Published papers

STUDY DESIGN.: A genetic association study of single nucleotide polymorphisms (SNPs) previously reported to be associated with curve progression of adolescent idiopathic scoliosis (AIS). OBJECTIVE.: To determine whether the association of 53 SNPs with curve progression reported in white patients with AIS are replicated in Japanese patients with AIS. SUMMARY OF BACKGROUND DATA.: Predicting curve progression is important in clinical practice of AIS. The progression of AIS is reported to be associated with a number of genes. Associations with 53 SNPs have been reported, and the SNPs are used for a progression test in white patients with AIS; however, there has been no replication study for their association. METHODS.: We recruited 2117 patients with AIS with 10 or more (Cobb angle) of scoliosis curves. They were divided into progression and nonprogression groups according to their Cobb angle. We defined the progression of the curve as Cobb angle more than 50 for skeletally mature subjects and more than 40 for immature patients, subjects. We defined the nonprogression of the curve as Cobb angle 50 or less only for skeletally mature subjects. Of the 2117 patients, 1714 patients with AIS were allocated to either the progression or nonprogression group. We evaluated the association of 53 SNPs with curve progression by comparing risk allele frequencies between the 2 groups. RESULTS.: We evaluated the progression (N = 600) and nonprogression (N = 1114) subjects. Their risk allele frequencies were not different significantly. We found no replication of the association on AIS curve progression in any of the SNPs. CONCLUSION.: The associations of the 53 SNPs with progression of AIS curve are not definite. Large-scale association studies based on appropriate criteria for progression would be necessary to identify SNPs associated with the curve progression. Copyright © 2013 Lippincott Williams & Wilkins.

Adolescent idiopathic scoliosis (AIS) is the most common pediatric skeletal disease. We previously reported a locus on chromosome 10q24.31 associated with AIS susceptibility in Japanese using a genome-wide association study (GWAS) consisting of 1,033 cases and 1,473 controls. To identify additional AIS-associated loci, we expanded the study by adding X-chromosome SNPs in the GWAS and increasing the size of the replication cohorts. Through a stepwise association study including 1,819 cases and 25,939 controls, we identified a new susceptibility locus on chromosome 6q24.1 in Japanese (P = 2.25 × 10 -10; odds ratio (OR) = 1.28). The most significantly associated SNP, rs6570507, was in GPR126 (encoding G protein-coupled receptor 126). Its association was replicated in Han Chinese and European-ancestry populations (combined P = 1.27 × 10-14; OR = 1.27). GPR126 was highly expressed in cartilage, and the knockdown of gpr126 in zebrafish caused delayed ossification of the developing spine. Our results should provide insights into the etiology and pathogenesis of AIS. © 2013 Nature America, Inc. All rights reserved.

Introduction: There are few studies on Modic changes of the cervical spine in patients suffering from whiplash. This study compared Modic changes seen in whiplash patients 10 years after the injury with those observed in asymptomatic volunteers. Methods: This is a follow-up study of 133 patients who suffered whiplash injuries in 1994-1996 and underwent MRI with a superconductive imager (63 men, 70 women, mean age 49.6 ± 15.3 years, mean follow-up 11.4 years). In addition, 223 healthy volunteers who underwent MRI during the same period were included as controls (123 men, 100 women, mean age 50.5 ± 15.0 years, mean follow-up 11.6 years). All participants underwent follow-up MRI. We examined all participants for Modic changes, and investigated relationships between Modic changes and clinical symptoms or potentially related factors. Results: Modic changes were observed in 4 patients (3%) and at 7 intervertebral levels in the initial study, and in 17 patients (12.8%) and at 30 intervertebral levels at the follow-up. Modic Type 2 changes were the most prevalent in the whiplash patients in both the initial and follow-up studies. There was no significant difference in the percentage of whiplash patients versus control subjects with positive Modic changes, either at the initial study or at follow-up. Modic changes were not related to clinical symptoms present at follow-up, but were associated with preexisting disc degeneration. There was no association between Modic changes and the details of the car accident that caused the injury. Conclusions: While Modic changes became more common in whiplash patients in the 10-year period after the accident, they occurred with a similar frequency in control subjects. We did not find any association between Modic changes and the nature of the car accident in which the whiplash occurred. Modic changes found in whiplash patients may be a result of the physiological ageing process rather than pathological findings relating to the whiplash injury. © 2012 Elsevier Ltd.

