Evaluation of crankshaft phenomenon after posterior fusion for early onset scoliosis using an inverse trigonometric function: a multicenter retrospective cohort study.

PURPOSE: The crankshaft phenomenon (CSP) is a corrective loss after posterior surgery for early onset scoliosis (EOS). However, an accurate method for CSP evaluation has yet to be developed. In this study, we evaluated pedicle screw (PS) length and rotation angle using an inverse trigonometric function and investigated the prevalence of the CSP. METHODS: Fifty patients from nine institutions (mean age 10.6 years, male/female ratio 4:46) who underwent early definitive fusion surgery at ≤ 11 years of age were included. The rotation angle was calculated as arctan (lateral/frontal PS length) using radiography. Measurements were taken at the apex and lower instrumented vertebra (LIV) immediate, 2-, and 5-year postoperatively. CSP was defined as a rotation angle progression ≥ 5°. We divided patients into CSP and non-CSP groups and measured the demographic parameters, Risser grade, state of the triradiate cartilage, major coronal Cobb angle, T1-T12 length, T1-S1 length, and presence of distal adding-on (DAO). We compared these variables between groups and investigated the correlation between the measured variables and vertebral rotation. Logistic regression analysis investigated factors associated with CSP. RESULTS: The rotation angle progressed by 2.4 and 1.3° over 5 years for the apex and LIV, respectively. CSP occurred in 15 cases (30%), DAO in 11 cases (22%), and CSP and DAO overlapped in 4 cases (8%). In the CSP group, the T1-T12 length was low immediate postoperatively. The rotation angle was negatively correlated with preoperative height (r = - 0.33), T1-T12 length (r = - 0.35), and T1-S1 length (r = - 0.30). A lower preoperative T1-T12 length was associated with CSP (odds ratio: 0.996, p = 0.048). CONCLUSIONS: CSP occurred in 30% of patients with EOS who underwent definitive fusion. The presence of CSP was associated with a lower preoperative T1-T12 length. LEVEL OF EVIDENCE: Diagnosis, level IV.

Rod fracture after multiple-rod technique for adult spinal deformity: a case report.

Here we report the case of a 71-year-old woman who complained of lower back and left leg pain due to rod fracture following instrumented fusion using the lateral lumbar interbody fusion and multi-rod technique to treat adult spinal deformity. Radiographic images revealed bilateral rod fractures at L4-5 and pseudoarthrosis at L2-5; lower lumbar lordosis was minimal, but upper lumbar hyperlordosis was noted. The patient underwent revision surgery, which included posterior spinal instrument replacement, L3-4 and L4-5 lateral lumbar interbody fusion cage removal, and L4 vertebral body replacement via the anterior approach. This is a rare case of reoperation with the multi-rod technique. Revision surgery should be performed in consideration of the proportion of lumbar lordosis and anterior bony fusion as the posterior component is resected and bony fusion can only be achieved anteriorly.

Instrumentation failure following pediatric spine deformity growth-sparing surgery using traditional growing rods or vertical expandable prosthetic titanium ribs.

BACKGROUND: Instrumentation failure (IF) is a major complication associated with growth-sparing surgery for pediatric spinal deformities; however, studies focusing on IF following each surgical procedure are lacking. We aimed to evaluate the incidence, timing, and rates of unplanned return to the operating room (UPROR) associated with IF following each surgical procedure in growth-sparing surgeries using traditional growing rods (TGRs) and vertical expandable prosthetic titanium ribs (VEPTRs). METHODS: We reviewed 1,139 surgical procedures documented in a Japanese multicenter database from 2015 to 2017. Of these, 544 TGR and 455 VEPTR procedures were included for evaluation on a per-surgery basis. IF was defined as the occurrence of an implant-related complication requiring revision surgery. RESULTS: The surgery-based incidences of IF requiring revision surgery in the TGR and VEPTR groups were 4.3% and 4.0%, respectively, with no significant intergroup difference. Remarkably, there was a negative correlation between IF incidence per surgical procedure and the number of lengthening surgeries in both groups. In addition, rod breakage in the TGR group and anchor-related complications in the VEPTR group tended to occur relatively early in the treatment course. The surgery-based rates of UPROR due to IF in the TGR and VEPTR groups were 2.0% and 1.5%, respectively, showing no statistically significant difference. CONCLUSIONS: We found that IF, such as anchor related-complications and rod breakage, occurs more frequently earlier in the course of lengthening surgeries. This finding may help in patient counseling and highlights the importance of close postoperative follow-up to detect IF and improve outcomes.

