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Study Design: A retrospective, multicenter study., Objective: To identify risk factors for proximal junctional kyphosis (PJK) when treating early-onset scoliosis (EOS) with dual-rod growing-rod (GR) procedure., Summary of Background Data: The risk factors for PJK associated with GR treatment for EOS have not been adequately studied., Methods: We evaluated clinical and radiographic results from 88 patients with EOS who underwent dual-rod GR surgery in 12 spine centers in Japan. The mean age at the time of the initial surgery was 6.5±2.2 years (range, 1.5-9.8 y), and the mean follow-up period was 3.9±2.6 years (range, 2.0-12.0 y). Risk factors for PJK were analyzed by binomial multiple logistic regression analysis. The potential factors analyzed were sex, etiology, age, the number of rod-lengthening procedures, coronal and sagittal parameters on radiographs, the type of foundation (pedicle screws or hooks), the uppermost level of the proximal foundation, and the lowermost level of the distal foundation., Results: PJK developed in 23 patients (26%); in 19 of these, the proximal foundation became dislodged following PJK. Binomial multiple logistic regression analysis identified the following significant independent risk factors for PJK: a lower instrumented vertebra at or cranial to L3 [odds ratio (OR), 3.32], a proximal thoracic scoliosis of ≥40 degrees (OR, 2.95), and a main thoracic kyphosis of ≥60 degrees (OR, 5.08)., Conclusions: The significant independent risk factors for PJK during dual-rod GR treatment for EOS were a lower instrumented vertebra at or cranial to L3, a proximal thoracic scoliosis of ≥40 degrees, and a main thoracic kyphosis of ≥60 degrees.

Flattening of the preimplantation rod contour in the sagittal plane influences thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. The effects of multilevel facetectomy and screw density on postoperative changes in spinal rod contour have not been documented. This study aimed to evaluate the effects of multilevel facetectomy and screw density on changes in spinal rod contour from before implantation to after surgical correction of thoracic curves in patients with AIS prospectively. The concave and convex rod shapes from patients with thoracic AIS (n = 49) were traced prior to insertion. Postoperative sagittal rod shape was determined by computed tomography. The angle of intersection of the tangents to the rod end points was measured. Multiple stepwise linear regression analysis was used to identify variables independently predictive of change in rod contour (Δθ). Average Δθ at the concave and convex side were 13.6° ± 7.5° and 4.3° ± 4.8°, respectively. The Δθ at the concave side was significantly greater than that of the convex side (P < 0.0001) and significantly correlated with Risser sign (P = 0.032), the preoperative main thoracic Cobb angle (P = 0.031), the preoperative TK angle (P = 0.012), and the number of facetectomy levels (P = 0.007). Furthermore, a Δθ at the concave side ≥14° significantly correlated with the postoperative TK angle (P = 0.003), the number of facetectomy levels (P = 0.021), and screw density at the concave side (P = 0.008). Rod deformation at the concave side suggests that corrective forces acting on that side are greater than on the convex side. Multilevel facetectomy and/or screw density at the concave side have positive effects on reducing the rod deformation that can lead to a loss of TK angle postoperatively., Competing Interests: The authors have declared that no competing interests exist.

Purpose: There is limited consensus on the optimal surgical strategy for double thoracic adolescent idiopathic scoliosis (AIS). Recent studies have reported that pedicle screw constructs to maximize scoliosis correction cause further thoracic spine lordosis. The objective of this study was to apply a new surgical technique for double thoracic AIS with rigid proximal thoracic (PT) curves and assess its clinical outcomes., Methods: Twenty one consecutive patients with Lenke 2 AIS and a rigid PT curve (Cobb angle ≥30º on side-bending radiographs, flexibility ≤30 %) treated with the simultaneous double-rod rotation technique (SDRRT) were included. In this technique, a temporary rod is placed at the concave side of the PT curve. Then, distraction force is applied to correct the PT curve, which reforms a sigmoid double thoracic curve into an approximate single thoracic curve. As a result, the PT curve is typically converted from an apex left to an apex right curve before applying the correction rod for PT and main thoracic curve., Results: All patients were followed for at least 2 years (average 2.7 years). The average main thoracic and PT Cobb angle correction rate at the final follow-up was 74.7 and 58.0 %, respectively. The average preoperative T5-T12 thoracic kyphosis was 9.3°, which improved significantly to 19.0° (p < 0.0001) at the final follow-up. Although 71 % patients had preoperative level shoulders or a positive radiographic shoulder height, all patients had mildly imbalanced or balanced shoulders at the final follow-up. The average preoperative main thoracic apical vertebral rotation angle of 20.7° improved significantly after surgery to 16.4° (p = 0.0046), while the average preoperative total SRS questionnaire score of 3.7 improved significantly to 4.4 (p = 0.0012) at the final follow-up., Conclusions: Radiographic findings and patient outcomes were satisfactory. Thoracic kyphosis can be maintained or improved, while coronal and axial deformities can be corrected using SDRRT for Lenke 2 AIS with a rigid PT curve.