Study Design: A retrospective case series. Objective: To evaluate the long-term effectiveness and problems of total en bloc spondylectomy (TES) for treating metastatic thyroid cancer of the spine. Summary of Background Data: Although TES is indicated for low-grade malignant spinal tumors, its efficacy in treating thyroid cancer metastases in the spine is uncertain. Methods: This study followed 8 patients who underwent TES for spinal metastasis of thyroid cancer (5 males, 3 females; mean age, 55.3 y; mean follow-up period, 6.4 y), 6 with follicular carcinomas and 2 with papillary carcinomas. In 6 patients without a marked paravertebral tumor extension, TES was performed using a posterior approach. Two patients had prominent anterior or anterolateral tumor extension into the thoracic and retroperitoneal cavities, and a combined anterior and posterior approach was used. We evaluated the patients' clinical symptoms, operative procedures, complications, and prognoses. Results: Before surgery, the patients' neurological status was evaluated by the Frankel classification (grade C, 4 patients; grade D, 1 patient; grade E, 3 patients) and Tokuhashi scores (9, 1 patient; 11, 2 patients; 13 and 14, 1 patient each; 15, 3 patients). One year after surgery, all the patients had improved by at least a Frankel grade, and 4 patients classified as grade C before surgery had become ambulatory. At the final follow-up (average of 6.4 y), 5 patients had a grade E Frankel classification and 1 had grade D, but 2 patients had suffered neurological deterioration, because of tumor recurrence, at the same level as the TES in one patient and at an adjacent level in the other. At follow-up, all patients were alive; 5 showed no evidence of disease. Two patients experienced rod breakage, at 2.8 and at 3.3 years after TES, and 1 patient suffered an endplate fracture 6 months after TES; this patient developed a late infection, 7 years after TES. Conclusions: TES was effective in controlling spinal thyroid cancer metastasis locally and in preserving the ability to walk. However, instrumentation failure and other late complications arose during the patients' long survival times after TES. Copyright © 2012 by Lippincott Williams & Wilkins.

STUDY DESIGN: A retrospective case-control study OBJECTIVE: Short fusion using pedicle screws (PSs) with an attempt to attain maximum correction of the main thoracic curve was conducted for patients with a Lenke type 1 curve, to prevent postoperative left shoulder elevation. The outcomes were compared with those of conventional surgery. SUMMARY OF BACKGROUND DATA: Excessive correction of the main thoracic curve by PSs causes problematic left shoulder elevation even in a Lenke type 1 curve. METHODS: Thirty-eight patients (3 male, 35 female, mean age 16.2 years, mean follow-up 24 mo) with Lenke type 1 curve underwent posterior corrective surgery using PSs. The upper instrumented vertebra was 1 level below the end vertebra in 14 patients (short, S group), and it was at the end vertebra in 24 patients (conventional, C group). There was no difference in the preoperative Cobb angle (51.8 vs. 58.0) or curve flexibility (49.7 vs. 46.1) between the 2 groups. Radiographic results, perioperative data, and scoliosis research society 22 scores were compared between the 2 groups. RESULTS: The postoperative Cobb angle of the main curve after surgery was 13.2±5.7 degrees in the S group and 10.6±7.3 degrees in the C group (not significant). The clavicle angle was -2.1±2.8 degrees versus -2.7±2.6 degrees before surgery (not significant), and 0.8±2.3 versus 3.8±2.4 after surgery (P<0.05). The number of fused vertebrae, mean surgical time, and estimated blood loss were significantly lower in the S group than in the C group. The scoliosis research society 22 score at follow-up was not different between the 2 groups. CONCLUSIONS: The short fusion strategy for a Lenke type 1 curve can produce equivalent correction of the main curve and clinical outcomes to conventional fusion strategy with less surgical time and blood loss, while maintaining better shoulder balance. Copyright © 2012 by Lippincott Williams & Wilkins.