Wedge-Shaped Deformity of the First Sacral Vertebra Associated with Adolescent Idiopathic Scoliosis: A Comparison of Cases with and without Scoliosis.

Introduction: Scoliosis is the three-dimensional (3D) deformity of the spine. Scoliosis curvatures, such as the lower lumbar curve and the angle of the upper endplate of the sacrum observable on radiographs, are associated with postoperative outcomes; however, the relationship between postoperative outcomes and sacral morphology remains unknown. This study aimed to investigate sacral morphology in patients with adolescent idiopathic scoliosis (AIS) and to clarify its relationship with wedge-shaped deformity of the first sacral vertebra and radiographic parameters. Methods: This study included 94 patients who underwent fusion surgery for AIS (scoliosis group). As the control group, 25 patients without scoliosis (<10°) under 50 years of age were also investigated. S1 wedging angle (S1WA) using 3D Computed tomography (CT) and Cobb angle, L4 tilt, and sacral slanting using radiography were measured. The relationship between S1WA and other radiographic parameters was analyzed using correlation coefficients. Differences in sacral morphology between the Lenke lumbar modifier types A and C were also investigated. Results: S1WA was significantly larger in the scoliosis group than the control group (scoliosis: 1.7°±2.5°, control: 0.1°±1.5°, p=0.002). Furthermore, the number of patients with S1WA >3° or >5° was significantly higher in the scoliosis group (>3°: 33%, 8%, p=0.012; >5°: 16%, 0%, p=0.039). S1WA correlated with sacral slanting (r=0.45, p<0.001) and L4 tilt (r=0.35, p<0.001) and was significantly greater with Lenke lumbar modifier C than A (2.4°±2.6°, 0.8°±2.0°; p<0.001). Conclusions: The S1 vertebra was deformed and wedge-shaped in AIS, especially in cases with a large lumbar curve. Additionally, S1WA is associated with sacral slanting and L4 tilt on radiography in AIS.

Evidence of causality of low body mass index on risk of adolescent idiopathic scoliosis: a Mendelian randomization study.

Introduction: Adolescent idiopathic scoliosis (AIS) is a disorder with a three-dimensional spinal deformity and is a common disease affecting 1-5% of adolescents. AIS is also known as a complex disease involved in environmental and genetic factors. A relation between AIS and body mass index (BMI) has been epidemiologically and genetically suggested. However, the causal relationship between AIS and BMI remains to be elucidated. Material and methods: Mendelian randomization (MR) analysis was performed using summary statistics from genome-wide association studies (GWASs) of AIS (Japanese cohort, 5,327 cases, 73,884 controls; US cohort: 1,468 cases, 20,158 controls) and BMI (Biobank Japan: 173430 individual; meta-analysis of genetic investigation of anthropometric traits and UK Biobank: 806334 individuals; European Children cohort: 39620 individuals; Population Architecture using Genomics and Epidemiology: 49335 individuals). In MR analyses evaluating the effect of BMI on AIS, the association between BMI and AIS summary statistics was evaluated using the inverse-variance weighted (IVW) method, weighted median method, and Egger regression (MR-Egger) methods in Japanese. Results: Significant causality of genetically decreased BMI on risk of AIS was estimated: IVW method (Estimate (beta) [SE] = -0.56 [0.16], p = 1.8 × 10-3), weighted median method (beta = -0.56 [0.18], p = 8.5 × 10-3) and MR-Egger method (beta = -1.50 [0.43], p = 4.7 × 10-3), respectively. Consistent results were also observed when using the US AIS summary statistic in three MR methods; however, no significant causality was observed when evaluating the effect of AIS on BMI. Conclusions: Our Mendelian randomization analysis using large studies of AIS and GWAS for BMI summary statistics revealed that genetic variants contributing to low BMI have a causal effect on the onset of AIS. This result was consistent with those of epidemiological studies and would contribute to the early detection of AIS.