Study Design: Retrospective analysis of a prospectively collected, consecutive, nonrandomized series of patients., Objective: To assess the surgical outcomes of the simultaneous double-rod rotation technique for treating Lenke 1 thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: With the increasing popularity of segmental pedicle screw spinal reconstruction for treating AIS, concerns regarding the limited ability to correct hypokyphosis have also increased., Methods: A consecutive series of 32 patients with Lenke 1 main thoracic AIS treated with the simultaneous double-rod rotation technique at our institution was included. Outcome measures included patient demographics, radiographical measurements, and Scoliosis Research Society questionnaire scores., Results: All 32 patients were followed up for a minimum of 2 years (average, 3.6 yr). The average main thoracic Cobb angle correction rate and the correction loss at the final follow-up were 67.8% and 3.3°, respectively. The average preoperative thoracic kyphosis (T5-T12) was 11.9°, which improved significantly to 20.5° (P < 0.0001) at the final follow-up. An increase in thoracic kyphosis was significantly correlated with an increase in lumbar lordosis at the final follow-up (r = 0.42). The average preoperative vertebral rotation angle was 19.7°, which improved significantly after surgery to 14.9° (P = 0.0001). There was no correlation between change in thoracic kyphosis and change in apical vertebral rotation (r =-0.123). The average preoperative total Scoliosis Research Society questionnaire score was 3.0, which significantly improved to 4.4 (P < 0.0001) at the final follow-up. Throughout surgery and even after, there were no instrumentation failures, pseudarthrosis, infection of the surgical site, or clinically relevant neurovascular complications., Conclusion: The simultaneous double-rod rotation technique for treating Lenke 1 AIS provides significant sagittal correction of the main thoracic curve while maintaining sagittal profiles and correcting coronal and axial deformities., Level of Evidence: 4.

Study Design: Retrospective review., Objective: To assess the long-term outcomes of anterior spinal fusion (ASF) for treating thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: Although ASF is reported to provide good coronal and sagittal correction of the main thoracic (MT) AIS curves, the long-term outcomes of ASF is unknown., Methods: A consecutive series of 25 patients with Lenke 1 MT AIS were included. Outcome measures comprised radiographical measurements, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores (preoperative SRS-30 scores were not documented). Postoperative surgical revisions and complications were recorded., Results: Twenty-five patients were followed-up for 12 to 18 years (average, 15.2 yr). The average MT Cobb angle correction rate and the correction loss at the final follow-up were 56.7% and 9.2°, respectively. The average preoperative instrumented level of kyphosis was 8.3°, which significantly improved to 18.6° (P = 0.0003) at the final follow-up. The average percent-predicted forced vital capacity and forced expiratory volume in 1 second were significantly decreased during long-term follow-up measurements (73% and 69%; P = 0.0004 and 0.0016, respectively). However, no patient had complaints related to pulmonary function. The average total SRS-30 score was 4.0. Implant breakage was not observed. All patients, except 1 who required revision surgery, demonstrated solid fusion. Late instrumentation-related bronchial problems were observed in 1 patient who required implant removal and bronchial tube repair, 13 years after the initial surgery., Conclusion: Overall radiographical findings and patient outcome measures of ASF for Lenke 1 MT AIS were satisfactory at an average follow-up of 15 years. ASF provides significant sagittal correction of the main thoracic curve with long-term maintenance of sagittal profiles. Percent-predicted values of forced vital capacity and forced expiratory volume in 1 second were decreased in this cohort; however, no patient had complaints related to pulmonary function.