Purpose To investigate the frequency of tandem lumbar and cervical intervertebral disc degeneration in asymptomatic subjects. Methods We evaluated magnetic resonance imaging (MRI) results from 94 volunteers (48 men and 46 women; mean age 48 years) for age-related intervertebral disc degeneration in the lumbar and cervical spine. Results MRI indicated degenerative changes in the lumbar spine in 79 subjects (84 %), with decreased disc signal intensity in 74.5 %, posterior disc protrusion in 78.7 %, anterior compression of the dura in 81.9 %, disc space narrowing in 21.3 %, and spinal canal stenosis in 12.8 %. These findings were more common in older subjects at caudal levels. MRI showed degenerative changes in both the lumbar and cervical spine in 78.7 % of the volunteers. Conclusions Degenerative findings in both the lumbar and cervical spine, suggesting tandem disc degeneration, was common in asymptomatic subjects. These results provide normative data for evaluating patients with degenerative lumbar and cervical disc diseases. © Springer-Verlag 2012.

Object. The authors undertook this study to evaluate curve progression, risk factors for curve progression, and outcomes after decompression surgery in patients with degenerative lumbar scoliosis with minimal to moderate curvature. Methods. Of 852 patients with lumbar canal stenosis treated by posterior decompression surgery, 50 patients had a lumbar curve greater than 10° at final follow-up. These patients were divided into 2 groups according to curve progression during the follow-up period: the P group (11 patients), with a curve progression of more than 5°, and the NP group (39 patients), with a curve progression of 5° or less. The authors compared preoperative parameters in these 2 groups to elucidate risk factors associated with curve progression and other surgical outcomes. Results. The average lumbar curve progression in the total group of 50 patients was 3.4° ± 3.9° (range -2.0° to 22.0°). In the P group the average curve progression was 8.5°, and in the NP group it was 2.0°. Multivariate logistic regression analysis showed no significant association between curve progression and any of the potential risk factors evaluated (including curve magnitude, decompression method, and degenerative intervertebral disc changes). Spur formation, evaluated with the Nathan classification at the concave side of the curve, tended to be greater in the P group, although the difference was not statistically significant. There was no significant difference in revision surgery rate, and none of the patients required arthrodesis due to curve progression. Clinical outcomes, evaluated with the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and the Scoliosis Research Society 22-question questionnaire, were also similar in the 2 groups. Conclusions. Surgical outcomes did not deteriorate in the P group. While curve progression after decompression surgery could not be predicted from the preoperative factors considered, spur formation at the concave side of the curve may be a candidate factor. The results of this study indicate that spinal fixation to halt deformity progression is not always necessary if the patient's pathological condition derives mainly from canal stenosis. Copyright © 1944-2012 American Association of Neurological Surgeons.

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 identifi ed several factors signifi cantly associated with adding-on, including the preoperative proximal thoracic curve, the apical translation of the main thoracic curve, Miyanji's subclassifi cation, 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% confi dence 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% confi dence interval: 1.9-23.9, P = 0.003) were signifi cantly 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 signifi cantly associated with addingon, 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. Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