Relationship between lumbosacral transitional vertebra and postoperative outcomes of patients with Lenke 5C adolescent idiopathic scoliosis: a minimum 5-year follow-up study.

PURPOSE: To assess the incidence of lumbosacral transitional vertebra (LSTV) in Lenke 5C adolescent idiopathic scoliosis (AIS) and evaluate the relationship between postoperative outcomes and LSTV when the lowest instrumented vertebra (LIV) is fixed at L3. METHODS: The study included 61 patients with Lenke 5C AIS who underwent fusion surgery of L3 as the LIV who were followed-up for a minimum of 5 years. Patients were divided into two groups: LSTV + and LSTV-. Demographic, surgical, and radiographic data, including L4 tilt and thoracolumbar/lumbar (TL/L) Cobb angle, were obtained and analyzed. RESULTS: LSTV was observed in 15 patients (24.5%). The L4 tilt was not significantly different between the two groups preoperatively (P = 0.54); however, it was significantly greater in the LSTV group postoperatively (2 weeks: LSTV + = 11.7 ± 3.1, LSTV - = 8.8 ± 3.2, P = 0.013; 2 years: LSTV + = 11.5 ± 3.5, LSTV - = 7.9 ± 4.1, P = 0.006; 5 years: LSTV + = 9.8 ± 3.1, LSTV - = 7.3 ± 4.5, P= 0.042). The postoperative TL/L curve was greater in the LSTV + group, with significant differences at 2 weeks and 2 years postoperatively (preoperative: LSTV + = 53.5 ± 11.2, LSTV - = 51.7 ± 10.3,P = 0.675; 2 weeks: LSTV + = 16.1 ± 5.0, LSTV- = 12.2 ± 6.6, P = 0.027; 2 years: LSTV + = 21.7 ± 5.9, LSTV - = 17.6 ± 5.9, P = 0.035; 5 years: LSTV + = 18.7 ± 5.8, LSTV - = 17.0 ± 6.1, P = 0.205). CONCLUSION: The prevalence of LSTV in Lenke 5C AIS patients was 24.5%. Lenke 5C AIS patients with LSTV with the LIV at L3 had a significantly greater postoperative L4 tilt than those without LSTV and retained the TL/L curve.

Cervical Spinal Cord Compression in Adult Scoliosis.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: The aim was to examine cervical spinal cord compression (SCC) in adult scoliosis and clarify the prevalence of and risk factors for cervical SCC. METHODS: This study included 270 adult scoliosis patients and 1211 healthy volunteers. Cervical SCC was evaluated on cervical magnetic resonance imaging (MRI). The rates of SCC for those with adult scoliosis and the healthy volunteers were compared. Logistic regression analysis was conducted to examine the factors associated with cervical SCC on MRI. RESULTS: In cases with adult scoliosis, preoperative major scoliosis curve was 56.0° ± 18.8°, and cervical SCC was detected in 25 patients (9.3%). Among the healthy volunteers, 64 cases with cervical SCC were detected. Only in cases with adult scoliosis, logistic regression analysis revealed higher age (OR 1.09, 95% CI 1.04-1.14, P < .001), narrow canal diameter (OR 2.27, 95% CI 1.35-3.85, P = .002), and inferior sagittal balance (OR 2.45, 95% CI 1.02-5.89, P = .04) as significant risk factors. In the logistic regression analysis in all subjects (including adult scoliosis and healthy volunteers), higher age (OR 1.08, 95% CI 1.06-1.10, P < .001) and narrow canal diameter (OR 1.62, 95% CI 1.37-1.92, P < .001) were also found to be significant risk factors, but the presence of scoliosis was not a significant factor. CONCLUSIONS: Adult scoliosis itself was not significantly associated with cervical SCC. Inferior sagittal balance in addition to scoliosis constituted a significant risk factor for cervical SCC.