Study Design: A retrospective, multicenter study., Objective: To investigate the occurrence of and factors related to postoperative adding-on in Lenke type 1A curve., Summary of Background Data: Although several studies have investigated factors associated with adding-on in Lenke type 1A curve, these factors have not been elucidated in a large study population., Methods: This study included 112 patients who were followed more than 2 years after undergoing selective posterior thoracic fusion surgery for Lenke Type 1A curve (8 males, 104 females; mean age at surgery, 16.1 yr; mean follow-up, 3.6 yr). The lower instrumented vertebra (LIV) was T12 in 22 patients, L1 in 55, L2 in 32, and L3 in 3. Distal to the main thoracic curve, the end vertebra, neutral vertebra, stable vertebra (SV), and the last vertebra touching the central sacral vertical line (last touching vertebra, LTV) were determined. The occurrence and factors associated with distal adding-on were investigated., Results: The mean Cobb angle and apical translation of the main thoracic curve were 54.6° ± 9.6° and 53.1 ± 20.4 mm before surgery, and 14.2 ± 7.4 and 16.2 ± 12.7 at follow-up, respectively. Distal adding-on was observed in 21 patients (18.8%) at follow-up. Univariate analyses identified several factors significantly associated with adding-on, including the preoperative proximal thoracic curve, the apical translation of the main thoracic curve, Miyanji's subclassification, the postsurgical proximal and main thoracic curves, the postsurgical apical translation of the main thoracic curve, the correction rate of the main thoracic curve and the clavicle angle immediately after surgery and at follow-up, and the difference in levels between the LIV and the end vertebra, neutral vertebra, LTV, and stable vertebra. Logistic regression analysis showed that the apical translation of the main thoracic curve immediately after surgery (apical translation >25 mm, odds ratio: 10.7, 95% confidence interval: 3.1-37.0, P = 0.001) and the difference in levels between LIV and LTV (LIV-LTV) (LIV-LTV <0, odds ratio: 6.7, 95% confidence interval: 1.9-23.9, P = 0.003) were significantly associated with adding-on., Conclusion: Since the residual apical translation of the main thoracic curve and the lowest instrumented vertebra more cranial to the last touching vertebra were significantly associated with adding-on, surgeons may need to obtain the maximum reduction of the apical translation of the main thoracic curve and to extend the LIV at least to the LTV to avoid postoperative adding-on.

Background: Anterior spinal fusion with instrumentation is used for the treatment of thoracolumbar/lumbar scoliosis. The aim of this long-term, retrospective, hospital-based cohort study was to determine the outcomes of anterior dual-rod instrumentation in a consecutive series of patients with thoracolumbar/lumbar adolescent idiopathic scoliosis managed by a single surgeon at a single institution., Methods: A consecutive series of thirty-two patients with Lenke type-5C thoracolumbar/lumbar adolescent idiopathic scoliosis were included. Outcome measures included patient demographics, radiographic measurements, adjacent-segment degeneration, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores. Perioperative and postoperative complications were recorded., Results: Thirty patients were followed for a mean of 17.2 years (range, twelve to twenty-three years). The mean thoracolumbar/lumbar Cobb angle correction rate and correction loss at the time of the latest follow-up were 79.8% and 3.4°, respectively. The average percent-predicted forced vital capacity and forced expiratory volume in one second were 91.8% and 81.8%, respectively. The average total SRS-30 score was 4.2. Mild degeneration below the fusion mass was observed in 23% of the patients. No instrumentation failure, pseudarthrosis, surgical site infection, or clinically relevant neurovascular complications were observed. Two patients required surgical revision with posterior spinal instrumentation, one because of subjacent disc wedging and the other because of progression of the thoracic curve deformity., Conclusions: Radiographic findings, pulmonary function, and clinical measures were satisfactory at the time of follow-up, at a minimum of twelve years. Anterior dual-rod instrumentation remains a useful surgical treatment for Lenke type-5C thoracolumbar/lumbar adolescent idiopathic scoliosis.

