) model of a sacral pedicle subtraction osteotomy (S1-PSO) and to compare biomechanical properties of various multi-rod configurations to stabilize S1-PSOs. METHODS: A previously validated FE spinopelvic model was used to develop a 30° PSO at the sacrum. Five multi-rod techniques spanning the S1-PSO were made using 4 iliac screws and a variety of primary rods (PR) and accessory rods (AR; lateral: Lat-AR or medial: Med-AR). All constructs, except one, utilized a horizontal rod (HR) connecting the iliac bolts to which PRs and Med-ARs were connected. Lat-ARs were connected to proximal iliac bolts. The simulation was performed in two steps with the acetabula fixed. For each model, PSO ROM and maximum stress on the PRs, ARs, and HRs were recorded and compared. The maximum stress on the L5-S1 disc and the PSO forces were captured and compared. RESULTS: Highest PSO ROMs were observed for 4-Rods (HR + 2 Med-AR). Constructs consisting of 5-Rods (HR + 2 Lat-ARs + 1 Med-AR) and 6-Rods (HR + 2 Lat-AR + 2 Med-AR) had the lowest PSO ROM. The least stress on the primary rods was seen with 6-Rods, followed by 5-Rods and 4-Rods (HR + 2 Lat-ARs). Lowest PSO forces and lowest L5-S1 disc stresses were observed for 4-Rod (Lat-AR), 5-Rod, and 6-Rod constructs, while 4-Rods (HR + Med-AR) had the highest. CONCLUSION: In this first FE analysis of an S1-PSO, the 4-Rod construct (HR + Med-AR) created the least rigid environment and highest PSO forces anteriorly. While 5- and 6-Rods created the stiffest constructs and lowest stresses on the primary rods, it also jeopardized load transfer to the anterior column, which may not be favorable for healing anteriorly. A balance between the construct's rigidity and anterior load sharing is essential.

The Advantages of 4-rod Construct over the 2-rod Techniques in Adult Spinal Deformity Patients who Underwent Pedicle Subtraction Osteotomy: A Multicenter Retrospective Comparative Study.

OBJECTIVE: In this retrospective study we compared clinicoradiologic outcomes and complication profiles of the traditional 2-rod construct versus the 4-rod construct in patients with adult spinal deformity (ASD) who underwent pedicle subtraction osteotomy (PSO). METHODS: We performed a retrospective review of 208 ASD patients at 2 referral centers who underwent lumbar PSO and long fusion from thoracic to the pelvis. Two different techniques, including the 4-rod construct and the traditional 2-rod technique, were used at the PSO level. Clinicoradiologic outcomes and complication profiles of the patients were documented and compared statistically between the groups. RESULTS: The 4-rod construct was associated with statistically lower rates of rod fracture (44.8% vs. 26.4%, P < 0.01), pedicular screw loosening at the PSO level (25.3% vs. 14.0%, P = 0.04), and reoperation (49.4% vs. 33.9%, P = 0.02). Radiologically, the 4-rod construct was associated with higher degree of lumbar lordosis (LL) (-37.4°vs. -26.8°; P < 0.01) and improved pelvic tilt (PT) (-17.2° vs. -9.9°; P < 0.01) and sacral vertical axis (SVA) corrections (-211.5° vs. -192.2°; P = 0.04). Overall, the 4-rod construct was associated with improved quality of life (P = 0.04) and statistically lower Oswestry Disability Index score at 12 months postoperatively (P < 0.01). CONCLUSIONS: Our results showed that the 4-rod construct was associated with statistically lower rates of rod fracture and pedicular screw loosening at the osteotomy level, higher degree of LL correction and improved PT and SVA than the 2-rod technique. The 4-rod construct was also associated with improved quality of life and Oswestry Disability Index and lower complication profiles.

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.

Posterior-based Osteotomies for Deformity Correction.