Incidence and causes of instrument-related complications after primary definitive fusion for pediatric spine deformity.

OBJECTIVE: Various complications have been reported in the treatment of pediatric spinal deformities. Among these, instrument-related complications could be critical concerns and risks of reoperation. This study aimed to identify the incidence and causes of complications after primary definitive fusion for pediatric spine deformities. METHODS: The authors retrospectively collected data from 14 institutions about patients who underwent primary definitive fusion between 2015 and 2017. There were 1490 eligible patients (1184 female and 306 male), with a mean age of 13.9 years. The incidence, causes, and reoperation rates were analyzed according to 4 etiologies of pediatric spine deformity (congenital, neuromuscular, syndromic, idiopathic). The complications were also categorized as screw-, hook-, or rod-related complications, implant loosening or backout, and junctional problems. RESULTS: The incidence of overall instrument-related complications was 5.6% (84 cases). Regarding etiology, the incidence rates were 4.3% (idiopathic), 6.8% (syndromic), 7.9% (congenital), and 10.4% (neuromuscular) (p < 0.05). The most common causes were pedicle screw malposition (60.7%), followed by implant backout or loosening (15.4%), junctional problems (13.1%), rod breakage (4.8%), and other complications (6.0%). Univariate analysis showed that etiology, type of deformity (kyphosis), surgical procedure, operation time, and estimated blood loss were significant factors. Multivariate analysis revealed that etiology (neuromuscular), surgical procedure (combined approach), and operation time (> 5 hours) remained as significant risk factors. Among all patients with instrument-related complications, 45% (38/84) required revision surgery. Of these cases, > 50% were related to pedicle screw malposition. Medial breach was the most common complication regardless of location, from upper thoracic to lumbar spine. CONCLUSIONS: Pedicle screw malposition was the primary cause of overall complications and subsequent reoperation. In addition to more precise screw insertion techniques, meticulous confirmation of pedicle screw placement, especially of medial breach, may reduce the overall instrument-related complications and revision rates.

Identification of a Functional Susceptibility Variant for Adolescent Idiopathic Scoliosis that Upregulates Early Growth Response 1 (EGR1)-Mediated UNCX Expression.

Adolescent idiopathic scoliosis (AIS) is a serious health problem affecting 3% of live births all over the world. Many loci associated with AIS have been identified by previous genome wide association studies, but their biological implication remains mostly unclear. In this study, we evaluated the AIS-associated variants in the 7p22.3 locus by combining in silico, in vitro, and in vivo analyses. rs78148157 was located in an enhancer of UNCX, a homeobox gene and its risk allele upregulated the UNCX expression. A transcription factor, early growth response 1 (EGR1), transactivated the rs78148157-located enhancer and showed a higher binding affinity for the risk allele of rs78148157. Furthermore, zebrafish larvae with UNCX messenger RNA (mRNA) injection developed body curvature and defective neurogenesis in a dose-dependent manner. rs78148157 confers the genetic susceptibility to AIS by enhancing the EGR1-regulated UNCX expression. © 2022 American Society for Bone and Mineral Research (ASBMR).

Atypical Sotos syndrome caused by a novel splice site variant.

Sotos syndrome is usually caused by haploinsufficiency of NSD1; it is characterized by overgrowth, craniofacial features, and learning disabilities. We describe a boy with Sotos syndrome caused by a splicing variant (c.4378+5G>A). The clinical manifestations included severe connective tissue involvement, including joint hypermobility, progressive scoliosis, pectus deformity, and skin hyperextensibility; no overgrowth was observed.

The L-type Amino Acid Transporter (LAT1) Expression in Patients with Scoliosis.