STUDY DESIGN.: A retrospective multicenter study. OBJECTIVE.: To identify risk factors for postoperative complications associated with growing-rod (GR) surgery for early-onset scoliosis (EOS). SUMMARY OF BACKGROUND DATA.: Results and complications of GR surgery for EOS have not been adequately studied. METHODS.: We evaluated clinical and radiographical results from 88 patients with EOS who underwent GR surgery in 12 spine centers in Japan. The mean age at the time of initial surgery was 6.5 ± 2.2 years (range, 1.5-9.8 yr) and the mean follow-up period was 3.9 ± 2.6 years (range, 2.0-12.0 yr). Risk factors for postoperative complications were analyzed using binomial multiple logistic regression analysis. We considered the potential factors of sex, age, number of rod-lengthening procedures, whether a pedicle screw foundation was used, the uppermost level of the proximal foundation and lowermost level of the distal foundation, Cobb angles of the proximal thoracic, main thoracic, and lumbar curves, and the kyphosis angles in the proximal, main thoracic, thoracolumbar, and lumbar spine. Kaplan-Meier analysis was used to determine the complication-free survival rate of GR surgery as a function of the number of surgical procedures. RESULTS.: Complications affected 50 of the patients (57%) and were associated with 119 of 538 surgical procedures, with 86 implant-related failures (72%), 19 infections (16%), 3 neurological impairments (3%), and 11 other complications. The most frequent implant-related failure was dislodged implant (71%) and 95% of the dislodgements occurred at the proximal foundation. Kaplan-Meier analysis demonstrated a linear decrease in complication-free rates as the number of rod-lengthening procedures increased. Binomial multiple logistic regression analysis found the following significant independent risk factors: 6 or more rod-lengthening procedures (odds ratio [OR], 6.534), an increase of every 20 in the proximal thoracic Cobb angle (OR, 3.091), and an increase of every 25 in the lumbar lordosis angle (OR, 2.607) in the preoperative condition. CONCLUSION.: Increases in the upper thoracic scoliotic curve, thoracic kyphosis, and number of rod-lengthening procedures are positively associated with an increased risk of complications after GR surgery for EOS.Level of Evidence: 4 © 2013, Lippincott Williams & Wilkins.

STUDY DESIGN.: A genetic association study of single nucleotide polymorphisms (SNPs) previously reported to be associated with curve progression of adolescent idiopathic scoliosis (AIS). OBJECTIVE.: To determine whether the association of 5 SNPs with curve progression reported in Chinese with AIS are replicated in Japanese patients with AIS. SUMMARY OF BACKGROUND DATA.: AIS is a common spinal deformity and has a strong genetic predisposition. Predicting curve progression is important in clinical practice. The progression of AIS is reported to be associated with a number of genes. Associations with neurotrophin 3, G protein-coupled estrogen receptor, and tissue inhibitor of metalloproteinase 2 have been reported in Han Chinese with AIS; however, there has been no replication study for them. METHODS.: We recruited 2117 patients with AIS with a Cobb angle of 10 or greater of scoliosis curves. They were grouped into progression and nonprogression groups according to their scoliosis curves. Patients whose scoliotic curves were 40 or greater were included in the progression group, and those whose scoliotic curves were less than 30 and had reached skeletal maturation in the nonprogression group. We evaluated the association of 5 SNPs (rs11063714 in neurotrophin 3, rs3808351, rs10269151, and rs4266553 in G protein-coupled estrogen receptor, and rs8179090 in tissue inhibitor of metalloproteinase 2 with curve progression by comparing risk allele frequencies between the 2 groups and the mean Cobb angle for each genotype. RESULTS.: We evaluated the progression (N = 880) and nonprogression (N = 492) subjects, and their risk allele frequencies were not significantly different. The mean Cobb angle for each genotype also did not have statistical difference. We found no replication of the association on AIS curve progression in any of the SNPs. CONCLUSION.: The associations of the 5 SNPs with progression of AIS curve are not definite. Large-scale association studies based on appropriate criteria for progression would be necessary to identify SNPs associated with the curve progression. © 2013, Lippincott Williams & Wilkins.

The hydroxyapatite (HAp) powder preparation process was optimized to fabricate inositol phosphate-HAp (IP6-HAp) cement with enhanced mechanical properties. Starting HAp powders were synthesized via a wet chemical process. The effect of the powder preparation process on the morphology, crystallinity, median particle size, and specific surface area (SSA) of the cement powders was examined, together with the mechanical properties of the resulting cement specimens. The smallest crystallite and median particle sizes, and the highest SSA were obtained from ball-milling of as-synthesized HAp powder under wet conditions and then freeze-drying. IP6-HAp cement fabricated with this powder had a maximum compressive strength of 23.1 ± 2.1 MPa. In vivo histological studies using rabbit models revealed that the IP6-HAp cements were directly in contact with newly formed and host bones. Thus, the present chelate-setting HAp cement is promising for application as a novel paste-like artificial bone. © 2012 Springer Science+Business Media New York.