Posterior-based osteotomies are crucial to the restoration of lordosis in adult spinal deformity. Posterior-column osteotomies are suited for patients with an unfused anterior column and non-focal sagittal deformity requiring modest correction in lordosis. When performed on multiple levels, posterior-column osteotomy may provide significant harmonious correction in patients who require more extensive correction. Pedicle subtraction osteotomy and vertebral column resection are appropriate for patients with a fused anterior column and more severe deformity, particularly focal and/or multiplanar deformity. The power of pedicle subtraction osteotomy and vertebral column resection to provide greater correction and to address multiplanar deformity comes at the cost of higher complication rates than posterior-column osteotomy.

The MIS PSO.

The MIS PSO is a hybrid approach using less-invasive surgical approaches combined with traditional open spinal deformity techniques for the treatment of adult spinal deformities. The MIS PSO allows for the correction of spinal deformities in the coronal and sagittal planes, even in the fixed spine, and simultaneously mitigating the morbidity of traditional open surgery by preserving the soft tissues and minimizing blood loss. This article discusses the surgical steps of the MIS PSO and reviews our experience.

Thoracic pediculectomy for acute spinal cord decompression in high-risk spinal deformity correction: illustrative case.

BACKGROUND: Neurological complications are higher in patients with severe spinal deformities (Cobb angle >100°). The authors highlight a known technique for thoracic concave apical pedicle resection that is useful for spinal cord decompression in patients with high-risk spinal deformities in the setting of intraoperative neuromonitoring (IONM) changes. OBSERVATIONS: A 14-year-old female with progressive idiopathic scoliosis presented for evaluation of her clinical deformity. Scoliosis radiographs showed a double major curve pattern comprising a 107° right main thoracic curve and a compensatory 88° left thoracolumbar curve. She underwent 2 weeks of halo-gravity traction that reduced her major thoracic curve to 72°. During thoracic posterior column osteotomies, the authors were alerted to decreases in IONM signals that were not responsive to increases in mean arterial pressure, traction weight reduction, and convex compression maneuvers. The dural surface was tightly draped over the two thoracic apical pedicles of T7 and T8, so emergent pediculectomies were performed at both levels for spinal cord decompression. IONM signals gradually improved and eventually became even better than baseline. The patient woke up without any neurological deficits. LESSONS: Pediculectomy of the concave apical pedicle(s) should be considered for spinal cord decompression if there are IONM changes during high-risk spinal deformity surgery.

Is the pelvic incidence a determinant factor for kyphosis curve patterns of ankylosing spondylitis patients?

To investigate the influence of pelvic incidence (PI) on the kyphosis curve patterns and clinical outcomes in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis and to construct a classification of AS according to the PI value for surgical decision-making. 107 AS patients underwent single-level lumbar pedicle subtraction osteotomy (PSO) and finished a minimal of 2-year follow-up. All patients were divided into three groups: low PI (PI ≤ 40°), moderate PI (40° < PI ≤ 60°), and high PI (PI > 60°). Standing lateral radiographs were taken to evaluate the location of kyphotic apex, thoracic kyphosis (TK), lumbar lordosis (LL), C7 sagittal vertical axis (SVA), spino-sacral angle (SSA), global kyphosis (GK), PI, sacral slope (SS), and pelvic tilt (PT). Visual Analogue Scale (VAS) score, Oswestry Disability Index (ODI) and Bath Ankylosing Spondylitis Functional Index (BASFI) were used to evaluate quality of life. Before surgery, a significant difference was shown in the average LL and the mean GK in high PI group was the largest among the three groups. Correction of SVA, GK and LL in high PI group was the smallest among the three group. No significant difference in clinical outcomes was found among the three groups before surgery and at the final follow-up. Regarding the preoperative sagittal profile, the kyphosis curve pattern of moderate PI group is similar to that of low PI group. For AS patients in these two groups, harmonious sagittal alignment can be restored by a single-level PSO. However, the sagittal imbalance is insufficiently realigned by a single-level PSO in a patient with high PI.