Introduction: Amino acid transporters are transmembrane proteins that are known to mediate the transfer of amino acids. As one of the amino acid transporters, LAT1, which is encoded by Slc7a5, mediates the cellular uptake of the essential amino acids. Recently, most studies have focused on examining the relationship between LAT1 and skeletal formation in terms of development. However, little is known regarding the clinical features of LAT1 in the cartilage, which might result in the development of skeletal deformities such as scoliosis. Thus, the aim of this study was to investigate the expression of L-type amino acid transporter 1 (LAT1) and its solute carrier transporter 7a5 (Slc7a5) in patients with pediatric scoliosis and to compare with the relationship between LAT1 and Slc7a5 expression and their clinical features. Methods: We have prospectively recruited 56 patients who underwent corrective spinal fusion for scoliosis. The patients comprised 40 girls and 16 boys, with a mean age of 13.1 years at the time of surgery. There were 34 idiopathic scoliosis (IS) patients, whereas 22 were congenital scoliosis (CS) patients. During the surgery, an epiphyseal part of the spinous process at apical vertebra was harvested; then, LAT1 and Slc7a5 expressions in the cartilage were evaluated. Results: As per our findings, LAT1 expression was observed in the cartilage in 60.7% (34 out of 56) of the patients. LAT1 expression in IS patients was 76%, which were statistically higher compared to 36% in CS patients. When compared with LAT1 expression, no statistical difference was noted in terms of age, gender, body mass index (BMI), Cobb angle, and Risser grade. Meanwhile, the mean Slc7a5 expression in IS patients was determined to be significantly higher than that in CS patients. No significant correlation was observed between Slc7a5 expression and age, BMI, and Cobb angle. Conclusions: LAT1 and Slc7a5 expression in IS and CS patients showed significant differences. These expressions were found to be not correlated with age, stature, and severity of the deformity.

Conditional inactivation of the L-type amino acid transporter LAT1 in chondrocytes models idiopathic scoliosis in mice.

Scoliosis, usually diagnosed in childhood and early adolescence, is an abnormal lateral curvature of the spine. L-type amino acid transporter 1 (LAT1), encoded by solute carrier transporter 7a5 (Slc7a5), plays a crucial role in amino acid sensing and signaling in specific cell types. We previously demonstrated the pivotal role of LAT1 on bone homeostasis in mice, and the expression of LAT1/SLC7A5 in vertebral cartilage of pediatric scoliosis patients; however, its role in chondrocytes on spinal homeostasis and implications regarding the underlying mechanisms during the onset and progression of scoliosis, remain unknown. Here, we identified LAT1 in mouse chondrocytes as an important regulator of postnatal spinal homeostasis. Conditional inactivation of LAT1 in chondrocytes resulted in a postnatal-onset severe thoracic scoliosis at the early adolescent stage with normal embryonic spinal development. Histological analyses revealed that Slc7a5 deletion in chondrocytes led to general disorganization of chondrocytes in the vertebral growth plate, along with an increase in apoptosis and a decrease in cell proliferation. Furthermore, loss of Slc7a5 in chondrocytes activated the general amino acid control (GAAC) pathway but inactivated the mechanistic target of rapamycin complex 1 (mTORC1) pathway in the vertebrae. The spinal deformity in Slc7a5-deficient mice was corrected by genetic inactivation of the GAAC pathway, but not by genetic activation of the mTORC1 pathway. These findings suggest that the LAT1-GAAC pathway in chondrocytes plays a critical role in the maintenance of proper spinal homeostasis by modulating cell proliferation and survivability.

A comparison of the inflammatory host response to particulate debris adjacent to unlocked and locked screws of a growth guidance system for early onset scoliosis.

