Introduction: Pedicle screw malposition is a serious complication in AIS surgeries. We report the accuracy and safety of a novel medial wall glide technique for pedicle screw insertion. Methods: 157 AIS patients were retrospectively reviewed. In this technique, the pedicle probe was advanced approximately 15mm deep and used to feel / glide along the medial aspect of the pedicle wall before advancing into the vertebral body. Dysplastic pedicles (type C and D) were excluded. Patients underwent computed tomography to evaluate screw placement at 4-6 months postoperatively. Screw perforation was classified into grade 0 (no violation), grade 1 (<2mm perforation), grade 2 (2–4mm), and grade 3 (>4 mm) (Rao et al. (2002)). Anterior perforations were classified into grade 0 (no violation), grade 1 (<4mm perforation), grade 2 (4–6mm), and grade 3 (>6mm). Results: 1595 screws were analyzed. When the lateral perforations of T1-T12 region were excluded, the overall perforation was 11.3% with 10.3% grade 1, 0.9% grade 2 and 0.1% grade 3 perforations. Highest perforation rate was at L1-L2 regions (22.4% and 20.8%, respectively). Critical (i.e., grade 2 and grade 3) perforation rate was 1.0% (15 perforations/1595 screws). Among the critical perforations, medial, lateral, anterior and inferior perforation rates were 60% (9/15 perforations), 20% (3/15 perforations), 20% (3/15 perforations) and 0%, respectively. There was neither neurologic complications nor abutment to vital structures noted. Conclusion: Overall perforation rate in the medial wall glide technique was 11.3%. Highest perforation rate was at L1-L2. Critical perforation rate was 1.0%.

Introduction: A short-segment pedicle instrumentation (SSPI) with an intermediate screw at the fracture level might offer a solution for intraoperative correction for traumatic thoracolumbar burst fractures (TBF), preventing implant failure and a satisfactory functional outcome. Aim of the study was to evaluate the efficacy of an additional pedicle screw at the fractured vertebra in SSPI for sagittal deformity correction and anterior fractured vertebra height restoration. Methods: Sixty-six patients (76% males, mean age 44 years) were diagnosed with TBF and surgically treated between 2009 and 2019. Patients were divided in two groups: group A patients treated with SSPI with an additional screw at fractured vertebra; group B patients treated with traditional long-segment pedicle instrumentation (LSPI). Pre and post-operative images (X-Rays and CT scan) were analyzed collecting vertebral body height (AFVH), anterior kyphosis angle (AKAFV) and local kyphosis angle (LKA) at the time of the trauma, one days after surgery and at 1-year follow-up. Results: According to Magerl’s classification, 71% of TBF was type A, and half of patients had no neurological deficits (ASIA E). There was a significant statistical difference (p<0.05) between the two groups in all post-operative measures (AKAFV, AFVH, LKA). Kaplan-Mayer survival analyses show that maintenance of local kyphosis correction between two groups is better achieved in thoraco-lumbar junction injury. Conclusions. Reinforcement of the fractured vertebra in SSPI by the placement of an intermediate additional screw is an effective method to correct and maintain sagittal post-traumatic deformity, anterior vertebral height and anterior kyphosis angle of the injured vertebral segment.

Introduction: Accurate prediction of operative duration is necessary for efficient operating room scheduling, minimizing surgical cancellations, and shortening surgical waitlists amongst other advantages. Prolonged operative duration is also associated with negative patient outcomes. The purpose of the study was to identify the various patient-specific, procedure-specific, and surgeon-specific variables which influence the operative duration in PSF for AIS, and determine its impact on early postoperative outcomes. Methods: Hospital records of 130 AIS patients who underwent PSF at a single center were retrospectively reviewed. Various patient-specific, procedure-specific, and surgeon-specific variables – deemed to be possibly affecting the operative duration – were analyzed. The association between each variable and the operative duration was assessed. A multivariate regression model was used to identify independent predictors of operative duration. The association between operative duration and selected early postoperative outcome measures was determined. Results: The final model obtained included the following factors: experience of the chief surgeon (β = -0.36; β = standardized regression coefficient), Cobb angle (β = 0.35), number of screws inserted (β = 0.28), coronal deformity angular ratio (β = 0.20) and extension of the construct to pelvis (β = 0.15). The model could explain 41% of variability in the operative duration (R2 = 0.41). The operative duration had a significant correlation with estimated blood loss, need for perioperative blood transfusion, and LOS. Conclusions: The experience of the chief surgeon and severity of the curve was determined to be the strongest predictors of the variability of the operative duration during PSF in AIS.