Object: Use of computer-assisted spine surgery (CASS) technologies, such as navigation systems, to improve the accuracy of pedicle screw (PS) placement is increasingly popular. Despite of their benefits, previous CASS systems are too expensive to be ubiquitously employed, and more affordable and portable systems are desirable. The aim of this study was to introduce a novel and affordable computer-assisted technique that 3-dimensionally visualizes anatomical features of the pedicles and assists in PS insertion. The authors have termed this the 3D-visual guidance technique for inserting pedicle screws (3D-VG TIPS)., Methods: The 3D-VG technique for placing PSs requires only a consumer-class computer with an inexpensive 3D DICOM viewer; other special equipment is unnecessary. Preoperative CT data of the spine were collected for each patient using the 3D-VG TIPS. In this technique, the anatomical axis of each pedicle can be analyzed by volume-rendered 3D models, as with existing navigation systems, and both the ideal entry point and the trajectory of each PS can be visualized on the surface of 3D-rendered images. Intraoperative guidance slides are made from these images and displayed on a TV monitor in the operating room. The surgeon can insert PSs according to these guidance slides. The authors enrolled 30 patients with adolescent idiopathic scoliosis (AIS) who underwent posterior fusion with segmental screw fixation for validation of this technique., Results: The novel technique allowed surgeons, from office or home, to evaluate the precise anatomy of each pedicle and the risks of screw misplacement, and to perform 3D preoperative planning for screw placement on their own computer. Looking at both 3D guidance images on a TV monitor and the bony structures of the posterior elements in each patient in the operating theater, surgeons were able to determine the best entry point for each PS with ease and confidence. Using the current technique, the screw malposition rate was 4.5% in the thoracic region in corrective surgery for AIS., Conclusions: The authors found that 3D-VG TIPS worked on a consumer-class computer and easily visualized the ideal entry point and trajectory of PSs in any operating theater without costly special equipment. This new technique is suitable for preoperative planning and intraoperative guidance when performing reconstructive surgery with PSs.

Study Design: Case report., Objective: To report an extremely rare case of hematoma derived from the ligamentum flavum within the thoracic spine., Summary of Background Data: Only one previous case has been reported of a hematoma derived from the ligamentum flavum in the thoracic spine. METHODS.: A 61-year-old man presented with gait disturbance and numbness below the navel. Magnetic resonance imaging on the 16th day after the onset of the symptoms showed spinal cord compression at the T10-T11 level caused by a round mass. This intraspinal, extradural space occupying lesion, continuous with ligamentum flavum was centrally hypointense and marginal hyperintense on a T1-weighted image and central heterogeneous and marginal hypointense on a T2-weighted image. The wall of the lesion was slightly enhanced after use of a contrast medium., Results: The patient underwent a T10 laminectomy and the mass was carefully resected from the dura mater. Histologic examination showed that the wall of the mass comprised fibrous connective tissue that contained elastic fibers derived from a degenerative ligamentum flavum tear. It also revealed that evidence of previous hemorrhagic events within the mass. There was no evidence of neoplastic nor synovial tissue. After surgery, the patient's numbness and gait disturbance disappeared., Conclusion: This report identifies an extremely rare case of spinal cord compression by a hematoma from the ligamentum flavum within the thoracic spine.

Study Design: A retrospective review., Objective: This study examined the clinical outcomes of circumferential spinal cord decompression through a posterior approach for thoracic ossification of posterior longitudinal ligament (OPLL), to determine the efficacy of this procedure and the incidence of complications., Summary of Background Data: Since posterior decompressive laminectomy is not always effective in the treatment of thoracic myelopathy caused by OPLL, circumferential spinal cord decompression through a single posterior approach seems to offer an effective treatment option. However, this procedure is technically demanding and has a high risk of postoperative neurologic deterioration. Long-term clinical outcome data and complication rates of this procedure are not well covered in the literature., Methods: Medical records of sequentially treated 30 patients, who had undergone circumferential spinal cord decompression through a single posterior approach, were reviewed to determine demographic data, neurologic examination, imaging findings, surgical procedure, and follow-up data. The Japanese Orthopedic Association (JOA) score was used to assess physical dysfunction and neurologic impairment., Results: The mean follow-up period was 8 years; the average operative time was 389 minutes; the mean blood loss was 1883 mL. An average of 4-level spinal cord decompression was performed on all 30 patients. Posterior spinal fusion was performed on 26 of the 30 patients. The mean preoperative JOA score was 3.4/11, and it improved to an average of 7.1/11 at final evaluation. Clinical symptoms and the JOA score improved in 24 patients, but were unchanged or worsened in the other 6 patients compared to the preoperative conditions. Surgical complications included dural tear in 12 patients (40%), deep infection in 3 (10%), and postoperative neurologic deterioration in 10 (33%). Statistical analysis showed that a risk factor associated with the unfavorable surgical outcomes was multiple level circumferential spinal cord decompression of 5 or more vertebral levels., Conclusion: Despite circumferential spinal cord decompression through posterior approach for thoracic OPLL providing effective neurologic recovery, there was a high rate of complications such as postoperative neurologic deterioration. Risk factor analysis shows that multiple level circumferential decompression of 5 or more vertebral levels to be associated with unfavorable surgical outcome.