PURPOSE: The SHILLA™ Growth Guidance system is a stainless-steel rod and screw system used for Early Onset Scoliosis which incorporates a unique flanged set screw designed to capture the rod, while allowing it to slide as the patient grows. Concomitant with this design is the potential for generation of wear debris and for an inflammatory host response. We hypothesized that the magnitude of the host response adjacent to the unlocked screws and rods would be greater than the host response to the locked rod/screws. METHODS: Seven tissue samples adjacent to locked (3) and unlocked screws (4) from three SHILLA patients (mean implantation time of 19 post-operative months) with infantile idiopathic scoliosis were obtained as part of an explant analysis protocol during a PMDA-approved clinical trial in Japan. Gross appearance, high-resolution radiographs, and histology were assessed. ISO Standard 10993 Part 6 was used to assess the host response. RESULTS: All three locked screw had no metallosis. In contrast, metallosis for unlocked screw tissue samples were rated as "ubiquitous" (2/4), "focal" (1/4), or "absent" (1/4). Microscopic metallic debris was found intracellularly and within interstices of fibrous connective tissues more frequently adjacent to unlocked screws compared to locked screws. Cell type and population scoring consistently showed a modestly larger inflammatory response (macrophages) in the unlocked tissue samples. CONCLUSIONS: The peri-prosthetic tissue response to the unlocked rods/screws had a higher reactivity grade (slight reaction, Δ = 4.0) per ISO 10993 Part 6 compared to the locked screws in three patients with the SHILLA™ Growth Guidance scoliosis system.

Factors affecting postoperative pulmonary function deterioration in adolescent idiopathic scoliosis: A prospective study using 3-dimensional image reconstruction by biplanar stereoradiography.

This study aimed both to evaluate rib cage parameters in patients with adolescent idiopathic scoliosis (AIS) by three-dimensional (3D) image reconstruction using biplanar stereoradiography (EOS) (EOS Imaging, Paris, France) and identify factors associated with postoperative pulmonary function deterioration (PFD). A total of 67 patients with Lenke type 1 or 2 AIS (59 females and 8 males; mean age, 14.4 years) undergoing posterior corrective fusion with a rod rotation maneuver based on segmental pedicle screw fixation were recruited. 3D images and pulmonary function test results were analyzed preoperatively and at 2 years postoperatively. The following parameters were measured: maximum thickness, maximum width, thoracic index, rib hump, rib cage volume (RCV), spinal penetration index (SPI), endothoracic hump ratio (EHR), vertebra-sternum angle (VSA), rib-vertebra angle difference, vertebral lateral decentering (VLD), forced vital capacity (FVC), and percent predicted FVC (%FVC). PFD was defined as a postoperative %FVC decline of 5% or greater. Patients were divided into two groups, namely PFD and non-PFD. FVC increased from 2.62 L to 2.73 L, while %FVC decreased from 88.7% to 82.7%. The maximum width diminished postoperatively in the PFD group. Patients in the PFD group exhibited a significantly smaller increase in RCV and VLD as well as a significantly smaller decrease in SPI, EHR, and VSA than those in the non-PFD group. The rib cage parameters quantified on 3D images reconstructed using EOS are useful in identifying factors affecting PFD in patients with AIS.

Surgical Predictors for Prevention of Postoperative Shoulder Imbalance in Lenke Type 2A Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Multicenter, retrospective cohort study. OBJECTIVE: The aim of this study was to investigate the occurrence and surgical predictors of postoperative shoulder imbalance (PSI) in Lenke type 2A adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Although several studies have investigated the factors influencing PSI in Lenke type 2 curves, no studies have analyzed PSI-related factors considering upper instrumented vertebra (UIV) and lumbar modifier type simultaneously. METHODS: Patients with Lenke Type 2A AIS treated by spinal fusion were retrospectively identified and their data were extracted from six spine centers in Japan. Inclusion criteria were age between 10 and 20 years at surgery, UIV = T2, major curve 40° to 90°, and follow-up for 24 to 30 months after surgery. We analyzed patient characteristics, surgical characteristics, and preoperative and immediate-postoperative radiographic parameters. We defined patients with lower instrumented vertebra (LIV) equal or proximal to the last touching vertebra (LTV) as selective thoracic fusion (STF-LTV) and patients with LIV distal to the LTV as non-STF-LTV. t Tests, Mann-Whitney U test, χ2 tests, Fisher exact tests, and multivariate logistic regression were used for statistical analyses. RESULTS: Among the 99 consecutive patients with a mean follow-up of 25.6 months, PSI was seen in 27 (27.3%) patients immediately after and in 17 (17.2%) patients at 24 to 30 months. The univariate analysis revealed that the significant risk factors of PSI were preoperative radiographical shoulder height, non-STF-LTV, and high main thoracic curve (MTC) correction (immediate-postoperative MTC correction rate: ≥70%), with PSI incidence of 40.0%. The multivariate logistic regression analysis indicated that interaction term of non-STF-LTV and high MTC correction was an independent risk factor for PSI (non-STF-LTV and high MTC correction, odds ratio: 5.167, 95% confidence interval: 1.470-18.159, P = 0.010). CONCLUSION: To prevent PSI in Lenke Type 2A AIS patients, surgeons should avoid the combination of non-STF-LTV and high MTC correction in those surgeries with UIV as T2.Level of Evidence: 4.