Introduction:
Vertebral body tethering (VBT) has shown improvements in coronal and sagittal planes, but axial correction overtime has not been assessed in adolescent idiopathic scoliosis (AIS) patients. Three-dimensional (3D) spine reconstruction was used to analyse the progression of correction in VBT surgery.

Methods:
VBT treated AIS patients, ≥ 1-year of follow-up, and 3D spine reconstructions created from biplanar radiographs were studied. Coronal, sagittal, and axial planes measurements were made and compared at pre-operative, immediate post-operative, 1-year and 2-years follow-up.

Results:
Seven patients (6 female, 1 male) with a mean age of 13.1 ± 1.1 years with right thoracic AIS (mean, 50.2º ± 8.7º) had a mean follow-up of 18.6 ± 4.6 months. Based on 3D reconstruction, the mean coronal Cobb angle correction was 29.7º, 21.2º and 15.5º for immediate post-op, 1-year and 2-years follow-up, respectively. There was minimal change in thoracic kyphosis and lumbar lordosis, which measured 36.2º, 38.6º, 34.8º and 40.9º for kyphosis; 47.1º, 44.0º, 41.8º and 48.5º for lordosis at preop, immediate post-op, 1-year and 2-years follow up. Apical axial rotation improved from pre-operative -4.9º (± 5.0) to immediate postop of -0.5º (± 4.5º) then deteriorated to -2.5º (± 4.5º) at 1 year.

Conclusion:
This is the first 3D reconstructed VBT study to describe progression in axial rotation correction despite improvement in coronal curvature and suggests that VBT may not be able to control changes in axial plane. More studies with larger samples and longer-term follow-up are needed to investigate axial correction overtime in VBT patients.

Background: Decompressing the spinal canal is of utmost importance in unstable burst fractures that are characterized by significant canal compromise by the retropulsed bone fragments. Besides subsiding the bone fragments anteriorly, partial corpectomy is one effective way of decompressing the canal especially when there is severe comminution . Complications like late fusion and cage subsidence are reduced and satisfactory clearance can be maintained. Through our study, we bring forth the efficacy of partial corpectomy in canal clearance for thoracolumbar burst fractures and we analyze the decompression achieved using a novel CT based area method which is nowhere described and is more precise than using the anteroposterior diameter as a reference.Objective: To assess canal clearance achieved following partial corpectomy in thoracolumbar burst fractures. Materials and methods: We evaluated 10 patients with thoracolumbar burst fractures who underwent partial corpectomy. Preoperative and postoperative CT scans in the immediate post op period and at 6 month follow up were done to measure canal clearance achieved. Neurological assessment was done at the above-mentioned time periods using ASIA score.Results: In 8 out of 10 patients ,100% canal decompression was achieved and maintained at 6 month follow up. Rest 2 patients too had greater than 95% clearance. No complications like cage subsidence or implant failure were observed and most of the patients had improvement of atleast 1 ASIA grade.Conclusions: Partial corpectomy achieves better canal clearance which can be precisely assessed using the area method. Complications like subsidence and graft failure are rarely seen.

Introduction: Arthrodesis has always been considered the main treatment of degenerative lumbar disease. Adjacent segment degeneration is one of the major topics related to fusion surgery. Non fusion surgery may prevent this because of the protective effect of persisting segmental motion. Aims were to describe the radiological outcomes in the adjacent vertebral segment after lumbar stabilization with DSS-HPS® system and verify the hypothesis that this system prevents the degeneration of the adjacent segment. Methods: Twenty-seven patients affected by degenerative lumbar disease underwent spinal hybrid stabilization with the DSS-HPS® system between January 2016 and January 2019. All patient completed 1-year radiological follow-up. Preoperative X-rays and magnetic resonance images, as well as postoperative radiographs at 1, 6 and 12 months were evaluated by one single observer. Pre- and postoperative anterior and posterior disc height at the dynamic (DL) and adjacent level (AL) were measured, relative lordotic angle (LA) of the dynamized level were measured. Results: There was a statistically significant decrease of both anterior (p=.0003 for the DL, p=.036 for the AL) and posterior disc height (p=.00000 for the DL, p=.00032 for the AL); there were a statistically significant variations of the relative lordotic angle (p=.00000). Eleven cases (40.7%) of radiological progression of disc degeneration were found. Conclusions: DSS-HPS® system is associated with high rate of progression of lumbar disc degeneration, both in the dynamized and adjacent level.