Severe cervical kyphosis requiring surgical treatment is rare in patients with neurofibromatosis Type 1 (NF1). When it occurs, however, dystrophic changes in the vertebrae make surgical correction and fusion of the deformity extremely difficult. The authors report on 3 cases of severe cervical kyphosis associated with NF1 that were successfully treated with combined anterior and posterior correction and fusion. All patients underwent halo-gravity traction for approximately 1 month prior to surgery to correct the deformity gradually. Posterior correction and fusion were performed with segmental spinal instrumentation consisting of lateral mass screws, lamina screws, pedicle screws, and polyethylene tape for sublaminar wiring. Anterior spinal fusion was performed using a fibula strut to induce solid bone fusion. All patients used a halo vest for postoperative external fixation. Preoperative CT scans showed dystrophic cervical spine changes, and MR images demonstrated extensive neurofibromas outside the cervical spine in all 3 patients. The preoperative kyphotic angles were as follows: Case 1, 140°; Case 2, 81°; and Case 3, 72°; after halo-gravity traction, the kyphosis angles improved to 50°, 55°, and 51°, respectively; and after surgery, they were 50°, 15°, and 27°, respectively. Solid bone union was observed in all patients at the latest follow-up. All three patients experienced postoperative complications consisting of superficial infection, severe pneumonia, and partial dislocation of the distal fibula graft after removing the halo vest, in one patient each. Although dystrophic cervical vertebral changes in these patients with NF1 complicated the correction of severe cervical kyphosis, the use of preoperative halo-gravity traction, a combination of spinal instrumentations, an anterior strut bone graft, and postoperative halo-vest fixation made it possible to correct the kyphosis, maintain the correction, and achieve solid bone fusion. © 2013 AANS.

Solitary bone cysts of the lumbar vertebrae are extremely rare. We report a 20-year-old man, who presented with a 5-year history of persistent low back pain. Radiographic examination, magnetic resonance imaging, and subsequent computed tomography revealed a well-circumscribed osteolytic and cystic lesion at the right pedicle of the L3 vertebra. On the basis of the radiologic findings, a simple bone cyst was considered the most probable diagnosis. The patient underwent a minimally invasive operation with the assistance of an endoscope. The gross total curettage resection of the lesion including the cyst walls was accomplished, followed by a combined graft consisting of granulated β-tricalcium phosphate and autologous iliac crest cancellous bone. At the 1-year follow-up, the patient's symptoms were resolved, bone union at the lesion site had been achieved, and he had returned to his previous level of physical activity. Copyright © 2013 by Lippincott Williams & Wilkins.

Study design: Retrospective case series. Objective: To evaluate our treatment strategy for cervical dumbbell neurinoma. Summary of background data: In treating cervical dumbbell neurinoma, possible difficulties include reoperation due to recurrent tumor, denervation due to nerve root resection, and postoperative spinal deformity due to extensive bony removal. Methods: We reviewed 75 cases of cervical dumbbell neurinoma that were treated surgically between 1985 and 2006. Postoperative neurological deficits, effects of surgical margins on tumor recurrence, and surgical complications were investigated retrospectively. Results: Sensory and motor deficits due to resection of specific nerve roots appeared temporarily in 33 and 23 % of all cases, and persisted in 8 and 8 % at final evaluation, respectively. Total, subtotal, and partial resection was performed in 57, 13, and 5 cases, respectively. The total resection rate was low in the tumors that had large extraforaminal components. Of the subtotally resected 13 cases, only two cases of high tumor-growth rate required re-operation or showed tumor growth. Among the five partially resected cases, re-operation was necessary in two cases 13 and 15 years later because of aggravated neurological symptoms due to tumor growth. Two patients who underwent C2 laminectomy developed kyphosis, and three patients who underwent facet joint resection and curettage of vertebral body lesions developed scoliosis. Conclusion: Total resection should be attempted for cervical dumbbell tumors. In cases where total resection was potentially of high risk, however, subtotal resection (within the capsule) was found to be a practical choice yielding favorable long-term outcome when the tumor growth rate (MIB-1 index) was low. © 2012 The Japanese Orthopaedic Association.