The reliability of the AOSpine Thoracolumbar Spine Injury Classification System in children: an international validation study.

PURPOSE: To evaluate the AOSpine Thoracolumbar Spine Injury Classification System and if it is reliable and reproducible when applied to the paediatric population globally. METHODS: A total of 12 paediatric orthopaedic surgeons were asked to review MRI and CT imaging of 25 paediatric patients with thoracolumbar spine traumatic injuries, in order to determine the classification of the lesions observed. The evaluators classified injuries into primary categories: A, B and C. Interobserver reliability was assessed for the initial reading by Fleiss's kappa coefficient (kF) along with 95% confidence intervals (CI). For A and B type injuries, sub-classification was conducted including A0-A4 and B1-B2 subtypes. Interobserver reliability across subclasses was assessed using Krippendorff's alpha (αk) along with bootstrapped 95% CIs. A second round of classification was performed one-month later. Intraobserver reproducibility was assessed for the primary classifications using Fleiss's kappa and sub-classification reproducibility was assessed by Krippendorff's alpha (αk) along with 95% CIs. RESULTS: In total, 25 cases were read for a total of 300 initial and 300 repeated evaluations. Adjusted interobserver reliability was almost perfect (kF = 0.74; 95% CI 0.71 to 0.78) across all observers. Sub-classification reliability was substantial (αk= 0.67; 95% CI 0.51 to 0.81), Adjusted intraobserver reproducibility was almost perfect (kF = 0.91; 95% CI 0.83 to 0.99) for both primary classifications and for sub-classifications (αk = 0.88; 95% CI 0.83 to 0.93). CONCLUSION: The inter- and intraobserver reliability for the AOSpine Thoracolumbar Spine Injury Classification System was high amongst paediatric orthopaedic surgeons. The AOSpine Thoracolumbar Spine Injury Classification System is a promising option as a uniform fracture classification in children. LEVEL OF EVIDENCE: III.

Does pulmonary function improve after surgical correction of adult idiopathic scoliosis?

PURPOSE: The aim was to investigate pulmonary function after surgical correction of adult idiopathic scoliosis. METHODS: This study included 146 adult scoliosis patients aged 20-50 years (main curve in thoracic spine). Respiratory function was assessed as predicted forced vital capacity (%FVC) and the ratio of forced expiratory volume in 1 s / FVC (%FEV1) preoperatively and 2 years postoperatively and classified as a normal function (≥ 80%), mild impairment (≥ 65% and < 80%), and moderate impairment (< 65%). RESULTS: Preoperative %FVC and %FEV1 were 85.3% and 85.4%, which were 81.5% and 87.5% at 2 years post-surgery. The preoperative %FVC was mild and moderate in 39 (26.7%) and 12 patients (11.6%), respectively. The %FVC significantly improved (+ 6.2% ± 11.4%, P < 0.001) postoperatively for moderate severity but significantly decreased postoperatively (- 6.4% ± 9.4%, P < 0.001) for normal function. The preoperative %FEV1 was mild and moderate in 27 (18.5%) and 0 patients, respectively. The %FEV1 significantly improved postoperatively (6.3% ± 5.3%, P < 0.001) for mild severity but did not significantly change for normal severity. Twenty-three (15.8%) and 41 (28.1%) patients showed improved ⊿%FVC and ⊿% FEV1 > 5%. Logistic regression analysis showed that preoperative %FVC and %FEV1 severities were independent factors affecting postoperative recovery of %FVC (OR 0.95) and %FEV1 (OR 0.85). CONCLUSION: Pulmonary function improved in patients with preoperative pulmonary impairment of < 65% in %FVC and < 80% in %FEV1, and the real improvement was limited to patients with severe preoperative impairment.