Introduction: The gold standard for surgical management Adolescent idiopathic scoliosis (AIS) patients remains spinal fusion, but recently non-fusion anterior scoliosis correction (NFASC) has gained interest. NFASC is a fusionless revolutionary motion preserving treatment method for surgical management of AIS, but the technique is novel and there is a visible dearth in clinical data related to the procedure. This study evaluates the radiological and clinical outcomes NFASC in patients with AIS. Methods: 45 AIS cases who underwent the NFASC with a mean 26±12.1months (12-48) follow-up, managed for structural major curve, between 40oand 80ohaving >50% flexibility on dynamic x-rays. Data collected include skeletal maturity, curve type, cobb angle and patient outcomes SRS-22 questionnaire. A Post hoc analysis following repeated measures ANOVA test was used to examine statistically significant trends. Results: 45 patients(43F,2M) with a mean age of 14.96 ±2.69 years were included. The mean Risser score and Sanders’s score was 4.22 ± 0.7 and 7.15 ±0.74 respectively. The mean Main thoracic (MT) Cobb angle at first follow-up (17.2 ± 5.36) and last follow-up (16.92 ± 5.06) were lower than the preoperative cobb angle (52.11 ± 7.74) (p<0.05). Mean Thoracolumbar/lumbar (TL/L) cobb angle at first follow-up (13.48 ± 5.11) and last follow-up (14.24 ±4.85) lower than the preoperative TL/L cobb angle (51.45 ±11.26). None of the patient had any complications till the recent follow up. Conclusion: NFASC offers promising correction and stabilization of curve progression in AIS with a low risk profile and proves to be a favorable alternative to fusion modality.

Introduction: AIS can affect both females and males. Males had been reported to have higher risk for corrective surgery. Methods: Patients were divided into group 1: male and group 2: female. Preoperative data collected were age, height, weight, body mass index, Lenke curve classification, preoperative Cobb angle, and preoperative flexibility. Intraoperative data collected were operation duration, intraoperative blood loss (IBL), amount of salvaged blood, number of patients required transfusion, number of screws and fusion level. Postoperative data collected were postoperative haemoglobin, postoperative Cobb angle, correction rate, length of postoperative hospital stay, and complications were also traced. PSM analysis was performed with match tolerance of 0.005 with nearest neighbour matching technique. Results: A total of 570 patients (84 male, 486 female) were recruited. When comparing between male and female patients before PSM analysis, age, height, weight, and fusion level showed significant difference (p <0.05). After PSM analysis, we found that there was no difference in the perioperative outcome parameters. When we matched patients excluding height and weight, we found that male patients had significantly longer wound, higher IBL and more blood salvaged from cell saver. When we matched patients excluding fusion levels, we found that male patients had significantly higher IBL. When we matched patients excluding age, we found no significant differences. Conclusions: In non-matched patients, surgeries were higher risk in males due to taller height, heavier weight, and longer fusion levels. However, after PSM, there was no difference in all perioperative outcomes for both groups.

Introduction: The Optimal UIV Tilt Angle was originally derived from the supervised supine side bending films and had good correlation with post-operative shoulder balance. Methods: The post-operative UIV tilt angle (minimum 2 years follow up) that was measured in 133 Lenke 1 & 2 AIS patients who underwent posterior spinal fusion (PSF) surgery and had good medial shoulder balance (T1 tilt measurement between -3⁰ and +3⁰) was considered the Optimal UIV Tilt Angle. Patients with distal adding-on phenomenon, coronal imbalance or lumbar decompensation were excluded. Pre-operative parameters such as clavicle angle (Cla-A), cervical axis, coronal balance, T1 tilt angle, UIV tilt angle, UIV level, Cobb angle, side-bending cobb angle and flexibility rate were included as predictors. Independent factors with p<0.05 from multivariate analysis were used to formulate the regression formula. Results: There were 118(88.7%) females, 15(11.3%) male patients, 99 Lenke 1 patients (74.4%) and 34 Lenke 2 patients (25.6%), respectively. Mean follow-up duration was 3.2 ± 0.7 years. The significant predictors from the pre-operative erect radiograph were pre-operative UIV tilt angle (β=0.396, p<0.001) and pre-operative T1 tilt angle (β=-0.349, p<0.001). A regression formula with an R2 value of 0.583 was derived. The regression formula for Optimal UIV Tilt Angle was [(0.396 x pre-operative UIV tilt angle) – (0.349 x pre-operative T1 tilt angle) – 0.871]. Conclusions: The Optimal UIV Tilt Angle can be predicted with the formula: [(0.396 x pre-operative UIV tilt angle) – (0.349 x pre-operative T1 tilt angle) – 0.871] with a R2 value of 0.583.