Background: XBP1 is a transcription factor that is activated by one of the ER stress sensors, IRE1. Results: XBP1 promotes the expression of PTH/PTH-related peptide receptor in osteoblasts and renders these cells responsive to PTH. Conclusion: The IRE1-XBP1 pathway indirectly regulates PTH-induced osteoclastogenesis. Significance: This study may be the first to reveal the potential link between ER stress sensors and the regulation of osteoclastogenesis. To address the "endoplasmic reticulum stress" triggered by the burden of protein synthesis, the unfolded protein response is induced during osteoblast differentiation. In this study, we show that the transcription of parathyroid hormone (PTH)/PTH-related peptide receptor (PTH1R) is regulated by one of the endoplasmic reticulum-stress mediators, the IRE1α-XBP1 pathway, in osteoblasts. We found that the increase in Pth1r transcription upon BMP2 treatment is significantly suppressed in mouse embryonic fibroblasts lacking IRE1α. As expected, gene silencing of Ire1α and Xbp1 resulted in a decrease in Pth1r transcripts in BMP2-treated embryonic fibroblasts. We identified two potential binding sites for XBP1 in the promoter region of Pth1r and found that XBP1 promotes the transcription of Pth1r by directly binding to those sites. Moreover, we confirmed that the gene silencing of Xbp1 suppresses PTH-induced Rankl expression in primary osteoblasts and thereby abolishes osteoclast formation in an in vitro model of osteoclastogenesis. Thus, the present study reveals potential involvement of the IRE1-XBP1 pathway in PTH-induced osteoclastogenesis through the regulation of PTH1R expression. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.

TNFα-converting enzyme (TACE/ADAM17) is a membrane-bound proteolytic enzyme with a diverse set of target molecules. Most importantly, TACE is indispensable for the release and activation of pro-TNFα and the ligands for epidermal growth factor receptor in vivo. Previous studies suggested that the overproduction of TACE is causally related to the pathogenesis of inflammatory diseases and cancers. To test this hypothesis, we generated a transgenic line in which the transcription of exogenous Tace is driven by a CAG promoter. The Tace-transgenic mice were viable and exhibited no overt defects, and the quantitative RT-PCR and Western blot analyses confirmed that the transgenically introduced Tace gene was highly expressed in all of the tissues examined. The Tace-transgenic mice were further crossed with Tace-/+ mice to abrogate the endogenous TACE expression, and the Tace-transgenic mice lacking endogenous Tace gene were also viable without any apparent defects. Furthermore, there was no difference in the serum TNFα levels after lipopolysaccharide injection between the transgenic mice and control littermates. These observations indicate that TACE activity is not necessarily dependent on transcriptional regulation and that excess TACE does not necessarily result in aberrant proteolytic activity in vivo. © 2013 Yoda et al.

Background: The purpose of this study was to test the hypothesis that direct vertebral derotation by pedicle screws (PS) causes hypokyphosis of the thoracic spine in adolescent idiopathic scoliosis (AIS) patients, using computer simulation. Methods: Twenty AIS patients with Lenke type 1 or 2 who underwent posterior correction surgeries using PS were included in this study. Simulated corrections of each patients scoliosis, as determined by the preoperative CT scan data, were performed on segmented 3D models of the whole spine. Two types of simulated extreme correction were performed: 1) complete coronal correction only (C method) and 2) complete coronal correction with complete derotation of vertebral bodies (C + D method). The kyphosis angle (T5-T12) and vertebral rotation angle at the apex were measured before and after the simulated corrections. Results: The mean kyphosis angle after the C + D method was significantly smaller than that after the C method (2.7 ± 10.0° vs. 15.0 ± 7.1°, p<0.01). The mean preoperative apical rotation angle of 15.2 ± 5.5° was completely corrected after the C + D method (0°) and was unchanged after the C method (17.6 ± 4.2°). Conclusions: In the 3D simulation study, kyphosis was reduced after complete correction of the coronal and rotational deformity, but it was maintained after the coronal-only correction. These results proved the hypothesis that the vertebral derotation obtained by PS causes hypokyphosis of the thoracic spine. © 2012 Watanabe et al. licensee BioMed Central Ltd.