Polygenic Risk Score of Adolescent Idiopathic Scoliosis for Potential Clinical Use.

Adolescent idiopathic scoliosis (AIS) is a common disease causing three-dimensional spinal deformity in as many as 3% of adolescents. Development of a method that can accurately predict the onset and progression of AIS is an immediate need for clinical practice. Because the heritability of AIS is estimated as high as 87.5% in twin studies, prediction of its onset and progression based on genetic data is a promising option. We show the usefulness of polygenic risk score (PRS) for the prediction of onset and progression of AIS. We used AIS genomewide association study (GWAS) data comprising 79,211 subjects in three cohorts and constructed a PRS based on association statistics in a discovery set including 31,999 female subjects. After calibration using a validation data set, we applied the PRS to a test data set. By integrating functional annotations showing heritability enrichment in the selection of variants, the PRS demonstrated an association with AIS susceptibility (p = 3.5 × 10-40 with area under the receiver-operating characteristic [AUROC] = 0.674, sensitivity = 0.644, and specificity = 0.622). The decile with the highest PRS showed an odds ratio of as high as 3.36 (p = 1.4 × 10-10 ) to develop AIS compared with the fifth in decile. The addition of a predictive model with only a single clinical parameter (body mass index) improved predictive ability for development of AIS (AUROC = 0.722, net reclassification improvement [NRI] 0.505 ± 0.054, p = 1.6 × 10-8 ), potentiating clinical use of the prediction model. Furthermore, we found the Cobb angle (CA), the severity measurement of AIS, to be a polygenic trait that showed a significant genetic correlation with AIS susceptibility (rg = 0.6, p = 3.0 × 10-4 ). The AIS PRS demonstrated a significant association with CA. These results indicate a shared polygenic architecture between onset and progression of AIS and the potential usefulness of PRS in clinical settings as a predictor to promote early intervention of AIS and avoid invasive surgery. © 2021 American Society for Bone and Mineral Research (ASBMR).

Three-dimensional reconstruction image by biplanar stereoradiography reflects pulmonary functional states inadolescent idiopathic scoliosis.

This study investigated whether the rib cage parameters estimated based on reconstructed three-dimensional (3D) images with biplanar stereoradiography reflect pulmonary functional states in adolescent idiopathic scoliosis (AIS) patients. A total of 67 Lenke type 1 or 2 AIS patients (59 females and 8 males, mean age 14.4 years) were enrolled. All patients underwent preoperative pulmonary functional tests (PFT) and biplanar stereoradiography. Vital capacity (VC) and forced vital capacity (FVC) pulmonary functional data were collected. Rib-cage parameters (maximum thickness, maximum width, thoracic index (TI), rib hump (RH), rib-cage volume (RCV), spinal penetration index (SPI), endothoracic hump ratio (EHR), vertebra-sternum angle (VSA), rib vertebral angle difference (RVAD), and vertebral lateral decentering (VLD)) were quantified from 3D images. Patients were divided into two groups: restrictive lung disorder (RLD) (%FVC < 80%) and non-RLD (%FVC ≥ 80%). The maximum width and RCV were significantly correlated with VC (p < 0.0001), and FVC (p < 0.0001). RH, EHR, and VSA were negatively correlated with %FVC (p < 0.01). TI, SPI, and RVAD were not correlated with any pulmonary parameters. The maximum widths of RLD patients were significantly shorter than those of the non-RLD patients (218.3 mm vs. 229.7 mm, p < 0.01). The RCV of RLD patients was significantly smaller than that of the non-RLD patients (3.94 L vs. 4.49 L, p < 0.0001). The maximum width and RCV measured by 3D images with biplanar stereoradiography reflected pulmonary functional variables in patients with AIS.