Study Design: Clinical results of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage for pyogenic spondylodiscitis were analyzed., Objectives: To report clinical results of transforaminal endoscopic surgery for pyogenic spondylodiscitis and to evaluate the effectiveness of this procedure in treatment of pyogenic spinal infections., Summary of Background Data: Pyogenic spinal infections have been increasing due to the development of medical treatment for patients with comorbid medical problems. Common treatments for spinal infections are administration of antibiotics or surgical debridement with bone grafts. There have been no reports, however, regarding the clinical outcome of posterolateral endoscopic treatment for pyogenic spinal infections., Methods: Fifteen consecutive patients with pyogenic spondylodiscitis in the thoracic or lumbar spine were enrolled. Preoperative antibiotic treatment had failed in all the patients. The procedures consisted of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage through single portal under the combination of local and intravenous anesthesia. Pain response using visual analog scale (VAS, 0-100 mm), inflammation parameters, and duration of antibiotic therapy were investigated. Radiologic evaluation focused on bony fusion, local kyphosis, disc height reduction, and abscess formation., Results: All patients showed immediate pain reduction after surgery. Averaged VAS for pain was 86 before surgery and 25 at postoperative 1 week. Average of CRP was 4.00 mg/dL before surgery and 1.88 mg/dL at postoperative 1 week. Averaged duration of antibiotics therapy was 3.7 weeks. Spinal fusion was obtained in 13 patients. Two patients with neurologic deficits due to epidural abscess returned to normal. Preoperative psoas abscess in 6 patients disappeared after surgery on MRI., Conclusions: Posterolateral spinal endoscopic debridement and irrigation brought immediate pain reduction and good clinical results to patients who had comorbid medical problems and had pyogenic spondylodiscitis.

Study Design: This is a biomechanical study using sheep thoracic spine to investigate the probability of mechanical failure of the thoracic spine with various sizes or locations of tumor metastasis., Objective: The objectives of this study were to investigate biomechanical effects of not only tumor sizes within the thoracic vertebral body but also its involvement of other spinal components on the probability of mechanical failures of the thoracic spine., Summary of Background Data: There have been no experimental studies concerning mechanical influences of destruction of costovertebral joint or posterior elements as well as vertebral body on the load-bearing capacity of the thoracic spine., Methods: Ninety-nine fresh sheep thoracic spine specimens with ribs were used (T7-T9, T10-T12). Within vertebral bodies of 39 specimens, only trabecular defects were created in different sizes. In other 48 specimens, not only vertebral body defects that were 40% to the cross-sectional area of the vertebral body but also additional destruction of costovertebral joint, pedicle, and facet joint were created. All specimens were subjected to destructive biomechanical testing., Results: The failure load decreased as the defect size in the vertebral body increased. A negative linear correlation was observed between the failure load and the size of vertebral body defect (r = 0.782). With 40% cross-sectional defect in the vertebral body, additional costovertebral joint destruction brought 25% reduction of the failure load, which was statistically significant., Conclusion: The load-bearing capacity of metastasized vertebrae in the thoracic spine was proportionally decreased when the defect size in the vertebral body increased. Destruction of costovertebral joint significantly increased the probability of vertebral collapse.

Abstract: Background context: With the increase of the elderly population, osteoporotic vertebral fractures have been frequently reported. Surgical intervention is usually recommended in osteoporotic vertebral collapse with neurologic deficits. However, very few reports on surgical interventions exist. Purpose: To compare surgical results of anterior and posterior procedures for treating osteoporotic thoracolumbar vertebral collapse with sustained neurologic deficits. Study design: Retrospective comparative study. Patient sample: Fifty patients who sustained osteoporotic thoracolumbar vertebral collapse with neurologic deficits were treated either by anterior decompression and strut graft (n=32) or by posterior decompression and pedicle screw fixation with vertebroplasty (n=18). Outcome measures: Incidence of complications, sagittal Cobb angle, spinal canal encroachment, and Japanese Orthopedic Association score. Methods: The authors retrospectively reviewed the results of a consecutive series of patients undergoing anterior decompression and strut graft or posterior decompression and pedicle screw fixation with vertebroplasty for osteoporotic thoracolumbar vertebral collapse with neurologic deficits. Operative notes, clinical charts, and radiographs were analyzed. Results: Operative time was similar between the groups, but intraoperative blood loss was significantly lower in the posterior group. All patients showed neurologic recovery. No significant difference was observed in the neurologic improvement, kyphosis correction angle, and loss of correction. Perioperative respiratory complications were found in 11 patients (34%) in the anterior group. In the anterior group, early posterior reinforcement was required in patients with very low bone density below 0.60 g/cm2 and/or in those with three segments of instrumentation for two vertebral collapses. Posterior group patients did not undergo additional surgery. Conclusions: Anterior reconstruction for osteoporotic vertebral collapse is significant because anterior elements, particularly those at the thoracolumbar junction, play a major role in load bearing. However, difficulties arise when anterior reconstruction is performed in cases with very low bone density and in those with multiple vertebral collapse. [Copyright &y& Elsevier]

The article provides an analysis of pedicle srew placement accuracy in posterior scoliosis surgery when compared to surgical techniques that are computer-assisted and conventional fluoroscopic. It involves 45 patients who were divided into two groups such as Group C as manual control with 25 patients and Group N as navigation surgery with 20 patients. It concludes that the Group C medial perforation happened around L1 when pedicle axis advanced towards anteroposterior sacral axis.

Background Context: Controversy exists regarding the effects of multilevel facetectomy and screw density on deformity correction, especially thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery.Purpose: This study aimed to evaluate the effects of multilevel facetectomy and screw density on sagittal plane correction in patients with main thoracic (MT) AIS curve.Study Design: A retrospective correlation and comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution was undertaken.Patient Sample: Sixty-four consecutive patients with Lenke type 1 AIS treated with posterior correction and fusion surgery using simultaneous double-rod rotation technique were included.Outcome Measures: Patient demographics and preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study.Methods: Multiple stepwise linear regression analysis was conducted between change in TK (T5-T12) and the following factors: age at surgery, Risser sign, number of facetectomy level, screw density, preoperative main thoracic curve, flexibility in main thoracic curve, coronal correction rate, preoperative TK, and preoperative lumbar lordosis. Patients were classified into two groups: TK<15° group defined by preoperative TK below the mean degree of TK for the entire cohort (<15°) and the TK≥15° group, defined by preoperative TK above the mean degree of kyphosis (≥15°). Independent sample t tests were used to compare demographic data as well as radiographic outcomes between the two groups. There were no study-specific biases related to conflicts of interest.Results: The average preoperative TK was 14.0°, which improved significantly to 23.1° (p<.0001) at the 2-year final follow-up. Greater change in TK was predicted by a low preoperative TK (p<.0001). The TK <15° group showed significant correlation between change in TK and number of facetectomy level (r=0.492, p=.002). Similarly, significant correlation was found between change in TK and screw density (r=0.333, p=.047). Conversely, in the TK ≥15° group, correlation was found neither between change in TK and number of facetectomy level (r=0.047, p=.812), nor with screw density (r=0.030, p=.880). Furthermore, in patients with preoperative TK<15°, change in TK was significantly correlated with screw density at the concave side (r=0.351, p=.036) but not at the convex side (r=0.144, p=.402).Conclusions: In patients with hypokyphotic thoracic spine, significant positive correlation was found between change in TK and multilevel facetectomy or screw density at the concave side. This indicates that in patients with AIS who have thoracic hypokyphosis as part of their deformity, the abovementioned factors must be considered in preoperative planning to correct hypokyphosis. [ABSTRACT FROM AUTHOR]